diff --git a/packages/pigeon/CHANGELOG.md b/packages/pigeon/CHANGELOG.md
index 13033b336a8..4fa98cd73e2 100644
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@@ -1,3 +1,12 @@
+## 20.0.0
+
+* Moves all codec logic to single custom codec per file.
+* **Breaking Change** Limits the number of total custom types to 126.
+  * If more than 126 custom types are needed, consider breaking up your definition files.
+* Fixes bug that prevented collection subtypes from being added properly.
+* [swift] Adds `@unchecked Sendable` to codec method.
+* [objc] [cpp] Fixes bug that prevented setting custom header import path.
+
 ## 19.0.2
 
 * [kotlin] Adds the `@JvmOverloads` to the `HostApi` setUp method. This prevents the calling Java code from having to provide an empty `String` as Kotlin provides it by default  
diff --git a/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java b/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java
index f8029ebcd92..4993909460e 100644
--- a/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java
+++ b/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java
@@ -181,7 +181,7 @@ ArrayList<Object> toList() {
       ArrayList<Object> toListResult = new ArrayList<Object>(4);
       toListResult.add(name);
       toListResult.add(description);
-      toListResult.add(code == null ? null : code.index);
+      toListResult.add(code);
       toListResult.add(data);
       return toListResult;
     }
@@ -193,13 +193,45 @@ ArrayList<Object> toList() {
       Object description = __pigeon_list.get(1);
       pigeonResult.setDescription((String) description);
       Object code = __pigeon_list.get(2);
-      pigeonResult.setCode(Code.values()[(int) code]);
+      pigeonResult.setCode((Code) code);
       Object data = __pigeon_list.get(3);
       pigeonResult.setData((Map<String, String>) data);
       return pigeonResult;
     }
   }
 
+  private static class PigeonCodec extends StandardMessageCodec {
+    public static final PigeonCodec INSTANCE = new PigeonCodec();
+
+    private PigeonCodec() {}
+
+    @Override
+    protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) {
+      switch (type) {
+        case (byte) 129:
+          return MessageData.fromList((ArrayList<Object>) readValue(buffer));
+        case (byte) 130:
+          Object value = readValue(buffer);
+          return value == null ? null : Code.values()[(int) value];
+        default:
+          return super.readValueOfType(type, buffer);
+      }
+    }
+
+    @Override
+    protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) {
+      if (value instanceof MessageData) {
+        stream.write(129);
+        writeValue(stream, ((MessageData) value).toList());
+      } else if (value instanceof Code) {
+        stream.write(130);
+        writeValue(stream, value == null ? null : ((Code) value).index);
+      } else {
+        super.writeValue(stream, value);
+      }
+    }
+  }
+
   /** Asynchronous error handling return type for non-nullable API method returns. */
   public interface Result<T> {
     /** Success case callback method for handling returns. */
@@ -224,33 +256,6 @@ public interface VoidResult {
     /** Failure case callback method for handling errors. */
     void error(@NonNull Throwable error);
   }
-
-  private static class ExampleHostApiCodec extends StandardMessageCodec {
-    public static final ExampleHostApiCodec INSTANCE = new ExampleHostApiCodec();
-
-    private ExampleHostApiCodec() {}
-
-    @Override
-    protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) {
-      switch (type) {
-        case (byte) 128:
-          return MessageData.fromList((ArrayList<Object>) readValue(buffer));
-        default:
-          return super.readValueOfType(type, buffer);
-      }
-    }
-
-    @Override
-    protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) {
-      if (value instanceof MessageData) {
-        stream.write(128);
-        writeValue(stream, ((MessageData) value).toList());
-      } else {
-        super.writeValue(stream, value);
-      }
-    }
-  }
-
   /** Generated interface from Pigeon that represents a handler of messages from Flutter. */
   public interface ExampleHostApi {
 
@@ -264,7 +269,7 @@ public interface ExampleHostApi {
 
     /** The codec used by ExampleHostApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return ExampleHostApiCodec.INSTANCE;
+      return PigeonCodec.INSTANCE;
     }
     /** Sets up an instance of `ExampleHostApi` to handle messages through the `binaryMessenger`. */
     static void setUp(@NonNull BinaryMessenger binaryMessenger, @Nullable ExampleHostApi api) {
@@ -382,7 +387,7 @@ public MessageFlutterApi(
     /** Public interface for sending reply. */
     /** The codec used by MessageFlutterApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return new StandardMessageCodec();
+      return PigeonCodec.INSTANCE;
     }
 
     public void flutterMethod(@Nullable String aStringArg, @NonNull Result<String> result) {
diff --git a/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt b/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt
index 7f0e75cefa9..6542e190e78 100644
--- a/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt
+++ b/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt
@@ -69,28 +69,31 @@ data class MessageData(
     fun fromList(__pigeon_list: List<Any?>): MessageData {
       val name = __pigeon_list[0] as String?
       val description = __pigeon_list[1] as String?
-      val code = Code.ofRaw(__pigeon_list[2] as Int)!!
+      val code = __pigeon_list[2] as Code
       val data = __pigeon_list[3] as Map<String?, String?>
       return MessageData(name, description, code, data)
     }
   }
 
   fun toList(): List<Any?> {
-    return listOf<Any?>(
+    return listOf(
         name,
         description,
-        code.raw,
+        code,
         data,
     )
   }
 }
 
-private object ExampleHostApiCodec : StandardMessageCodec() {
+private object MessagesPigeonCodec : StandardMessageCodec() {
   override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
     return when (type) {
-      128.toByte() -> {
+      129.toByte() -> {
         return (readValue(buffer) as? List<Any?>)?.let { MessageData.fromList(it) }
       }
+      130.toByte() -> {
+        return (readValue(buffer) as Int?)?.let { Code.ofRaw(it) }
+      }
       else -> super.readValueOfType(type, buffer)
     }
   }
@@ -98,9 +101,13 @@ private object ExampleHostApiCodec : StandardMessageCodec() {
   override fun writeValue(stream: ByteArrayOutputStream, value: Any?) {
     when (value) {
       is MessageData -> {
-        stream.write(128)
+        stream.write(129)
         writeValue(stream, value.toList())
       }
+      is Code -> {
+        stream.write(130)
+        writeValue(stream, value.raw)
+      }
       else -> super.writeValue(stream, value)
     }
   }
@@ -116,7 +123,7 @@ interface ExampleHostApi {
 
   companion object {
     /** The codec used by ExampleHostApi. */
-    val codec: MessageCodec<Any?> by lazy { ExampleHostApiCodec }
+    val codec: MessageCodec<Any?> by lazy { MessagesPigeonCodec }
     /** Sets up an instance of `ExampleHostApi` to handle messages through the `binaryMessenger`. */
     @JvmOverloads
     fun setUp(
@@ -136,7 +143,7 @@ interface ExampleHostApi {
           channel.setMessageHandler { _, reply ->
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.getHostLanguage())
+                  listOf(api.getHostLanguage())
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -159,7 +166,7 @@ interface ExampleHostApi {
             val bArg = args[1].let { num -> if (num is Int) num.toLong() else num as Long }
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.add(aArg, bArg))
+                  listOf(api.add(aArg, bArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -203,7 +210,7 @@ class MessageFlutterApi(
 ) {
   companion object {
     /** The codec used by MessageFlutterApi. */
-    val codec: MessageCodec<Any?> by lazy { StandardMessageCodec() }
+    val codec: MessageCodec<Any?> by lazy { MessagesPigeonCodec }
   }
 
   fun flutterMethod(aStringArg: String?, callback: (Result<String>) -> Unit) {
diff --git a/packages/pigeon/example/app/ios/Runner/Messages.g.swift b/packages/pigeon/example/app/ios/Runner/Messages.g.swift
index 51b3cfa61de..3d5362cc4f1 100644
--- a/packages/pigeon/example/app/ios/Runner/Messages.g.swift
+++ b/packages/pigeon/example/app/ios/Runner/Messages.g.swift
@@ -89,7 +89,7 @@ struct MessageData {
   static func fromList(_ __pigeon_list: [Any?]) -> MessageData? {
     let name: String? = nilOrValue(__pigeon_list[0])
     let description: String? = nilOrValue(__pigeon_list[1])
-    let code = Code(rawValue: __pigeon_list[2] as! Int)!
+    let code = __pigeon_list[2] as! Code
     let data = __pigeon_list[3] as! [String?: String?]
 
     return MessageData(
@@ -103,46 +103,55 @@ struct MessageData {
     return [
       name,
       description,
-      code.rawValue,
+      code,
       data,
     ]
   }
 }
-
-private class ExampleHostApiCodecReader: FlutterStandardReader {
+private class MessagesPigeonCodecReader: FlutterStandardReader {
   override func readValue(ofType type: UInt8) -> Any? {
     switch type {
-    case 128:
+    case 129:
       return MessageData.fromList(self.readValue() as! [Any?])
+    case 130:
+      var enumResult: Code? = nil
+      let enumResultAsInt: Int? = nilOrValue(self.readValue() as? Int)
+      if let enumResultAsInt = enumResultAsInt {
+        enumResult = Code(rawValue: enumResultAsInt)
+      }
+      return enumResult
     default:
       return super.readValue(ofType: type)
     }
   }
 }
 
-private class ExampleHostApiCodecWriter: FlutterStandardWriter {
+private class MessagesPigeonCodecWriter: FlutterStandardWriter {
   override func writeValue(_ value: Any) {
     if let value = value as? MessageData {
-      super.writeByte(128)
+      super.writeByte(129)
       super.writeValue(value.toList())
+    } else if let value = value as? Code {
+      super.writeByte(130)
+      super.writeValue(value.rawValue)
     } else {
       super.writeValue(value)
     }
   }
 }
 
-private class ExampleHostApiCodecReaderWriter: FlutterStandardReaderWriter {
+private class MessagesPigeonCodecReaderWriter: FlutterStandardReaderWriter {
   override func reader(with data: Data) -> FlutterStandardReader {
-    return ExampleHostApiCodecReader(data: data)
+    return MessagesPigeonCodecReader(data: data)
   }
 
   override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return ExampleHostApiCodecWriter(data: data)
+    return MessagesPigeonCodecWriter(data: data)
   }
 }
 
-class ExampleHostApiCodec: FlutterStandardMessageCodec {
-  static let shared = ExampleHostApiCodec(readerWriter: ExampleHostApiCodecReaderWriter())
+class MessagesPigeonCodec: FlutterStandardMessageCodec, @unchecked Sendable {
+  static let shared = MessagesPigeonCodec(readerWriter: MessagesPigeonCodecReaderWriter())
 }
 
 /// Generated protocol from Pigeon that represents a handler of messages from Flutter.
@@ -154,8 +163,7 @@ protocol ExampleHostApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class ExampleHostApiSetup {
-  /// The codec used by ExampleHostApi.
-  static var codec: FlutterStandardMessageCodec { ExampleHostApiCodec.shared }
+  static var codec: FlutterStandardMessageCodec { MessagesPigeonCodec.shared }
   /// Sets up an instance of `ExampleHostApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: ExampleHostApi?, messageChannelSuffix: String = ""
@@ -228,12 +236,16 @@ class MessageFlutterApi: MessageFlutterApiProtocol {
     self.binaryMessenger = binaryMessenger
     self.messageChannelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
   }
+  var codec: MessagesPigeonCodec {
+    return MessagesPigeonCodec.shared
+  }
   func flutterMethod(
     aString aStringArg: String?, completion: @escaping (Result<String, PigeonError>) -> Void
   ) {
     let channelName: String =
       "dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod\(messageChannelSuffix)"
-    let channel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: binaryMessenger)
+    let channel = FlutterBasicMessageChannel(
+      name: channelName, binaryMessenger: binaryMessenger, codec: codec)
     channel.sendMessage([aStringArg] as [Any?]) { response in
       guard let listResponse = response as? [Any?] else {
         completion(.failure(createConnectionError(withChannelName: channelName)))
diff --git a/packages/pigeon/example/app/lib/src/messages.g.dart b/packages/pigeon/example/app/lib/src/messages.g.dart
index 071711ffaa9..d8d4fde551c 100644
--- a/packages/pigeon/example/app/lib/src/messages.g.dart
+++ b/packages/pigeon/example/app/lib/src/messages.g.dart
@@ -54,7 +54,7 @@ class MessageData {
     return <Object?>[
       name,
       description,
-      code.index,
+      code,
       data,
     ];
   }
@@ -64,19 +64,22 @@ class MessageData {
     return MessageData(
       name: result[0] as String?,
       description: result[1] as String?,
-      code: Code.values[result[2]! as int],
+      code: result[2]! as Code,
       data: (result[3] as Map<Object?, Object?>?)!.cast<String?, String?>(),
     );
   }
 }
 
-class _ExampleHostApiCodec extends StandardMessageCodec {
-  const _ExampleHostApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
     if (value is MessageData) {
-      buffer.putUint8(128);
+      buffer.putUint8(129);
       writeValue(buffer, value.encode());
+    } else if (value is Code) {
+      buffer.putUint8(130);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -85,8 +88,11 @@ class _ExampleHostApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
+      case 129:
         return MessageData.decode(readValue(buffer)!);
+      case 130:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : Code.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -104,8 +110,7 @@ class ExampleHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _ExampleHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -198,8 +203,7 @@ class ExampleHostApi {
 }
 
 abstract class MessageFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   String flutterMethod(String? aString);
 
diff --git a/packages/pigeon/example/app/macos/Runner/messages.g.h b/packages/pigeon/example/app/macos/Runner/messages.g.h
index db20dcba17e..8a51885ec9f 100644
--- a/packages/pigeon/example/app/macos/Runner/messages.g.h
+++ b/packages/pigeon/example/app/macos/Runner/messages.g.h
@@ -39,8 +39,8 @@ typedef NS_ENUM(NSUInteger, PGNCode) {
 @property(nonatomic, copy) NSDictionary<NSString *, NSString *> *data;
 @end
 
-/// The codec used by PGNExampleHostApi.
-NSObject<FlutterMessageCodec> *PGNExampleHostApiGetCodec(void);
+/// The codec used by all APIs.
+NSObject<FlutterMessageCodec> *PGNGetMessagesCodec(void);
 
 @protocol PGNExampleHostApi
 /// @return `nil` only when `error != nil`.
@@ -60,9 +60,6 @@ extern void SetUpPGNExampleHostApiWithSuffix(id<FlutterBinaryMessenger> binaryMe
                                              NSObject<PGNExampleHostApi> *_Nullable api,
                                              NSString *messageChannelSuffix);
 
-/// The codec used by PGNMessageFlutterApi.
-NSObject<FlutterMessageCodec> *PGNMessageFlutterApiGetCodec(void);
-
 @interface PGNMessageFlutterApi : NSObject
 - (instancetype)initWithBinaryMessenger:(id<FlutterBinaryMessenger>)binaryMessenger;
 - (instancetype)initWithBinaryMessenger:(id<FlutterBinaryMessenger>)binaryMessenger
diff --git a/packages/pigeon/example/app/macos/Runner/messages.g.m b/packages/pigeon/example/app/macos/Runner/messages.g.m
index 90bd065401c..1471345b880 100644
--- a/packages/pigeon/example/app/macos/Runner/messages.g.m
+++ b/packages/pigeon/example/app/macos/Runner/messages.g.m
@@ -16,7 +16,7 @@
 #error File requires ARC to be enabled.
 #endif
 
-static NSArray *wrapResult(id result, FlutterError *error) {
+static NSArray<id> *wrapResult(id result, FlutterError *error) {
   if (error) {
     return @[
       error.code ?: [NSNull null], error.message ?: [NSNull null], error.details ?: [NSNull null]
@@ -34,7 +34,7 @@
             details:@""];
 }
 
-static id GetNullableObjectAtIndex(NSArray *array, NSInteger key) {
+static id GetNullableObjectAtIndex(NSArray<id> *array, NSInteger key) {
   id result = array[key];
   return (result == [NSNull null]) ? nil : result;
 }
@@ -50,9 +50,9 @@ - (instancetype)initWithValue:(PGNCode)value {
 @end
 
 @interface PGNMessageData ()
-+ (PGNMessageData *)fromList:(NSArray *)list;
-+ (nullable PGNMessageData *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (PGNMessageData *)fromList:(NSArray<id> *)list;
++ (nullable PGNMessageData *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @implementation PGNMessageData
@@ -67,75 +67,84 @@ + (instancetype)makeWithName:(nullable NSString *)name
   pigeonResult.data = data;
   return pigeonResult;
 }
-+ (PGNMessageData *)fromList:(NSArray *)list {
++ (PGNMessageData *)fromList:(NSArray<id> *)list {
   PGNMessageData *pigeonResult = [[PGNMessageData alloc] init];
   pigeonResult.name = GetNullableObjectAtIndex(list, 0);
   pigeonResult.description = GetNullableObjectAtIndex(list, 1);
-  pigeonResult.code = [GetNullableObjectAtIndex(list, 2) integerValue];
+  PGNCodeBox *enumBox = GetNullableObjectAtIndex(list, 2);
+  pigeonResult.code = enumBox.value;
   pigeonResult.data = GetNullableObjectAtIndex(list, 3);
   return pigeonResult;
 }
-+ (nullable PGNMessageData *)nullableFromList:(NSArray *)list {
++ (nullable PGNMessageData *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [PGNMessageData fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.name ?: [NSNull null],
     self.description ?: [NSNull null],
-    @(self.code),
+    [[PGNCodeBox alloc] initWithValue:self.code],
     self.data ?: [NSNull null],
   ];
 }
 @end
 
-@interface PGNExampleHostApiCodecReader : FlutterStandardReader
+@interface PGNMessagesPigeonCodecReader : FlutterStandardReader
 @end
-@implementation PGNExampleHostApiCodecReader
+@implementation PGNMessagesPigeonCodecReader
 - (nullable id)readValueOfType:(UInt8)type {
   switch (type) {
-    case 128:
+    case 129:
       return [PGNMessageData fromList:[self readValue]];
+    case 130: {
+      NSNumber *enumAsNumber = [self readValue];
+      return enumAsNumber == nil ? nil
+                                 : [[PGNCodeBox alloc] initWithValue:[enumAsNumber integerValue]];
+    }
     default:
       return [super readValueOfType:type];
   }
 }
 @end
 
-@interface PGNExampleHostApiCodecWriter : FlutterStandardWriter
+@interface PGNMessagesPigeonCodecWriter : FlutterStandardWriter
 @end
-@implementation PGNExampleHostApiCodecWriter
+@implementation PGNMessagesPigeonCodecWriter
 - (void)writeValue:(id)value {
   if ([value isKindOfClass:[PGNMessageData class]]) {
-    [self writeByte:128];
+    [self writeByte:129];
     [self writeValue:[value toList]];
+  } else if ([value isKindOfClass:[PGNCodeBox class]]) {
+    PGNCodeBox *box = (PGNCodeBox *)value;
+    [self writeByte:130];
+    [self writeValue:(value == nil ? [NSNull null] : [NSNumber numberWithInteger:box.value])];
   } else {
     [super writeValue:value];
   }
 }
 @end
 
-@interface PGNExampleHostApiCodecReaderWriter : FlutterStandardReaderWriter
+@interface PGNMessagesPigeonCodecReaderWriter : FlutterStandardReaderWriter
 @end
-@implementation PGNExampleHostApiCodecReaderWriter
+@implementation PGNMessagesPigeonCodecReaderWriter
 - (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[PGNExampleHostApiCodecWriter alloc] initWithData:data];
+  return [[PGNMessagesPigeonCodecWriter alloc] initWithData:data];
 }
 - (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[PGNExampleHostApiCodecReader alloc] initWithData:data];
+  return [[PGNMessagesPigeonCodecReader alloc] initWithData:data];
 }
 @end
 
-NSObject<FlutterMessageCodec> *PGNExampleHostApiGetCodec(void) {
+NSObject<FlutterMessageCodec> *PGNGetMessagesCodec(void) {
   static FlutterStandardMessageCodec *sSharedObject = nil;
   static dispatch_once_t sPred = 0;
   dispatch_once(&sPred, ^{
-    PGNExampleHostApiCodecReaderWriter *readerWriter =
-        [[PGNExampleHostApiCodecReaderWriter alloc] init];
+    PGNMessagesPigeonCodecReaderWriter *readerWriter =
+        [[PGNMessagesPigeonCodecReaderWriter alloc] init];
     sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
   });
   return sSharedObject;
 }
-
 void SetUpPGNExampleHostApi(id<FlutterBinaryMessenger> binaryMessenger,
                             NSObject<PGNExampleHostApi> *api) {
   SetUpPGNExampleHostApiWithSuffix(binaryMessenger, api, @"");
@@ -154,7 +163,7 @@ void SetUpPGNExampleHostApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger
                                                    @"ExampleHostApi.getHostLanguage",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:PGNExampleHostApiGetCodec()];
+                  codec:PGNGetMessagesCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(getHostLanguageWithError:)],
@@ -177,14 +186,14 @@ void SetUpPGNExampleHostApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger
                                     @"dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.add",
                                     messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:PGNExampleHostApiGetCodec()];
+                  codec:PGNGetMessagesCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(addNumber:toNumber:error:)],
           @"PGNExampleHostApi api (%@) doesn't respond to @selector(addNumber:toNumber:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_a = [GetNullableObjectAtIndex(args, 0) integerValue];
         NSInteger arg_b = [GetNullableObjectAtIndex(args, 1) integerValue];
         FlutterError *error;
@@ -202,14 +211,14 @@ void SetUpPGNExampleHostApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger
                                                    @"ExampleHostApi.sendMessage",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:PGNExampleHostApiGetCodec()];
+                  codec:PGNGetMessagesCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(sendMessageMessage:completion:)],
                 @"PGNExampleHostApi api (%@) doesn't respond to "
                 @"@selector(sendMessageMessage:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         PGNMessageData *arg_message = GetNullableObjectAtIndex(args, 0);
         [api sendMessageMessage:arg_message
                      completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -221,12 +230,6 @@ void SetUpPGNExampleHostApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger
     }
   }
 }
-NSObject<FlutterMessageCodec> *PGNMessageFlutterApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  sSharedObject = [FlutterStandardMessageCodec sharedInstance];
-  return sSharedObject;
-}
-
 @interface PGNMessageFlutterApi ()
 @property(nonatomic, strong) NSObject<FlutterBinaryMessenger> *binaryMessenger;
 @property(nonatomic, strong) NSString *messageChannelSuffix;
@@ -257,7 +260,7 @@ - (void)flutterMethodAString:(nullable NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:PGNMessageFlutterApiGetCodec()];
+                                                   codec:PGNGetMessagesCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
diff --git a/packages/pigeon/example/app/windows/runner/messages.g.cpp b/packages/pigeon/example/app/windows/runner/messages.g.cpp
index 5f6e25a18db..7a43ec397a3 100644
--- a/packages/pigeon/example/app/windows/runner/messages.g.cpp
+++ b/packages/pigeon/example/app/windows/runner/messages.g.cpp
@@ -82,14 +82,15 @@ EncodableList MessageData::ToEncodableList() const {
   list.push_back(name_ ? EncodableValue(*name_) : EncodableValue());
   list.push_back(description_ ? EncodableValue(*description_)
                               : EncodableValue());
-  list.push_back(EncodableValue((int)code_));
+  list.push_back(CustomEncodableValue(code_));
   list.push_back(EncodableValue(data_));
   return list;
 }
 
 MessageData MessageData::FromEncodableList(const EncodableList& list) {
-  MessageData decoded((Code)(std::get<int32_t>(list[2])),
-                      std::get<EncodableMap>(list[3]));
+  MessageData decoded(
+      std::any_cast<const Code&>(std::get<CustomEncodableValue>(list[2])),
+      std::get<EncodableMap>(list[3]));
   auto& encodable_name = list[0];
   if (!encodable_name.IsNull()) {
     decoded.set_name(std::get<std::string>(encodable_name));
@@ -101,31 +102,46 @@ MessageData MessageData::FromEncodableList(const EncodableList& list) {
   return decoded;
 }
 
-ExampleHostApiCodecSerializer::ExampleHostApiCodecSerializer() {}
+PigeonCodecSerializer::PigeonCodecSerializer() {}
 
-EncodableValue ExampleHostApiCodecSerializer::ReadValueOfType(
+EncodableValue PigeonCodecSerializer::ReadValueOfType(
     uint8_t type, flutter::ByteStreamReader* stream) const {
   switch (type) {
-    case 128:
+    case 129:
       return CustomEncodableValue(MessageData::FromEncodableList(
           std::get<EncodableList>(ReadValue(stream))));
+    case 130: {
+      const auto& encodable_enum_arg = ReadValue(stream);
+      const int64_t enum_arg_value =
+          encodable_enum_arg.IsNull() ? 0 : encodable_enum_arg.LongValue();
+      return encodable_enum_arg.IsNull()
+                 ? EncodableValue()
+                 : CustomEncodableValue(static_cast<Code>(enum_arg_value));
+    }
     default:
       return flutter::StandardCodecSerializer::ReadValueOfType(type, stream);
   }
 }
 
-void ExampleHostApiCodecSerializer::WriteValue(
+void PigeonCodecSerializer::WriteValue(
     const EncodableValue& value, flutter::ByteStreamWriter* stream) const {
   if (const CustomEncodableValue* custom_value =
           std::get_if<CustomEncodableValue>(&value)) {
     if (custom_value->type() == typeid(MessageData)) {
-      stream->WriteByte(128);
+      stream->WriteByte(129);
       WriteValue(
           EncodableValue(
               std::any_cast<MessageData>(*custom_value).ToEncodableList()),
           stream);
       return;
     }
+    if (custom_value->type() == typeid(Code)) {
+      stream->WriteByte(130);
+      WriteValue(
+          EncodableValue(static_cast<int>(std::any_cast<Code>(*custom_value))),
+          stream);
+      return;
+    }
   }
   flutter::StandardCodecSerializer::WriteValue(value, stream);
 }
@@ -133,7 +149,7 @@ void ExampleHostApiCodecSerializer::WriteValue(
 /// The codec used by ExampleHostApi.
 const flutter::StandardMessageCodec& ExampleHostApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &ExampleHostApiCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 // Sets up an instance of `ExampleHostApi` to handle messages through the
@@ -282,7 +298,7 @@ MessageFlutterApi::MessageFlutterApi(flutter::BinaryMessenger* binary_messenger,
 
 const flutter::StandardMessageCodec& MessageFlutterApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &flutter::StandardCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 void MessageFlutterApi::FlutterMethod(
diff --git a/packages/pigeon/example/app/windows/runner/messages.g.h b/packages/pigeon/example/app/windows/runner/messages.g.h
index 1b9ca3626cb..84368cbb1df 100644
--- a/packages/pigeon/example/app/windows/runner/messages.g.h
+++ b/packages/pigeon/example/app/windows/runner/messages.g.h
@@ -89,20 +89,19 @@ class MessageData {
   static MessageData FromEncodableList(const flutter::EncodableList& list);
   flutter::EncodableList ToEncodableList() const;
   friend class ExampleHostApi;
-  friend class ExampleHostApiCodecSerializer;
   friend class MessageFlutterApi;
-  friend class MessageFlutterApiCodecSerializer;
+  friend class PigeonCodecSerializer;
   std::optional<std::string> name_;
   std::optional<std::string> description_;
   Code code_;
   flutter::EncodableMap data_;
 };
 
-class ExampleHostApiCodecSerializer : public flutter::StandardCodecSerializer {
+class PigeonCodecSerializer : public flutter::StandardCodecSerializer {
  public:
-  ExampleHostApiCodecSerializer();
-  inline static ExampleHostApiCodecSerializer& GetInstance() {
-    static ExampleHostApiCodecSerializer sInstance;
+  PigeonCodecSerializer();
+  inline static PigeonCodecSerializer& GetInstance() {
+    static PigeonCodecSerializer sInstance;
     return sInstance;
   }
 
diff --git a/packages/pigeon/lib/ast.dart b/packages/pigeon/lib/ast.dart
index d7bc2139729..b3469b03295 100644
--- a/packages/pigeon/lib/ast.dart
+++ b/packages/pigeon/lib/ast.dart
@@ -515,6 +515,18 @@ class TypeDeclaration {
     );
   }
 
+  /// Returns duplicated `TypeDeclaration` with attached `associatedProxyApi` value.
+  TypeDeclaration copyWithTypeArguments(List<TypeDeclaration> types) {
+    return TypeDeclaration(
+      baseName: baseName,
+      isNullable: isNullable,
+      typeArguments: types,
+      associatedClass: associatedClass,
+      associatedEnum: associatedEnum,
+      associatedProxyApi: associatedProxyApi,
+    );
+  }
+
   @override
   String toString() {
     final String typeArgumentsStr =
diff --git a/packages/pigeon/lib/cpp_generator.dart b/packages/pigeon/lib/cpp_generator.dart
index 00a156b0c5d..5c42df0b082 100644
--- a/packages/pigeon/lib/cpp_generator.dart
+++ b/packages/pigeon/lib/cpp_generator.dart
@@ -18,7 +18,10 @@ const DocumentCommentSpecification _docCommentSpec =
     DocumentCommentSpecification(_commentPrefix);
 
 /// The default serializer for Flutter.
-const String _defaultCodecSerializer = 'flutter::StandardCodecSerializer';
+const String _standardCodecSerializer = 'flutter::StandardCodecSerializer';
+
+/// The name of the codec serializer.
+const String _codecSerializerName = 'PigeonCodecSerializer';
 
 /// Options that control how C++ code will be generated.
 class CppOptions {
@@ -47,7 +50,7 @@ class CppOptions {
   /// `x = CppOptions.fromMap(x.toMap())`.
   static CppOptions fromMap(Map<String, Object> map) {
     return CppOptions(
-      headerIncludePath: map['header'] as String?,
+      headerIncludePath: map['headerIncludePath'] as String?,
       namespace: map['namespace'] as String?,
       copyrightHeader: map['copyrightHeader'] as Iterable<String>?,
       headerOutPath: map['cppHeaderOut'] as String?,
@@ -58,7 +61,7 @@ class CppOptions {
   /// `x = CppOptions.fromMap(x.toMap())`.
   Map<String, Object> toMap() {
     final Map<String, Object> result = <String, Object>{
-      if (headerIncludePath != null) 'header': headerIncludePath!,
+      if (headerIncludePath != null) 'headerIncludePath': headerIncludePath!,
       if (namespace != null) 'namespace': namespace!,
       if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
     };
@@ -332,8 +335,8 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
           // TODO(gaaclarke): Find a way to be more precise with our
           // friendships.
           indent.writeln('friend class ${api.name};');
-          indent.writeln('friend class ${_getCodecSerializerName(api)};');
         }
+        indent.writeln('friend class $_codecSerializerName;');
         if (testFixtureClass != null) {
           indent.writeln('friend class $testFixtureClass;');
         }
@@ -349,6 +352,49 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     indent.newln();
   }
 
+  @override
+  void writeGeneralCodec(
+    CppOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    indent.write(
+        'class $_codecSerializerName : public $_standardCodecSerializer ');
+    indent.addScoped('{', '};', () {
+      _writeAccessBlock(indent, _ClassAccess.public, () {
+        _writeFunctionDeclaration(indent, _codecSerializerName,
+            isConstructor: true);
+        _writeFunctionDeclaration(indent, 'GetInstance',
+            returnType: '$_codecSerializerName&',
+            isStatic: true, inlineBody: () {
+          indent.writeln('static $_codecSerializerName sInstance;');
+          indent.writeln('return sInstance;');
+        });
+        indent.newln();
+        _writeFunctionDeclaration(indent, 'WriteValue',
+            returnType: _voidType,
+            parameters: <String>[
+              'const flutter::EncodableValue& value',
+              'flutter::ByteStreamWriter* stream'
+            ],
+            isConst: true,
+            isOverride: true);
+      });
+      indent.writeScoped(' protected:', '', () {
+        _writeFunctionDeclaration(indent, 'ReadValueOfType',
+            returnType: 'flutter::EncodableValue',
+            parameters: <String>[
+              'uint8_t type',
+              'flutter::ByteStreamReader* stream'
+            ],
+            isConst: true,
+            isOverride: true);
+      });
+    }, nestCount: 0);
+    indent.newln();
+  }
+
   @override
   void writeFlutterApi(
     CppOptions generatorOptions,
@@ -357,9 +403,6 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(generatorOptions, root, indent, api);
-    }
     const List<String> generatedMessages = <String>[
       ' Generated class from Pigeon that represents Flutter messages that can be called from C++.'
     ];
@@ -415,9 +458,6 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     AstHostApi api, {
     required String dartPackageName,
   }) {
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(generatorOptions, root, indent, api);
-    }
     const List<String> generatedMessages = <String>[
       ' Generated interface from Pigeon that represents a handler of messages from Flutter.'
     ];
@@ -521,45 +561,6 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     indent.newln();
   }
 
-  void _writeCodec(
-      CppOptions generatorOptions, Root root, Indent indent, Api api) {
-    assert(getCodecClasses(api, root).isNotEmpty);
-    final String codeSerializerName = _getCodecSerializerName(api);
-    indent
-        .write('class $codeSerializerName : public $_defaultCodecSerializer ');
-    indent.addScoped('{', '};', () {
-      _writeAccessBlock(indent, _ClassAccess.public, () {
-        _writeFunctionDeclaration(indent, codeSerializerName,
-            isConstructor: true);
-        _writeFunctionDeclaration(indent, 'GetInstance',
-            returnType: '$codeSerializerName&', isStatic: true, inlineBody: () {
-          indent.writeln('static $codeSerializerName sInstance;');
-          indent.writeln('return sInstance;');
-        });
-        indent.newln();
-        _writeFunctionDeclaration(indent, 'WriteValue',
-            returnType: _voidType,
-            parameters: <String>[
-              'const flutter::EncodableValue& value',
-              'flutter::ByteStreamWriter* stream'
-            ],
-            isConst: true,
-            isOverride: true);
-      });
-      indent.writeScoped(' protected:', '', () {
-        _writeFunctionDeclaration(indent, 'ReadValueOfType',
-            returnType: 'flutter::EncodableValue',
-            parameters: <String>[
-              'uint8_t type',
-              'flutter::ByteStreamReader* stream'
-            ],
-            isConst: true,
-            isOverride: true);
-      });
-    }, nestCount: 0);
-    indent.newln();
-  }
-
   void _writeFlutterError(Indent indent) {
     indent.format('''
 
@@ -810,16 +811,14 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     // Returns the expression to convert the given EncodableValue to a field
     // value.
     String getValueExpression(NamedType field, String encodable) {
-      if (field.type.isEnum) {
-        return '(${field.type.baseName})(std::get<int32_t>($encodable))';
-      } else if (field.type.baseName == 'int') {
+      if (field.type.baseName == 'int') {
         return '$encodable.LongValue()';
       } else if (field.type.baseName == 'Object') {
         return encodable;
       } else {
         final HostDatatype hostDatatype =
             getFieldHostDatatype(field, _shortBaseCppTypeForBuiltinDartType);
-        if (field.type.isClass) {
+        if (field.type.isClass || field.type.isEnum) {
           return _classReferenceFromEncodableValue(hostDatatype, encodable);
         } else {
           return 'std::get<${hostDatatype.datatype}>($encodable)';
@@ -875,6 +874,90 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     });
   }
 
+  @override
+  void writeGeneralCodec(
+    CppOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    final Iterable<EnumeratedType> customTypes = getEnumeratedTypes(root);
+    indent.newln();
+    _writeFunctionDefinition(indent, _codecSerializerName,
+        scope: _codecSerializerName);
+    _writeFunctionDefinition(indent, 'ReadValueOfType',
+        scope: _codecSerializerName,
+        returnType: 'EncodableValue',
+        parameters: <String>[
+          'uint8_t type',
+          'flutter::ByteStreamReader* stream',
+        ],
+        isConst: true, body: () {
+      if (customTypes.isNotEmpty) {
+        indent.writeln('switch (type) {');
+        indent.inc();
+        for (final EnumeratedType customType in customTypes) {
+          indent.writeln('case ${customType.enumeration}:');
+          indent.nest(1, () {
+            if (customType.type == CustomTypes.customClass) {
+              indent.writeln(
+                  'return CustomEncodableValue(${customType.name}::FromEncodableList(std::get<EncodableList>(ReadValue(stream))));');
+            } else if (customType.type == CustomTypes.customEnum) {
+              indent.writeScoped('{', '}', () {
+                indent.writeln(
+                    'const auto& encodable_enum_arg = ReadValue(stream);');
+                indent.writeln(
+                    'const int64_t enum_arg_value = encodable_enum_arg.IsNull() ? 0 : encodable_enum_arg.LongValue();');
+                indent.writeln(
+                    'return encodable_enum_arg.IsNull() ? EncodableValue() : CustomEncodableValue(static_cast<${customType.name}>(enum_arg_value));');
+              });
+            }
+          });
+        }
+        indent.writeln('default:');
+        indent.inc();
+      }
+      indent.writeln(
+          'return $_standardCodecSerializer::ReadValueOfType(type, stream);');
+      if (customTypes.isNotEmpty) {
+        indent.dec();
+        indent.writeln('}');
+        indent.dec();
+      }
+    });
+    _writeFunctionDefinition(indent, 'WriteValue',
+        scope: _codecSerializerName,
+        returnType: _voidType,
+        parameters: <String>[
+          'const EncodableValue& value',
+          'flutter::ByteStreamWriter* stream',
+        ],
+        isConst: true, body: () {
+      if (customTypes.isNotEmpty) {
+        indent.write(
+            'if (const CustomEncodableValue* custom_value = std::get_if<CustomEncodableValue>(&value)) ');
+        indent.addScoped('{', '}', () {
+          for (final EnumeratedType customType in customTypes) {
+            indent.write(
+                'if (custom_value->type() == typeid(${customType.name})) ');
+            indent.addScoped('{', '}', () {
+              indent.writeln('stream->WriteByte(${customType.enumeration});');
+              if (customType.type == CustomTypes.customClass) {
+                indent.writeln(
+                    'WriteValue(EncodableValue(std::any_cast<${customType.name}>(*custom_value).ToEncodableList()), stream);');
+              } else if (customType.type == CustomTypes.customEnum) {
+                indent.writeln(
+                    'WriteValue(EncodableValue(static_cast<int>(std::any_cast<${customType.name}>(*custom_value))), stream);');
+              }
+              indent.writeln('return;');
+            });
+          }
+        });
+      }
+      indent.writeln('$_standardCodecSerializer::WriteValue(value, stream);');
+    });
+  }
+
   @override
   void writeFlutterApi(
     CppOptions generatorOptions,
@@ -883,9 +966,6 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(generatorOptions, root, indent, api);
-    }
     indent.writeln(
         '$_commentPrefix Generated class from Pigeon that represents Flutter messages that can be called from C++.');
     _writeFunctionDefinition(
@@ -913,9 +993,6 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
         'message_channel_suffix_(message_channel_suffix.length() > 0 ? std::string(".") + message_channel_suffix : "")'
       ],
     );
-    final String codeSerializerName = getCodecClasses(api, root).isNotEmpty
-        ? _getCodecSerializerName(api)
-        : _defaultCodecSerializer;
     _writeFunctionDefinition(
       indent,
       'GetCodec',
@@ -923,7 +1000,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
       returnType: 'const flutter::StandardMessageCodec&',
       body: () {
         indent.writeln(
-            'return flutter::StandardMessageCodec::GetInstance(&$codeSerializerName::GetInstance());');
+            'return flutter::StandardMessageCodec::GetInstance(&$_codecSerializerName::GetInstance());');
       },
     );
     for (final Method func in api.methods) {
@@ -1023,19 +1100,12 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     AstHostApi api, {
     required String dartPackageName,
   }) {
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(generatorOptions, root, indent, api);
-    }
-
-    final String codeSerializerName = getCodecClasses(api, root).isNotEmpty
-        ? _getCodecSerializerName(api)
-        : _defaultCodecSerializer;
     indent.writeln('/// The codec used by ${api.name}.');
     _writeFunctionDefinition(indent, 'GetCodec',
         scope: api.name,
         returnType: 'const flutter::StandardMessageCodec&', body: () {
       indent.writeln(
-          'return flutter::StandardMessageCodec::GetInstance(&$codeSerializerName::GetInstance());');
+          'return flutter::StandardMessageCodec::GetInstance(&$_codecSerializerName::GetInstance());');
     });
     indent.writeln(
         '$_commentPrefix Sets up an instance of `${api.name}` to handle messages through the `binary_messenger`.');
@@ -1177,67 +1247,6 @@ return EncodableValue(EncodableList{
     });
   }
 
-  void _writeCodec(
-    CppOptions generatorOptions,
-    Root root,
-    Indent indent,
-    Api api,
-  ) {
-    assert(getCodecClasses(api, root).isNotEmpty);
-    final String codeSerializerName = _getCodecSerializerName(api);
-    indent.newln();
-    _writeFunctionDefinition(indent, codeSerializerName,
-        scope: codeSerializerName);
-    _writeFunctionDefinition(indent, 'ReadValueOfType',
-        scope: codeSerializerName,
-        returnType: 'EncodableValue',
-        parameters: <String>[
-          'uint8_t type',
-          'flutter::ByteStreamReader* stream',
-        ],
-        isConst: true, body: () {
-      indent.write('switch (type) ');
-      indent.addScoped('{', '}', () {
-        for (final EnumeratedClass customClass in getCodecClasses(api, root)) {
-          indent.writeln('case ${customClass.enumeration}:');
-          indent.nest(1, () {
-            indent.writeln(
-                'return CustomEncodableValue(${customClass.name}::FromEncodableList(std::get<EncodableList>(ReadValue(stream))));');
-          });
-        }
-        indent.writeln('default:');
-        indent.nest(1, () {
-          indent.writeln(
-              'return $_defaultCodecSerializer::ReadValueOfType(type, stream);');
-        });
-      });
-    });
-    _writeFunctionDefinition(indent, 'WriteValue',
-        scope: codeSerializerName,
-        returnType: _voidType,
-        parameters: <String>[
-          'const EncodableValue& value',
-          'flutter::ByteStreamWriter* stream',
-        ],
-        isConst: true, body: () {
-      indent.write(
-          'if (const CustomEncodableValue* custom_value = std::get_if<CustomEncodableValue>(&value)) ');
-      indent.addScoped('{', '}', () {
-        for (final EnumeratedClass customClass in getCodecClasses(api, root)) {
-          indent.write(
-              'if (custom_value->type() == typeid(${customClass.name})) ');
-          indent.addScoped('{', '}', () {
-            indent.writeln('stream->WriteByte(${customClass.enumeration});');
-            indent.writeln(
-                'WriteValue(EncodableValue(std::any_cast<${customClass.name}>(*custom_value).ToEncodableList()), stream);');
-            indent.writeln('return;');
-          });
-        }
-      });
-      indent.writeln('$_defaultCodecSerializer::WriteValue(value, stream);');
-    });
-  }
-
   void _writeClassConstructor(Root root, Indent indent, Class classDefinition,
       Iterable<NamedType> params) {
     final Iterable<_HostNamedType> hostParams = params.map((NamedType param) {
@@ -1396,10 +1405,6 @@ return EncodableValue(EncodableList{
     final String errorGetter;
 
     const String nullValue = 'EncodableValue()';
-    String enumPrefix = '';
-    if (returnType.isEnum) {
-      enumPrefix = '(int) ';
-    }
     if (returnType.isVoid) {
       nonErrorPath = '${prefix}wrapped.push_back($nullValue);';
       errorCondition = 'output.has_value()';
@@ -1409,22 +1414,21 @@ return EncodableValue(EncodableList{
           getHostDatatype(returnType, _shortBaseCppTypeForBuiltinDartType);
 
       const String extractedValue = 'std::move(output).TakeValue()';
-      final String wrapperType = hostType.isBuiltin || returnType.isEnum
-          ? 'EncodableValue'
-          : 'CustomEncodableValue';
+      final String wrapperType =
+          hostType.isBuiltin ? 'EncodableValue' : 'CustomEncodableValue';
       if (returnType.isNullable) {
         // The value is a std::optional, so needs an extra layer of
         // handling.
         nonErrorPath = '''
 ${prefix}auto output_optional = $extractedValue;
 ${prefix}if (output_optional) {
-$prefix\twrapped.push_back($wrapperType(${enumPrefix}std::move(output_optional).value()));
+$prefix\twrapped.push_back($wrapperType(std::move(output_optional).value()));
 $prefix} else {
 $prefix\twrapped.push_back($nullValue);
 $prefix}''';
       } else {
         nonErrorPath =
-            '${prefix}wrapped.push_back($wrapperType($enumPrefix$extractedValue));';
+            '${prefix}wrapped.push_back($wrapperType($extractedValue));';
       }
       errorCondition = 'output.has_error()';
       errorGetter = 'error';
@@ -1465,17 +1469,12 @@ ${prefix}reply(EncodableValue(std::move(wrapped)));''';
     bool isNestedClass,
   ) {
     final String encodableValue;
-    if (!hostType.isBuiltin &&
-        root.classes.any((Class c) => c.name == dartType.baseName)) {
-      final String nonNullValue = hostType.isNullable || isNestedClass
-          ? '*$variableName'
-          : variableName;
-      encodableValue = 'CustomEncodableValue($nonNullValue)';
-    } else if (!hostType.isBuiltin &&
-        root.enums.any((Enum e) => e.name == dartType.baseName)) {
+    if (!hostType.isBuiltin) {
       final String nonNullValue =
-          hostType.isNullable ? '(*$variableName)' : variableName;
-      encodableValue = 'EncodableValue((int)$nonNullValue)';
+          hostType.isNullable || (!hostType.isEnum && isNestedClass)
+              ? '*$variableName'
+              : variableName;
+      encodableValue = 'CustomEncodableValue($nonNullValue)';
     } else if (dartType.baseName == 'Object') {
       final String operator = hostType.isNullable ? '*' : '';
       encodableValue = '$operator$variableName';
@@ -1521,18 +1520,13 @@ ${prefix}reply(EncodableValue(std::move(wrapped)));''';
         indent.writeln(
             'const auto* $argName = std::get_if<${hostType.datatype}>(&$encodableArgName);');
       } else if (hostType.isEnum) {
-        final String valueVarName = '${argName}_value';
-        indent.writeln(
-            'const int64_t $valueVarName = $encodableArgName.IsNull() ? 0 : $encodableArgName.LongValue();');
-        if (apiType == ApiType.flutter) {
-          indent.writeln(
-              'const ${hostType.datatype} enum_$argName = (${hostType.datatype})$valueVarName;');
-          indent.writeln(
-              'const auto* $argName = $encodableArgName.IsNull() ? nullptr : &enum_$argName;');
-        } else {
-          indent.writeln(
-              'const auto $argName = $encodableArgName.IsNull() ? std::nullopt : std::make_optional<${hostType.datatype}>(static_cast<${hostType.datatype}>(${argName}_value));');
-        }
+        indent.format('''
+${hostType.datatype} ${argName}_value;
+const ${hostType.datatype}* $argName = nullptr;
+if (!$encodableArgName.IsNull()) {
+  ${argName}_value = ${_classReferenceFromEncodableValue(hostType, encodableArgName)};
+  $argName = &${argName}_value;
+}''');
       } else {
         indent.writeln(
             'const auto* $argName = &(${_classReferenceFromEncodableValue(hostType, encodableArgName)});');
@@ -1555,9 +1549,6 @@ ${prefix}reply(EncodableValue(std::move(wrapped)));''';
       } else if (hostType.isBuiltin) {
         indent.writeln(
             'const auto& $argName = std::get<${hostType.datatype}>($encodableArgName);');
-      } else if (hostType.isEnum) {
-        indent.writeln(
-            'const ${hostType.datatype}& $argName = (${hostType.datatype})$encodableArgName.LongValue();');
       } else {
         indent.writeln(
             'const auto& $argName = ${_classReferenceFromEncodableValue(hostType, encodableArgName)};');
@@ -1599,8 +1590,6 @@ class _IndexedField {
   final NamedType field;
 }
 
-String _getCodecSerializerName(Api api) => '${api.name}CodecSerializer';
-
 const String _encodablePrefix = 'encodable';
 
 String _getArgumentName(int count, NamedType argument) =>
diff --git a/packages/pigeon/lib/dart/templates.dart b/packages/pigeon/lib/dart/templates.dart
index 212a06e7b4f..48c5859dc3d 100644
--- a/packages/pigeon/lib/dart/templates.dart
+++ b/packages/pigeon/lib/dart/templates.dart
@@ -262,7 +262,7 @@ abstract class $proxyApiBaseClassName {
 /// adds support to convert instances to their corresponding identifier from an
 /// `InstanceManager` and vice versa.
 const String proxyApiBaseCodec = '''
-class $_proxyApiCodecName extends StandardMessageCodec {
+class $_proxyApiCodecName extends _PigeonCodec {
  const $_proxyApiCodecName(this.instanceManager);
  final $instanceManagerClassName instanceManager;
  @override
diff --git a/packages/pigeon/lib/dart_generator.dart b/packages/pigeon/lib/dart_generator.dart
index 5769f09bb65..b5c0e42d365 100644
--- a/packages/pigeon/lib/dart_generator.dart
+++ b/packages/pigeon/lib/dart_generator.dart
@@ -15,14 +15,8 @@ import 'generator_tools.dart';
 /// Documentation comment open symbol.
 const String _docCommentPrefix = '///';
 
-/// Prefix for all local variables in host API methods.
-///
-/// This lowers the chances of variable name collisions with
-/// user defined parameters.
-const String _varNamePrefix = '__pigeon_';
-
 /// Name of the variable that contains the message channel suffix for APIs.
-const String _suffixVarName = '${_varNamePrefix}messageChannelSuffix';
+const String _suffixVarName = '${varNamePrefix}messageChannelSuffix';
 
 /// Name of the `InstanceManager` variable for a ProxyApi class;
 const String _instanceManagerVarName =
@@ -35,8 +29,8 @@ const String _pigeonChannelCodec = 'pigeonChannelCodec';
 const DocumentCommentSpecification _docCommentSpec =
     DocumentCommentSpecification(_docCommentPrefix);
 
-/// The standard codec for Flutter, used for any non custom codecs and extended for custom codecs.
-const String _standardMessageCodec = 'StandardMessageCodec';
+/// The custom codec used for all pigeon APIs.
+const String _pigeonCodec = '_PigeonCodec';
 
 /// Options that control how Dart code will be generated.
 class DartOptions {
@@ -229,14 +223,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
       indent.addScoped('[', '];', () {
         for (final NamedType field
             in getFieldsInSerializationOrder(classDefinition)) {
-          final String conditional = field.type.isNullable ? '?' : '';
-          if (field.type.isEnum) {
-            indent.writeln(
-              '${field.name}$conditional.index,',
-            );
-          } else {
-            indent.writeln('${field.name},');
-          }
+          indent.writeln('${field.name},');
         }
       });
     });
@@ -256,18 +243,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
       final String genericType = _makeGenericTypeArguments(field.type);
       final String castCall = _makeGenericCastCall(field.type);
       final String nullableTag = field.type.isNullable ? '?' : '';
-      if (field.type.isEnum) {
-        final String nonNullValue =
-            '${field.type.baseName}.values[$resultAt! as int]';
-        if (field.type.isNullable) {
-          indent.format('''
-$resultAt != null
-\t\t? $nonNullValue
-\t\t: null''', leadingSpace: false, trailingNewline: false);
-        } else {
-          indent.add(nonNullValue);
-        }
-      } else if (field.type.typeArguments.isNotEmpty) {
+      if (field.type.typeArguments.isNotEmpty) {
         indent.add(
           '($resultAt as $genericType?)$castCallPrefix$castCall',
         );
@@ -300,6 +276,69 @@ $resultAt != null
     });
   }
 
+  @override
+  void writeGeneralCodec(
+    DartOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    indent.newln();
+    final Iterable<EnumeratedType> enumeratedTypes = getEnumeratedTypes(root);
+    indent.newln();
+    indent.write('class $_pigeonCodec extends StandardMessageCodec');
+    indent.addScoped(' {', '}', () {
+      indent.writeln('const $_pigeonCodec();');
+      if (enumeratedTypes.isNotEmpty) {
+        indent.writeln('@override');
+        indent.write('void writeValue(WriteBuffer buffer, Object? value) ');
+        indent.addScoped('{', '}', () {
+          enumerate(enumeratedTypes,
+              (int index, final EnumeratedType customType) {
+            indent.writeScoped('if (value is ${customType.name}) {', '} else ',
+                () {
+              indent.writeln('buffer.putUint8(${customType.enumeration});');
+              if (customType.type == CustomTypes.customClass) {
+                indent.writeln('writeValue(buffer, value.encode());');
+              } else if (customType.type == CustomTypes.customEnum) {
+                indent.writeln('writeValue(buffer, value.index);');
+              }
+            }, addTrailingNewline: false);
+          });
+          indent.addScoped('{', '}', () {
+            indent.writeln('super.writeValue(buffer, value);');
+          });
+        });
+        indent.newln();
+        indent.writeln('@override');
+        indent.write('Object? readValueOfType(int type, ReadBuffer buffer) ');
+        indent.addScoped('{', '}', () {
+          indent.write('switch (type) ');
+          indent.addScoped('{', '}', () {
+            for (final EnumeratedType customType in enumeratedTypes) {
+              indent.writeln('case ${customType.enumeration}: ');
+              indent.nest(1, () {
+                if (customType.type == CustomTypes.customClass) {
+                  indent.writeln(
+                      'return ${customType.name}.decode(readValue(buffer)!);');
+                } else if (customType.type == CustomTypes.customEnum) {
+                  indent
+                      .writeln('final int? value = readValue(buffer) as int?;');
+                  indent.writeln(
+                      'return value == null ? null : ${customType.name}.values[value];');
+                }
+              });
+            }
+            indent.writeln('default:');
+            indent.nest(1, () {
+              indent.writeln('return super.readValueOfType(type, buffer);');
+            });
+          });
+        });
+      }
+    });
+  }
+
   /// Writes the code for host [Api], [api].
   /// Example:
   /// class FooCodec extends StandardMessageCodec {...}
@@ -319,11 +358,6 @@ $resultAt != null
     bool isMockHandler = false,
     required String dartPackageName,
   }) {
-    String codecName = _standardMessageCodec;
-    if (getCodecClasses(api, root).isNotEmpty) {
-      codecName = _getCodecName(api);
-      _writeCodec(indent, codecName, api, root);
-    }
     indent.newln();
     addDocumentationComments(
         indent, api.documentationComments, _docCommentSpec);
@@ -335,7 +369,7 @@ $resultAt != null
             'static TestDefaultBinaryMessengerBinding? get _testBinaryMessengerBinding => TestDefaultBinaryMessengerBinding.instance;');
       }
       indent.writeln(
-          'static const MessageCodec<Object?> $_pigeonChannelCodec = $codecName();');
+          'static const MessageCodec<Object?> $_pigeonChannelCodec = $_pigeonCodec();');
       indent.newln();
       for (final Method func in api.methods) {
         addDocumentationComments(
@@ -399,11 +433,6 @@ $resultAt != null
     AstHostApi api, {
     required String dartPackageName,
   }) {
-    String codecName = _standardMessageCodec;
-    if (getCodecClasses(api, root).isNotEmpty) {
-      codecName = _getCodecName(api);
-      _writeCodec(indent, codecName, api, root);
-    }
     indent.newln();
     bool first = true;
     addDocumentationComments(
@@ -415,13 +444,13 @@ $resultAt != null
 /// available for dependency injection.  If it is left null, the default
 /// BinaryMessenger will be used which routes to the host platform.
 ${api.name}({BinaryMessenger? binaryMessenger, String messageChannelSuffix = ''})
-    : ${_varNamePrefix}binaryMessenger = binaryMessenger,
-      ${_varNamePrefix}messageChannelSuffix = messageChannelSuffix.isNotEmpty ? '.\$messageChannelSuffix' : '';
-final BinaryMessenger? ${_varNamePrefix}binaryMessenger;
+    : ${varNamePrefix}binaryMessenger = binaryMessenger,
+      ${varNamePrefix}messageChannelSuffix = messageChannelSuffix.isNotEmpty ? '.\$messageChannelSuffix' : '';
+final BinaryMessenger? ${varNamePrefix}binaryMessenger;
 ''');
 
       indent.writeln(
-          'static const MessageCodec<Object?> $_pigeonChannelCodec = $codecName();');
+          'static const MessageCodec<Object?> $_pigeonChannelCodec = $_pigeonCodec();');
       indent.newln();
       indent.writeln('final String $_suffixVarName;');
       indent.newln();
@@ -822,6 +851,8 @@ final BinaryMessenger? ${_varNamePrefix}binaryMessenger;
           relativeDartPath.replaceFirst(RegExp(r'^.*/lib/'), '');
       indent.writeln("import 'package:$dartOutputPackageName/$path';");
     }
+    writeGeneralCodec(generatorOptions, root, indent,
+        dartPackageName: dartPackageName);
     for (final AstHostApi api in root.apis.whereType<AstHostApi>()) {
       if (api.dartHostTestHandler != null) {
         final AstFlutterApi mockApi = AstFlutterApi(
@@ -961,18 +992,14 @@ PlatformException _createConnectionError(String channelName) {
       final Iterable<String> argExpressions =
           indexMap(parameters, (int index, NamedType type) {
         final String name = _getParameterName(index, type);
-        if (type.type.isEnum) {
-          return '$name${type.type.isNullable ? '?' : ''}.index';
-        } else {
-          return name;
-        }
+        return name;
       });
       sendArgument = '<Object?>[${argExpressions.join(', ')}]';
     }
     final String channelSuffix = addSuffixVariable ? '\$$_suffixVarName' : '';
     final String constOrFinal = addSuffixVariable ? 'final' : 'const';
     indent.writeln(
-        "$constOrFinal String ${_varNamePrefix}channelName = '$channelName$channelSuffix';");
+        "$constOrFinal String ${varNamePrefix}channelName = '$channelName$channelSuffix';");
     indent.writeScoped(
         'final BasicMessageChannel<Object?> ${varNamePrefix}channel = BasicMessageChannel<Object?>(',
         ');', () {
@@ -990,15 +1017,7 @@ PlatformException _createConnectionError(String channelName) {
     final String nullHandler =
         returnType.isNullable ? (genericCastCall.isEmpty ? '' : '?') : '!';
     String returnStatement = 'return';
-    if (returnType.isEnum) {
-      if (returnType.isNullable) {
-        returnStatement =
-            '$returnStatement ($accessor as int?) == null ? null : $returnTypeName.values[$accessor! as int]';
-      } else {
-        returnStatement =
-            '$returnStatement $returnTypeName.values[$accessor! as int]';
-      }
-    } else if (!returnType.isVoid) {
+    if (!returnType.isVoid) {
       returnStatement =
           '$returnStatement $nullablyTypedAccessor$nullHandler$genericCastCall';
     }
@@ -1094,13 +1113,10 @@ if (${varNamePrefix}replyList == null) {
               final String castCall = _makeGenericCastCall(arg.type);
 
               final String leftHandSide = 'final $argType? $argName';
-              if (arg.type.isEnum) {
-                indent.writeln(
-                    '$leftHandSide = $argsArray[$count] == null ? null : $argType.values[$argsArray[$count]! as int];');
-              } else {
-                indent.writeln(
-                    '$leftHandSide = ($argsArray[$count] as $genericArgType?)${castCall.isEmpty ? '' : '?$castCall'};');
-              }
+
+              indent.writeln(
+                  '$leftHandSide = ($argsArray[$count] as $genericArgType?)${castCall.isEmpty ? '' : '?$castCall'};');
+
               if (!arg.type.isNullable) {
                 indent.writeln('assert($argName != null,');
                 indent.writeln(
@@ -1130,12 +1146,9 @@ if (${varNamePrefix}replyList == null) {
               }
 
               const String returnExpression = 'output';
-              final String nullability = returnType.isNullable ? '?' : '';
-              final String valueExtraction =
-                  returnType.isEnum ? '$nullability.index' : '';
               final String returnStatement = isMockHandler
-                  ? 'return <Object?>[$returnExpression$valueExtraction];'
-                  : 'return wrapResponse(result: $returnExpression$valueExtraction);';
+                  ? 'return <Object?>[$returnExpression];'
+                  : 'return wrapResponse(result: $returnExpression);';
               indent.writeln(returnStatement);
             }
           }, addTrailingNewline: false);
@@ -1980,60 +1993,6 @@ String _escapeForDartSingleQuotedString(String raw) {
       .replaceAll(r"'", r"\'");
 }
 
-/// Calculates the name of the codec class that will be generated for [api].
-String _getCodecName(Api api) => '_${api.name}Codec';
-
-/// Writes the codec that will be used by [api].
-/// Example:
-///
-/// class FooCodec extends StandardMessageCodec {...}
-void _writeCodec(Indent indent, String codecName, Api api, Root root) {
-  assert(getCodecClasses(api, root).isNotEmpty);
-  final Iterable<EnumeratedClass> codecClasses = getCodecClasses(api, root);
-  indent.newln();
-  indent.write('class $codecName extends $_standardMessageCodec');
-  indent.addScoped(' {', '}', () {
-    indent.writeln('const $codecName();');
-    indent.writeln('@override');
-    indent.write('void writeValue(WriteBuffer buffer, Object? value) ');
-    indent.addScoped('{', '}', () {
-      enumerate(codecClasses, (int index, final EnumeratedClass customClass) {
-        final String ifValue = 'if (value is ${customClass.name}) ';
-        if (index == 0) {
-          indent.write('');
-        }
-        indent.add(ifValue);
-        indent.addScoped('{', '} else ', () {
-          indent.writeln('buffer.putUint8(${customClass.enumeration});');
-          indent.writeln('writeValue(buffer, value.encode());');
-        }, addTrailingNewline: false);
-      });
-      indent.addScoped('{', '}', () {
-        indent.writeln('super.writeValue(buffer, value);');
-      });
-    });
-    indent.newln();
-    indent.writeln('@override');
-    indent.write('Object? readValueOfType(int type, ReadBuffer buffer) ');
-    indent.addScoped('{', '}', () {
-      indent.write('switch (type) ');
-      indent.addScoped('{', '}', () {
-        for (final EnumeratedClass customClass in codecClasses) {
-          indent.writeln('case ${customClass.enumeration}: ');
-          indent.nest(1, () {
-            indent.writeln(
-                'return ${customClass.name}.decode(readValue(buffer)!);');
-          });
-        }
-        indent.writeln('default:');
-        indent.nest(1, () {
-          indent.writeln('return super.readValueOfType(type, buffer);');
-        });
-      });
-    });
-  });
-}
-
 /// Creates a Dart type where all type arguments are [Objects].
 String _makeGenericTypeArguments(TypeDeclaration type) {
   return type.typeArguments.isNotEmpty
diff --git a/packages/pigeon/lib/generator.dart b/packages/pigeon/lib/generator.dart
index 3711fd28dbe..952b80e8987 100644
--- a/packages/pigeon/lib/generator.dart
+++ b/packages/pigeon/lib/generator.dart
@@ -95,6 +95,13 @@ abstract class StructuredGenerator<T> extends Generator<T> {
       dartPackageName: dartPackageName,
     );
 
+    writeGeneralCodec(
+      generatorOptions,
+      root,
+      indent,
+      dartPackageName: dartPackageName,
+    );
+
     writeApis(
       generatorOptions,
       root,
@@ -205,6 +212,14 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     }
   }
 
+  /// Writes the custom codec to [indent].
+  void writeGeneralCodec(
+    T generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  });
+
   /// Writes a single data class to [indent].
   void writeDataClass(
     T generatorOptions,
diff --git a/packages/pigeon/lib/generator_tools.dart b/packages/pigeon/lib/generator_tools.dart
index a02efc0fe84..415113c7ff7 100644
--- a/packages/pigeon/lib/generator_tools.dart
+++ b/packages/pigeon/lib/generator_tools.dart
@@ -13,7 +13,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '19.0.2';
+const String pigeonVersion = '20.0.0';
 
 /// Prefix for all local variables in methods.
 ///
@@ -37,7 +37,7 @@ bool debugGenerators = false;
 
 /// A helper class for managing indentation, wrapping a [StringSink].
 class Indent {
-  /// Constructor which takes a [StringSink] [Ident] will wrap.
+  /// Constructor which takes a [StringSink] [Indent] will wrap.
   Indent(this._sink);
 
   int _count = 0;
@@ -381,16 +381,26 @@ Map<String, Object> mergeMaps(
   return result;
 }
 
-/// A class name that is enumerated.
-class EnumeratedClass {
+/// A type name that is enumerated.
+class EnumeratedType {
   /// Constructor.
-  EnumeratedClass(this.name, this.enumeration);
+  EnumeratedType(this.name, this.enumeration, this.type,
+      {this.associatedClass, this.associatedEnum});
 
-  /// The name of the class.
+  /// The name of the type.
   final String name;
 
   /// The enumeration of the class.
   final int enumeration;
+
+  /// The type of custom type of the enumerated type.
+  final CustomTypes type;
+
+  /// The associated Class that is represented by the [EnumeratedType].
+  final Class? associatedClass;
+
+  /// The associated Enum that is represented by the [EnumeratedType].
+  final Enum? associatedEnum;
 }
 
 /// Supported basic datatypes.
@@ -410,7 +420,7 @@ const List<String> validTypes = <String>[
 
 /// Custom codecs' custom types are enumerated from 255 down to this number to
 /// avoid collisions with the StandardMessageCodec.
-const int _minimumCodecFieldKey = 128;
+const int _minimumCodecFieldKey = 129;
 
 Iterable<TypeDeclaration> _getTypeArguments(TypeDeclaration type) sync* {
   for (final TypeDeclaration typeArg in type.typeArguments) {
@@ -494,39 +504,42 @@ Map<TypeDeclaration, List<int>> getReferencedTypes(
   return references.map;
 }
 
-/// Returns true if the concrete type cannot be determined at compile-time.
-bool _isConcreteTypeAmbiguous(TypeDeclaration type) {
-  return (type.baseName == 'List' && type.typeArguments.isEmpty) ||
-      (type.baseName == 'Map' && type.typeArguments.isEmpty) ||
-      type.baseName == 'Object';
+/// All custom definable data types.
+enum CustomTypes {
+  /// A custom Class.
+  customClass,
+
+  /// A custom Enum.
+  customEnum,
 }
 
-/// Given an [Api], return the enumerated classes that must exist in the codec
+/// Return the enumerated types that must exist in the codec
 /// where the enumeration should be the key used in the buffer.
-Iterable<EnumeratedClass> getCodecClasses(Api api, Root root) sync* {
-  final Set<String> enumNames = root.enums.map((Enum e) => e.name).toSet();
-  final Map<TypeDeclaration, List<int>> referencedTypes =
-      getReferencedTypes(<Api>[api], root.classes);
-  final Iterable<String> allTypeNames =
-      referencedTypes.keys.any(_isConcreteTypeAmbiguous)
-          ? root.classes.map((Class aClass) => aClass.name)
-          : referencedTypes.keys.map((TypeDeclaration e) => e.baseName);
-  final List<String> sortedNames = allTypeNames
-      .where((String element) =>
-          element != 'void' &&
-          !validTypes.contains(element) &&
-          !enumNames.contains(element))
-      .toList();
-  sortedNames.sort();
-  int enumeration = _minimumCodecFieldKey;
+Iterable<EnumeratedType> getEnumeratedTypes(Root root) sync* {
   const int maxCustomClassesPerApi = 255 - _minimumCodecFieldKey;
-  if (sortedNames.length > maxCustomClassesPerApi) {
+  if (root.classes.length + root.enums.length > maxCustomClassesPerApi) {
     throw Exception(
-        "Pigeon doesn't support more than $maxCustomClassesPerApi referenced custom classes per API, try splitting up your APIs.");
+        "Pigeon doesn't currently support more than $maxCustomClassesPerApi referenced custom classes per file.");
+  }
+  int index = 0;
+  for (final Class customClass in root.classes) {
+    yield EnumeratedType(
+      customClass.name,
+      index + _minimumCodecFieldKey,
+      CustomTypes.customClass,
+      associatedClass: customClass,
+    );
+    index += 1;
   }
-  for (final String name in sortedNames) {
-    yield EnumeratedClass(name, enumeration);
-    enumeration += 1;
+
+  for (final Enum customEnum in root.enums) {
+    yield EnumeratedType(
+      customEnum.name,
+      index + _minimumCodecFieldKey,
+      CustomTypes.customEnum,
+      associatedEnum: customEnum,
+    );
+    index += 1;
   }
 }
 
@@ -685,3 +698,13 @@ class OutputFileOptions<T> {
   /// Options for specified language across all file types.
   T languageOptions;
 }
+
+/// Converts strings to Upper Camel Case.
+String toUpperCamelCase(String text) {
+  final RegExp separatorPattern = RegExp(r'[ _-]');
+  return text.split(separatorPattern).map((String word) {
+    return word.isEmpty
+        ? ''
+        : word.substring(0, 1).toUpperCase() + word.substring(1);
+  }).join();
+}
diff --git a/packages/pigeon/lib/java_generator.dart b/packages/pigeon/lib/java_generator.dart
index f8e15bb24f9..55622995b71 100644
--- a/packages/pigeon/lib/java_generator.dart
+++ b/packages/pigeon/lib/java_generator.dart
@@ -26,7 +26,7 @@ const DocumentCommentSpecification _docCommentSpec =
 );
 
 /// The standard codec for Flutter, used for any non custom codecs and extended for custom codecs.
-const String _standardMessageCodec = 'StandardMessageCodec';
+const String _codecName = 'PigeonCodec';
 
 /// Options that control how Java code will be generated.
 class JavaOptions {
@@ -339,14 +339,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
           'ArrayList<Object> toListResult = new ArrayList<Object>(${classDefinition.fields.length});');
       for (final NamedType field
           in getFieldsInSerializationOrder(classDefinition)) {
-        String toWriteValue = '';
-        final String fieldName = field.name;
-        if (field.type.isEnum) {
-          toWriteValue = '$fieldName == null ? null : $fieldName.index';
-        } else {
-          toWriteValue = field.name;
-        }
-        indent.writeln('toListResult.add($toWriteValue);');
+        indent.writeln('toListResult.add(${field.name});');
       }
       indent.writeln('return toListResult;');
     });
@@ -373,18 +366,86 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
         final String setter = _makeSetter(field);
         indent.writeln(
             'Object $fieldVariable = ${varNamePrefix}list.get($index);');
-        if (field.type.isEnum) {
-          indent.writeln(
-              '$result.$setter(${_intToEnum(fieldVariable, field.type.baseName, field.type.isNullable)});');
-        } else {
-          indent.writeln(
-              '$result.$setter(${_castObject(field, fieldVariable)});');
-        }
+        indent
+            .writeln('$result.$setter(${_castObject(field, fieldVariable)});');
       });
       indent.writeln('return $result;');
     });
   }
 
+  @override
+  void writeGeneralCodec(
+    JavaOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    final Iterable<EnumeratedType> enumeratedTypes = getEnumeratedTypes(root);
+    indent.newln();
+    indent.write(
+        'private static class $_codecName extends StandardMessageCodec ');
+    indent.addScoped('{', '}', () {
+      indent.writeln(
+          'public static final $_codecName INSTANCE = new $_codecName();');
+      indent.newln();
+      indent.writeln('private $_codecName() {}');
+      indent.newln();
+      indent.writeln('@Override');
+      indent.write(
+          'protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) ');
+      indent.addScoped('{', '}', () {
+        indent.write('switch (type) ');
+        indent.addScoped('{', '}', () {
+          for (final EnumeratedType customType in enumeratedTypes) {
+            indent.writeln('case (byte) ${customType.enumeration}:');
+            indent.nest(1, () {
+              if (customType.type == CustomTypes.customClass) {
+                indent.writeln(
+                    'return ${customType.name}.fromList((ArrayList<Object>) readValue(buffer));');
+              } else if (customType.type == CustomTypes.customEnum) {
+                indent.writeln('Object value = readValue(buffer);');
+                indent.writeln(
+                    'return ${_intToEnum('value', customType.name, true)};');
+              }
+            });
+          }
+          indent.writeln('default:');
+          indent.nest(1, () {
+            indent.writeln('return super.readValueOfType(type, buffer);');
+          });
+        });
+      });
+      indent.newln();
+      indent.writeln('@Override');
+      indent.write(
+          'protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) ');
+      indent.addScoped('{', '}', () {
+        bool firstClass = true;
+        for (final EnumeratedType customType in enumeratedTypes) {
+          if (firstClass) {
+            indent.write('');
+            firstClass = false;
+          }
+          indent.add('if (value instanceof ${customType.name}) ');
+          indent.addScoped('{', '} else ', () {
+            indent.writeln('stream.write(${customType.enumeration});');
+            if (customType.type == CustomTypes.customClass) {
+              indent.writeln(
+                  'writeValue(stream, ((${customType.name}) value).toList());');
+            } else {
+              indent.writeln(
+                  'writeValue(stream, value == null ? null : ((${customType.name}) value).index);');
+            }
+          }, addTrailingNewline: false);
+        }
+        indent.addScoped('{', '}', () {
+          indent.writeln('super.writeValue(stream, value);');
+        });
+      });
+    });
+    indent.newln();
+  }
+
   /// Writes the code for a flutter [Api], [api].
   /// Example:
   /// public static final class Foo {
@@ -402,20 +463,11 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    /// Returns an argument name that can be used in a context where it is possible to collide
-    /// and append `.index` to enums.
-    String getEnumSafeArgumentExpression(int count, NamedType argument) {
-      if (argument.type.isEnum) {
-        return argument.type.isNullable
-            ? '${_getArgumentName(count, argument)}Arg == null ? null : ${_getArgumentName(count, argument)}Arg.index'
-            : '${_getArgumentName(count, argument)}Arg.index';
-      }
+    /// Returns an argument name that can be used in a context where it is possible to collide.
+    String getSafeArgumentExpression(int count, NamedType argument) {
       return '${_getArgumentName(count, argument)}Arg';
     }
 
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(indent, api, root);
-    }
     const List<String> generatedMessages = <String>[
       ' Generated class from Pigeon that represents Flutter messages that can be called from Java.'
     ];
@@ -441,16 +493,10 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
       });
       indent.newln();
       indent.writeln('/** Public interface for sending reply. */ ');
-      final String codecName = _getCodecName(api);
       indent.writeln('/** The codec used by ${api.name}. */');
       indent.write('static @NonNull MessageCodec<Object> getCodec() ');
       indent.addScoped('{', '}', () {
-        indent.write('return ');
-        if (getCodecClasses(api, root).isNotEmpty) {
-          indent.addln('$codecName.INSTANCE;');
-        } else {
-          indent.addln('new $_standardMessageCodec();');
-        }
+        indent.writeln('return $_codecName.INSTANCE;');
       });
 
       for (final Method func in api.methods) {
@@ -471,7 +517,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
           final Iterable<String> argNames =
               indexMap(func.parameters, _getSafeArgumentName);
           final Iterable<String> enumSafeArgNames =
-              indexMap(func.parameters, getEnumSafeArgumentExpression);
+              indexMap(func.parameters, getSafeArgumentExpression);
           if (func.parameters.length == 1) {
             sendArgument =
                 'new ArrayList<Object>(Collections.singletonList(${enumSafeArgNames.first}))';
@@ -526,14 +572,6 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
                     if (func.returnType.baseName == 'int') {
                       outputExpression =
                           'listReply.get(0) == null ? null : ((Number) listReply.get(0)).longValue();';
-                    } else if (func.returnType.isEnum) {
-                      if (func.returnType.isNullable) {
-                        outputExpression =
-                            'listReply.get(0) == null ? null : $returnType.values()[(int) listReply.get(0)];';
-                      } else {
-                        outputExpression =
-                            '$returnType.values()[(int) listReply.get(0)];';
-                      }
                     } else {
                       outputExpression =
                           '${_cast('listReply.get(0)', javaType: returnType)};';
@@ -586,9 +624,6 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     AstHostApi api, {
     required String dartPackageName,
   }) {
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(indent, api, root);
-    }
     const List<String> generatedMessages = <String>[
       ' Generated interface from Pigeon that represents a handler of messages from Flutter.'
     ];
@@ -601,16 +636,10 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
         _writeInterfaceMethod(generatorOptions, root, indent, api, method);
       }
       indent.newln();
-      final String codecName = _getCodecName(api);
       indent.writeln('/** The codec used by ${api.name}. */');
       indent.write('static @NonNull MessageCodec<Object> getCodec() ');
       indent.addScoped('{', '}', () {
-        indent.write('return ');
-        if (getCodecClasses(api, root).isNotEmpty) {
-          indent.addln('$codecName.INSTANCE;');
-        } else {
-          indent.addln('new $_standardMessageCodec();');
-        }
+        indent.writeln('return $_codecName.INSTANCE;');
       });
 
       indent.writeln(
@@ -716,7 +745,6 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
         indent.nest(2, () {
           indent.write('(message, reply) -> ');
           indent.addScoped('{', '});', () {
-            String enumTag = '';
             final String returnType = method.returnType.isVoid
                 ? 'Void'
                 : _javaTypeForDartType(method.returnType);
@@ -738,10 +766,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
                     ? '($argName == null) ? null : $argName.longValue()'
                     : argName;
                 String accessor = 'args.get($index)';
-                if (arg.type.isEnum) {
-                  accessor = _intToEnum(
-                      accessor, arg.type.baseName, arg.type.isNullable);
-                } else if (argType != 'Object') {
+                if (argType != 'Object') {
                   accessor = _cast(accessor, javaType: argType);
                 }
                 indent.writeln('$argType $argName = $accessor;');
@@ -751,16 +776,11 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
             if (method.isAsynchronous) {
               final String resultValue =
                   method.returnType.isVoid ? 'null' : 'result';
-              if (method.returnType.isEnum) {
-                enumTag = method.returnType.isNullable
-                    ? ' == null ? null : $resultValue.index'
-                    : '.index';
-              }
               final String resultType = _getResultType(method.returnType);
               final String resultParam =
                   method.returnType.isVoid ? '' : '$returnType result';
               final String addResultArg =
-                  method.returnType.isVoid ? 'null' : '$resultValue$enumTag';
+                  method.returnType.isVoid ? 'null' : resultValue;
               const String resultName = 'resultCallback';
               indent.format('''
 $resultType $resultName =
@@ -789,13 +809,8 @@ $resultType $resultName =
                   indent.writeln('$call;');
                   indent.writeln('wrapped.add(0, null);');
                 } else {
-                  if (method.returnType.isEnum) {
-                    enumTag = method.returnType.isNullable
-                        ? ' == null ? null : output.index'
-                        : '.index';
-                  }
                   indent.writeln('$returnType output = $call;');
-                  indent.writeln('wrapped.add(0, output$enumTag);');
+                  indent.writeln('wrapped.add(0, output);');
                 }
               });
               indent.add(' catch (Throwable exception) ');
@@ -819,67 +834,6 @@ $resultType $resultName =
     });
   }
 
-  /// Writes the codec class that will be used by [api].
-  /// Example:
-  /// private static class FooCodec extends StandardMessageCodec {...}
-  void _writeCodec(Indent indent, Api api, Root root) {
-    assert(getCodecClasses(api, root).isNotEmpty);
-    final Iterable<EnumeratedClass> codecClasses = getCodecClasses(api, root);
-    final String codecName = _getCodecName(api);
-    indent.newln();
-    indent.write(
-        'private static class $codecName extends $_standardMessageCodec ');
-    indent.addScoped('{', '}', () {
-      indent.writeln(
-          'public static final $codecName INSTANCE = new $codecName();');
-      indent.newln();
-      indent.writeln('private $codecName() {}');
-      indent.newln();
-      indent.writeln('@Override');
-      indent.write(
-          'protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) ');
-      indent.addScoped('{', '}', () {
-        indent.write('switch (type) ');
-        indent.addScoped('{', '}', () {
-          for (final EnumeratedClass customClass in codecClasses) {
-            indent.writeln('case (byte) ${customClass.enumeration}:');
-            indent.nest(1, () {
-              indent.writeln(
-                  'return ${customClass.name}.fromList((ArrayList<Object>) readValue(buffer));');
-            });
-          }
-          indent.writeln('default:');
-          indent.nest(1, () {
-            indent.writeln('return super.readValueOfType(type, buffer);');
-          });
-        });
-      });
-      indent.newln();
-      indent.writeln('@Override');
-      indent.write(
-          'protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) ');
-      indent.addScoped('{', '}', () {
-        bool firstClass = true;
-        for (final EnumeratedClass customClass in codecClasses) {
-          if (firstClass) {
-            indent.write('');
-            firstClass = false;
-          }
-          indent.add('if (value instanceof ${customClass.name}) ');
-          indent.addScoped('{', '} else ', () {
-            indent.writeln('stream.write(${customClass.enumeration});');
-            indent.writeln(
-                'writeValue(stream, ((${customClass.name}) value).toList());');
-          }, addTrailingNewline: false);
-        }
-        indent.addScoped('{', '}', () {
-          indent.writeln('super.writeValue(stream, value);');
-        });
-      });
-    });
-    indent.newln();
-  }
-
   void _writeResultInterfaces(Indent indent) {
     indent.writeln(
         '/** Asynchronous error handling return type for non-nullable API method returns. */');
@@ -1026,9 +980,6 @@ protected static ArrayList<Object> wrapError(@NonNull Throwable exception) {
   }
 }
 
-/// Calculates the name of the codec that will be generated for [api].
-String _getCodecName(Api api) => '${api.name}Codec';
-
 /// Converts an expression that evaluates to an nullable int to an expression
 /// that evaluates to a nullable enum.
 String _intToEnum(String expression, String enumName, bool nullable) => nullable
diff --git a/packages/pigeon/lib/kotlin_generator.dart b/packages/pigeon/lib/kotlin_generator.dart
index e805034ee2c..1d827aff164 100644
--- a/packages/pigeon/lib/kotlin_generator.dart
+++ b/packages/pigeon/lib/kotlin_generator.dart
@@ -25,6 +25,8 @@ const DocumentCommentSpecification _docCommentSpec =
   blockContinuationToken: _docCommentContinuation,
 );
 
+String _codecName = 'PigeonCodec';
+
 /// Options that control how Kotlin code will be generated.
 class KotlinOptions {
   /// Creates a [KotlinOptions] object
@@ -33,6 +35,7 @@ class KotlinOptions {
     this.copyrightHeader,
     this.errorClassName,
     this.includeErrorClass = true,
+    this.fileSpecificClassNameComponent,
   });
 
   /// The package where the generated class will live.
@@ -50,6 +53,9 @@ class KotlinOptions {
   /// Kotlin file in the same directory.
   final bool includeErrorClass;
 
+  /// A String to augment class names to avoid cross file collisions.
+  final String? fileSpecificClassNameComponent;
+
   /// Creates a [KotlinOptions] from a Map representation where:
   /// `x = KotlinOptions.fromMap(x.toMap())`.
   static KotlinOptions fromMap(Map<String, Object> map) {
@@ -58,6 +64,8 @@ class KotlinOptions {
       copyrightHeader: map['copyrightHeader'] as Iterable<String>?,
       errorClassName: map['errorClassName'] as String?,
       includeErrorClass: map['includeErrorClass'] as bool? ?? true,
+      fileSpecificClassNameComponent:
+          map['fileSpecificClassNameComponent'] as String?,
     );
   }
 
@@ -69,6 +77,8 @@ class KotlinOptions {
       if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
       if (errorClassName != null) 'errorClassName': errorClassName!,
       'includeErrorClass': includeErrorClass,
+      if (fileSpecificClassNameComponent != null)
+        'fileSpecificClassNameComponent': fileSpecificClassNameComponent!,
     };
     return result;
   }
@@ -216,19 +226,12 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
   }) {
     indent.write('fun toList(): List<Any?> ');
     indent.addScoped('{', '}', () {
-      indent.write('return listOf<Any?>');
+      indent.write('return listOf');
       indent.addScoped('(', ')', () {
         for (final NamedType field
             in getFieldsInSerializationOrder(classDefinition)) {
-          String toWriteValue = '';
           final String fieldName = field.name;
-          final String safeCall = field.type.isNullable ? '?' : '';
-          if (field.type.isEnum) {
-            toWriteValue = '$fieldName$safeCall.raw';
-          } else {
-            toWriteValue = fieldName;
-          }
-          indent.writeln('$toWriteValue,');
+          indent.writeln('$fieldName,');
         }
       });
     });
@@ -254,28 +257,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         enumerate(getFieldsInSerializationOrder(classDefinition),
             (int index, final NamedType field) {
           final String listValue = '${varNamePrefix}list[$index]';
-          final String fieldType = _kotlinTypeForDartType(field.type);
-
-          if (field.type.isNullable) {
-            if (field.type.isEnum) {
-              indent.write('val ${field.name}: $fieldType? = ');
-              indent.add('($listValue as Int?)?.let ');
-              indent.addScoped('{ num ->', '}', () {
-                indent.writeln('$fieldType.ofRaw(num)');
-              });
-            } else {
-              indent.writeln(
-                  'val ${field.name} = ${_cast(indent, listValue, type: field.type)}');
-            }
-          } else {
-            if (field.type.isEnum) {
-              indent.writeln(
-                  'val ${field.name} = $fieldType.ofRaw($listValue as Int)!!');
-            } else {
-              indent.writeln(
-                  'val ${field.name} = ${_cast(indent, listValue, type: field.type)}');
-            }
-          }
+          indent.writeln(
+              'val ${field.name} = ${_cast(indent, listValue, type: field.type)}');
         });
 
         indent.write('return $className(');
@@ -317,6 +300,75 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         dartPackageName: dartPackageName);
   }
 
+  @override
+  void writeGeneralCodec(
+    KotlinOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    final Iterable<EnumeratedType> enumeratedTypes = getEnumeratedTypes(root);
+    indent.write(
+        'private object ${generatorOptions.fileSpecificClassNameComponent}$_codecName : StandardMessageCodec() ');
+    indent.addScoped('{', '}', () {
+      indent.write(
+          'override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? ');
+      indent.addScoped('{', '}', () {
+        indent.write('return ');
+        if (root.classes.isNotEmpty || root.enums.isNotEmpty) {
+          indent.add('when (type) ');
+          indent.addScoped('{', '}', () {
+            for (final EnumeratedType customType in enumeratedTypes) {
+              indent.write('${customType.enumeration}.toByte() -> ');
+              indent.addScoped('{', '}', () {
+                if (customType.type == CustomTypes.customClass) {
+                  indent
+                      .write('return (readValue(buffer) as? List<Any?>)?.let ');
+                  indent.addScoped('{', '}', () {
+                    indent.writeln('${customType.name}.fromList(it)');
+                  });
+                } else if (customType.type == CustomTypes.customEnum) {
+                  indent.write('return (readValue(buffer) as Int?)?.let ');
+                  indent.addScoped('{', '}', () {
+                    indent.writeln('${customType.name}.ofRaw(it)');
+                  });
+                }
+              });
+            }
+            indent.writeln('else -> super.readValueOfType(type, buffer)');
+          });
+        } else {
+          indent.writeln('super.readValueOfType(type, buffer)');
+        }
+      });
+
+      indent.write(
+          'override fun writeValue(stream: ByteArrayOutputStream, value: Any?) ');
+      indent.writeScoped('{', '}', () {
+        if (root.classes.isNotEmpty || root.enums.isNotEmpty) {
+          indent.write('when (value) ');
+          indent.addScoped('{', '}', () {
+            for (final EnumeratedType customType in enumeratedTypes) {
+              indent.write('is ${customType.name} -> ');
+              indent.addScoped('{', '}', () {
+                indent.writeln('stream.write(${customType.enumeration})');
+                if (customType.type == CustomTypes.customClass) {
+                  indent.writeln('writeValue(stream, value.toList())');
+                } else if (customType.type == CustomTypes.customEnum) {
+                  indent.writeln('writeValue(stream, value.raw)');
+                }
+              });
+            }
+            indent.writeln('else -> super.writeValue(stream, value)');
+          });
+        } else {
+          indent.writeln('super.writeValue(stream, value)');
+        }
+      });
+    });
+    indent.newln();
+  }
+
   /// Writes the code for a flutter [Api], [api].
   /// Example:
   /// class Foo(private val binaryMessenger: BinaryMessenger) {
@@ -330,11 +382,6 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
-    if (isCustomCodec) {
-      _writeCodec(indent, api, root);
-    }
-
     const List<String> generatedMessages = <String>[
       ' Generated class from Pigeon that represents Flutter messages that can be called from Kotlin.'
     ];
@@ -350,11 +397,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         indent.writeln('/** The codec used by $apiName. */');
         indent.write('val codec: MessageCodec<Any?> by lazy ');
         indent.addScoped('{', '}', () {
-          if (isCustomCodec) {
-            indent.writeln(_getCodecName(api));
-          } else {
-            indent.writeln('StandardMessageCodec()');
-          }
+          indent.writeln(
+              '${generatorOptions.fileSpecificClassNameComponent}$_codecName');
         });
       });
 
@@ -392,11 +436,6 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
   }) {
     final String apiName = api.name;
 
-    final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
-    if (isCustomCodec) {
-      _writeCodec(indent, api, root);
-    }
-
     const List<String> generatedMessages = <String>[
       ' Generated interface from Pigeon that represents a handler of messages from Flutter.'
     ];
@@ -422,11 +461,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         indent.writeln('/** The codec used by $apiName. */');
         indent.write('val codec: MessageCodec<Any?> by lazy ');
         indent.addScoped('{', '}', () {
-          if (isCustomCodec) {
-            indent.writeln(_getCodecName(api));
-          } else {
-            indent.writeln('StandardMessageCodec()');
-          }
+          indent.writeln(
+              '${generatorOptions.fileSpecificClassNameComponent}$_codecName');
         });
         indent.writeln(
             '/** Sets up an instance of `$apiName` to handle messages through the `binaryMessenger`. */');
@@ -453,52 +489,6 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     });
   }
 
-  /// Writes the codec class that will be used by [api].
-  /// Example:
-  /// private static class FooCodec extends StandardMessageCodec {...}
-  void _writeCodec(Indent indent, Api api, Root root) {
-    assert(getCodecClasses(api, root).isNotEmpty);
-    final Iterable<EnumeratedClass> codecClasses = getCodecClasses(api, root);
-    final String codecName = _getCodecName(api);
-    indent.write('private object $codecName : StandardMessageCodec() ');
-    indent.addScoped('{', '}', () {
-      indent.write(
-          'override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? ');
-      indent.addScoped('{', '}', () {
-        indent.write('return when (type) ');
-        indent.addScoped('{', '}', () {
-          for (final EnumeratedClass customClass in codecClasses) {
-            indent.write('${customClass.enumeration}.toByte() -> ');
-            indent.addScoped('{', '}', () {
-              indent.write('return (readValue(buffer) as? List<Any?>)?.let ');
-              indent.addScoped('{', '}', () {
-                indent.writeln('${customClass.name}.fromList(it)');
-              });
-            });
-          }
-          indent.writeln('else -> super.readValueOfType(type, buffer)');
-        });
-      });
-
-      indent.write(
-          'override fun writeValue(stream: ByteArrayOutputStream, value: Any?) ');
-      indent.writeScoped('{', '}', () {
-        indent.write('when (value) ');
-        indent.addScoped('{', '}', () {
-          for (final EnumeratedClass customClass in codecClasses) {
-            indent.write('is ${customClass.name} -> ');
-            indent.addScoped('{', '}', () {
-              indent.writeln('stream.write(${customClass.enumeration})');
-              indent.writeln('writeValue(stream, value.toList())');
-            });
-          }
-          indent.writeln('else -> super.writeValue(stream, value)');
-        });
-      });
-    });
-    indent.newln();
-  }
-
   void _writeWrapResult(Indent indent) {
     indent.newln();
     indent.write('private fun wrapResult(result: Any?): List<Any?> ');
@@ -693,25 +683,21 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
               : 'api.$name(${methodArguments.join(', ')})';
 
           if (isAsynchronous) {
-            indent.write('$call ');
             final String resultType = returnType.isVoid
                 ? 'Unit'
                 : _nullSafeKotlinTypeForDartType(returnType);
+            indent.write(methodArguments.isNotEmpty ? '$call ' : 'api.$name');
             indent.addScoped('{ result: Result<$resultType> ->', '}', () {
               indent.writeln('val error = result.exceptionOrNull()');
               indent.writeScoped('if (error != null) {', '}', () {
                 indent.writeln('reply.reply(wrapError(error))');
               }, addTrailingNewline: false);
               indent.addScoped(' else {', '}', () {
-                final String enumTagNullablePrefix =
-                    returnType.isNullable ? '?' : '!!';
-                final String enumTag =
-                    returnType.isEnum ? '$enumTagNullablePrefix.raw' : '';
                 if (returnType.isVoid) {
                   indent.writeln('reply.reply(wrapResult(null))');
                 } else {
                   indent.writeln('val data = result.getOrNull()');
-                  indent.writeln('reply.reply(wrapResult(data$enumTag))');
+                  indent.writeln('reply.reply(wrapResult(data))');
                 }
               });
             });
@@ -719,14 +705,9 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
             indent.writeScoped('val wrapped: List<Any?> = try {', '}', () {
               if (returnType.isVoid) {
                 indent.writeln(call);
-                indent.writeln('listOf<Any?>(null)');
+                indent.writeln('listOf(null)');
               } else {
-                String enumTag = '';
-                if (returnType.isEnum) {
-                  final String safeUnwrap = returnType.isNullable ? '?' : '';
-                  enumTag = '$safeUnwrap.raw';
-                }
-                indent.writeln('listOf<Any?>($call$enumTag)');
+                indent.writeln('listOf($call)');
               }
             }, addTrailingNewline: false);
             indent.add(' catch (exception: Throwable) ');
@@ -819,18 +800,10 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
           if (returnType.isVoid) {
             indent.writeln('callback(Result.success(Unit))');
           } else {
-            const String output = 'output';
-            // Nullable enums require special handling.
-            if (returnType.isEnum && returnType.isNullable) {
-              indent.writeScoped(
-                  'val $output = (it[0] as Int?)?.let { num ->', '}', () {
-                indent.writeln('${returnType.baseName}.ofRaw(num)');
-              });
-            } else {
-              indent.writeln(
-                  'val $output = ${_cast(indent, 'it[0]', type: returnType)}');
-            }
-            indent.writeln('callback(Result.success($output))');
+            indent.writeln(
+                'val output = ${_cast(indent, 'it[0]', type: returnType)}');
+
+            indent.writeln('callback(Result.success(output))');
           }
         });
       }, addTrailingNewline: false);
@@ -842,9 +815,6 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
   }
 }
 
-/// Calculates the name of the codec that will be generated for [api].
-String _getCodecName(Api api) => '${api.name}Codec';
-
 String _getErrorClassName(KotlinOptions generatorOptions) =>
     generatorOptions.errorClassName ?? 'FlutterError';
 
@@ -854,11 +824,6 @@ String _getArgumentName(int count, NamedType argument) =>
 /// Returns an argument name that can be used in a context where it is possible to collide
 /// and append `.index` to enums.
 String _getEnumSafeArgumentExpression(int count, NamedType argument) {
-  if (argument.type.isEnum) {
-    return argument.type.isNullable
-        ? '${_getArgumentName(count, argument)}Arg?.raw'
-        : '${_getArgumentName(count, argument)}Arg.raw';
-  }
   return '${_getArgumentName(count, argument)}Arg';
 }
 
@@ -867,14 +832,7 @@ String _getSafeArgumentName(int count, NamedType argument) =>
     '${_getArgumentName(count, argument)}Arg';
 
 String _castForceUnwrap(String value, TypeDeclaration type, Indent indent) {
-  if (type.isEnum) {
-    final String forceUnwrap = type.isNullable ? '' : '!!';
-    final String nullableConditionPrefix =
-        type.isNullable ? 'if ($value == null) null else ' : '';
-    return '$nullableConditionPrefix${_kotlinTypeForDartType(type)}.ofRaw($value as Int)$forceUnwrap';
-  } else {
-    return _cast(indent, value, type: type);
-  }
+  return _cast(indent, value, type: type);
 }
 
 /// Converts a [List] of [TypeDeclaration]s to a comma separated [String] to be
@@ -947,14 +905,6 @@ String _cast(Indent indent, String variable, {required TypeDeclaration type}) {
   if (typeString == 'Int' || typeString == 'Long') {
     return '$variable${_castInt(type.isNullable)}';
   }
-  if (type.isEnum) {
-    if (type.isNullable) {
-      return '($variable as Int?)?.let { num ->\n'
-          '${indent.str}  $typeString.ofRaw(num)\n'
-          '${indent.str}}';
-    }
-    return '${type.baseName}.ofRaw($variable as Int)!!';
-  }
   return '$variable as ${_nullSafeKotlinTypeForDartType(type)}';
 }
 
diff --git a/packages/pigeon/lib/objc_generator.dart b/packages/pigeon/lib/objc_generator.dart
index 5e7784bf8ba..e378fbac1c2 100644
--- a/packages/pigeon/lib/objc_generator.dart
+++ b/packages/pigeon/lib/objc_generator.dart
@@ -22,6 +22,7 @@ class ObjcOptions {
     this.headerIncludePath,
     this.prefix,
     this.copyrightHeader,
+    this.fileSpecificClassNameComponent,
   });
 
   /// The path to the header that will get placed in the source filed (example:
@@ -34,15 +35,20 @@ class ObjcOptions {
   /// A copyright header that will get prepended to generated code.
   final Iterable<String>? copyrightHeader;
 
+  /// A String to augment class names to avoid cross file collisions.
+  final String? fileSpecificClassNameComponent;
+
   /// Creates a [ObjcOptions] from a Map representation where:
   /// `x = ObjcOptions.fromMap(x.toMap())`.
   static ObjcOptions fromMap(Map<String, Object> map) {
     final Iterable<dynamic>? copyrightHeader =
         map['copyrightHeader'] as Iterable<dynamic>?;
     return ObjcOptions(
-      headerIncludePath: map['header'] as String?,
+      headerIncludePath: map['headerIncludePath'] as String?,
       prefix: map['prefix'] as String?,
       copyrightHeader: copyrightHeader?.cast<String>(),
+      fileSpecificClassNameComponent:
+          map['fileSpecificClassNameComponent'] as String?,
     );
   }
 
@@ -50,9 +56,11 @@ class ObjcOptions {
   /// `x = ObjcOptions.fromMap(x.toMap())`.
   Map<String, Object> toMap() {
     final Map<String, Object> result = <String, Object>{
-      if (headerIncludePath != null) 'header': headerIncludePath!,
+      if (headerIncludePath != null) 'headerIncludePath': headerIncludePath!,
       if (prefix != null) 'prefix': prefix!,
       if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
+      if (fileSpecificClassNameComponent != null)
+        'fileSpecificClassNameComponent': fileSpecificClassNameComponent!,
     };
     return result;
   }
@@ -199,8 +207,6 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     Class classDefinition, {
     required String dartPackageName,
   }) {
-    final List<Class> classes = root.classes;
-    final List<Enum> enums = root.enums;
     final String? prefix = generatorOptions.prefix;
 
     addDocumentationComments(
@@ -221,8 +227,6 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
         generatorOptions,
         root,
         classDefinition,
-        classes,
-        enums,
         prefix,
       );
       indent.addln(';');
@@ -273,6 +277,18 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     required String dartPackageName,
   }) {}
 
+  @override
+  void writeGeneralCodec(
+    ObjcOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    indent.writeln('$_docCommentPrefix The codec used by all APIs.');
+    indent.writeln(
+        'NSObject<FlutterMessageCodec> *${generatorOptions.prefix}Get${toUpperCamelCase(generatorOptions.fileSpecificClassNameComponent ?? '')}Codec(void);');
+  }
+
   @override
   void writeApis(
     ObjcOptions generatorOptions,
@@ -293,10 +309,6 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     Api api, {
     required String dartPackageName,
   }) {
-    indent.writeln(
-        '$_docCommentPrefix The codec used by ${_className(generatorOptions.prefix, api.name)}.');
-    indent.writeln(
-        'NSObject<FlutterMessageCodec> *${_getCodecGetterName(generatorOptions.prefix, api.name)}(void);');
     indent.newln();
     final String apiName = _className(generatorOptions.prefix, api.name);
     addDocumentationComments(
@@ -338,10 +350,6 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     Api api, {
     required String dartPackageName,
   }) {
-    indent.writeln(
-        '$_docCommentPrefix The codec used by ${_className(generatorOptions.prefix, api.name)}.');
-    indent.writeln(
-        'NSObject<FlutterMessageCodec> *${_getCodecGetterName(generatorOptions.prefix, api.name)}(void);');
     indent.newln();
     final String apiName = _className(generatorOptions.prefix, api.name);
     addDocumentationComments(
@@ -552,12 +560,12 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     Class classDefinition, {
     required String dartPackageName,
   }) {
-    indent.write('- (NSArray *)toList ');
+    indent.write('- (NSArray<id> *)toList ');
     indent.addScoped('{', '}', () {
       indent.write('return');
       indent.addScoped(' @[', '];', () {
         for (final NamedType field in classDefinition.fields) {
-          indent.writeln('${_arrayValue(field)},');
+          indent.writeln('${_arrayValue(field, generatorOptions.prefix)},');
         }
       });
     });
@@ -573,24 +581,26 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
   }) {
     final String className =
         _className(generatorOptions.prefix, classDefinition.name);
-    indent.write('+ ($className *)fromList:(NSArray *)list ');
+    indent.write('+ ($className *)fromList:(NSArray<id> *)list ');
     indent.addScoped('{', '}', () {
       const String resultName = 'pigeonResult';
       indent.writeln('$className *$resultName = [[$className alloc] init];');
       enumerate(getFieldsInSerializationOrder(classDefinition),
           (int index, final NamedType field) {
-        final bool isEnumType = field.type.isEnum;
         final String valueGetter = 'GetNullableObjectAtIndex(list, $index)';
         final String? primitiveExtractionMethod =
             _nsnumberExtractionMethod(field.type);
         final String ivarValueExpression;
-        if (primitiveExtractionMethod != null) {
+        if (field.type.isEnum && !field.type.isNullable) {
+          _writeEnumBoxToEnum(
+            indent,
+            field,
+            valueGetter,
+            prefix: generatorOptions.prefix,
+          );
+          ivarValueExpression = 'enumBox.value';
+        } else if (primitiveExtractionMethod != null) {
           ivarValueExpression = '[$valueGetter $primitiveExtractionMethod]';
-        } else if (isEnumType) {
-          indent.writeln('NSNumber *${field.name}AsNumber = $valueGetter;');
-          indent.writeln(
-              '${_enumName(field.type.baseName, suffix: ' *', prefix: generatorOptions.prefix, box: true)}${field.name} = ${field.name}AsNumber == nil ? nil : [[${_enumName(field.type.baseName, prefix: generatorOptions.prefix, box: true)} alloc] initWithValue:[${field.name}AsNumber integerValue]];');
-          ivarValueExpression = field.name;
         } else {
           ivarValueExpression = valueGetter;
         }
@@ -599,21 +609,124 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
       indent.writeln('return $resultName;');
     });
 
-    indent.write('+ (nullable $className *)nullableFromList:(NSArray *)list ');
+    indent.write(
+        '+ (nullable $className *)nullableFromList:(NSArray<id> *)list ');
     indent.addScoped('{', '}', () {
       indent.writeln('return (list) ? [$className fromList:list] : nil;');
     });
   }
 
-  void _writeCodecAndGetter(
-      ObjcOptions generatorOptions, Root root, Indent indent, Api api) {
-    final String codecName = _getCodecName(generatorOptions.prefix, api.name);
-    if (getCodecClasses(api, root).isNotEmpty) {
-      _writeCodec(indent, codecName, generatorOptions, api, root);
-      indent.newln();
-    }
-    _writeCodecGetter(indent, codecName, generatorOptions, api, root);
+  @override
+  void writeGeneralCodec(
+    ObjcOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    const String codecName = 'PigeonCodec';
+    final Iterable<EnumeratedType> codecClasses = getEnumeratedTypes(root);
+    final String readerWriterName =
+        '${generatorOptions.prefix}${toUpperCamelCase(generatorOptions.fileSpecificClassNameComponent ?? '')}${codecName}ReaderWriter';
+    final String readerName =
+        '${generatorOptions.prefix}${toUpperCamelCase(generatorOptions.fileSpecificClassNameComponent ?? '')}${codecName}Reader';
+    final String writerName =
+        '${generatorOptions.prefix}${toUpperCamelCase(generatorOptions.fileSpecificClassNameComponent ?? '')}${codecName}Writer';
+    indent.writeln('@interface $readerName : FlutterStandardReader');
+    indent.writeln('@end');
+    indent.writeln('@implementation $readerName');
+    indent.write('- (nullable id)readValueOfType:(UInt8)type ');
+    indent.addScoped('{', '}', () {
+      indent.write('switch (type) ');
+      indent.addScoped('{', '}', () {
+        for (final EnumeratedType customType in codecClasses) {
+          indent.writeln('case ${customType.enumeration}: ');
+          indent.nest(1, () {
+            if (customType.type == CustomTypes.customClass) {
+              indent.writeln(
+                  'return [${_className(generatorOptions.prefix, customType.name)} fromList:[self readValue]];');
+            } else if (customType.type == CustomTypes.customEnum) {
+              indent.writeScoped('{', '}', () {
+                indent.writeln('NSNumber *enumAsNumber = [self readValue];');
+                indent.writeln(
+                    'return enumAsNumber == nil ? nil : [[${_enumName(customType.name, prefix: generatorOptions.prefix, box: true)} alloc] initWithValue:[enumAsNumber integerValue]];');
+              });
+            }
+          });
+        }
+        indent.writeln('default:');
+        indent.nest(1, () {
+          indent.writeln('return [super readValueOfType:type];');
+        });
+      });
+    });
+    indent.writeln('@end');
     indent.newln();
+    indent.writeln('@interface $writerName : FlutterStandardWriter');
+    indent.writeln('@end');
+    indent.writeln('@implementation $writerName');
+    indent.write('- (void)writeValue:(id)value ');
+    indent.addScoped('{', '}', () {
+      bool firstClass = true;
+      for (final EnumeratedType customClass in codecClasses) {
+        if (firstClass) {
+          indent.write('');
+          firstClass = false;
+        }
+        if (customClass.type == CustomTypes.customClass) {
+          indent.add(
+              'if ([value isKindOfClass:[${_className(generatorOptions.prefix, customClass.name)} class]]) ');
+          indent.addScoped('{', '} else ', () {
+            indent.writeln('[self writeByte:${customClass.enumeration}];');
+            indent.writeln('[self writeValue:[value toList]];');
+          }, addTrailingNewline: false);
+        } else if (customClass.type == CustomTypes.customEnum) {
+          final String boxName = _enumName(customClass.name,
+              prefix: generatorOptions.prefix, box: true);
+          indent.add('if ([value isKindOfClass:[$boxName class]]) ');
+          indent.addScoped('{', '} else ', () {
+            indent.writeln('$boxName * box = ($boxName *)value;');
+            indent.writeln('[self writeByte:${customClass.enumeration}];');
+            indent.writeln(
+                '[self writeValue:(value == nil ? [NSNull null] : [NSNumber numberWithInteger:box.value])];');
+          }, addTrailingNewline: false);
+        }
+      }
+      indent.addScoped('{', '}', () {
+        indent.writeln('[super writeValue:value];');
+      });
+    });
+    indent.writeln('@end');
+    indent.newln();
+    indent.format('''
+@interface $readerWriterName : FlutterStandardReaderWriter
+@end
+@implementation $readerWriterName
+- (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
+\treturn [[$writerName alloc] initWithData:data];
+}
+- (FlutterStandardReader *)readerWithData:(NSData *)data {
+\treturn [[$readerName alloc] initWithData:data];
+}
+@end''');
+    indent.newln();
+
+    indent.write(
+        'NSObject<FlutterMessageCodec> *${generatorOptions.prefix}Get${toUpperCamelCase(generatorOptions.fileSpecificClassNameComponent ?? '')}Codec(void) ');
+    indent.addScoped('{', '}', () {
+      indent
+          .writeln('static FlutterStandardMessageCodec *sSharedObject = nil;');
+
+      indent.writeln('static dispatch_once_t sPred = 0;');
+      indent.write('dispatch_once(&sPred, ^');
+      indent.addScoped('{', '});', () {
+        indent.writeln(
+            '$readerWriterName *readerWriter = [[$readerWriterName alloc] init];');
+        indent.writeln(
+            'sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];');
+      });
+
+      indent.writeln('return sSharedObject;');
+    });
   }
 
   @override
@@ -626,8 +739,6 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
   }) {
     final String apiName = _className(generatorOptions.prefix, api.name);
 
-    _writeCodecAndGetter(generatorOptions, root, indent, api);
-
     _writeExtension(indent, apiName);
     indent.newln();
     indent.writeln('@implementation $apiName');
@@ -657,8 +768,6 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
   }) {
     final String apiName = _className(generatorOptions.prefix, api.name);
 
-    _writeCodecAndGetter(generatorOptions, root, indent, api);
-
     const String channelName = 'channel';
     indent.write(
         'void SetUp$apiName(id<FlutterBinaryMessenger> binaryMessenger, NSObject<$apiName> *api) ');
@@ -735,7 +844,7 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
 
   void _writeWrapError(Indent indent) {
     indent.format('''
-static NSArray *wrapResult(id result, FlutterError *error) {
+static NSArray<id> *wrapResult(id result, FlutterError *error) {
 \tif (error) {
 \t\treturn @[
 \t\t\terror.code ?: [NSNull null], error.message ?: [NSNull null], error.details ?: [NSNull null]
@@ -747,7 +856,7 @@ static NSArray *wrapResult(id result, FlutterError *error) {
 
   void _writeGetNullableObjectAtIndex(Indent indent) {
     indent.format('''
-static id GetNullableObjectAtIndex(NSArray *array, NSInteger key) {
+static id GetNullableObjectAtIndex(NSArray<id> *array, NSInteger key) {
 \tid result = array[key];
 \treturn (result == [NSNull null]) ? nil : result;
 }''');
@@ -763,7 +872,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
   void _writeChannelApiBinding(ObjcOptions generatorOptions, Root root,
       Indent indent, String apiName, Method func, String channel) {
     void unpackArgs(String variable) {
-      indent.writeln('NSArray *args = $variable;');
+      indent.writeln('NSArray<id> *args = $variable;');
       int count = 0;
       for (final NamedType arg in func.parameters) {
         final String argName = _getSafeArgName(count, arg);
@@ -774,16 +883,30 @@ static FlutterError *createConnectionError(NSString *channelName) {
           generatorOptions.prefix,
           arg.type,
         );
-        if (primitiveExtractionMethod != null) {
-          indent.writeln(
-              '${objcArgType.beforeString}$argName = [$valueGetter $primitiveExtractionMethod];');
-        } else if (arg.type.isEnum) {
-          indent.writeln('NSNumber *${argName}AsNumber = $valueGetter;');
-          indent.writeln(
-              '${_enumName(arg.type.baseName, suffix: ' *', prefix: generatorOptions.prefix, box: true)}$argName = ${argName}AsNumber == nil ? nil : [[${_enumName(arg.type.baseName, prefix: generatorOptions.prefix, box: true)} alloc] initWithValue:[${argName}AsNumber integerValue]];');
+        final String ivarValueExpression;
+        String beforeString = objcArgType.beforeString;
+        if (arg.type.isEnum && !arg.type.isNullable) {
+          _writeEnumBoxToEnum(
+            indent,
+            arg,
+            valueGetter,
+            prefix: generatorOptions.prefix,
+          );
+          ivarValueExpression = 'enumBox.value';
+        } else if (primitiveExtractionMethod != null) {
+          ivarValueExpression = '[$valueGetter $primitiveExtractionMethod]';
         } else {
-          indent.writeln('${objcArgType.beforeString}$argName = $valueGetter;');
+          if (arg.type.isEnum) {
+            beforeString = _enumName(
+              arg.type.baseName,
+              prefix: generatorOptions.prefix,
+              box: true,
+              suffix: ' *',
+            );
+          }
+          ivarValueExpression = valueGetter;
         }
+        indent.writeln('$beforeString$argName = $ivarValueExpression;');
         count++;
       }
     }
@@ -808,30 +931,21 @@ static FlutterError *createConnectionError(NSString *channelName) {
       } else {
         const String callback = 'callback(wrapResult(output, error));';
         String returnTypeString = '${returnType.beforeString}_Nullable output';
-        const String numberOutput = 'NSNumber *output =';
-        const String enumConversionExpression =
-            'enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];';
 
         if (func.returnType.isEnum) {
           returnTypeString =
-              '${_enumName(func.returnType.baseName, suffix: ' *_Nullable', prefix: generatorOptions.prefix, box: true)} enumValue';
+              '${_enumName(func.returnType.baseName, suffix: ' *_Nullable', prefix: generatorOptions.prefix, box: true)} output';
         }
         if (func.parameters.isEmpty) {
           indent.writeScoped(
               '[api ${selectorComponents.first}:^($returnTypeString, FlutterError *_Nullable error) {',
               '}];', () {
-            if (func.returnType.isEnum) {
-              indent.writeln('$numberOutput $enumConversionExpression');
-            }
             indent.writeln(callback);
           });
         } else {
           indent.writeScoped(
               '[api $callSignature ${selectorComponents.last}:^($returnTypeString, FlutterError *_Nullable error) {',
               '}];', () {
-            if (func.returnType.isEnum) {
-              indent.writeln('$numberOutput $enumConversionExpression');
-            }
             indent.writeln(callback);
           });
         }
@@ -846,9 +960,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
       } else {
         if (func.returnType.isEnum) {
           indent.writeln(
-              '${_enumName(func.returnType.baseName, suffix: ' *', prefix: generatorOptions.prefix, box: true)} enumBox = $call;');
-          indent.writeln(
-              'NSNumber *output = enumBox == nil ? nil : [NSNumber numberWithInteger:enumBox.value];');
+              '${_enumName(func.returnType.baseName, suffix: ' *', prefix: generatorOptions.prefix, box: true)} output = $call;');
         } else {
           indent.writeln('${returnType.beforeString}output = $call;');
         }
@@ -910,8 +1022,8 @@ static FlutterError *createConnectionError(NSString *channelName) {
             'initWithName:[NSString stringWithFormat:@"%@%@", @"${makeChannelName(api, func, dartPackageName)}", messageChannelSuffix]');
         indent.writeln('binaryMessenger:binaryMessenger');
         indent.write('codec:');
-        indent
-            .add('${_getCodecGetterName(generatorOptions.prefix, api.name)}()');
+        indent.add(
+            '${generatorOptions.prefix}Get${toUpperCamelCase(generatorOptions.fileSpecificClassNameComponent ?? '')}Codec()');
 
         if (taskQueue != null) {
           indent.newln();
@@ -929,10 +1041,10 @@ static FlutterError *createConnectionError(NSString *channelName) {
         _className(languageOptions.prefix, classDefinition.name);
     indent.newln();
     indent.writeln('@interface $className ()');
-    indent.writeln('+ ($className *)fromList:(NSArray *)list;');
-    indent
-        .writeln('+ (nullable $className *)nullableFromList:(NSArray *)list;');
-    indent.writeln('- (NSArray *)toList;');
+    indent.writeln('+ ($className *)fromList:(NSArray<id> *)list;');
+    indent.writeln(
+        '+ (nullable $className *)nullableFromList:(NSArray<id> *)list;');
+    indent.writeln('- (NSArray<id> *)toList;');
     indent.writeln('@end');
   }
 
@@ -950,8 +1062,6 @@ static FlutterError *createConnectionError(NSString *channelName) {
       languageOptions,
       root,
       classDefinition,
-      root.classes,
-      root.enums,
       languageOptions.prefix,
     );
     indent.writeScoped(' {', '}', () {
@@ -964,222 +1074,116 @@ static FlutterError *createConnectionError(NSString *channelName) {
       indent.writeln('return $result;');
     });
   }
-
-  /// Writes the codec that will be used for encoding messages for the [api].
-  ///
-  /// Example:
-  /// @interface FooHostApiCodecReader : FlutterStandardReader
-  /// ...
-  /// @interface FooHostApiCodecWriter : FlutterStandardWriter
-  /// ...
-  /// @interface FooHostApiCodecReaderWriter : FlutterStandardReaderWriter
-  /// ...
-  /// NSObject<FlutterMessageCodec> *FooHostApiCodecGetCodec(void) {...}
-  void _writeCodec(
-      Indent indent, String name, ObjcOptions options, Api api, Root root) {
-    assert(getCodecClasses(api, root).isNotEmpty);
-    final Iterable<EnumeratedClass> codecClasses = getCodecClasses(api, root);
-    final String readerWriterName = '${name}ReaderWriter';
-    final String readerName = '${name}Reader';
-    final String writerName = '${name}Writer';
-    indent.writeln('@interface $readerName : FlutterStandardReader');
-    indent.writeln('@end');
-    indent.writeln('@implementation $readerName');
-    indent.write('- (nullable id)readValueOfType:(UInt8)type ');
-    indent.addScoped('{', '}', () {
-      indent.write('switch (type) ');
-      indent.addScoped('{', '}', () {
-        for (final EnumeratedClass customClass in codecClasses) {
-          indent.writeln('case ${customClass.enumeration}: ');
-          indent.nest(1, () {
-            indent.writeln(
-                'return [${_className(options.prefix, customClass.name)} fromList:[self readValue]];');
-          });
-        }
-        indent.writeln('default:');
-        indent.nest(1, () {
-          indent.writeln('return [super readValueOfType:type];');
-        });
-      });
-    });
-    indent.writeln('@end');
-    indent.newln();
-    indent.writeln('@interface $writerName : FlutterStandardWriter');
-    indent.writeln('@end');
-    indent.writeln('@implementation $writerName');
-    indent.write('- (void)writeValue:(id)value ');
-    indent.addScoped('{', '}', () {
-      bool firstClass = true;
-      for (final EnumeratedClass customClass in codecClasses) {
-        if (firstClass) {
-          indent.write('');
-          firstClass = false;
-        }
-        indent.add(
-            'if ([value isKindOfClass:[${_className(options.prefix, customClass.name)} class]]) ');
-        indent.addScoped('{', '} else ', () {
-          indent.writeln('[self writeByte:${customClass.enumeration}];');
-          indent.writeln('[self writeValue:[value toList]];');
-        }, addTrailingNewline: false);
-      }
-      indent.addScoped('{', '}', () {
-        indent.writeln('[super writeValue:value];');
-      });
-    });
-    indent.writeln('@end');
-    indent.newln();
-    indent.format('''
-@interface $readerWriterName : FlutterStandardReaderWriter
-@end
-@implementation $readerWriterName
-- (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-\treturn [[$writerName alloc] initWithData:data];
 }
-- (FlutterStandardReader *)readerWithData:(NSData *)data {
-\treturn [[$readerName alloc] initWithData:data];
-}
-@end''');
-  }
 
-  void _writeCodecGetter(
-      Indent indent, String name, ObjcOptions options, Api api, Root root) {
-    final String readerWriterName = '${name}ReaderWriter';
+void _writeMethod(
+  ObjcOptions languageOptions,
+  Root root,
+  Indent indent,
+  Api api,
+  Method func, {
+  required String dartPackageName,
+}) {
+  final _ObjcType returnType = _objcTypeForDartType(
+    languageOptions.prefix,
+    func.returnType,
+    // Nullability is required since the return must be nil if NSError is set.
+    forceNullability: true,
+  );
+  final String callbackType =
+      _callbackForType(func.returnType, returnType, languageOptions);
 
-    indent.write(
-        'NSObject<FlutterMessageCodec> *${_getCodecGetterName(options.prefix, api.name)}(void) ');
-    indent.addScoped('{', '}', () {
-      indent
-          .writeln('static FlutterStandardMessageCodec *sSharedObject = nil;');
-      if (getCodecClasses(api, root).isNotEmpty) {
-        indent.writeln('static dispatch_once_t sPred = 0;');
-        indent.write('dispatch_once(&sPred, ^');
-        indent.addScoped('{', '});', () {
-          indent.writeln(
-              '$readerWriterName *readerWriter = [[$readerWriterName alloc] init];');
-          indent.writeln(
-              'sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];');
-        });
-      } else {
-        indent.writeln(
-            'sSharedObject = [FlutterStandardMessageCodec sharedInstance];');
+  String argNameFunc(int count, NamedType arg) => _getSafeArgName(count, arg);
+  String sendArgument;
+  if (func.parameters.isEmpty) {
+    sendArgument = 'nil';
+  } else {
+    int count = 0;
+    String makeVarOrNSNullExpression(NamedType arg) {
+      final String argName = argNameFunc(count, arg);
+      String varExpression = _collectionSafeExpression(argName, arg.type);
+      if (arg.type.isEnum) {
+        if (arg.type.isNullable) {
+          varExpression =
+              '${argNameFunc(count, arg)} == nil ? [NSNull null] : $argName';
+        } else {
+          varExpression = _getEnumToEnumBox(arg, argNameFunc(count, arg),
+              prefix: languageOptions.prefix);
+        }
       }
+      count++;
+      return varExpression;
+    }
 
-      indent.writeln('return sSharedObject;');
-    });
+    sendArgument =
+        '@[${func.parameters.map(makeVarOrNSNullExpression).join(', ')}]';
   }
+  indent.write(_makeObjcSignature(
+    func: func,
+    options: languageOptions,
+    returnType: 'void',
+    lastArgName: 'completion',
+    lastArgType: callbackType,
+    argNameFunc: argNameFunc,
+  ));
+  indent.addScoped(' {', '}', () {
+    indent.writeln(
+        'NSString *channelName = [NSString stringWithFormat:@"%@%@", @"${makeChannelName(api, func, dartPackageName)}", _messageChannelSuffix];');
+    indent.writeln('FlutterBasicMessageChannel *channel =');
 
-  void _writeMethod(
-    ObjcOptions languageOptions,
-    Root root,
-    Indent indent,
-    Api api,
-    Method func, {
-    required String dartPackageName,
-  }) {
-    final _ObjcType returnType = _objcTypeForDartType(
-      languageOptions.prefix,
-      func.returnType,
-      // Nullability is required since the return must be nil if NSError is set.
-      forceNullability: true,
-    );
-    final String callbackType =
-        _callbackForType(func.returnType, returnType, languageOptions);
-
-    String argNameFunc(int count, NamedType arg) => _getSafeArgName(count, arg);
-    String sendArgument;
-    if (func.parameters.isEmpty) {
-      sendArgument = 'nil';
-    } else {
-      int count = 0;
-      String makeVarOrNSNullExpression(NamedType arg) {
-        final String argName = argNameFunc(count, arg);
-        String varExpression = _collectionSafeExpression(argName, arg.type);
-        if (arg.type.isEnum) {
-          if (arg.type.isNullable) {
-            varExpression =
-                '${argNameFunc(count, arg)} == nil ? [NSNull null] : [NSNumber numberWithInteger:$argName.value]';
-          } else {
-            varExpression = '[NSNumber numberWithInteger:$argName]';
-          }
-        }
-        count++;
-        return varExpression;
-      }
-
-      sendArgument =
-          '@[${func.parameters.map(makeVarOrNSNullExpression).join(', ')}]';
-    }
-    indent.write(_makeObjcSignature(
-      func: func,
-      options: languageOptions,
-      returnType: 'void',
-      lastArgName: 'completion',
-      lastArgType: callbackType,
-      argNameFunc: argNameFunc,
-    ));
-    indent.addScoped(' {', '}', () {
-      indent.writeln(
-          'NSString *channelName = [NSString stringWithFormat:@"%@%@", @"${makeChannelName(api, func, dartPackageName)}", _messageChannelSuffix];');
-      indent.writeln('FlutterBasicMessageChannel *channel =');
+    indent.nest(1, () {
+      indent.writeln('[FlutterBasicMessageChannel');
       indent.nest(1, () {
-        indent.writeln('[FlutterBasicMessageChannel');
-        indent.nest(1, () {
-          indent.writeln('messageChannelWithName:channelName');
-          indent.writeln('binaryMessenger:self.binaryMessenger');
-          indent.write(
-              'codec:${_getCodecGetterName(languageOptions.prefix, api.name)}()');
-          indent.addln('];');
-        });
+        indent.writeln('messageChannelWithName:channelName');
+        indent.writeln('binaryMessenger:self.binaryMessenger');
+        indent.write(
+            'codec:${languageOptions.prefix}Get${toUpperCamelCase(languageOptions.fileSpecificClassNameComponent ?? '')}Codec()');
+        indent.addln('];');
       });
-      final String valueOnErrorResponse = func.returnType.isVoid ? '' : 'nil, ';
-      indent.write(
-          '[channel sendMessage:$sendArgument reply:^(NSArray<id> *reply) ');
-      indent.addScoped('{', '}];', () {
-        indent.writeScoped('if (reply != nil) {', '} ', () {
-          indent.writeScoped('if (reply.count > 1) {', '} ', () {
-            indent.writeln(
-                'completion($valueOnErrorResponse[FlutterError errorWithCode:reply[0] message:reply[1] details:reply[2]]);');
-          }, addTrailingNewline: false);
-          indent.addScoped('else {', '}', () {
-            const String nullCheck =
-                'reply[0] == [NSNull null] ? nil : reply[0]';
-            if (func.returnType.isVoid) {
-              indent.writeln('completion(nil);');
+    });
+    final String valueOnErrorResponse = func.returnType.isVoid ? '' : 'nil, ';
+    indent.write(
+        '[channel sendMessage:$sendArgument reply:^(NSArray<id> *reply) ');
+    indent.addScoped('{', '}];', () {
+      indent.writeScoped('if (reply != nil) {', '} ', () {
+        indent.writeScoped('if (reply.count > 1) {', '} ', () {
+          indent.writeln(
+              'completion($valueOnErrorResponse[FlutterError errorWithCode:reply[0] message:reply[1] details:reply[2]]);');
+        }, addTrailingNewline: false);
+        indent.addScoped('else {', '}', () {
+          const String nullCheck = 'reply[0] == [NSNull null] ? nil : reply[0]';
+          if (func.returnType.isVoid) {
+            indent.writeln('completion(nil);');
+          } else {
+            if (func.returnType.isEnum) {
+              final String enumName = _enumName(func.returnType.baseName,
+                  prefix: languageOptions.prefix, box: true);
+              indent.writeln('$enumName *output = $nullCheck;');
             } else {
-              if (func.returnType.isEnum) {
-                final String enumName = _enumName(func.returnType.baseName,
-                    prefix: languageOptions.prefix, box: true);
-                indent.writeln('NSNumber *outputAsNumber = $nullCheck;');
-                indent.writeln(
-                    '$enumName *output = outputAsNumber == nil ? nil : [[$enumName alloc] initWithValue:[outputAsNumber integerValue]];');
-              } else {
-                indent
-                    .writeln('${returnType.beforeString}output = $nullCheck;');
-              }
-              indent.writeln('completion(output, nil);');
+              indent.writeln('${returnType.beforeString}output = $nullCheck;');
             }
-          });
-        }, addTrailingNewline: false);
-        indent.addScoped('else {', '} ', () {
-          indent.writeln(
-              'completion(${valueOnErrorResponse}createConnectionError(channelName));');
+            indent.writeln('completion(output, nil);');
+          }
         });
+      }, addTrailingNewline: false);
+      indent.addScoped('else {', '} ', () {
+        indent.writeln(
+            'completion(${valueOnErrorResponse}createConnectionError(channelName));');
       });
     });
-  }
+  });
 }
 
 /// Writes the method declaration for the initializer.
 ///
 /// Example '+ (instancetype)makeWithFoo:(NSString *)foo'
 void _writeObjcSourceClassInitializerDeclaration(
-    Indent indent,
-    ObjcOptions generatorOptions,
-    Root root,
-    Class classDefinition,
-    List<Class> classes,
-    List<Enum> enums,
-    String? prefix) {
+  Indent indent,
+  ObjcOptions generatorOptions,
+  Root root,
+  Class classDefinition,
+  String? prefix,
+) {
   indent.write('+ (instancetype)makeWith');
   bool isFirst = true;
   indent.nest(2, () {
@@ -1242,7 +1246,10 @@ class _ObjcType {
   final bool hasAsterisk;
 
   @override
-  String toString() => hasAsterisk ? '$baseName *' : baseName;
+  String toString() =>
+      hasAsterisk ? '$baseName$listGenericTag *' : '$baseName$listGenericTag';
+
+  String get listGenericTag => baseName == 'NSArray' ? '<id>' : '';
 
   /// Returns a version of the string form that can be used directly before
   /// another string (e.g., a variable name) and handle spacing correctly for
@@ -1333,10 +1340,14 @@ String? _nsnumberExtractionMethod(
 /// arguments for use in generics.
 /// Example: ('FOO', ['Foo', 'Bar']) -> 'FOOFoo *, FOOBar *').
 String _flattenTypeArguments(String? classPrefix, List<TypeDeclaration> args) {
-  final String result = args
-      .map<String>((TypeDeclaration e) =>
-          _objcTypeForDartType(classPrefix, e).toString())
-      .join(', ');
+  final String result = args.map<String>((TypeDeclaration e) {
+    // print(e);
+    if (e.isEnum) {
+      return _enumName(e.baseName,
+          prefix: classPrefix, box: true, suffix: ' *');
+    }
+    return _objcTypeForDartType(classPrefix, e).toString();
+  }).join(', ');
   return result;
 }
 
@@ -1405,15 +1416,6 @@ String _propertyTypeForDartType(TypeDeclaration type,
   return 'strong';
 }
 
-/// Generates the name of the codec that will be generated.
-String _getCodecName(String? prefix, String className) =>
-    '${_className(prefix, className)}Codec';
-
-/// Generates the name of the function for accessing the codec instance used by
-/// the api class named [className].
-String _getCodecGetterName(String? prefix, String className) =>
-    '${_className(prefix, className)}GetCodec';
-
 String _capitalize(String str) =>
     (str.isEmpty) ? '' : str[0].toUpperCase() + str.substring(1);
 
@@ -1499,12 +1501,9 @@ String _makeObjcSignature({
 /// provided [options].
 void generateObjcHeader(ObjcOptions options, Root root, Indent indent) {}
 
-String _arrayValue(NamedType field) {
-  if (field.type.isEnum) {
-    if (field.type.isNullable) {
-      return '(self.${field.name} == nil ? [NSNull null] : [NSNumber numberWithInteger:self.${field.name}.value])';
-    }
-    return '@(self.${field.name})';
+String _arrayValue(NamedType field, String? prefix) {
+  if (field.type.isEnum && !field.type.isNullable) {
+    return _getEnumToEnumBox(field, 'self.${field.name}', prefix: prefix);
   } else {
     return _collectionSafeExpression(
       'self.${field.name}',
@@ -1569,3 +1568,21 @@ List<Error> validateObjc(ObjcOptions options, Root root) {
 
   return errors;
 }
+
+void _writeEnumBoxToEnum(
+  Indent indent,
+  NamedType field,
+  String valueGetter, {
+  String? prefix = '',
+}) {
+  indent.writeln(
+      '${_enumName(field.type.baseName, prefix: prefix, box: true, suffix: ' *')}enumBox = $valueGetter;');
+}
+
+String _getEnumToEnumBox(
+  NamedType field,
+  String valueSetter, {
+  String? prefix = '',
+}) {
+  return '[[${_enumName(field.type.baseName, prefix: prefix, box: true)} alloc] initWithValue:$valueSetter]';
+}
diff --git a/packages/pigeon/lib/pigeon_lib.dart b/packages/pigeon/lib/pigeon_lib.dart
index 42da8b060f1..2592dd24c55 100644
--- a/packages/pigeon/lib/pigeon_lib.dart
+++ b/packages/pigeon/lib/pigeon_lib.dart
@@ -621,6 +621,12 @@ class ObjcGeneratorAdapter implements GeneratorAdapter {
       StringSink sink, PigeonOptions options, Root root, FileType fileType) {
     final ObjcOptions objcOptions = options.objcOptions ?? const ObjcOptions();
     final ObjcOptions objcOptionsWithHeader = objcOptions.merge(ObjcOptions(
+      fileSpecificClassNameComponent: options.objcSourceOut
+              ?.split('/')
+              .lastOrNull
+              ?.split('.')
+              .firstOrNull ??
+          '',
       copyrightHeader: options.copyrightHeader != null
           ? _lineReader(
               path.posix.join(options.basePath ?? '', options.copyrightHeader))
@@ -701,6 +707,8 @@ class SwiftGeneratorAdapter implements GeneratorAdapter {
       StringSink sink, PigeonOptions options, Root root, FileType fileType) {
     SwiftOptions swiftOptions = options.swiftOptions ?? const SwiftOptions();
     swiftOptions = swiftOptions.merge(SwiftOptions(
+      fileSpecificClassNameComponent:
+          options.swiftOut?.split('/').lastOrNull?.split('.').firstOrNull ?? '',
       copyrightHeader: options.copyrightHeader != null
           ? _lineReader(
               path.posix.join(options.basePath ?? '', options.copyrightHeader))
@@ -784,6 +792,9 @@ class KotlinGeneratorAdapter implements GeneratorAdapter {
     kotlinOptions = kotlinOptions.merge(KotlinOptions(
       errorClassName: kotlinOptions.errorClassName ?? 'FlutterError',
       includeErrorClass: kotlinOptions.includeErrorClass,
+      fileSpecificClassNameComponent:
+          options.kotlinOut?.split('/').lastOrNull?.split('.').firstOrNull ??
+              '',
       copyrightHeader: options.copyrightHeader != null
           ? _lineReader(
               path.posix.join(options.basePath ?? '', options.copyrightHeader))
@@ -1346,12 +1357,20 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
               (Api apiDefinition) => apiDefinition.name == type.baseName,
             );
     if (assocClass != null) {
-      return type.copyWithClass(assocClass);
+      type = type.copyWithClass(assocClass);
     } else if (assocEnum != null) {
-      return type.copyWithEnum(assocEnum);
+      type = type.copyWithEnum(assocEnum);
     } else if (assocProxyApi != null) {
-      return type.copyWithProxyApi(assocProxyApi);
+      type = type.copyWithProxyApi(assocProxyApi);
     }
+    if (type.typeArguments.isNotEmpty) {
+      final List<TypeDeclaration> newTypes = <TypeDeclaration>[];
+      for (final TypeDeclaration type in type.typeArguments) {
+        newTypes.add(_attachAssociatedDefinition(type));
+      }
+      type = type.copyWithTypeArguments(newTypes);
+    }
+
     return type;
   }
 
@@ -1981,7 +2000,7 @@ class Pigeon {
   }
 
   /// Reads the file located at [path] and generates [ParseResults] by parsing
-  /// it.  [types] optionally filters out what datatypes are actually parsed.
+  /// it. [types] optionally filters out what datatypes are actually parsed.
   /// [sdkPath] for specifying the Dart SDK path for
   /// [AnalysisContextCollection].
   ParseResults parseFile(String inputPath, {String? sdkPath}) {
@@ -2249,14 +2268,16 @@ ${_argParser.usage}''';
       options = options.merge(PigeonOptions(
           objcOptions: (options.objcOptions ?? const ObjcOptions()).merge(
               ObjcOptions(
-                  headerIncludePath: path.basename(options.objcHeaderOut!)))));
+                  headerIncludePath: options.objcOptions?.headerIncludePath ??
+                      path.basename(options.objcHeaderOut!)))));
     }
 
     if (options.cppHeaderOut != null) {
       options = options.merge(PigeonOptions(
           cppOptions: (options.cppOptions ?? const CppOptions()).merge(
               CppOptions(
-                  headerIncludePath: path.basename(options.cppHeaderOut!)))));
+                  headerIncludePath: options.cppOptions?.headerIncludePath ??
+                      path.basename(options.cppHeaderOut!)))));
     }
 
     for (final GeneratorAdapter adapter in safeGeneratorAdapters) {
diff --git a/packages/pigeon/lib/swift_generator.dart b/packages/pigeon/lib/swift_generator.dart
index db5701e371b..99ad77f39e7 100644
--- a/packages/pigeon/lib/swift_generator.dart
+++ b/packages/pigeon/lib/swift_generator.dart
@@ -19,12 +19,16 @@ class SwiftOptions {
   /// Creates a [SwiftOptions] object
   const SwiftOptions({
     this.copyrightHeader,
+    this.fileSpecificClassNameComponent,
     this.errorClassName,
   });
 
   /// A copyright header that will get prepended to generated code.
   final Iterable<String>? copyrightHeader;
 
+  /// A String to augment class names to avoid cross file collisions.
+  final String? fileSpecificClassNameComponent;
+
   /// The name of the error class used for passing custom error parameters.
   final String? errorClassName;
 
@@ -33,6 +37,8 @@ class SwiftOptions {
   static SwiftOptions fromList(Map<String, Object> map) {
     return SwiftOptions(
       copyrightHeader: map['copyrightHeader'] as Iterable<String>?,
+      fileSpecificClassNameComponent:
+          map['fileSpecificClassNameComponent'] as String?,
       errorClassName: map['errorClassName'] as String?,
     );
   }
@@ -42,6 +48,8 @@ class SwiftOptions {
   Map<String, Object> toMap() {
     final Map<String, Object> result = <String, Object>{
       if (copyrightHeader != null) 'copyrightHeader': copyrightHeader!,
+      if (fileSpecificClassNameComponent != null)
+        'fileSpecificClassNameComponent': fileSpecificClassNameComponent!,
       if (errorClassName != null) 'errorClassName': errorClassName!,
     };
     return result;
@@ -115,6 +123,110 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
     });
   }
 
+  @override
+  void writeGeneralCodec(
+    SwiftOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    final String codecName = _getCodecName(generatorOptions);
+    final String readerWriterName = '${codecName}ReaderWriter';
+    final String readerName = '${codecName}Reader';
+    final String writerName = '${codecName}Writer';
+
+    final Iterable<EnumeratedType> allTypes = getEnumeratedTypes(root);
+    // Generate Reader
+    indent.write('private class $readerName: FlutterStandardReader ');
+    indent.addScoped('{', '}', () {
+      if (allTypes.isNotEmpty) {
+        indent.write('override func readValue(ofType type: UInt8) -> Any? ');
+        indent.addScoped('{', '}', () {
+          indent.write('switch type ');
+          indent.addScoped('{', '}', nestCount: 0, () {
+            for (final EnumeratedType customType in allTypes) {
+              indent.writeln('case ${customType.enumeration}:');
+              indent.nest(1, () {
+                if (customType.type == CustomTypes.customEnum) {
+                  indent.writeln('var enumResult: ${customType.name}? = nil');
+                  indent.writeln(
+                      'let enumResultAsInt: Int? = nilOrValue(self.readValue() as? Int)');
+                  indent.writeScoped(
+                      'if let enumResultAsInt = enumResultAsInt {', '}', () {
+                    indent.writeln(
+                        'enumResult = ${customType.name}(rawValue: enumResultAsInt)');
+                  });
+                  indent.writeln('return enumResult');
+                } else {
+                  indent.writeln(
+                      'return ${customType.name}.fromList(self.readValue() as! [Any?])');
+                }
+              });
+            }
+            indent.writeln('default:');
+            indent.nest(1, () {
+              indent.writeln('return super.readValue(ofType: type)');
+            });
+          });
+        });
+      }
+    });
+
+    // Generate Writer
+    indent.newln();
+    indent.write('private class $writerName: FlutterStandardWriter ');
+    indent.addScoped('{', '}', () {
+      if (allTypes.isNotEmpty) {
+        indent.write('override func writeValue(_ value: Any) ');
+        indent.addScoped('{', '}', () {
+          indent.write('');
+          for (final EnumeratedType customType in allTypes) {
+            indent.add('if let value = value as? ${customType.name} ');
+            indent.addScoped('{', '} else ', () {
+              indent.writeln('super.writeByte(${customType.enumeration})');
+              if (customType.type == CustomTypes.customEnum) {
+                indent.writeln('super.writeValue(value.rawValue)');
+              } else if (customType.type == CustomTypes.customClass) {
+                indent.writeln('super.writeValue(value.toList())');
+              }
+            }, addTrailingNewline: false);
+          }
+          indent.addScoped('{', '}', () {
+            indent.writeln('super.writeValue(value)');
+          });
+        });
+      }
+    });
+    indent.newln();
+
+    // Generate ReaderWriter
+    indent
+        .write('private class $readerWriterName: FlutterStandardReaderWriter ');
+    indent.addScoped('{', '}', () {
+      indent.write(
+          'override func reader(with data: Data) -> FlutterStandardReader ');
+      indent.addScoped('{', '}', () {
+        indent.writeln('return $readerName(data: data)');
+      });
+      indent.newln();
+      indent.write(
+          'override func writer(with data: NSMutableData) -> FlutterStandardWriter ');
+      indent.addScoped('{', '}', () {
+        indent.writeln('return $writerName(data: data)');
+      });
+    });
+    indent.newln();
+
+    // Generate Codec
+    indent.write(
+        'class $codecName: FlutterStandardMessageCodec, @unchecked Sendable ');
+    indent.addScoped('{', '}', () {
+      indent.writeln(
+          'static let shared = $codecName(readerWriter: $readerWriterName())');
+    });
+    indent.newln();
+  }
+
   @override
   void writeDataClass(
     SwiftOptions generatorOptions,
@@ -216,16 +328,7 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
         final String separator = classDefinition.fields.length > 1 ? ',' : '';
         for (final NamedType field
             in getFieldsInSerializationOrder(classDefinition)) {
-          String toWriteValue = '';
-          final String fieldName = field.name;
-          final String nullsafe = field.type.isNullable ? '?' : '';
-          if (field.type.isEnum) {
-            toWriteValue = '$fieldName$nullsafe.rawValue';
-          } else {
-            toWriteValue = field.name;
-          }
-
-          indent.writeln('$toWriteValue$separator');
+          indent.writeln('${field.name}$separator');
         }
       });
     });
@@ -249,10 +352,11 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
           (int index, final NamedType field) {
         final String listValue = '${varNamePrefix}list[$index]';
 
-        _writeDecodeCasting(
+        _writeGenericCasting(
           indent: indent,
           value: listValue,
           variableName: field.name,
+          fieldType: _swiftTypeForDartType(field.type),
           type: field.type,
         );
       });
@@ -303,11 +407,6 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
     AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
-    if (isCustomCodec) {
-      _writeCodec(indent, api, root);
-    }
-
     const List<String> generatedComments = <String>[
       ' Generated protocol from Pigeon that represents Flutter messages that can be called from Swift.'
     ];
@@ -341,15 +440,11 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
         indent.writeln(
             r'self.messageChannelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""');
       });
-      final String codecName = _getCodecName(api);
-      String codecArgumentString = '';
-      if (getCodecClasses(api, root).isNotEmpty) {
-        codecArgumentString = ', codec: codec';
-        indent.write('var codec: FlutterStandardMessageCodec ');
-        indent.addScoped('{', '}', () {
-          indent.writeln('return $codecName.shared');
-        });
-      }
+      final String codecName = _getCodecName(generatorOptions);
+      indent.write('var codec: $codecName ');
+      indent.addScoped('{', '}', () {
+        indent.writeln('return $codecName.shared');
+      });
 
       for (final Method func in api.methods) {
         addDocumentationComments(
@@ -361,7 +456,6 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
           channelName: makeChannelName(api, func, dartPackageName),
           parameters: func.parameters,
           returnType: func.returnType,
-          codecArgumentString: codecArgumentString,
           swiftFunction: func.swiftFunction,
         );
       }
@@ -383,10 +477,6 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
   }) {
     final String apiName = api.name;
 
-    final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
-    if (isCustomCodec) {
-      _writeCodec(indent, api, root);
-    }
     const List<String> generatedComments = <String>[
       ' Generated protocol from Pigeon that represents a handler of messages from Flutter.'
     ];
@@ -414,14 +504,8 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
         '$_docCommentPrefix Generated setup class from Pigeon to handle messages through the `binaryMessenger`.');
     indent.write('class ${apiName}Setup ');
     indent.addScoped('{', '}', () {
-      final String codecName = _getCodecName(api);
-      indent.writeln('$_docCommentPrefix The codec used by $apiName.');
-      String codecArgumentString = '';
-      if (getCodecClasses(api, root).isNotEmpty) {
-        codecArgumentString = ', codec: codec';
-        indent.writeln(
-            'static var codec: FlutterStandardMessageCodec { $codecName.shared }');
-      }
+      indent.writeln(
+          'static var codec: FlutterStandardMessageCodec { ${_getCodecName(generatorOptions)}.shared }');
       indent.writeln(
           '$_docCommentPrefix Sets up an instance of `$apiName` to handle messages through the `binaryMessenger`.');
       indent.write(
@@ -437,7 +521,6 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
             parameters: method.parameters,
             returnType: method.returnType,
             isAsynchronous: method.isAsynchronous,
-            codecArgumentString: codecArgumentString,
             swiftFunction: method.swiftFunction,
             documentationComments: method.documentationComments,
           );
@@ -446,104 +529,9 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
     });
   }
 
-  /// Writes the codec class will be used for encoding messages for the [api].
-  /// Example:
-  /// private class FooHostApiCodecReader: FlutterStandardReader {...}
-  /// private class FooHostApiCodecWriter: FlutterStandardWriter {...}
-  /// private class FooHostApiCodecReaderWriter: FlutterStandardReaderWriter {...}
-  void _writeCodec(Indent indent, Api api, Root root) {
-    assert(getCodecClasses(api, root).isNotEmpty);
-    final String codecName = _getCodecName(api);
-    final String readerWriterName = '${codecName}ReaderWriter';
-    final String readerName = '${codecName}Reader';
-    final String writerName = '${codecName}Writer';
-
-    // Generate Reader
-    indent.write('private class $readerName: FlutterStandardReader ');
-    indent.addScoped('{', '}', () {
-      if (getCodecClasses(api, root).isNotEmpty) {
-        indent.write('override func readValue(ofType type: UInt8) -> Any? ');
-        indent.addScoped('{', '}', () {
-          indent.write('switch type ');
-          indent.addScoped('{', '}', nestCount: 0, () {
-            for (final EnumeratedClass customClass
-                in getCodecClasses(api, root)) {
-              indent.writeln('case ${customClass.enumeration}:');
-              indent.nest(1, () {
-                indent.writeln(
-                    'return ${customClass.name}.fromList(self.readValue() as! [Any?])');
-              });
-            }
-            indent.writeln('default:');
-            indent.nest(1, () {
-              indent.writeln('return super.readValue(ofType: type)');
-            });
-          });
-        });
-      }
-    });
-
-    // Generate Writer
-    indent.newln();
-    indent.write('private class $writerName: FlutterStandardWriter ');
-    indent.addScoped('{', '}', () {
-      if (getCodecClasses(api, root).isNotEmpty) {
-        indent.write('override func writeValue(_ value: Any) ');
-        indent.addScoped('{', '}', () {
-          indent.write('');
-          for (final EnumeratedClass customClass
-              in getCodecClasses(api, root)) {
-            indent.add('if let value = value as? ${customClass.name} ');
-            indent.addScoped('{', '} else ', () {
-              indent.writeln('super.writeByte(${customClass.enumeration})');
-              indent.writeln('super.writeValue(value.toList())');
-            }, addTrailingNewline: false);
-          }
-          indent.addScoped('{', '}', () {
-            indent.writeln('super.writeValue(value)');
-          });
-        });
-      }
-    });
-    indent.newln();
-
-    // Generate ReaderWriter
-    indent
-        .write('private class $readerWriterName: FlutterStandardReaderWriter ');
-    indent.addScoped('{', '}', () {
-      indent.write(
-          'override func reader(with data: Data) -> FlutterStandardReader ');
-      indent.addScoped('{', '}', () {
-        indent.writeln('return $readerName(data: data)');
-      });
-      indent.newln();
-      indent.write(
-          'override func writer(with data: NSMutableData) -> FlutterStandardWriter ');
-      indent.addScoped('{', '}', () {
-        indent.writeln('return $writerName(data: data)');
-      });
-    });
-    indent.newln();
-
-    // Generate Codec
-    indent.write('class $codecName: FlutterStandardMessageCodec ');
-    indent.addScoped('{', '}', () {
-      indent.writeln(
-          'static let shared = $codecName(readerWriter: $readerWriterName())');
-    });
-    indent.newln();
-  }
-
   String _castForceUnwrap(String value, TypeDeclaration type) {
     assert(!type.isVoid);
-    if (type.isEnum) {
-      String output =
-          '${_swiftTypeForDartType(type)}(rawValue: $value as! Int)!';
-      if (type.isNullable) {
-        output = 'isNullish($value) ? nil : $output';
-      }
-      return output;
-    } else if (type.baseName == 'Object') {
+    if (type.baseName == 'Object') {
       return value + (type.isNullable ? '' : '!');
     } else if (type.baseName == 'int') {
       if (type.isNullable) {
@@ -575,36 +563,6 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
     }
   }
 
-  /// Writes decode and casting code for any type.
-  ///
-  /// Optional parameters should only be used for class decoding.
-  void _writeDecodeCasting({
-    required Indent indent,
-    required String value,
-    required String variableName,
-    required TypeDeclaration type,
-  }) {
-    final String fieldType = _swiftTypeForDartType(type);
-    if (type.isNullable && type.isEnum) {
-      indent.writeln('var $variableName: $fieldType? = nil');
-      indent.writeln(
-          'let ${variableName}EnumVal: Int? = ${_castForceUnwrap(value, const TypeDeclaration(baseName: 'Int', isNullable: true))}');
-      indent.write('if let ${variableName}RawValue = ${variableName}EnumVal ');
-      indent.addScoped('{', '}', () {
-        indent.writeln(
-            '$variableName = $fieldType(rawValue: ${variableName}RawValue)!');
-      });
-    } else {
-      _writeGenericCasting(
-        indent: indent,
-        value: value,
-        variableName: variableName,
-        fieldType: fieldType,
-        type: type,
-      );
-    }
-  }
-
   void _writeIsNullish(Indent indent) {
     indent.newln();
     indent.write('private func isNullish(_ value: Any?) -> Bool ');
@@ -708,7 +666,6 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
     required String channelName,
     required List<Parameter> parameters,
     required TypeDeclaration returnType,
-    required String codecArgumentString,
     required String? swiftFunction,
   }) {
     final String methodSignature = _getMethodSignature(
@@ -723,12 +680,7 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
 
     /// Returns an argument name that can be used in a context where it is possible to collide.
     String getEnumSafeArgumentExpression(int count, NamedType argument) {
-      String enumTag = '';
-      if (argument.type.isEnum) {
-        enumTag = argument.type.isNullable ? '?.rawValue' : '.rawValue';
-      }
-
-      return '${_getArgumentName(count, argument)}Arg$enumTag';
+      return '${_getArgumentName(count, argument)}Arg';
     }
 
     indent.writeScoped('$methodSignature {', '}', () {
@@ -742,7 +694,7 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
       indent.writeln(
           'let channelName: String = "$channelName\\(messageChannelSuffix)"');
       indent.writeln(
-          'let $channel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: binaryMessenger$codecArgumentString)');
+          'let $channel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: binaryMessenger, codec: codec)');
       indent.write('$channel.sendMessage($sendArgument) ');
 
       indent.addScoped('{ response in', '}', () {
@@ -791,7 +743,6 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
     required Iterable<Parameter> parameters,
     required TypeDeclaration returnType,
     required bool isAsynchronous,
-    required String codecArgumentString,
     required String? swiftFunction,
     List<String> documentationComments = const <String>[],
   }) {
@@ -805,7 +756,7 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
     final String varChannelName = '${name}Channel';
     addDocumentationComments(indent, documentationComments, _docCommentSpec);
     indent.writeln(
-        'let $varChannelName = FlutterBasicMessageChannel(name: "$channelName\\(channelSuffix)", binaryMessenger: binaryMessenger$codecArgumentString)');
+        'let $varChannelName = FlutterBasicMessageChannel(name: "$channelName\\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)');
     indent.write('if let api = api ');
     indent.addScoped('{', '}', () {
       indent.write('$varChannelName.setMessageHandler ');
@@ -851,12 +802,9 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
           indent.addScoped('{ result in', '}', () {
             indent.write('switch result ');
             indent.addScoped('{', '}', nestCount: 0, () {
-              final String nullsafe = returnType.isNullable ? '?' : '';
-              final String enumTag =
-                  returnType.isEnum ? '$nullsafe.rawValue' : '';
               indent.writeln('case .success$successVariableInit:');
               indent.nest(1, () {
-                indent.writeln('reply(wrapResult($resultName$enumTag))');
+                indent.writeln('reply(wrapResult($resultName))');
               });
               indent.writeln('case .failure(let error):');
               indent.nest(1, () {
@@ -871,15 +819,8 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
               indent.writeln(call);
               indent.writeln('reply(wrapResult(nil))');
             } else {
-              String enumTag = '';
-              if (returnType.isEnum) {
-                enumTag = '.rawValue';
-              }
-              enumTag = returnType.isNullable && returnType.isEnum
-                  ? '?$enumTag'
-                  : enumTag;
               indent.writeln('let result = $call');
-              indent.writeln('reply(wrapResult(result$enumTag))');
+              indent.writeln('reply(wrapResult(result))');
             }
           }, addTrailingNewline: false);
           indent.addScoped(' catch {', '}', () {
@@ -922,17 +863,22 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
 }
 
 /// Calculates the name of the codec that will be generated for [api].
-String _getCodecName(Api api) => '${api.name}Codec';
+String _getCodecName(SwiftOptions options) {
+  return '${options.fileSpecificClassNameComponent}PigeonCodec';
+}
 
-String _getErrorClassName(SwiftOptions generatorOptions) =>
-    generatorOptions.errorClassName ?? 'PigeonError';
+String _getErrorClassName(SwiftOptions generatorOptions) {
+  return generatorOptions.errorClassName ?? 'PigeonError';
+}
 
-String _getArgumentName(int count, NamedType argument) =>
-    argument.name.isEmpty ? 'arg$count' : argument.name;
+String _getArgumentName(int count, NamedType argument) {
+  return argument.name.isEmpty ? 'arg$count' : argument.name;
+}
 
 /// Returns an argument name that can be used in a context where it is possible to collide.
-String _getSafeArgumentName(int count, NamedType argument) =>
-    '${_getArgumentName(count, argument)}Arg';
+String _getSafeArgumentName(int count, NamedType argument) {
+  return '${_getArgumentName(count, argument)}Arg';
+}
 
 String _camelCase(String text) {
   final String pascal = text.split('_').map((String part) {
diff --git a/packages/pigeon/pigeons/core_tests.dart b/packages/pigeon/pigeons/core_tests.dart
index 50f8d476014..b4dc3fdfb02 100644
--- a/packages/pigeon/pigeons/core_tests.dart
+++ b/packages/pigeon/pigeons/core_tests.dart
@@ -23,11 +23,21 @@ class AllTypes {
     required this.a4ByteArray,
     required this.a8ByteArray,
     required this.aFloatArray,
-    this.list = const <Object?>[],
-    this.aMap = const <String?, Object?>{},
     this.anEnum = AnEnum.one,
     this.aString = '',
     this.anObject = 0,
+
+    // Lists
+    // This name is in a different format than the others to ensure that name
+    // collision with the work 'list' doesn't occur in the generated files.
+    required this.list,
+    required this.stringList,
+    required this.intList,
+    required this.doubleList,
+    required this.boolList,
+
+    // Maps
+    required this.map,
   });
 
   bool aBool;
@@ -38,15 +48,21 @@ class AllTypes {
   Int32List a4ByteArray;
   Int64List a8ByteArray;
   Float64List aFloatArray;
-  // This name is in a different format than the others to ensure that name
-  // collision with the work 'list' doesn't occur in the generated files.
-  // ignore: always_specify_types, strict_raw_type
-  List list;
-  // ignore: always_specify_types, strict_raw_type
-  Map aMap;
   AnEnum anEnum;
   String aString;
   Object anObject;
+
+  // Lists
+  // ignore: strict_raw_type, always_specify_types
+  List list;
+  List<String?> stringList;
+  List<int?> intList;
+  List<double?> doubleList;
+  List<bool?> boolList;
+
+  // Maps
+  // ignore: strict_raw_type, always_specify_types
+  Map map;
 }
 
 /// A class containing all supported nullable types.
@@ -61,8 +77,6 @@ class AllNullableTypes {
     this.aNullable4ByteArray,
     this.aNullable8ByteArray,
     this.aNullableFloatArray,
-    this.aNullableList,
-    this.aNullableMap,
     this.nullableNestedList,
     this.nullableMapWithAnnotations,
     this.nullableMapWithObject,
@@ -70,6 +84,17 @@ class AllNullableTypes {
     this.aNullableString,
     this.aNullableObject,
     this.allNullableTypes,
+
+    // Lists
+    this.list,
+    this.stringList,
+    this.intList,
+    this.doubleList,
+    this.boolList,
+    this.nestedClassList,
+
+    //Maps
+    this.map,
   );
 
   bool? aNullableBool;
@@ -80,10 +105,6 @@ class AllNullableTypes {
   Int32List? aNullable4ByteArray;
   Int64List? aNullable8ByteArray;
   Float64List? aNullableFloatArray;
-  // ignore: always_specify_types, strict_raw_type
-  List? aNullableList;
-  // ignore: always_specify_types, strict_raw_type
-  Map? aNullableMap;
   List<List<bool?>?>? nullableNestedList;
   Map<String?, String?>? nullableMapWithAnnotations;
   Map<String?, Object?>? nullableMapWithObject;
@@ -91,6 +112,19 @@ class AllNullableTypes {
   String? aNullableString;
   Object? aNullableObject;
   AllNullableTypes? allNullableTypes;
+
+  // Lists
+  // ignore: strict_raw_type, always_specify_types
+  List? list;
+  List<String?>? stringList;
+  List<int?>? intList;
+  List<double?>? doubleList;
+  List<bool?>? boolList;
+  List<AllNullableTypes?>? nestedClassList;
+
+  // Maps
+  // ignore: strict_raw_type, always_specify_types
+  Map? map;
 }
 
 /// The primary purpose for this class is to ensure coverage of Swift structs
@@ -106,14 +140,22 @@ class AllNullableTypesWithoutRecursion {
     this.aNullable4ByteArray,
     this.aNullable8ByteArray,
     this.aNullableFloatArray,
-    this.aNullableList,
-    this.aNullableMap,
     this.nullableNestedList,
     this.nullableMapWithAnnotations,
     this.nullableMapWithObject,
     this.aNullableEnum,
     this.aNullableString,
     this.aNullableObject,
+
+    // Lists
+    this.list,
+    this.stringList,
+    this.intList,
+    this.doubleList,
+    this.boolList,
+
+    //Maps
+    this.map,
   );
 
   bool? aNullableBool;
@@ -124,16 +166,24 @@ class AllNullableTypesWithoutRecursion {
   Int32List? aNullable4ByteArray;
   Int64List? aNullable8ByteArray;
   Float64List? aNullableFloatArray;
-  // ignore: always_specify_types, strict_raw_type
-  List? aNullableList;
-  // ignore: always_specify_types, strict_raw_type
-  Map? aNullableMap;
   List<List<bool?>?>? nullableNestedList;
   Map<String?, String?>? nullableMapWithAnnotations;
   Map<String?, Object?>? nullableMapWithObject;
   AnEnum? aNullableEnum;
   String? aNullableString;
   Object? aNullableObject;
+
+  // Lists
+  // ignore: strict_raw_type, always_specify_types
+  List? list;
+  List<String?>? stringList;
+  List<int?>? intList;
+  List<double?>? doubleList;
+  List<bool?>? boolList;
+
+  // Maps
+  // ignore: strict_raw_type, always_specify_types
+  Map? map;
 }
 
 /// A class for testing nested class handling.
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
index 2c8f609bf78..d0b5b600836 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
@@ -198,6 +198,45 @@ public void setAFloatArray(@NonNull double[] setterArg) {
       this.aFloatArray = setterArg;
     }
 
+    private @NonNull AnEnum anEnum;
+
+    public @NonNull AnEnum getAnEnum() {
+      return anEnum;
+    }
+
+    public void setAnEnum(@NonNull AnEnum setterArg) {
+      if (setterArg == null) {
+        throw new IllegalStateException("Nonnull field \"anEnum\" is null.");
+      }
+      this.anEnum = setterArg;
+    }
+
+    private @NonNull String aString;
+
+    public @NonNull String getAString() {
+      return aString;
+    }
+
+    public void setAString(@NonNull String setterArg) {
+      if (setterArg == null) {
+        throw new IllegalStateException("Nonnull field \"aString\" is null.");
+      }
+      this.aString = setterArg;
+    }
+
+    private @NonNull Object anObject;
+
+    public @NonNull Object getAnObject() {
+      return anObject;
+    }
+
+    public void setAnObject(@NonNull Object setterArg) {
+      if (setterArg == null) {
+        throw new IllegalStateException("Nonnull field \"anObject\" is null.");
+      }
+      this.anObject = setterArg;
+    }
+
     private @NonNull List<Object> list;
 
     public @NonNull List<Object> getList() {
@@ -211,56 +250,69 @@ public void setList(@NonNull List<Object> setterArg) {
       this.list = setterArg;
     }
 
-    private @NonNull Map<Object, Object> aMap;
+    private @NonNull List<String> stringList;
 
-    public @NonNull Map<Object, Object> getAMap() {
-      return aMap;
+    public @NonNull List<String> getStringList() {
+      return stringList;
     }
 
-    public void setAMap(@NonNull Map<Object, Object> setterArg) {
+    public void setStringList(@NonNull List<String> setterArg) {
       if (setterArg == null) {
-        throw new IllegalStateException("Nonnull field \"aMap\" is null.");
+        throw new IllegalStateException("Nonnull field \"stringList\" is null.");
       }
-      this.aMap = setterArg;
+      this.stringList = setterArg;
     }
 
-    private @NonNull AnEnum anEnum;
+    private @NonNull List<Long> intList;
 
-    public @NonNull AnEnum getAnEnum() {
-      return anEnum;
+    public @NonNull List<Long> getIntList() {
+      return intList;
     }
 
-    public void setAnEnum(@NonNull AnEnum setterArg) {
+    public void setIntList(@NonNull List<Long> setterArg) {
       if (setterArg == null) {
-        throw new IllegalStateException("Nonnull field \"anEnum\" is null.");
+        throw new IllegalStateException("Nonnull field \"intList\" is null.");
       }
-      this.anEnum = setterArg;
+      this.intList = setterArg;
     }
 
-    private @NonNull String aString;
+    private @NonNull List<Double> doubleList;
 
-    public @NonNull String getAString() {
-      return aString;
+    public @NonNull List<Double> getDoubleList() {
+      return doubleList;
     }
 
-    public void setAString(@NonNull String setterArg) {
+    public void setDoubleList(@NonNull List<Double> setterArg) {
       if (setterArg == null) {
-        throw new IllegalStateException("Nonnull field \"aString\" is null.");
+        throw new IllegalStateException("Nonnull field \"doubleList\" is null.");
       }
-      this.aString = setterArg;
+      this.doubleList = setterArg;
     }
 
-    private @NonNull Object anObject;
+    private @NonNull List<Boolean> boolList;
 
-    public @NonNull Object getAnObject() {
-      return anObject;
+    public @NonNull List<Boolean> getBoolList() {
+      return boolList;
     }
 
-    public void setAnObject(@NonNull Object setterArg) {
+    public void setBoolList(@NonNull List<Boolean> setterArg) {
       if (setterArg == null) {
-        throw new IllegalStateException("Nonnull field \"anObject\" is null.");
+        throw new IllegalStateException("Nonnull field \"boolList\" is null.");
       }
-      this.anObject = setterArg;
+      this.boolList = setterArg;
+    }
+
+    private @NonNull Map<Object, Object> map;
+
+    public @NonNull Map<Object, Object> getMap() {
+      return map;
+    }
+
+    public void setMap(@NonNull Map<Object, Object> setterArg) {
+      if (setterArg == null) {
+        throw new IllegalStateException("Nonnull field \"map\" is null.");
+      }
+      this.map = setterArg;
     }
 
     /** Constructor is non-public to enforce null safety; use Builder. */
@@ -332,6 +384,30 @@ public static final class Builder {
         return this;
       }
 
+      private @Nullable AnEnum anEnum;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setAnEnum(@NonNull AnEnum setterArg) {
+        this.anEnum = setterArg;
+        return this;
+      }
+
+      private @Nullable String aString;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setAString(@NonNull String setterArg) {
+        this.aString = setterArg;
+        return this;
+      }
+
+      private @Nullable Object anObject;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setAnObject(@NonNull Object setterArg) {
+        this.anObject = setterArg;
+        return this;
+      }
+
       private @Nullable List<Object> list;
 
       @CanIgnoreReturnValue
@@ -340,35 +416,43 @@ public static final class Builder {
         return this;
       }
 
-      private @Nullable Map<Object, Object> aMap;
+      private @Nullable List<String> stringList;
 
       @CanIgnoreReturnValue
-      public @NonNull Builder setAMap(@NonNull Map<Object, Object> setterArg) {
-        this.aMap = setterArg;
+      public @NonNull Builder setStringList(@NonNull List<String> setterArg) {
+        this.stringList = setterArg;
         return this;
       }
 
-      private @Nullable AnEnum anEnum;
+      private @Nullable List<Long> intList;
 
       @CanIgnoreReturnValue
-      public @NonNull Builder setAnEnum(@NonNull AnEnum setterArg) {
-        this.anEnum = setterArg;
+      public @NonNull Builder setIntList(@NonNull List<Long> setterArg) {
+        this.intList = setterArg;
         return this;
       }
 
-      private @Nullable String aString;
+      private @Nullable List<Double> doubleList;
 
       @CanIgnoreReturnValue
-      public @NonNull Builder setAString(@NonNull String setterArg) {
-        this.aString = setterArg;
+      public @NonNull Builder setDoubleList(@NonNull List<Double> setterArg) {
+        this.doubleList = setterArg;
         return this;
       }
 
-      private @Nullable Object anObject;
+      private @Nullable List<Boolean> boolList;
 
       @CanIgnoreReturnValue
-      public @NonNull Builder setAnObject(@NonNull Object setterArg) {
-        this.anObject = setterArg;
+      public @NonNull Builder setBoolList(@NonNull List<Boolean> setterArg) {
+        this.boolList = setterArg;
+        return this;
+      }
+
+      private @Nullable Map<Object, Object> map;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setMap(@NonNull Map<Object, Object> setterArg) {
+        this.map = setterArg;
         return this;
       }
 
@@ -382,18 +466,22 @@ public static final class Builder {
         pigeonReturn.setA4ByteArray(a4ByteArray);
         pigeonReturn.setA8ByteArray(a8ByteArray);
         pigeonReturn.setAFloatArray(aFloatArray);
-        pigeonReturn.setList(list);
-        pigeonReturn.setAMap(aMap);
         pigeonReturn.setAnEnum(anEnum);
         pigeonReturn.setAString(aString);
         pigeonReturn.setAnObject(anObject);
+        pigeonReturn.setList(list);
+        pigeonReturn.setStringList(stringList);
+        pigeonReturn.setIntList(intList);
+        pigeonReturn.setDoubleList(doubleList);
+        pigeonReturn.setBoolList(boolList);
+        pigeonReturn.setMap(map);
         return pigeonReturn;
       }
     }
 
     @NonNull
     ArrayList<Object> toList() {
-      ArrayList<Object> toListResult = new ArrayList<Object>(13);
+      ArrayList<Object> toListResult = new ArrayList<Object>(17);
       toListResult.add(aBool);
       toListResult.add(anInt);
       toListResult.add(anInt64);
@@ -402,11 +490,15 @@ ArrayList<Object> toList() {
       toListResult.add(a4ByteArray);
       toListResult.add(a8ByteArray);
       toListResult.add(aFloatArray);
-      toListResult.add(list);
-      toListResult.add(aMap);
-      toListResult.add(anEnum == null ? null : anEnum.index);
+      toListResult.add(anEnum);
       toListResult.add(aString);
       toListResult.add(anObject);
+      toListResult.add(list);
+      toListResult.add(stringList);
+      toListResult.add(intList);
+      toListResult.add(doubleList);
+      toListResult.add(boolList);
+      toListResult.add(map);
       return toListResult;
     }
 
@@ -432,16 +524,24 @@ ArrayList<Object> toList() {
       pigeonResult.setA8ByteArray((long[]) a8ByteArray);
       Object aFloatArray = __pigeon_list.get(7);
       pigeonResult.setAFloatArray((double[]) aFloatArray);
-      Object list = __pigeon_list.get(8);
-      pigeonResult.setList((List<Object>) list);
-      Object aMap = __pigeon_list.get(9);
-      pigeonResult.setAMap((Map<Object, Object>) aMap);
-      Object anEnum = __pigeon_list.get(10);
-      pigeonResult.setAnEnum(AnEnum.values()[(int) anEnum]);
-      Object aString = __pigeon_list.get(11);
+      Object anEnum = __pigeon_list.get(8);
+      pigeonResult.setAnEnum((AnEnum) anEnum);
+      Object aString = __pigeon_list.get(9);
       pigeonResult.setAString((String) aString);
-      Object anObject = __pigeon_list.get(12);
+      Object anObject = __pigeon_list.get(10);
       pigeonResult.setAnObject(anObject);
+      Object list = __pigeon_list.get(11);
+      pigeonResult.setList((List<Object>) list);
+      Object stringList = __pigeon_list.get(12);
+      pigeonResult.setStringList((List<String>) stringList);
+      Object intList = __pigeon_list.get(13);
+      pigeonResult.setIntList((List<Long>) intList);
+      Object doubleList = __pigeon_list.get(14);
+      pigeonResult.setDoubleList((List<Double>) doubleList);
+      Object boolList = __pigeon_list.get(15);
+      pigeonResult.setBoolList((List<Boolean>) boolList);
+      Object map = __pigeon_list.get(16);
+      pigeonResult.setMap((Map<Object, Object>) map);
       return pigeonResult;
     }
   }
@@ -532,26 +632,6 @@ public void setANullableFloatArray(@Nullable double[] setterArg) {
       this.aNullableFloatArray = setterArg;
     }
 
-    private @Nullable List<Object> aNullableList;
-
-    public @Nullable List<Object> getANullableList() {
-      return aNullableList;
-    }
-
-    public void setANullableList(@Nullable List<Object> setterArg) {
-      this.aNullableList = setterArg;
-    }
-
-    private @Nullable Map<Object, Object> aNullableMap;
-
-    public @Nullable Map<Object, Object> getANullableMap() {
-      return aNullableMap;
-    }
-
-    public void setANullableMap(@Nullable Map<Object, Object> setterArg) {
-      this.aNullableMap = setterArg;
-    }
-
     private @Nullable List<List<Boolean>> nullableNestedList;
 
     public @Nullable List<List<Boolean>> getNullableNestedList() {
@@ -622,6 +702,76 @@ public void setAllNullableTypes(@Nullable AllNullableTypes setterArg) {
       this.allNullableTypes = setterArg;
     }
 
+    private @Nullable List<Object> list;
+
+    public @Nullable List<Object> getList() {
+      return list;
+    }
+
+    public void setList(@Nullable List<Object> setterArg) {
+      this.list = setterArg;
+    }
+
+    private @Nullable List<String> stringList;
+
+    public @Nullable List<String> getStringList() {
+      return stringList;
+    }
+
+    public void setStringList(@Nullable List<String> setterArg) {
+      this.stringList = setterArg;
+    }
+
+    private @Nullable List<Long> intList;
+
+    public @Nullable List<Long> getIntList() {
+      return intList;
+    }
+
+    public void setIntList(@Nullable List<Long> setterArg) {
+      this.intList = setterArg;
+    }
+
+    private @Nullable List<Double> doubleList;
+
+    public @Nullable List<Double> getDoubleList() {
+      return doubleList;
+    }
+
+    public void setDoubleList(@Nullable List<Double> setterArg) {
+      this.doubleList = setterArg;
+    }
+
+    private @Nullable List<Boolean> boolList;
+
+    public @Nullable List<Boolean> getBoolList() {
+      return boolList;
+    }
+
+    public void setBoolList(@Nullable List<Boolean> setterArg) {
+      this.boolList = setterArg;
+    }
+
+    private @Nullable List<AllNullableTypes> nestedClassList;
+
+    public @Nullable List<AllNullableTypes> getNestedClassList() {
+      return nestedClassList;
+    }
+
+    public void setNestedClassList(@Nullable List<AllNullableTypes> setterArg) {
+      this.nestedClassList = setterArg;
+    }
+
+    private @Nullable Map<Object, Object> map;
+
+    public @Nullable Map<Object, Object> getMap() {
+      return map;
+    }
+
+    public void setMap(@Nullable Map<Object, Object> setterArg) {
+      this.map = setterArg;
+    }
+
     public static final class Builder {
 
       private @Nullable Boolean aNullableBool;
@@ -688,22 +838,6 @@ public static final class Builder {
         return this;
       }
 
-      private @Nullable List<Object> aNullableList;
-
-      @CanIgnoreReturnValue
-      public @NonNull Builder setANullableList(@Nullable List<Object> setterArg) {
-        this.aNullableList = setterArg;
-        return this;
-      }
-
-      private @Nullable Map<Object, Object> aNullableMap;
-
-      @CanIgnoreReturnValue
-      public @NonNull Builder setANullableMap(@Nullable Map<Object, Object> setterArg) {
-        this.aNullableMap = setterArg;
-        return this;
-      }
-
       private @Nullable List<List<Boolean>> nullableNestedList;
 
       @CanIgnoreReturnValue
@@ -761,6 +895,62 @@ public static final class Builder {
         return this;
       }
 
+      private @Nullable List<Object> list;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setList(@Nullable List<Object> setterArg) {
+        this.list = setterArg;
+        return this;
+      }
+
+      private @Nullable List<String> stringList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setStringList(@Nullable List<String> setterArg) {
+        this.stringList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<Long> intList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setIntList(@Nullable List<Long> setterArg) {
+        this.intList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<Double> doubleList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setDoubleList(@Nullable List<Double> setterArg) {
+        this.doubleList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<Boolean> boolList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setBoolList(@Nullable List<Boolean> setterArg) {
+        this.boolList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<AllNullableTypes> nestedClassList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setNestedClassList(@Nullable List<AllNullableTypes> setterArg) {
+        this.nestedClassList = setterArg;
+        return this;
+      }
+
+      private @Nullable Map<Object, Object> map;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setMap(@Nullable Map<Object, Object> setterArg) {
+        this.map = setterArg;
+        return this;
+      }
+
       public @NonNull AllNullableTypes build() {
         AllNullableTypes pigeonReturn = new AllNullableTypes();
         pigeonReturn.setANullableBool(aNullableBool);
@@ -771,8 +961,6 @@ public static final class Builder {
         pigeonReturn.setANullable4ByteArray(aNullable4ByteArray);
         pigeonReturn.setANullable8ByteArray(aNullable8ByteArray);
         pigeonReturn.setANullableFloatArray(aNullableFloatArray);
-        pigeonReturn.setANullableList(aNullableList);
-        pigeonReturn.setANullableMap(aNullableMap);
         pigeonReturn.setNullableNestedList(nullableNestedList);
         pigeonReturn.setNullableMapWithAnnotations(nullableMapWithAnnotations);
         pigeonReturn.setNullableMapWithObject(nullableMapWithObject);
@@ -780,13 +968,20 @@ public static final class Builder {
         pigeonReturn.setANullableString(aNullableString);
         pigeonReturn.setANullableObject(aNullableObject);
         pigeonReturn.setAllNullableTypes(allNullableTypes);
+        pigeonReturn.setList(list);
+        pigeonReturn.setStringList(stringList);
+        pigeonReturn.setIntList(intList);
+        pigeonReturn.setDoubleList(doubleList);
+        pigeonReturn.setBoolList(boolList);
+        pigeonReturn.setNestedClassList(nestedClassList);
+        pigeonReturn.setMap(map);
         return pigeonReturn;
       }
     }
 
     @NonNull
     ArrayList<Object> toList() {
-      ArrayList<Object> toListResult = new ArrayList<Object>(17);
+      ArrayList<Object> toListResult = new ArrayList<Object>(22);
       toListResult.add(aNullableBool);
       toListResult.add(aNullableInt);
       toListResult.add(aNullableInt64);
@@ -795,15 +990,20 @@ ArrayList<Object> toList() {
       toListResult.add(aNullable4ByteArray);
       toListResult.add(aNullable8ByteArray);
       toListResult.add(aNullableFloatArray);
-      toListResult.add(aNullableList);
-      toListResult.add(aNullableMap);
       toListResult.add(nullableNestedList);
       toListResult.add(nullableMapWithAnnotations);
       toListResult.add(nullableMapWithObject);
-      toListResult.add(aNullableEnum == null ? null : aNullableEnum.index);
+      toListResult.add(aNullableEnum);
       toListResult.add(aNullableString);
       toListResult.add(aNullableObject);
       toListResult.add(allNullableTypes);
+      toListResult.add(list);
+      toListResult.add(stringList);
+      toListResult.add(intList);
+      toListResult.add(doubleList);
+      toListResult.add(boolList);
+      toListResult.add(nestedClassList);
+      toListResult.add(map);
       return toListResult;
     }
 
@@ -833,25 +1033,34 @@ ArrayList<Object> toList() {
       pigeonResult.setANullable8ByteArray((long[]) aNullable8ByteArray);
       Object aNullableFloatArray = __pigeon_list.get(7);
       pigeonResult.setANullableFloatArray((double[]) aNullableFloatArray);
-      Object aNullableList = __pigeon_list.get(8);
-      pigeonResult.setANullableList((List<Object>) aNullableList);
-      Object aNullableMap = __pigeon_list.get(9);
-      pigeonResult.setANullableMap((Map<Object, Object>) aNullableMap);
-      Object nullableNestedList = __pigeon_list.get(10);
+      Object nullableNestedList = __pigeon_list.get(8);
       pigeonResult.setNullableNestedList((List<List<Boolean>>) nullableNestedList);
-      Object nullableMapWithAnnotations = __pigeon_list.get(11);
+      Object nullableMapWithAnnotations = __pigeon_list.get(9);
       pigeonResult.setNullableMapWithAnnotations((Map<String, String>) nullableMapWithAnnotations);
-      Object nullableMapWithObject = __pigeon_list.get(12);
+      Object nullableMapWithObject = __pigeon_list.get(10);
       pigeonResult.setNullableMapWithObject((Map<String, Object>) nullableMapWithObject);
-      Object aNullableEnum = __pigeon_list.get(13);
-      pigeonResult.setANullableEnum(
-          aNullableEnum == null ? null : AnEnum.values()[(int) aNullableEnum]);
-      Object aNullableString = __pigeon_list.get(14);
+      Object aNullableEnum = __pigeon_list.get(11);
+      pigeonResult.setANullableEnum((AnEnum) aNullableEnum);
+      Object aNullableString = __pigeon_list.get(12);
       pigeonResult.setANullableString((String) aNullableString);
-      Object aNullableObject = __pigeon_list.get(15);
+      Object aNullableObject = __pigeon_list.get(13);
       pigeonResult.setANullableObject(aNullableObject);
-      Object allNullableTypes = __pigeon_list.get(16);
+      Object allNullableTypes = __pigeon_list.get(14);
       pigeonResult.setAllNullableTypes((AllNullableTypes) allNullableTypes);
+      Object list = __pigeon_list.get(15);
+      pigeonResult.setList((List<Object>) list);
+      Object stringList = __pigeon_list.get(16);
+      pigeonResult.setStringList((List<String>) stringList);
+      Object intList = __pigeon_list.get(17);
+      pigeonResult.setIntList((List<Long>) intList);
+      Object doubleList = __pigeon_list.get(18);
+      pigeonResult.setDoubleList((List<Double>) doubleList);
+      Object boolList = __pigeon_list.get(19);
+      pigeonResult.setBoolList((List<Boolean>) boolList);
+      Object nestedClassList = __pigeon_list.get(20);
+      pigeonResult.setNestedClassList((List<AllNullableTypes>) nestedClassList);
+      Object map = __pigeon_list.get(21);
+      pigeonResult.setMap((Map<Object, Object>) map);
       return pigeonResult;
     }
   }
@@ -943,26 +1152,6 @@ public void setANullableFloatArray(@Nullable double[] setterArg) {
       this.aNullableFloatArray = setterArg;
     }
 
-    private @Nullable List<Object> aNullableList;
-
-    public @Nullable List<Object> getANullableList() {
-      return aNullableList;
-    }
-
-    public void setANullableList(@Nullable List<Object> setterArg) {
-      this.aNullableList = setterArg;
-    }
-
-    private @Nullable Map<Object, Object> aNullableMap;
-
-    public @Nullable Map<Object, Object> getANullableMap() {
-      return aNullableMap;
-    }
-
-    public void setANullableMap(@Nullable Map<Object, Object> setterArg) {
-      this.aNullableMap = setterArg;
-    }
-
     private @Nullable List<List<Boolean>> nullableNestedList;
 
     public @Nullable List<List<Boolean>> getNullableNestedList() {
@@ -1023,6 +1212,66 @@ public void setANullableObject(@Nullable Object setterArg) {
       this.aNullableObject = setterArg;
     }
 
+    private @Nullable List<Object> list;
+
+    public @Nullable List<Object> getList() {
+      return list;
+    }
+
+    public void setList(@Nullable List<Object> setterArg) {
+      this.list = setterArg;
+    }
+
+    private @Nullable List<String> stringList;
+
+    public @Nullable List<String> getStringList() {
+      return stringList;
+    }
+
+    public void setStringList(@Nullable List<String> setterArg) {
+      this.stringList = setterArg;
+    }
+
+    private @Nullable List<Long> intList;
+
+    public @Nullable List<Long> getIntList() {
+      return intList;
+    }
+
+    public void setIntList(@Nullable List<Long> setterArg) {
+      this.intList = setterArg;
+    }
+
+    private @Nullable List<Double> doubleList;
+
+    public @Nullable List<Double> getDoubleList() {
+      return doubleList;
+    }
+
+    public void setDoubleList(@Nullable List<Double> setterArg) {
+      this.doubleList = setterArg;
+    }
+
+    private @Nullable List<Boolean> boolList;
+
+    public @Nullable List<Boolean> getBoolList() {
+      return boolList;
+    }
+
+    public void setBoolList(@Nullable List<Boolean> setterArg) {
+      this.boolList = setterArg;
+    }
+
+    private @Nullable Map<Object, Object> map;
+
+    public @Nullable Map<Object, Object> getMap() {
+      return map;
+    }
+
+    public void setMap(@Nullable Map<Object, Object> setterArg) {
+      this.map = setterArg;
+    }
+
     public static final class Builder {
 
       private @Nullable Boolean aNullableBool;
@@ -1089,22 +1338,6 @@ public static final class Builder {
         return this;
       }
 
-      private @Nullable List<Object> aNullableList;
-
-      @CanIgnoreReturnValue
-      public @NonNull Builder setANullableList(@Nullable List<Object> setterArg) {
-        this.aNullableList = setterArg;
-        return this;
-      }
-
-      private @Nullable Map<Object, Object> aNullableMap;
-
-      @CanIgnoreReturnValue
-      public @NonNull Builder setANullableMap(@Nullable Map<Object, Object> setterArg) {
-        this.aNullableMap = setterArg;
-        return this;
-      }
-
       private @Nullable List<List<Boolean>> nullableNestedList;
 
       @CanIgnoreReturnValue
@@ -1154,6 +1387,54 @@ public static final class Builder {
         return this;
       }
 
+      private @Nullable List<Object> list;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setList(@Nullable List<Object> setterArg) {
+        this.list = setterArg;
+        return this;
+      }
+
+      private @Nullable List<String> stringList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setStringList(@Nullable List<String> setterArg) {
+        this.stringList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<Long> intList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setIntList(@Nullable List<Long> setterArg) {
+        this.intList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<Double> doubleList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setDoubleList(@Nullable List<Double> setterArg) {
+        this.doubleList = setterArg;
+        return this;
+      }
+
+      private @Nullable List<Boolean> boolList;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setBoolList(@Nullable List<Boolean> setterArg) {
+        this.boolList = setterArg;
+        return this;
+      }
+
+      private @Nullable Map<Object, Object> map;
+
+      @CanIgnoreReturnValue
+      public @NonNull Builder setMap(@Nullable Map<Object, Object> setterArg) {
+        this.map = setterArg;
+        return this;
+      }
+
       public @NonNull AllNullableTypesWithoutRecursion build() {
         AllNullableTypesWithoutRecursion pigeonReturn = new AllNullableTypesWithoutRecursion();
         pigeonReturn.setANullableBool(aNullableBool);
@@ -1164,21 +1445,25 @@ public static final class Builder {
         pigeonReturn.setANullable4ByteArray(aNullable4ByteArray);
         pigeonReturn.setANullable8ByteArray(aNullable8ByteArray);
         pigeonReturn.setANullableFloatArray(aNullableFloatArray);
-        pigeonReturn.setANullableList(aNullableList);
-        pigeonReturn.setANullableMap(aNullableMap);
         pigeonReturn.setNullableNestedList(nullableNestedList);
         pigeonReturn.setNullableMapWithAnnotations(nullableMapWithAnnotations);
         pigeonReturn.setNullableMapWithObject(nullableMapWithObject);
         pigeonReturn.setANullableEnum(aNullableEnum);
         pigeonReturn.setANullableString(aNullableString);
         pigeonReturn.setANullableObject(aNullableObject);
+        pigeonReturn.setList(list);
+        pigeonReturn.setStringList(stringList);
+        pigeonReturn.setIntList(intList);
+        pigeonReturn.setDoubleList(doubleList);
+        pigeonReturn.setBoolList(boolList);
+        pigeonReturn.setMap(map);
         return pigeonReturn;
       }
     }
 
     @NonNull
     ArrayList<Object> toList() {
-      ArrayList<Object> toListResult = new ArrayList<Object>(16);
+      ArrayList<Object> toListResult = new ArrayList<Object>(20);
       toListResult.add(aNullableBool);
       toListResult.add(aNullableInt);
       toListResult.add(aNullableInt64);
@@ -1187,14 +1472,18 @@ ArrayList<Object> toList() {
       toListResult.add(aNullable4ByteArray);
       toListResult.add(aNullable8ByteArray);
       toListResult.add(aNullableFloatArray);
-      toListResult.add(aNullableList);
-      toListResult.add(aNullableMap);
       toListResult.add(nullableNestedList);
       toListResult.add(nullableMapWithAnnotations);
       toListResult.add(nullableMapWithObject);
-      toListResult.add(aNullableEnum == null ? null : aNullableEnum.index);
+      toListResult.add(aNullableEnum);
       toListResult.add(aNullableString);
       toListResult.add(aNullableObject);
+      toListResult.add(list);
+      toListResult.add(stringList);
+      toListResult.add(intList);
+      toListResult.add(doubleList);
+      toListResult.add(boolList);
+      toListResult.add(map);
       return toListResult;
     }
 
@@ -1225,23 +1514,30 @@ ArrayList<Object> toList() {
       pigeonResult.setANullable8ByteArray((long[]) aNullable8ByteArray);
       Object aNullableFloatArray = __pigeon_list.get(7);
       pigeonResult.setANullableFloatArray((double[]) aNullableFloatArray);
-      Object aNullableList = __pigeon_list.get(8);
-      pigeonResult.setANullableList((List<Object>) aNullableList);
-      Object aNullableMap = __pigeon_list.get(9);
-      pigeonResult.setANullableMap((Map<Object, Object>) aNullableMap);
-      Object nullableNestedList = __pigeon_list.get(10);
+      Object nullableNestedList = __pigeon_list.get(8);
       pigeonResult.setNullableNestedList((List<List<Boolean>>) nullableNestedList);
-      Object nullableMapWithAnnotations = __pigeon_list.get(11);
+      Object nullableMapWithAnnotations = __pigeon_list.get(9);
       pigeonResult.setNullableMapWithAnnotations((Map<String, String>) nullableMapWithAnnotations);
-      Object nullableMapWithObject = __pigeon_list.get(12);
+      Object nullableMapWithObject = __pigeon_list.get(10);
       pigeonResult.setNullableMapWithObject((Map<String, Object>) nullableMapWithObject);
-      Object aNullableEnum = __pigeon_list.get(13);
-      pigeonResult.setANullableEnum(
-          aNullableEnum == null ? null : AnEnum.values()[(int) aNullableEnum]);
-      Object aNullableString = __pigeon_list.get(14);
+      Object aNullableEnum = __pigeon_list.get(11);
+      pigeonResult.setANullableEnum((AnEnum) aNullableEnum);
+      Object aNullableString = __pigeon_list.get(12);
       pigeonResult.setANullableString((String) aNullableString);
-      Object aNullableObject = __pigeon_list.get(15);
+      Object aNullableObject = __pigeon_list.get(13);
       pigeonResult.setANullableObject(aNullableObject);
+      Object list = __pigeon_list.get(14);
+      pigeonResult.setList((List<Object>) list);
+      Object stringList = __pigeon_list.get(15);
+      pigeonResult.setStringList((List<String>) stringList);
+      Object intList = __pigeon_list.get(16);
+      pigeonResult.setIntList((List<Long>) intList);
+      Object doubleList = __pigeon_list.get(17);
+      pigeonResult.setDoubleList((List<Double>) doubleList);
+      Object boolList = __pigeon_list.get(18);
+      pigeonResult.setBoolList((List<Boolean>) boolList);
+      Object map = __pigeon_list.get(19);
+      pigeonResult.setMap((Map<Object, Object>) map);
       return pigeonResult;
     }
   }
@@ -1399,49 +1695,27 @@ ArrayList<Object> toList() {
     }
   }
 
-  /** Asynchronous error handling return type for non-nullable API method returns. */
-  public interface Result<T> {
-    /** Success case callback method for handling returns. */
-    void success(@NonNull T result);
-
-    /** Failure case callback method for handling errors. */
-    void error(@NonNull Throwable error);
-  }
-  /** Asynchronous error handling return type for nullable API method returns. */
-  public interface NullableResult<T> {
-    /** Success case callback method for handling returns. */
-    void success(@Nullable T result);
-
-    /** Failure case callback method for handling errors. */
-    void error(@NonNull Throwable error);
-  }
-  /** Asynchronous error handling return type for void API method returns. */
-  public interface VoidResult {
-    /** Success case callback method for handling returns. */
-    void success();
-
-    /** Failure case callback method for handling errors. */
-    void error(@NonNull Throwable error);
-  }
+  private static class PigeonCodec extends StandardMessageCodec {
+    public static final PigeonCodec INSTANCE = new PigeonCodec();
 
-  private static class HostIntegrationCoreApiCodec extends StandardMessageCodec {
-    public static final HostIntegrationCoreApiCodec INSTANCE = new HostIntegrationCoreApiCodec();
-
-    private HostIntegrationCoreApiCodec() {}
+    private PigeonCodec() {}
 
     @Override
     protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) {
       switch (type) {
-        case (byte) 128:
-          return AllClassesWrapper.fromList((ArrayList<Object>) readValue(buffer));
         case (byte) 129:
-          return AllNullableTypes.fromList((ArrayList<Object>) readValue(buffer));
+          return AllTypes.fromList((ArrayList<Object>) readValue(buffer));
         case (byte) 130:
-          return AllNullableTypesWithoutRecursion.fromList((ArrayList<Object>) readValue(buffer));
+          return AllNullableTypes.fromList((ArrayList<Object>) readValue(buffer));
         case (byte) 131:
-          return AllTypes.fromList((ArrayList<Object>) readValue(buffer));
+          return AllNullableTypesWithoutRecursion.fromList((ArrayList<Object>) readValue(buffer));
         case (byte) 132:
+          return AllClassesWrapper.fromList((ArrayList<Object>) readValue(buffer));
+        case (byte) 133:
           return TestMessage.fromList((ArrayList<Object>) readValue(buffer));
+        case (byte) 134:
+          Object value = readValue(buffer);
+          return value == null ? null : AnEnum.values()[(int) value];
         default:
           return super.readValueOfType(type, buffer);
       }
@@ -1449,27 +1723,54 @@ protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) {
 
     @Override
     protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) {
-      if (value instanceof AllClassesWrapper) {
-        stream.write(128);
-        writeValue(stream, ((AllClassesWrapper) value).toList());
-      } else if (value instanceof AllNullableTypes) {
+      if (value instanceof AllTypes) {
         stream.write(129);
+        writeValue(stream, ((AllTypes) value).toList());
+      } else if (value instanceof AllNullableTypes) {
+        stream.write(130);
         writeValue(stream, ((AllNullableTypes) value).toList());
       } else if (value instanceof AllNullableTypesWithoutRecursion) {
-        stream.write(130);
-        writeValue(stream, ((AllNullableTypesWithoutRecursion) value).toList());
-      } else if (value instanceof AllTypes) {
         stream.write(131);
-        writeValue(stream, ((AllTypes) value).toList());
-      } else if (value instanceof TestMessage) {
+        writeValue(stream, ((AllNullableTypesWithoutRecursion) value).toList());
+      } else if (value instanceof AllClassesWrapper) {
         stream.write(132);
+        writeValue(stream, ((AllClassesWrapper) value).toList());
+      } else if (value instanceof TestMessage) {
+        stream.write(133);
         writeValue(stream, ((TestMessage) value).toList());
+      } else if (value instanceof AnEnum) {
+        stream.write(134);
+        writeValue(stream, value == null ? null : ((AnEnum) value).index);
       } else {
         super.writeValue(stream, value);
       }
     }
   }
 
+  /** Asynchronous error handling return type for non-nullable API method returns. */
+  public interface Result<T> {
+    /** Success case callback method for handling returns. */
+    void success(@NonNull T result);
+
+    /** Failure case callback method for handling errors. */
+    void error(@NonNull Throwable error);
+  }
+  /** Asynchronous error handling return type for nullable API method returns. */
+  public interface NullableResult<T> {
+    /** Success case callback method for handling returns. */
+    void success(@Nullable T result);
+
+    /** Failure case callback method for handling errors. */
+    void error(@NonNull Throwable error);
+  }
+  /** Asynchronous error handling return type for void API method returns. */
+  public interface VoidResult {
+    /** Success case callback method for handling returns. */
+    void success();
+
+    /** Failure case callback method for handling errors. */
+    void error(@NonNull Throwable error);
+  }
   /**
    * The core interface that each host language plugin must implement in platform_test integration
    * tests.
@@ -1725,7 +2026,7 @@ void callFlutterEchoNullableEnum(
 
     /** The codec used by HostIntegrationCoreApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return HostIntegrationCoreApiCodec.INSTANCE;
+      return PigeonCodec.INSTANCE;
     }
     /**
      * Sets up an instance of `HostIntegrationCoreApi` to handle messages through the
@@ -2109,10 +2410,10 @@ static void setUp(
               (message, reply) -> {
                 ArrayList<Object> wrapped = new ArrayList<Object>();
                 ArrayList<Object> args = (ArrayList<Object>) message;
-                AnEnum anEnumArg = AnEnum.values()[(int) args.get(0)];
+                AnEnum anEnumArg = (AnEnum) args.get(0);
                 try {
                   AnEnum output = api.echoEnum(anEnumArg);
-                  wrapped.add(0, output.index);
+                  wrapped.add(0, output);
                 } catch (Throwable exception) {
                   ArrayList<Object> wrappedError = wrapError(exception);
                   wrapped = wrappedError;
@@ -2594,10 +2895,10 @@ static void setUp(
               (message, reply) -> {
                 ArrayList<Object> wrapped = new ArrayList<Object>();
                 ArrayList<Object> args = (ArrayList<Object>) message;
-                AnEnum anEnumArg = args.get(0) == null ? null : AnEnum.values()[(int) args.get(0)];
+                AnEnum anEnumArg = (AnEnum) args.get(0);
                 try {
                   AnEnum output = api.echoNullableEnum(anEnumArg);
-                  wrapped.add(0, output == null ? null : output.index);
+                  wrapped.add(0, output);
                 } catch (Throwable exception) {
                   ArrayList<Object> wrappedError = wrapError(exception);
                   wrapped = wrappedError;
@@ -2960,11 +3261,11 @@ public void error(Throwable error) {
               (message, reply) -> {
                 ArrayList<Object> wrapped = new ArrayList<Object>();
                 ArrayList<Object> args = (ArrayList<Object>) message;
-                AnEnum anEnumArg = AnEnum.values()[(int) args.get(0)];
+                AnEnum anEnumArg = (AnEnum) args.get(0);
                 Result<AnEnum> resultCallback =
                     new Result<AnEnum>() {
                       public void success(AnEnum result) {
-                        wrapped.add(0, result.index);
+                        wrapped.add(0, result);
                         reply.reply(wrapped);
                       }
 
@@ -3437,11 +3738,11 @@ public void error(Throwable error) {
               (message, reply) -> {
                 ArrayList<Object> wrapped = new ArrayList<Object>();
                 ArrayList<Object> args = (ArrayList<Object>) message;
-                AnEnum anEnumArg = args.get(0) == null ? null : AnEnum.values()[(int) args.get(0)];
+                AnEnum anEnumArg = (AnEnum) args.get(0);
                 NullableResult<AnEnum> resultCallback =
                     new NullableResult<AnEnum>() {
                       public void success(AnEnum result) {
-                        wrapped.add(0, result == null ? null : result.index);
+                        wrapped.add(0, result);
                         reply.reply(wrapped);
                       }
 
@@ -3957,11 +4258,11 @@ public void error(Throwable error) {
               (message, reply) -> {
                 ArrayList<Object> wrapped = new ArrayList<Object>();
                 ArrayList<Object> args = (ArrayList<Object>) message;
-                AnEnum anEnumArg = AnEnum.values()[(int) args.get(0)];
+                AnEnum anEnumArg = (AnEnum) args.get(0);
                 Result<AnEnum> resultCallback =
                     new Result<AnEnum>() {
                       public void success(AnEnum result) {
-                        wrapped.add(0, result.index);
+                        wrapped.add(0, result);
                         reply.reply(wrapped);
                       }
 
@@ -4214,11 +4515,11 @@ public void error(Throwable error) {
               (message, reply) -> {
                 ArrayList<Object> wrapped = new ArrayList<Object>();
                 ArrayList<Object> args = (ArrayList<Object>) message;
-                AnEnum anEnumArg = args.get(0) == null ? null : AnEnum.values()[(int) args.get(0)];
+                AnEnum anEnumArg = (AnEnum) args.get(0);
                 NullableResult<AnEnum> resultCallback =
                     new NullableResult<AnEnum>() {
                       public void success(AnEnum result) {
-                        wrapped.add(0, result == null ? null : result.index);
+                        wrapped.add(0, result);
                         reply.reply(wrapped);
                       }
 
@@ -4268,54 +4569,6 @@ public void error(Throwable error) {
       }
     }
   }
-
-  private static class FlutterIntegrationCoreApiCodec extends StandardMessageCodec {
-    public static final FlutterIntegrationCoreApiCodec INSTANCE =
-        new FlutterIntegrationCoreApiCodec();
-
-    private FlutterIntegrationCoreApiCodec() {}
-
-    @Override
-    protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) {
-      switch (type) {
-        case (byte) 128:
-          return AllClassesWrapper.fromList((ArrayList<Object>) readValue(buffer));
-        case (byte) 129:
-          return AllNullableTypes.fromList((ArrayList<Object>) readValue(buffer));
-        case (byte) 130:
-          return AllNullableTypesWithoutRecursion.fromList((ArrayList<Object>) readValue(buffer));
-        case (byte) 131:
-          return AllTypes.fromList((ArrayList<Object>) readValue(buffer));
-        case (byte) 132:
-          return TestMessage.fromList((ArrayList<Object>) readValue(buffer));
-        default:
-          return super.readValueOfType(type, buffer);
-      }
-    }
-
-    @Override
-    protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) {
-      if (value instanceof AllClassesWrapper) {
-        stream.write(128);
-        writeValue(stream, ((AllClassesWrapper) value).toList());
-      } else if (value instanceof AllNullableTypes) {
-        stream.write(129);
-        writeValue(stream, ((AllNullableTypes) value).toList());
-      } else if (value instanceof AllNullableTypesWithoutRecursion) {
-        stream.write(130);
-        writeValue(stream, ((AllNullableTypesWithoutRecursion) value).toList());
-      } else if (value instanceof AllTypes) {
-        stream.write(131);
-        writeValue(stream, ((AllTypes) value).toList());
-      } else if (value instanceof TestMessage) {
-        stream.write(132);
-        writeValue(stream, ((TestMessage) value).toList());
-      } else {
-        super.writeValue(stream, value);
-      }
-    }
-  }
-
   /**
    * The core interface that the Dart platform_test code implements for host integration tests to
    * call into.
@@ -4339,7 +4592,7 @@ public FlutterIntegrationCoreApi(
     /** Public interface for sending reply. */
     /** The codec used by FlutterIntegrationCoreApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return FlutterIntegrationCoreApiCodec.INSTANCE;
+      return PigeonCodec.INSTANCE;
     }
     /**
      * A no-op function taking no arguments and returning no value, to sanity test basic calling.
@@ -4853,7 +5106,7 @@ public void echoEnum(@NonNull AnEnum anEnumArg, @NonNull Result<AnEnum> result)
       BasicMessageChannel<Object> channel =
           new BasicMessageChannel<>(binaryMessenger, channelName, getCodec());
       channel.send(
-          new ArrayList<Object>(Collections.singletonList(anEnumArg.index)),
+          new ArrayList<Object>(Collections.singletonList(anEnumArg)),
           channelReply -> {
             if (channelReply instanceof List) {
               List<Object> listReply = (List<Object>) channelReply;
@@ -4871,7 +5124,7 @@ public void echoEnum(@NonNull AnEnum anEnumArg, @NonNull Result<AnEnum> result)
                         ""));
               } else {
                 @SuppressWarnings("ConstantConditions")
-                AnEnum output = AnEnum.values()[(int) listReply.get(0)];
+                AnEnum output = (AnEnum) listReply.get(0);
                 result.success(output);
               }
             } else {
@@ -5092,8 +5345,7 @@ public void echoNullableEnum(
       BasicMessageChannel<Object> channel =
           new BasicMessageChannel<>(binaryMessenger, channelName, getCodec());
       channel.send(
-          new ArrayList<Object>(
-              Collections.singletonList(anEnumArg == null ? null : anEnumArg.index)),
+          new ArrayList<Object>(Collections.singletonList(anEnumArg)),
           channelReply -> {
             if (channelReply instanceof List) {
               List<Object> listReply = (List<Object>) channelReply;
@@ -5105,8 +5357,7 @@ public void echoNullableEnum(
                         (String) listReply.get(2)));
               } else {
                 @SuppressWarnings("ConstantConditions")
-                AnEnum output =
-                    listReply.get(0) == null ? null : AnEnum.values()[(int) listReply.get(0)];
+                AnEnum output = (AnEnum) listReply.get(0);
                 result.success(output);
               }
             } else {
@@ -5189,7 +5440,7 @@ public interface HostTrivialApi {
 
     /** The codec used by HostTrivialApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return new StandardMessageCodec();
+      return PigeonCodec.INSTANCE;
     }
     /** Sets up an instance of `HostTrivialApi` to handle messages through the `binaryMessenger`. */
     static void setUp(@NonNull BinaryMessenger binaryMessenger, @Nullable HostTrivialApi api) {
@@ -5240,7 +5491,7 @@ public interface HostSmallApi {
 
     /** The codec used by HostSmallApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return new StandardMessageCodec();
+      return PigeonCodec.INSTANCE;
     }
     /** Sets up an instance of `HostSmallApi` to handle messages through the `binaryMessenger`. */
     static void setUp(@NonNull BinaryMessenger binaryMessenger, @Nullable HostSmallApi api) {
@@ -5316,33 +5567,6 @@ public void error(Throwable error) {
       }
     }
   }
-
-  private static class FlutterSmallApiCodec extends StandardMessageCodec {
-    public static final FlutterSmallApiCodec INSTANCE = new FlutterSmallApiCodec();
-
-    private FlutterSmallApiCodec() {}
-
-    @Override
-    protected Object readValueOfType(byte type, @NonNull ByteBuffer buffer) {
-      switch (type) {
-        case (byte) 128:
-          return TestMessage.fromList((ArrayList<Object>) readValue(buffer));
-        default:
-          return super.readValueOfType(type, buffer);
-      }
-    }
-
-    @Override
-    protected void writeValue(@NonNull ByteArrayOutputStream stream, Object value) {
-      if (value instanceof TestMessage) {
-        stream.write(128);
-        writeValue(stream, ((TestMessage) value).toList());
-      } else {
-        super.writeValue(stream, value);
-      }
-    }
-  }
-
   /**
    * A simple API called in some unit tests.
    *
@@ -5365,7 +5589,7 @@ public FlutterSmallApi(
     /** Public interface for sending reply. */
     /** The codec used by FlutterSmallApi. */
     static @NonNull MessageCodec<Object> getCodec() {
-      return FlutterSmallApiCodec.INSTANCE;
+      return PigeonCodec.INSTANCE;
     }
 
     public void echoWrappedList(@NonNull TestMessage msgArg, @NonNull Result<TestMessage> result) {
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/AllDatatypesTest.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/AllDatatypesTest.java
index b15c2bfa682..c5f7857915a 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/AllDatatypesTest.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/AllDatatypesTest.java
@@ -33,13 +33,17 @@ void compareAllTypes(AllTypes firstTypes, AllTypes secondTypes) {
     assertArrayEquals(firstTypes.getA4ByteArray(), secondTypes.getA4ByteArray());
     assertArrayEquals(firstTypes.getA8ByteArray(), secondTypes.getA8ByteArray());
     assertTrue(floatArraysEqual(firstTypes.getAFloatArray(), secondTypes.getAFloatArray()));
+    assertEquals(firstTypes.getAnEnum(), secondTypes.getAnEnum());
+    assertEquals(firstTypes.getAnObject(), secondTypes.getAnObject());
     assertArrayEquals(firstTypes.getList().toArray(), secondTypes.getList().toArray());
+    assertArrayEquals(firstTypes.getStringList().toArray(), secondTypes.getStringList().toArray());
+    assertArrayEquals(firstTypes.getBoolList().toArray(), secondTypes.getBoolList().toArray());
+    assertArrayEquals(firstTypes.getDoubleList().toArray(), secondTypes.getDoubleList().toArray());
+    assertArrayEquals(firstTypes.getIntList().toArray(), secondTypes.getIntList().toArray());
     assertArrayEquals(
-        firstTypes.getAMap().keySet().toArray(), secondTypes.getAMap().keySet().toArray());
+        firstTypes.getMap().keySet().toArray(), secondTypes.getMap().keySet().toArray());
     assertArrayEquals(
-        firstTypes.getAMap().values().toArray(), secondTypes.getAMap().values().toArray());
-    assertEquals(firstTypes.getAnEnum(), secondTypes.getAnEnum());
-    assertEquals(firstTypes.getAnObject(), secondTypes.getAnObject());
+        firstTypes.getMap().values().toArray(), secondTypes.getMap().values().toArray());
   }
 
   void compareAllNullableTypes(AllNullableTypes firstTypes, AllNullableTypes secondTypes) {
@@ -57,18 +61,19 @@ void compareAllNullableTypes(AllNullableTypes firstTypes, AllNullableTypes secon
     assertTrue(
         floatArraysEqual(
             firstTypes.getANullableFloatArray(), secondTypes.getANullableFloatArray()));
-    assertArrayEquals(
-        firstTypes.getANullableList().toArray(), secondTypes.getANullableList().toArray());
-    assertArrayEquals(
-        firstTypes.getANullableMap().keySet().toArray(),
-        secondTypes.getANullableMap().keySet().toArray());
-    assertArrayEquals(
-        firstTypes.getANullableMap().values().toArray(),
-        secondTypes.getANullableMap().values().toArray());
     assertArrayEquals(
         firstTypes.getNullableMapWithObject().values().toArray(),
         secondTypes.getNullableMapWithObject().values().toArray());
     assertEquals(firstTypes.getANullableObject(), secondTypes.getANullableObject());
+    assertArrayEquals(firstTypes.getList().toArray(), secondTypes.getList().toArray());
+    assertArrayEquals(firstTypes.getStringList().toArray(), secondTypes.getStringList().toArray());
+    assertArrayEquals(firstTypes.getBoolList().toArray(), secondTypes.getBoolList().toArray());
+    assertArrayEquals(firstTypes.getDoubleList().toArray(), secondTypes.getDoubleList().toArray());
+    assertArrayEquals(firstTypes.getIntList().toArray(), secondTypes.getIntList().toArray());
+    assertArrayEquals(
+        firstTypes.getMap().keySet().toArray(), secondTypes.getMap().keySet().toArray());
+    assertArrayEquals(
+        firstTypes.getMap().values().toArray(), secondTypes.getMap().values().toArray());
   }
 
   @Test
@@ -105,9 +110,13 @@ public void success(AllNullableTypes result) {
             assertNull(everything.getANullable4ByteArray());
             assertNull(everything.getANullable8ByteArray());
             assertNull(everything.getANullableFloatArray());
-            assertNull(everything.getANullableList());
-            assertNull(everything.getANullableMap());
             assertNull(everything.getNullableMapWithObject());
+            assertNull(everything.getList());
+            assertNull(everything.getDoubleList());
+            assertNull(everything.getIntList());
+            assertNull(everything.getStringList());
+            assertNull(everything.getBoolList());
+            assertNull(everything.getMap());
           }
 
           public void error(Throwable error) {
@@ -154,10 +163,14 @@ public void hasValues() {
             .setA4ByteArray(new int[] {1, 2, 3, 4})
             .setA8ByteArray(new long[] {1, 2, 3, 4})
             .setAFloatArray(new double[] {0.5, 0.25, 1.5, 1.25})
-            .setList(Arrays.asList(new int[] {1, 2, 3}))
-            .setAMap(makeMap("hello", 1234))
             .setAnEnum(CoreTests.AnEnum.ONE)
             .setAnObject(0)
+            .setBoolList(Arrays.asList(new Boolean[] {true, false}))
+            .setDoubleList(Arrays.asList(new Double[] {0.5, 0.25, 1.5, 1.25}))
+            .setIntList(Arrays.asList(new Long[] {1l, 2l, 3l, 4l}))
+            .setList(Arrays.asList(new int[] {1, 2, 3, 4}))
+            .setStringList(Arrays.asList(new String[] {"string", "another one"}))
+            .setMap(makeMap("hello", 1234))
             .build();
 
     AllNullableTypes everything =
@@ -170,10 +183,14 @@ public void hasValues() {
             .setANullable4ByteArray(new int[] {1, 2, 3, 4})
             .setANullable8ByteArray(new long[] {1, 2, 3, 4})
             .setANullableFloatArray(new double[] {0.5, 0.25, 1.5, 1.25})
-            .setANullableList(Arrays.asList(new int[] {1, 2, 3}))
-            .setANullableMap(makeMap("hello", 1234))
             .setNullableMapWithObject(makeStringMap("hello", 1234))
             .setANullableObject(0)
+            .setBoolList(Arrays.asList(new Boolean[] {true, false}))
+            .setDoubleList(Arrays.asList(new Double[] {0.5, 0.25, 1.5, 1.25}))
+            .setIntList(Arrays.asList(new Long[] {1l, 2l, 3l, 4l}))
+            .setList(Arrays.asList(new int[] {1, 2, 3, 4}))
+            .setStringList(Arrays.asList(new String[] {"string", "another one"}))
+            .setMap(makeMap("hello", 1234))
             .build();
 
     BinaryMessenger binaryMessenger = mock(BinaryMessenger.class);
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/NullFieldsTest.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/NullFieldsTest.java
index 621a8a64f83..545ab13121d 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/NullFieldsTest.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/NullFieldsTest.java
@@ -166,7 +166,7 @@ public void replyToMapWithValues() {
     assertEquals(list.get(1), "error");
     assertEquals(list.get(2), Arrays.asList(1L, 2L, 3L));
     assertEquals(list.get(3), reply.getRequest());
-    assertEquals(list.get(4), NullFields.NullFieldsSearchReplyType.SUCCESS.ordinal());
+    assertEquals(list.get(4), NullFields.NullFieldsSearchReplyType.SUCCESS);
   }
 
   @Test
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/project.pbxproj b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/project.pbxproj
index 4fced65c686..d922c88e3d4 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/project.pbxproj
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/project.pbxproj
@@ -266,7 +266,7 @@
 		97C146E61CF9000F007C117D /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 1430;
+				LastUpgradeCheck = 1510;
 				ORGANIZATIONNAME = "";
 				TargetAttributes = {
 					33AA165E291EB8B600ECBEEB = {
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
index 28b953fd126..d19488d45ea 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1430"
+   LastUpgradeVersion = "1510"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AllDatatypesTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AllDatatypesTest.m
index bcc8c4972a7..a605276d159 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AllDatatypesTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AllDatatypesTest.m
@@ -19,7 +19,7 @@ @implementation AllDatatypesTest
 - (void)testAllNull {
   FLTAllNullableTypes *everything = [[FLTAllNullableTypes alloc] init];
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:FLTFlutterIntegrationCoreApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   FLTFlutterIntegrationCoreApi *api =
       [[FLTFlutterIntegrationCoreApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
@@ -33,8 +33,12 @@ - (void)testAllNull {
                    XCTAssertNil(result.aNullable4ByteArray);
                    XCTAssertNil(result.aNullable8ByteArray);
                    XCTAssertNil(result.aNullableFloatArray);
-                   XCTAssertNil(result.aNullableList);
-                   XCTAssertNil(result.aNullableMap);
+                   XCTAssertNil(result.list);
+                   XCTAssertNil(result.boolList);
+                   XCTAssertNil(result.intList);
+                   XCTAssertNil(result.doubleList);
+                   XCTAssertNil(result.stringList);
+                   XCTAssertNil(result.map);
                    [expectation fulfill];
                  }];
   [self waitForExpectations:@[ expectation ] timeout:1.0];
@@ -54,11 +58,15 @@ - (void)testAllEquals {
       typedDataWithInt64:[@"12345678" dataUsingEncoding:NSUTF8StringEncoding]];
   everything.aNullableFloatArray = [FlutterStandardTypedData
       typedDataWithFloat64:[@"12345678" dataUsingEncoding:NSUTF8StringEncoding]];
-  everything.aNullableList = @[ @(1), @(2) ];
-  everything.aNullableMap = @{@"hello" : @(1234)};
   everything.nullableMapWithObject = @{@"hello" : @(1234), @"goodbye" : @"world"};
+  everything.boolList = @[ @YES, @NO ];
+  everything.intList = @[ @1, @2 ];
+  everything.doubleList = @[ @1.1, @2.2 ];
+  everything.stringList = @[ @"string", @"another one" ];
+  everything.list = @[ @"string", @1 ];
+  everything.map = @{@"hello" : @(1234), @"goodbye" : @"world"};
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:FLTFlutterIntegrationCoreApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   FLTFlutterIntegrationCoreApi *api =
       [[FLTFlutterIntegrationCoreApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
@@ -76,10 +84,14 @@ - (void)testAllEquals {
                                          everything.aNullable8ByteArray.data);
                    XCTAssertEqualObjects(result.aNullableFloatArray.data,
                                          everything.aNullableFloatArray.data);
-                   XCTAssertEqualObjects(result.aNullableList, everything.aNullableList);
-                   XCTAssertEqualObjects(result.aNullableMap, everything.aNullableMap);
                    XCTAssertEqualObjects(result.nullableMapWithObject,
                                          everything.nullableMapWithObject);
+                   XCTAssertEqualObjects(result.list, everything.list);
+                   XCTAssertEqualObjects(result.boolList, everything.boolList);
+                   XCTAssertEqualObjects(result.intList, everything.intList);
+                   XCTAssertEqualObjects(result.doubleList, everything.doubleList);
+                   XCTAssertEqualObjects(result.stringList, everything.stringList);
+                   XCTAssertEqualObjects(result.map, everything.map);
                    [expectation fulfill];
                  }];
   [self waitForExpectations:@[ expectation ] timeout:1.0];
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AsyncHandlersTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AsyncHandlersTest.m
index 660911086c3..af3e4770350 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AsyncHandlersTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/AsyncHandlersTest.m
@@ -42,7 +42,7 @@ @implementation AsyncHandlersTest
 
 - (void)testAsyncHost2Flutter {
   MockBinaryMessenger *binaryMessenger =
-      [[MockBinaryMessenger alloc] initWithCodec:FLTFlutterIntegrationCoreApiGetCodec()];
+      [[MockBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   NSString *value = @"Test";
   binaryMessenger.result = value;
   FLTFlutterIntegrationCoreApi *flutterApi =
@@ -58,7 +58,7 @@ - (void)testAsyncHost2Flutter {
 
 - (void)testAsyncFlutter2HostVoidVoid {
   MockBinaryMessenger *binaryMessenger =
-      [[MockBinaryMessenger alloc] initWithCodec:FLTHostSmallApiGetCodec()];
+      [[MockBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   MockHostSmallApi *mockHostSmallApi = [[MockHostSmallApi alloc] init];
   SetUpFLTHostSmallApi(binaryMessenger, mockHostSmallApi);
   NSString *channelName = @"dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.voidVoid";
@@ -66,7 +66,7 @@ - (void)testAsyncFlutter2HostVoidVoid {
 
   XCTestExpectation *expectation = [self expectationWithDescription:@"voidvoid callback"];
   binaryMessenger.handlers[channelName](nil, ^(NSData *data) {
-    NSArray *outputList = [binaryMessenger.codec decode:data];
+    NSArray<id> *outputList = [binaryMessenger.codec decode:data];
     XCTAssertEqualObjects(outputList[0], [NSNull null]);
     [expectation fulfill];
   });
@@ -75,7 +75,7 @@ - (void)testAsyncFlutter2HostVoidVoid {
 
 - (void)testAsyncFlutter2HostVoidVoidError {
   MockBinaryMessenger *binaryMessenger =
-      [[MockBinaryMessenger alloc] initWithCodec:FLTHostSmallApiGetCodec()];
+      [[MockBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   MockHostSmallApi *mockHostSmallApi = [[MockHostSmallApi alloc] init];
   mockHostSmallApi.voidVoidError = [FlutterError errorWithCode:@"code"
                                                        message:@"message"
@@ -86,7 +86,7 @@ - (void)testAsyncFlutter2HostVoidVoidError {
 
   XCTestExpectation *expectation = [self expectationWithDescription:@"voidvoid callback"];
   binaryMessenger.handlers[channelName](nil, ^(NSData *data) {
-    NSArray *outputList = [binaryMessenger.codec decode:data];
+    NSArray<id> *outputList = [binaryMessenger.codec decode:data];
     XCTAssertNotNil(outputList);
     XCTAssertEqualObjects(outputList[0], mockHostSmallApi.voidVoidError.code);
     [expectation fulfill];
@@ -96,7 +96,7 @@ - (void)testAsyncFlutter2HostVoidVoidError {
 
 - (void)testAsyncFlutter2Host {
   MockBinaryMessenger *binaryMessenger =
-      [[MockBinaryMessenger alloc] initWithCodec:FLTHostSmallApiGetCodec()];
+      [[MockBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   MockHostSmallApi *mockHostSmallApi = [[MockHostSmallApi alloc] init];
   NSString *value = @"Test";
   mockHostSmallApi.output = value;
@@ -107,7 +107,7 @@ - (void)testAsyncFlutter2Host {
   NSData *inputEncoded = [binaryMessenger.codec encode:@[ value ]];
   XCTestExpectation *expectation = [self expectationWithDescription:@"echo callback"];
   binaryMessenger.handlers[channelName](inputEncoded, ^(NSData *data) {
-    NSArray *outputList = [binaryMessenger.codec decode:data];
+    NSArray<id> *outputList = [binaryMessenger.codec decode:data];
     NSString *output = outputList[0];
     XCTAssertEqualObjects(output, value);
     [expectation fulfill];
@@ -117,7 +117,7 @@ - (void)testAsyncFlutter2Host {
 
 - (void)testAsyncFlutter2HostError {
   MockBinaryMessenger *binaryMessenger =
-      [[MockBinaryMessenger alloc] initWithCodec:FLTHostSmallApiGetCodec()];
+      [[MockBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   MockHostSmallApi *mockHostSmallApi = [[MockHostSmallApi alloc] init];
   SetUpFLTHostSmallApi(binaryMessenger, mockHostSmallApi);
   NSString *channelName = @"dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo";
@@ -126,7 +126,7 @@ - (void)testAsyncFlutter2HostError {
   NSData *inputEncoded = [binaryMessenger.codec encode:@[ @"Test" ]];
   XCTestExpectation *expectation = [self expectationWithDescription:@"echo callback"];
   binaryMessenger.handlers[channelName](inputEncoded, ^(NSData *data) {
-    NSArray *outputList = [binaryMessenger.codec decode:data];
+    NSArray<id> *outputList = [binaryMessenger.codec decode:data];
     XCTAssertNotNil(outputList);
     XCTAssertEqualObjects(outputList[0], @"hey");
     XCTAssertEqualObjects(outputList[1], @"ho");
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EchoMessenger.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EchoMessenger.m
index 95db64e8cee..fe925b1729d 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EchoMessenger.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EchoMessenger.m
@@ -29,7 +29,7 @@ - (void)sendOnChannel:(nonnull NSString *)channel message:(NSData *_Nullable)mes
 - (void)sendOnChannel:(nonnull NSString *)channel
               message:(NSData *_Nullable)message
           binaryReply:(FlutterBinaryReply _Nullable)callback {
-  NSArray *args = [self.codec decode:message];
+  NSArray<id> *args = [self.codec decode:message];
   callback([self.codec encode:args]);
 }
 
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EnumTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EnumTest.m
index 7a3350ee9e0..a9d14641011 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EnumTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/EnumTest.m
@@ -21,7 +21,7 @@ - (void)testEcho {
   PGNEnumStateBox *stateBox = [[PGNEnumStateBox alloc] initWithValue:PGNEnumStateError];
   data.state = stateBox;
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PGNEnumApi2HostGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:PGNGetEnumCodec()];
   PGNEnumApi2Flutter *api = [[PGNEnumApi2Flutter alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   [api echoData:data
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.h b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.h
index e05042ea27e..99bda6b508e 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.h
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.h
@@ -7,7 +7,7 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-typedef id _Nullable (^HandlerBinaryMessengerHandler)(NSArray *_Nonnull args);
+typedef id _Nullable (^HandlerBinaryMessengerHandler)(NSArray<id> *_Nonnull args);
 
 /// A FlutterBinaryMessenger that calls a supplied method when a call is
 /// invoked.
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.m
index 05c38f82dfe..281bfa5976a 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/HandlerBinaryMessenger.m
@@ -32,7 +32,7 @@ - (void)sendOnChannel:(nonnull NSString *)channel message:(NSData *_Nullable)mes
 - (void)sendOnChannel:(nonnull NSString *)channel
               message:(NSData *_Nullable)message
           binaryReply:(FlutterBinaryReply _Nullable)callback {
-  NSArray *args = [self.codec decode:message];
+  NSArray<id> *args = [self.codec decode:message];
   id result = self.handler(args);
   callback([self.codec encode:result]);
 }
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/ListTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/ListTest.m
index 54bea7f0e78..882f3c6bedf 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/ListTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/ListTest.m
@@ -22,7 +22,7 @@ - (void)testListInList {
   inside.testList = @[ @1, @2, @3 ];
   top.testList = @[ inside ];
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:FLTFlutterSmallApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:FLTGetCoreTestsCodec()];
   FLTFlutterSmallApi *api = [[FLTFlutterSmallApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   [api echoWrappedList:top
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/MultipleArityTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/MultipleArityTest.m
index 6e0541554fb..5f82547f308 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/MultipleArityTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/MultipleArityTest.m
@@ -18,8 +18,8 @@ @implementation MultipleAritytest
 
 - (void)testSimple {
   HandlerBinaryMessenger *binaryMessenger = [[HandlerBinaryMessenger alloc]
-      initWithCodec:MultipleArityHostApiGetCodec()
-            handler:^id _Nullable(NSArray *_Nonnull args) {
+      initWithCodec:GetMultipleArityCodec()
+            handler:^id _Nullable(NSArray<id> *_Nonnull args) {
               return @[ @([args[0] intValue] - [args[1] intValue]) ];
             }];
   MultipleArityFlutterApi *api =
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullFieldsTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullFieldsTest.m
index 48b48b61a68..d4dacda1c75 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullFieldsTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullFieldsTest.m
@@ -11,14 +11,14 @@
 
 ///////////////////////////////////////////////////////////////////////////////////////////
 @interface NullFieldsSearchRequest ()
-+ (NullFieldsSearchRequest *)fromList:(NSArray *)list;
-- (NSArray *)toList;
++ (NullFieldsSearchRequest *)fromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 ///////////////////////////////////////////////////////////////////////////////////////////
 @interface NullFieldsSearchReply ()
-+ (NullFieldsSearchReply *)fromList:(NSArray *)list;
-- (NSArray *)toList;
++ (NullFieldsSearchReply *)fromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 ///////////////////////////////////////////////////////////////////////////////////////////
@@ -39,7 +39,7 @@ - (void)testMakeWithValues {
                                                                request:request
                                                                   type:typeWrapper];
 
-  NSArray *indices = @[ @1, @2, @3 ];
+  NSArray<id> *indices = @[ @1, @2, @3 ];
   XCTAssertEqualObjects(@"result", reply.result);
   XCTAssertEqualObjects(@"error", reply.error);
   XCTAssertEqualObjects(indices, reply.indices);
@@ -66,7 +66,7 @@ - (void)testMakeReplyWithNulls {
 }
 
 - (void)testRequestFromListWithValues {
-  NSArray *list = @[
+  NSArray<id> *list = @[
     @"hello",
     @1,
   ];
@@ -75,7 +75,7 @@ - (void)testRequestFromListWithValues {
 }
 
 - (void)testRequestFromListWithNulls {
-  NSArray *list = @[
+  NSArray<id> *list = @[
     [NSNull null],
     @1,
   ];
@@ -84,18 +84,24 @@ - (void)testRequestFromListWithNulls {
 }
 
 - (void)testReplyFromListWithValues {
-  NSArray *indices = @[ @1, @2, @3 ];
-  NullFieldsSearchRequest *request = [NullFieldsSearchRequest makeWithQuery:@"hello" identifier:1];
-
   NullFieldsSearchReplyTypeBox *typeWrapper =
       [[NullFieldsSearchReplyTypeBox alloc] initWithValue:NullFieldsSearchReplyTypeSuccess];
-  NullFieldsSearchReply *input = [NullFieldsSearchReply makeWithResult:@"result"
-                                                                 error:@"error"
-                                                               indices:indices
-                                                               request:request
-                                                                  type:typeWrapper];
 
-  NullFieldsSearchReply *reply = [NullFieldsSearchReply fromList:[input toList]];
+  NSArray<id> *listRequest = @[
+    @"hello",
+    @1,
+  ];
+  NSArray<id> *listReply = @[
+    @"result",
+    @"error",
+    @[ @1, @2, @3 ],
+    [NullFieldsSearchRequest fromList:listRequest],
+    typeWrapper,
+  ];
+
+  NSArray<id> *indices = @[ @1, @2, @3 ];
+  NullFieldsSearchReply *reply = [NullFieldsSearchReply fromList:listReply];
+
   XCTAssertEqualObjects(@"result", reply.result);
   XCTAssertEqualObjects(@"error", reply.error);
   XCTAssertEqualObjects(indices, reply.indices);
@@ -104,7 +110,7 @@ - (void)testReplyFromListWithValues {
 }
 
 - (void)testReplyFromListWithNulls {
-  NSArray *list = @[
+  NSArray<id> *list = @[
     [NSNull null],
     [NSNull null],
     [NSNull null],
@@ -121,13 +127,13 @@ - (void)testReplyFromListWithNulls {
 
 - (void)testRequestToListWithValuess {
   NullFieldsSearchRequest *request = [NullFieldsSearchRequest makeWithQuery:@"hello" identifier:1];
-  NSArray *list = [request toList];
+  NSArray<id> *list = [request toList];
   XCTAssertEqual(@"hello", list[0]);
 }
 
 - (void)testRequestToListWithNulls {
   NullFieldsSearchRequest *request = [NullFieldsSearchRequest makeWithQuery:nil identifier:1];
-  NSArray *list = [request toList];
+  NSArray<id> *list = [request toList];
   XCTAssertEqual([NSNull null], list[0]);
 }
 
@@ -140,15 +146,13 @@ - (void)testReplyToListWithValuess {
              indices:@[ @1, @2, @3 ]
              request:[NullFieldsSearchRequest makeWithQuery:@"hello" identifier:1]
                 type:typeWrapper];
-  NSArray *list = [reply toList];
-  NSArray *indices = @[ @1, @2, @3 ];
+  NSArray<id> *list = [reply toList];
+  NSArray<id> *indices = @[ @1, @2, @3 ];
   XCTAssertEqualObjects(@"result", list[0]);
   XCTAssertEqualObjects(@"error", list[1]);
   XCTAssertEqualObjects(indices, list[2]);
   XCTAssertEqualObjects(@"hello", ((NullFieldsSearchRequest *)list[3]).query);
-  NSNumber *typeNumber = list[4];
-  NullFieldsSearchReplyTypeBox *output =
-      [[NullFieldsSearchReplyTypeBox alloc] initWithValue:[typeNumber integerValue]];
+  NullFieldsSearchReplyTypeBox *output = list[4];
 
   XCTAssertEqual(typeWrapper.value, output.value);
 }
@@ -159,7 +163,7 @@ - (void)testReplyToListWithNulls {
                                                                indices:nil
                                                                request:nil
                                                                   type:nil];
-  NSArray *list = [reply toList];
+  NSArray<id> *list = [reply toList];
   XCTAssertEqual([NSNull null], list[0]);
   XCTAssertEqual([NSNull null], list[1]);
   XCTAssertEqual([NSNull null], list[2]);
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullableReturnsTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullableReturnsTest.m
index 3cd45e6fbc4..54ee040313d 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullableReturnsTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/NullableReturnsTest.m
@@ -35,7 +35,7 @@ @implementation NullableReturnsTest
 
 - (void)testNullableParameterWithFlutterApi {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:NullableArgHostApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetNullableReturnsCodec()];
   NullableArgFlutterApi *api =
       [[NullableArgFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
@@ -50,12 +50,12 @@ - (void)testNullableParameterWithFlutterApi {
 - (void)testNullableParameterWithHostApi {
   MockNullableArgHostApi *api = [[MockNullableArgHostApi alloc] init];
   MockBinaryMessenger *binaryMessenger =
-      [[MockBinaryMessenger alloc] initWithCodec:NullableArgHostApiGetCodec()];
+      [[MockBinaryMessenger alloc] initWithCodec:GetNullableReturnsCodec()];
   NSString *channel = @"dev.flutter.pigeon.pigeon_integration_tests.NullableArgHostApi.doit";
   SetUpNullableArgHostApi(binaryMessenger, api);
   XCTAssertNotNil(binaryMessenger.handlers[channel]);
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
-  NSData *arguments = [NullableArgHostApiGetCodec() encode:@[ [NSNull null] ]];
+  NSData *arguments = [GetNullableReturnsCodec() encode:@[ [NSNull null] ]];
   binaryMessenger.handlers[channel](arguments, ^(NSData *data) {
     [expectation fulfill];
   });
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/PrimitiveTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/PrimitiveTest.m
index 2c6b7af178f..380fc9bdc6c 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/PrimitiveTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/PrimitiveTest.m
@@ -18,7 +18,7 @@ @implementation PrimitiveTest
 
 - (void)testIntPrimitive {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PrimitiveFlutterApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetPrimitiveCodec()];
   PrimitiveFlutterApi *api = [[PrimitiveFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   [api anIntValue:1
@@ -31,7 +31,7 @@ - (void)testIntPrimitive {
 
 - (void)testBoolPrimitive {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PrimitiveFlutterApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetPrimitiveCodec()];
   PrimitiveFlutterApi *api = [[PrimitiveFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   BOOL arg = YES;
@@ -46,7 +46,7 @@ - (void)testBoolPrimitive {
 
 - (void)testDoublePrimitive {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PrimitiveFlutterApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetPrimitiveCodec()];
   PrimitiveFlutterApi *api = [[PrimitiveFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   NSInteger arg = 1.5;
@@ -61,7 +61,7 @@ - (void)testDoublePrimitive {
 
 - (void)testStringPrimitive {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PrimitiveFlutterApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetPrimitiveCodec()];
   PrimitiveFlutterApi *api = [[PrimitiveFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   NSString *arg = @"hello";
@@ -75,12 +75,12 @@ - (void)testStringPrimitive {
 
 - (void)testListPrimitive {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PrimitiveFlutterApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetPrimitiveCodec()];
   PrimitiveFlutterApi *api = [[PrimitiveFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
-  NSArray *arg = @[ @"hello" ];
+  NSArray<id> *arg = @[ @"hello" ];
   [api aListValue:arg
-       completion:^(NSArray *_Nonnull result, FlutterError *_Nullable err) {
+       completion:^(NSArray<id> *_Nonnull result, FlutterError *_Nullable err) {
          XCTAssertEqualObjects(arg, result);
          [expectation fulfill];
        }];
@@ -89,7 +89,7 @@ - (void)testListPrimitive {
 
 - (void)testMapPrimitive {
   EchoBinaryMessenger *binaryMessenger =
-      [[EchoBinaryMessenger alloc] initWithCodec:PrimitiveFlutterApiGetCodec()];
+      [[EchoBinaryMessenger alloc] initWithCodec:GetPrimitiveCodec()];
   PrimitiveFlutterApi *api = [[PrimitiveFlutterApi alloc] initWithBinaryMessenger:binaryMessenger];
   XCTestExpectation *expectation = [self expectationWithDescription:@"callback"];
   NSDictionary *arg = @{@"hello" : @1};
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/RunnerTests.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/RunnerTests.m
index 60220b7a859..a81c169d003 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/RunnerTests.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/RunnerTests.m
@@ -7,8 +7,8 @@
 @import alternate_language_test_plugin;
 
 @interface ACMessageSearchReply ()
-+ (ACMessageSearchReply *)fromList:(NSArray *)list;
-- (NSArray *)toList;
++ (ACMessageSearchReply *)fromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface RunnerTests : XCTestCase
@@ -20,7 +20,7 @@ @implementation RunnerTests
 - (void)testToMapAndBack {
   ACMessageSearchReply *reply = [[ACMessageSearchReply alloc] init];
   reply.result = @"foobar";
-  NSArray *list = [reply toList];
+  NSArray<id> *list = [reply toList];
   ACMessageSearchReply *copy = [ACMessageSearchReply fromList:list];
   XCTAssertEqual(reply.result, copy.result);
 }
@@ -28,7 +28,7 @@ - (void)testToMapAndBack {
 - (void)testHandlesNull {
   ACMessageSearchReply *reply = [[ACMessageSearchReply alloc] init];
   reply.result = nil;
-  NSArray *list = [reply toList];
+  NSArray<id> *list = [reply toList];
   ACMessageSearchReply *copy = [ACMessageSearchReply fromList:list];
   XCTAssertNil(copy.result);
 }
@@ -36,7 +36,7 @@ - (void)testHandlesNull {
 - (void)testHandlesNullFirst {
   ACMessageSearchReply *reply = [[ACMessageSearchReply alloc] init];
   reply.error = @"foobar";
-  NSArray *list = [reply toList];
+  NSArray<id> *list = [reply toList];
   ACMessageSearchReply *copy = [ACMessageSearchReply fromList:list];
   XCTAssertEqual(reply.error, copy.error);
 }
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h
index ada05bf3801..2bf7bbf26be 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h
@@ -46,11 +46,15 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
                   a4ByteArray:(FlutterStandardTypedData *)a4ByteArray
                   a8ByteArray:(FlutterStandardTypedData *)a8ByteArray
                   aFloatArray:(FlutterStandardTypedData *)aFloatArray
-                         list:(NSArray *)list
-                         aMap:(NSDictionary *)aMap
                        anEnum:(FLTAnEnum)anEnum
                       aString:(NSString *)aString
-                     anObject:(id)anObject;
+                     anObject:(id)anObject
+                         list:(NSArray<id> *)list
+                   stringList:(NSArray<NSString *> *)stringList
+                      intList:(NSArray<NSNumber *> *)intList
+                   doubleList:(NSArray<NSNumber *> *)doubleList
+                     boolList:(NSArray<NSNumber *> *)boolList
+                          map:(NSDictionary *)map;
 @property(nonatomic, assign) BOOL aBool;
 @property(nonatomic, assign) NSInteger anInt;
 @property(nonatomic, assign) NSInteger anInt64;
@@ -59,11 +63,15 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
 @property(nonatomic, strong) FlutterStandardTypedData *a4ByteArray;
 @property(nonatomic, strong) FlutterStandardTypedData *a8ByteArray;
 @property(nonatomic, strong) FlutterStandardTypedData *aFloatArray;
-@property(nonatomic, copy) NSArray *list;
-@property(nonatomic, copy) NSDictionary *aMap;
 @property(nonatomic, assign) FLTAnEnum anEnum;
 @property(nonatomic, copy) NSString *aString;
 @property(nonatomic, strong) id anObject;
+@property(nonatomic, copy) NSArray<id> *list;
+@property(nonatomic, copy) NSArray<NSString *> *stringList;
+@property(nonatomic, copy) NSArray<NSNumber *> *intList;
+@property(nonatomic, copy) NSArray<NSNumber *> *doubleList;
+@property(nonatomic, copy) NSArray<NSNumber *> *boolList;
+@property(nonatomic, copy) NSDictionary *map;
 @end
 
 /// A class containing all supported nullable types.
@@ -76,8 +84,6 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
@@ -85,7 +91,14 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
                         aNullableEnum:(nullable FLTAnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
                       aNullableObject:(nullable id)aNullableObject
-                     allNullableTypes:(nullable FLTAllNullableTypes *)allNullableTypes;
+                     allNullableTypes:(nullable FLTAllNullableTypes *)allNullableTypes
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                      nestedClassList:(nullable NSArray<FLTAllNullableTypes *> *)nestedClassList
+                                  map:(nullable NSDictionary *)map;
 @property(nonatomic, strong, nullable) NSNumber *aNullableBool;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt64;
@@ -94,8 +107,6 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable4ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable8ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullableFloatArray;
-@property(nonatomic, copy, nullable) NSArray *aNullableList;
-@property(nonatomic, copy, nullable) NSDictionary *aNullableMap;
 @property(nonatomic, copy, nullable) NSArray<NSArray<NSNumber *> *> *nullableNestedList;
 @property(nonatomic, copy, nullable)
     NSDictionary<NSString *, NSString *> *nullableMapWithAnnotations;
@@ -104,6 +115,13 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
 @property(nonatomic, copy, nullable) NSString *aNullableString;
 @property(nonatomic, strong, nullable) id aNullableObject;
 @property(nonatomic, strong, nullable) FLTAllNullableTypes *allNullableTypes;
+@property(nonatomic, copy, nullable) NSArray<id> *list;
+@property(nonatomic, copy, nullable) NSArray<NSString *> *stringList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *intList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *doubleList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *boolList;
+@property(nonatomic, copy, nullable) NSArray<FLTAllNullableTypes *> *nestedClassList;
+@property(nonatomic, copy, nullable) NSDictionary *map;
 @end
 
 /// The primary purpose for this class is to ensure coverage of Swift structs
@@ -118,15 +136,19 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
                 nullableMapWithObject:(nullable NSDictionary<NSString *, id> *)nullableMapWithObject
                         aNullableEnum:(nullable FLTAnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
-                      aNullableObject:(nullable id)aNullableObject;
+                      aNullableObject:(nullable id)aNullableObject
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                                  map:(nullable NSDictionary *)map;
 @property(nonatomic, strong, nullable) NSNumber *aNullableBool;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt64;
@@ -135,8 +157,6 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable4ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable8ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullableFloatArray;
-@property(nonatomic, copy, nullable) NSArray *aNullableList;
-@property(nonatomic, copy, nullable) NSDictionary *aNullableMap;
 @property(nonatomic, copy, nullable) NSArray<NSArray<NSNumber *> *> *nullableNestedList;
 @property(nonatomic, copy, nullable)
     NSDictionary<NSString *, NSString *> *nullableMapWithAnnotations;
@@ -144,6 +164,12 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
 @property(nonatomic, strong, nullable) FLTAnEnumBox *aNullableEnum;
 @property(nonatomic, copy, nullable) NSString *aNullableString;
 @property(nonatomic, strong, nullable) id aNullableObject;
+@property(nonatomic, copy, nullable) NSArray<id> *list;
+@property(nonatomic, copy, nullable) NSArray<NSString *> *stringList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *intList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *doubleList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *boolList;
+@property(nonatomic, copy, nullable) NSDictionary *map;
 @end
 
 /// A class for testing nested class handling.
@@ -166,12 +192,12 @@ typedef NS_ENUM(NSUInteger, FLTAnEnum) {
 
 /// A data class containing a List, used in unit tests.
 @interface FLTTestMessage : NSObject
-+ (instancetype)makeWithTestList:(nullable NSArray *)testList;
-@property(nonatomic, copy, nullable) NSArray *testList;
++ (instancetype)makeWithTestList:(nullable NSArray<id> *)testList;
+@property(nonatomic, copy, nullable) NSArray<id> *testList;
 @end
 
-/// The codec used by FLTHostIntegrationCoreApi.
-NSObject<FlutterMessageCodec> *FLTHostIntegrationCoreApiGetCodec(void);
+/// The codec used by all APIs.
+NSObject<FlutterMessageCodec> *FLTGetCoreTestsCodec(void);
 
 /// The core interface that each host language plugin must implement in
 /// platform_test integration tests.
@@ -486,9 +512,6 @@ extern void SetUpFLTHostIntegrationCoreApiWithSuffix(
     id<FlutterBinaryMessenger> binaryMessenger, NSObject<FLTHostIntegrationCoreApi> *_Nullable api,
     NSString *messageChannelSuffix);
 
-/// The codec used by FLTFlutterIntegrationCoreApi.
-NSObject<FlutterMessageCodec> *FLTFlutterIntegrationCoreApiGetCodec(void);
-
 /// The core interface that the Dart platform_test code implements for host
 /// integration tests to call into.
 @interface FLTFlutterIntegrationCoreApi : NSObject
@@ -592,9 +615,6 @@ NSObject<FlutterMessageCodec> *FLTFlutterIntegrationCoreApiGetCodec(void);
              completion:(void (^)(NSString *_Nullable, FlutterError *_Nullable))completion;
 @end
 
-/// The codec used by FLTHostTrivialApi.
-NSObject<FlutterMessageCodec> *FLTHostTrivialApiGetCodec(void);
-
 /// An API that can be implemented for minimal, compile-only tests.
 @protocol FLTHostTrivialApi
 - (void)noopWithError:(FlutterError *_Nullable *_Nonnull)error;
@@ -607,9 +627,6 @@ extern void SetUpFLTHostTrivialApiWithSuffix(id<FlutterBinaryMessenger> binaryMe
                                              NSObject<FLTHostTrivialApi> *_Nullable api,
                                              NSString *messageChannelSuffix);
 
-/// The codec used by FLTHostSmallApi.
-NSObject<FlutterMessageCodec> *FLTHostSmallApiGetCodec(void);
-
 /// A simple API implemented in some unit tests.
 @protocol FLTHostSmallApi
 - (void)echoString:(NSString *)aString
@@ -624,9 +641,6 @@ extern void SetUpFLTHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                            NSObject<FLTHostSmallApi> *_Nullable api,
                                            NSString *messageChannelSuffix);
 
-/// The codec used by FLTFlutterSmallApi.
-NSObject<FlutterMessageCodec> *FLTFlutterSmallApiGetCodec(void);
-
 /// A simple API called in some unit tests.
 @interface FLTFlutterSmallApi : NSObject
 - (instancetype)initWithBinaryMessenger:(id<FlutterBinaryMessenger>)binaryMessenger;
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m
index 92c72d59598..6dae6ff2abd 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m
@@ -17,7 +17,7 @@
 #error File requires ARC to be enabled.
 #endif
 
-static NSArray *wrapResult(id result, FlutterError *error) {
+static NSArray<id> *wrapResult(id result, FlutterError *error) {
   if (error) {
     return @[
       error.code ?: [NSNull null], error.message ?: [NSNull null], error.details ?: [NSNull null]
@@ -35,7 +35,7 @@
             details:@""];
 }
 
-static id GetNullableObjectAtIndex(NSArray *array, NSInteger key) {
+static id GetNullableObjectAtIndex(NSArray<id> *array, NSInteger key) {
   id result = array[key];
   return (result == [NSNull null]) ? nil : result;
 }
@@ -51,33 +51,33 @@ - (instancetype)initWithValue:(FLTAnEnum)value {
 @end
 
 @interface FLTAllTypes ()
-+ (FLTAllTypes *)fromList:(NSArray *)list;
-+ (nullable FLTAllTypes *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (FLTAllTypes *)fromList:(NSArray<id> *)list;
++ (nullable FLTAllTypes *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface FLTAllNullableTypes ()
-+ (FLTAllNullableTypes *)fromList:(NSArray *)list;
-+ (nullable FLTAllNullableTypes *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (FLTAllNullableTypes *)fromList:(NSArray<id> *)list;
++ (nullable FLTAllNullableTypes *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface FLTAllNullableTypesWithoutRecursion ()
-+ (FLTAllNullableTypesWithoutRecursion *)fromList:(NSArray *)list;
-+ (nullable FLTAllNullableTypesWithoutRecursion *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (FLTAllNullableTypesWithoutRecursion *)fromList:(NSArray<id> *)list;
++ (nullable FLTAllNullableTypesWithoutRecursion *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface FLTAllClassesWrapper ()
-+ (FLTAllClassesWrapper *)fromList:(NSArray *)list;
-+ (nullable FLTAllClassesWrapper *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (FLTAllClassesWrapper *)fromList:(NSArray<id> *)list;
++ (nullable FLTAllClassesWrapper *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface FLTTestMessage ()
-+ (FLTTestMessage *)fromList:(NSArray *)list;
-+ (nullable FLTTestMessage *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (FLTTestMessage *)fromList:(NSArray<id> *)list;
++ (nullable FLTTestMessage *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @implementation FLTAllTypes
@@ -89,11 +89,15 @@ + (instancetype)makeWithABool:(BOOL)aBool
                   a4ByteArray:(FlutterStandardTypedData *)a4ByteArray
                   a8ByteArray:(FlutterStandardTypedData *)a8ByteArray
                   aFloatArray:(FlutterStandardTypedData *)aFloatArray
-                         list:(NSArray *)list
-                         aMap:(NSDictionary *)aMap
                        anEnum:(FLTAnEnum)anEnum
                       aString:(NSString *)aString
-                     anObject:(id)anObject {
+                     anObject:(id)anObject
+                         list:(NSArray<id> *)list
+                   stringList:(NSArray<NSString *> *)stringList
+                      intList:(NSArray<NSNumber *> *)intList
+                   doubleList:(NSArray<NSNumber *> *)doubleList
+                     boolList:(NSArray<NSNumber *> *)boolList
+                          map:(NSDictionary *)map {
   FLTAllTypes *pigeonResult = [[FLTAllTypes alloc] init];
   pigeonResult.aBool = aBool;
   pigeonResult.anInt = anInt;
@@ -103,14 +107,18 @@ + (instancetype)makeWithABool:(BOOL)aBool
   pigeonResult.a4ByteArray = a4ByteArray;
   pigeonResult.a8ByteArray = a8ByteArray;
   pigeonResult.aFloatArray = aFloatArray;
-  pigeonResult.list = list;
-  pigeonResult.aMap = aMap;
   pigeonResult.anEnum = anEnum;
   pigeonResult.aString = aString;
   pigeonResult.anObject = anObject;
+  pigeonResult.list = list;
+  pigeonResult.stringList = stringList;
+  pigeonResult.intList = intList;
+  pigeonResult.doubleList = doubleList;
+  pigeonResult.boolList = boolList;
+  pigeonResult.map = map;
   return pigeonResult;
 }
-+ (FLTAllTypes *)fromList:(NSArray *)list {
++ (FLTAllTypes *)fromList:(NSArray<id> *)list {
   FLTAllTypes *pigeonResult = [[FLTAllTypes alloc] init];
   pigeonResult.aBool = [GetNullableObjectAtIndex(list, 0) boolValue];
   pigeonResult.anInt = [GetNullableObjectAtIndex(list, 1) integerValue];
@@ -120,17 +128,22 @@ + (FLTAllTypes *)fromList:(NSArray *)list {
   pigeonResult.a4ByteArray = GetNullableObjectAtIndex(list, 5);
   pigeonResult.a8ByteArray = GetNullableObjectAtIndex(list, 6);
   pigeonResult.aFloatArray = GetNullableObjectAtIndex(list, 7);
-  pigeonResult.list = GetNullableObjectAtIndex(list, 8);
-  pigeonResult.aMap = GetNullableObjectAtIndex(list, 9);
-  pigeonResult.anEnum = [GetNullableObjectAtIndex(list, 10) integerValue];
-  pigeonResult.aString = GetNullableObjectAtIndex(list, 11);
-  pigeonResult.anObject = GetNullableObjectAtIndex(list, 12);
+  FLTAnEnumBox *enumBox = GetNullableObjectAtIndex(list, 8);
+  pigeonResult.anEnum = enumBox.value;
+  pigeonResult.aString = GetNullableObjectAtIndex(list, 9);
+  pigeonResult.anObject = GetNullableObjectAtIndex(list, 10);
+  pigeonResult.list = GetNullableObjectAtIndex(list, 11);
+  pigeonResult.stringList = GetNullableObjectAtIndex(list, 12);
+  pigeonResult.intList = GetNullableObjectAtIndex(list, 13);
+  pigeonResult.doubleList = GetNullableObjectAtIndex(list, 14);
+  pigeonResult.boolList = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.map = GetNullableObjectAtIndex(list, 16);
   return pigeonResult;
 }
-+ (nullable FLTAllTypes *)nullableFromList:(NSArray *)list {
++ (nullable FLTAllTypes *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [FLTAllTypes fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     @(self.aBool),
     @(self.anInt),
@@ -140,11 +153,15 @@ - (NSArray *)toList {
     self.a4ByteArray ?: [NSNull null],
     self.a8ByteArray ?: [NSNull null],
     self.aFloatArray ?: [NSNull null],
-    self.list ?: [NSNull null],
-    self.aMap ?: [NSNull null],
-    @(self.anEnum),
+    [[FLTAnEnumBox alloc] initWithValue:self.anEnum],
     self.aString ?: [NSNull null],
     self.anObject ?: [NSNull null],
+    self.list ?: [NSNull null],
+    self.stringList ?: [NSNull null],
+    self.intList ?: [NSNull null],
+    self.doubleList ?: [NSNull null],
+    self.boolList ?: [NSNull null],
+    self.map ?: [NSNull null],
   ];
 }
 @end
@@ -158,8 +175,6 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
@@ -167,7 +182,14 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
                         aNullableEnum:(nullable FLTAnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
                       aNullableObject:(nullable id)aNullableObject
-                     allNullableTypes:(nullable FLTAllNullableTypes *)allNullableTypes {
+                     allNullableTypes:(nullable FLTAllNullableTypes *)allNullableTypes
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                      nestedClassList:(nullable NSArray<FLTAllNullableTypes *> *)nestedClassList
+                                  map:(nullable NSDictionary *)map {
   FLTAllNullableTypes *pigeonResult = [[FLTAllNullableTypes alloc] init];
   pigeonResult.aNullableBool = aNullableBool;
   pigeonResult.aNullableInt = aNullableInt;
@@ -177,8 +199,6 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
   pigeonResult.aNullable4ByteArray = aNullable4ByteArray;
   pigeonResult.aNullable8ByteArray = aNullable8ByteArray;
   pigeonResult.aNullableFloatArray = aNullableFloatArray;
-  pigeonResult.aNullableList = aNullableList;
-  pigeonResult.aNullableMap = aNullableMap;
   pigeonResult.nullableNestedList = nullableNestedList;
   pigeonResult.nullableMapWithAnnotations = nullableMapWithAnnotations;
   pigeonResult.nullableMapWithObject = nullableMapWithObject;
@@ -186,9 +206,16 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
   pigeonResult.aNullableString = aNullableString;
   pigeonResult.aNullableObject = aNullableObject;
   pigeonResult.allNullableTypes = allNullableTypes;
+  pigeonResult.list = list;
+  pigeonResult.stringList = stringList;
+  pigeonResult.intList = intList;
+  pigeonResult.doubleList = doubleList;
+  pigeonResult.boolList = boolList;
+  pigeonResult.nestedClassList = nestedClassList;
+  pigeonResult.map = map;
   return pigeonResult;
 }
-+ (FLTAllNullableTypes *)fromList:(NSArray *)list {
++ (FLTAllNullableTypes *)fromList:(NSArray<id> *)list {
   FLTAllNullableTypes *pigeonResult = [[FLTAllNullableTypes alloc] init];
   pigeonResult.aNullableBool = GetNullableObjectAtIndex(list, 0);
   pigeonResult.aNullableInt = GetNullableObjectAtIndex(list, 1);
@@ -198,26 +225,26 @@ + (FLTAllNullableTypes *)fromList:(NSArray *)list {
   pigeonResult.aNullable4ByteArray = GetNullableObjectAtIndex(list, 5);
   pigeonResult.aNullable8ByteArray = GetNullableObjectAtIndex(list, 6);
   pigeonResult.aNullableFloatArray = GetNullableObjectAtIndex(list, 7);
-  pigeonResult.aNullableList = GetNullableObjectAtIndex(list, 8);
-  pigeonResult.aNullableMap = GetNullableObjectAtIndex(list, 9);
-  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 10);
-  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 11);
-  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 12);
-  NSNumber *aNullableEnumAsNumber = GetNullableObjectAtIndex(list, 13);
-  FLTAnEnumBox *aNullableEnum =
-      aNullableEnumAsNumber == nil
-          ? nil
-          : [[FLTAnEnumBox alloc] initWithValue:[aNullableEnumAsNumber integerValue]];
-  pigeonResult.aNullableEnum = aNullableEnum;
-  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 14);
-  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 15);
-  pigeonResult.allNullableTypes = GetNullableObjectAtIndex(list, 16);
+  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 8);
+  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 9);
+  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 10);
+  pigeonResult.aNullableEnum = GetNullableObjectAtIndex(list, 11);
+  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 12);
+  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 13);
+  pigeonResult.allNullableTypes = GetNullableObjectAtIndex(list, 14);
+  pigeonResult.list = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.stringList = GetNullableObjectAtIndex(list, 16);
+  pigeonResult.intList = GetNullableObjectAtIndex(list, 17);
+  pigeonResult.doubleList = GetNullableObjectAtIndex(list, 18);
+  pigeonResult.boolList = GetNullableObjectAtIndex(list, 19);
+  pigeonResult.nestedClassList = GetNullableObjectAtIndex(list, 20);
+  pigeonResult.map = GetNullableObjectAtIndex(list, 21);
   return pigeonResult;
 }
-+ (nullable FLTAllNullableTypes *)nullableFromList:(NSArray *)list {
++ (nullable FLTAllNullableTypes *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [FLTAllNullableTypes fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.aNullableBool ?: [NSNull null],
     self.aNullableInt ?: [NSNull null],
@@ -227,16 +254,20 @@ - (NSArray *)toList {
     self.aNullable4ByteArray ?: [NSNull null],
     self.aNullable8ByteArray ?: [NSNull null],
     self.aNullableFloatArray ?: [NSNull null],
-    self.aNullableList ?: [NSNull null],
-    self.aNullableMap ?: [NSNull null],
     self.nullableNestedList ?: [NSNull null],
     self.nullableMapWithAnnotations ?: [NSNull null],
     self.nullableMapWithObject ?: [NSNull null],
-    (self.aNullableEnum == nil ? [NSNull null]
-                               : [NSNumber numberWithInteger:self.aNullableEnum.value]),
+    self.aNullableEnum ?: [NSNull null],
     self.aNullableString ?: [NSNull null],
     self.aNullableObject ?: [NSNull null],
     self.allNullableTypes ?: [NSNull null],
+    self.list ?: [NSNull null],
+    self.stringList ?: [NSNull null],
+    self.intList ?: [NSNull null],
+    self.doubleList ?: [NSNull null],
+    self.boolList ?: [NSNull null],
+    self.nestedClassList ?: [NSNull null],
+    self.map ?: [NSNull null],
   ];
 }
 @end
@@ -250,15 +281,19 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
                 nullableMapWithObject:(nullable NSDictionary<NSString *, id> *)nullableMapWithObject
                         aNullableEnum:(nullable FLTAnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
-                      aNullableObject:(nullable id)aNullableObject {
+                      aNullableObject:(nullable id)aNullableObject
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                                  map:(nullable NSDictionary *)map {
   FLTAllNullableTypesWithoutRecursion *pigeonResult =
       [[FLTAllNullableTypesWithoutRecursion alloc] init];
   pigeonResult.aNullableBool = aNullableBool;
@@ -269,17 +304,21 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
   pigeonResult.aNullable4ByteArray = aNullable4ByteArray;
   pigeonResult.aNullable8ByteArray = aNullable8ByteArray;
   pigeonResult.aNullableFloatArray = aNullableFloatArray;
-  pigeonResult.aNullableList = aNullableList;
-  pigeonResult.aNullableMap = aNullableMap;
   pigeonResult.nullableNestedList = nullableNestedList;
   pigeonResult.nullableMapWithAnnotations = nullableMapWithAnnotations;
   pigeonResult.nullableMapWithObject = nullableMapWithObject;
   pigeonResult.aNullableEnum = aNullableEnum;
   pigeonResult.aNullableString = aNullableString;
   pigeonResult.aNullableObject = aNullableObject;
+  pigeonResult.list = list;
+  pigeonResult.stringList = stringList;
+  pigeonResult.intList = intList;
+  pigeonResult.doubleList = doubleList;
+  pigeonResult.boolList = boolList;
+  pigeonResult.map = map;
   return pigeonResult;
 }
-+ (FLTAllNullableTypesWithoutRecursion *)fromList:(NSArray *)list {
++ (FLTAllNullableTypesWithoutRecursion *)fromList:(NSArray<id> *)list {
   FLTAllNullableTypesWithoutRecursion *pigeonResult =
       [[FLTAllNullableTypesWithoutRecursion alloc] init];
   pigeonResult.aNullableBool = GetNullableObjectAtIndex(list, 0);
@@ -290,25 +329,24 @@ + (FLTAllNullableTypesWithoutRecursion *)fromList:(NSArray *)list {
   pigeonResult.aNullable4ByteArray = GetNullableObjectAtIndex(list, 5);
   pigeonResult.aNullable8ByteArray = GetNullableObjectAtIndex(list, 6);
   pigeonResult.aNullableFloatArray = GetNullableObjectAtIndex(list, 7);
-  pigeonResult.aNullableList = GetNullableObjectAtIndex(list, 8);
-  pigeonResult.aNullableMap = GetNullableObjectAtIndex(list, 9);
-  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 10);
-  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 11);
-  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 12);
-  NSNumber *aNullableEnumAsNumber = GetNullableObjectAtIndex(list, 13);
-  FLTAnEnumBox *aNullableEnum =
-      aNullableEnumAsNumber == nil
-          ? nil
-          : [[FLTAnEnumBox alloc] initWithValue:[aNullableEnumAsNumber integerValue]];
-  pigeonResult.aNullableEnum = aNullableEnum;
-  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 14);
-  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 8);
+  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 9);
+  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 10);
+  pigeonResult.aNullableEnum = GetNullableObjectAtIndex(list, 11);
+  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 12);
+  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 13);
+  pigeonResult.list = GetNullableObjectAtIndex(list, 14);
+  pigeonResult.stringList = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.intList = GetNullableObjectAtIndex(list, 16);
+  pigeonResult.doubleList = GetNullableObjectAtIndex(list, 17);
+  pigeonResult.boolList = GetNullableObjectAtIndex(list, 18);
+  pigeonResult.map = GetNullableObjectAtIndex(list, 19);
   return pigeonResult;
 }
-+ (nullable FLTAllNullableTypesWithoutRecursion *)nullableFromList:(NSArray *)list {
++ (nullable FLTAllNullableTypesWithoutRecursion *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [FLTAllNullableTypesWithoutRecursion fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.aNullableBool ?: [NSNull null],
     self.aNullableInt ?: [NSNull null],
@@ -318,15 +356,18 @@ - (NSArray *)toList {
     self.aNullable4ByteArray ?: [NSNull null],
     self.aNullable8ByteArray ?: [NSNull null],
     self.aNullableFloatArray ?: [NSNull null],
-    self.aNullableList ?: [NSNull null],
-    self.aNullableMap ?: [NSNull null],
     self.nullableNestedList ?: [NSNull null],
     self.nullableMapWithAnnotations ?: [NSNull null],
     self.nullableMapWithObject ?: [NSNull null],
-    (self.aNullableEnum == nil ? [NSNull null]
-                               : [NSNumber numberWithInteger:self.aNullableEnum.value]),
+    self.aNullableEnum ?: [NSNull null],
     self.aNullableString ?: [NSNull null],
     self.aNullableObject ?: [NSNull null],
+    self.list ?: [NSNull null],
+    self.stringList ?: [NSNull null],
+    self.intList ?: [NSNull null],
+    self.doubleList ?: [NSNull null],
+    self.boolList ?: [NSNull null],
+    self.map ?: [NSNull null],
   ];
 }
 @end
@@ -342,17 +383,17 @@ + (instancetype)makeWithAllNullableTypes:(FLTAllNullableTypes *)allNullableTypes
   pigeonResult.allTypes = allTypes;
   return pigeonResult;
 }
-+ (FLTAllClassesWrapper *)fromList:(NSArray *)list {
++ (FLTAllClassesWrapper *)fromList:(NSArray<id> *)list {
   FLTAllClassesWrapper *pigeonResult = [[FLTAllClassesWrapper alloc] init];
   pigeonResult.allNullableTypes = GetNullableObjectAtIndex(list, 0);
   pigeonResult.allNullableTypesWithoutRecursion = GetNullableObjectAtIndex(list, 1);
   pigeonResult.allTypes = GetNullableObjectAtIndex(list, 2);
   return pigeonResult;
 }
-+ (nullable FLTAllClassesWrapper *)nullableFromList:(NSArray *)list {
++ (nullable FLTAllClassesWrapper *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [FLTAllClassesWrapper fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.allNullableTypes ?: [NSNull null],
     self.allNullableTypesWithoutRecursion ?: [NSNull null],
@@ -362,94 +403,102 @@ - (NSArray *)toList {
 @end
 
 @implementation FLTTestMessage
-+ (instancetype)makeWithTestList:(nullable NSArray *)testList {
++ (instancetype)makeWithTestList:(nullable NSArray<id> *)testList {
   FLTTestMessage *pigeonResult = [[FLTTestMessage alloc] init];
   pigeonResult.testList = testList;
   return pigeonResult;
 }
-+ (FLTTestMessage *)fromList:(NSArray *)list {
++ (FLTTestMessage *)fromList:(NSArray<id> *)list {
   FLTTestMessage *pigeonResult = [[FLTTestMessage alloc] init];
   pigeonResult.testList = GetNullableObjectAtIndex(list, 0);
   return pigeonResult;
 }
-+ (nullable FLTTestMessage *)nullableFromList:(NSArray *)list {
++ (nullable FLTTestMessage *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [FLTTestMessage fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.testList ?: [NSNull null],
   ];
 }
 @end
 
-@interface FLTHostIntegrationCoreApiCodecReader : FlutterStandardReader
+@interface FLTCoreTestsPigeonCodecReader : FlutterStandardReader
 @end
-@implementation FLTHostIntegrationCoreApiCodecReader
+@implementation FLTCoreTestsPigeonCodecReader
 - (nullable id)readValueOfType:(UInt8)type {
   switch (type) {
-    case 128:
-      return [FLTAllClassesWrapper fromList:[self readValue]];
     case 129:
-      return [FLTAllNullableTypes fromList:[self readValue]];
+      return [FLTAllTypes fromList:[self readValue]];
     case 130:
-      return [FLTAllNullableTypesWithoutRecursion fromList:[self readValue]];
+      return [FLTAllNullableTypes fromList:[self readValue]];
     case 131:
-      return [FLTAllTypes fromList:[self readValue]];
+      return [FLTAllNullableTypesWithoutRecursion fromList:[self readValue]];
     case 132:
+      return [FLTAllClassesWrapper fromList:[self readValue]];
+    case 133:
       return [FLTTestMessage fromList:[self readValue]];
+    case 134: {
+      NSNumber *enumAsNumber = [self readValue];
+      return enumAsNumber == nil ? nil
+                                 : [[FLTAnEnumBox alloc] initWithValue:[enumAsNumber integerValue]];
+    }
     default:
       return [super readValueOfType:type];
   }
 }
 @end
 
-@interface FLTHostIntegrationCoreApiCodecWriter : FlutterStandardWriter
+@interface FLTCoreTestsPigeonCodecWriter : FlutterStandardWriter
 @end
-@implementation FLTHostIntegrationCoreApiCodecWriter
+@implementation FLTCoreTestsPigeonCodecWriter
 - (void)writeValue:(id)value {
-  if ([value isKindOfClass:[FLTAllClassesWrapper class]]) {
-    [self writeByte:128];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTAllNullableTypes class]]) {
+  if ([value isKindOfClass:[FLTAllTypes class]]) {
     [self writeByte:129];
     [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTAllNullableTypesWithoutRecursion class]]) {
+  } else if ([value isKindOfClass:[FLTAllNullableTypes class]]) {
     [self writeByte:130];
     [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTAllTypes class]]) {
+  } else if ([value isKindOfClass:[FLTAllNullableTypesWithoutRecursion class]]) {
     [self writeByte:131];
     [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTTestMessage class]]) {
+  } else if ([value isKindOfClass:[FLTAllClassesWrapper class]]) {
     [self writeByte:132];
     [self writeValue:[value toList]];
+  } else if ([value isKindOfClass:[FLTTestMessage class]]) {
+    [self writeByte:133];
+    [self writeValue:[value toList]];
+  } else if ([value isKindOfClass:[FLTAnEnumBox class]]) {
+    FLTAnEnumBox *box = (FLTAnEnumBox *)value;
+    [self writeByte:134];
+    [self writeValue:(value == nil ? [NSNull null] : [NSNumber numberWithInteger:box.value])];
   } else {
     [super writeValue:value];
   }
 }
 @end
 
-@interface FLTHostIntegrationCoreApiCodecReaderWriter : FlutterStandardReaderWriter
+@interface FLTCoreTestsPigeonCodecReaderWriter : FlutterStandardReaderWriter
 @end
-@implementation FLTHostIntegrationCoreApiCodecReaderWriter
+@implementation FLTCoreTestsPigeonCodecReaderWriter
 - (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[FLTHostIntegrationCoreApiCodecWriter alloc] initWithData:data];
+  return [[FLTCoreTestsPigeonCodecWriter alloc] initWithData:data];
 }
 - (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[FLTHostIntegrationCoreApiCodecReader alloc] initWithData:data];
+  return [[FLTCoreTestsPigeonCodecReader alloc] initWithData:data];
 }
 @end
 
-NSObject<FlutterMessageCodec> *FLTHostIntegrationCoreApiGetCodec(void) {
+NSObject<FlutterMessageCodec> *FLTGetCoreTestsCodec(void) {
   static FlutterStandardMessageCodec *sSharedObject = nil;
   static dispatch_once_t sPred = 0;
   dispatch_once(&sPred, ^{
-    FLTHostIntegrationCoreApiCodecReaderWriter *readerWriter =
-        [[FLTHostIntegrationCoreApiCodecReaderWriter alloc] init];
+    FLTCoreTestsPigeonCodecReaderWriter *readerWriter =
+        [[FLTCoreTestsPigeonCodecReaderWriter alloc] init];
     sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
   });
   return sSharedObject;
 }
-
 void SetUpFLTHostIntegrationCoreApi(id<FlutterBinaryMessenger> binaryMessenger,
                                     NSObject<FLTHostIntegrationCoreApi> *api) {
   SetUpFLTHostIntegrationCoreApiWithSuffix(binaryMessenger, api, @"");
@@ -470,7 +519,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.noop",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(noopWithError:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(noopWithError:)",
@@ -492,14 +541,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAllTypes",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoAllTypes:error:)],
           @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoAllTypes:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FLTAllTypes *output = [api echoAllTypes:arg_everything error:&error];
@@ -517,7 +566,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.throwError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(throwErrorWithError:)],
@@ -540,7 +589,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.throwErrorFromVoid",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwErrorFromVoidWithError:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -563,7 +612,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.throwFlutterError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwFlutterErrorWithError:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -586,13 +635,13 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoInt:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoInt:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         FlutterError *error;
         NSNumber *output = [api echoInt:arg_anInt error:&error];
@@ -610,14 +659,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoDouble:error:)],
           @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoDouble:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         FlutterError *error;
         NSNumber *output = [api echoDouble:arg_aDouble error:&error];
@@ -635,13 +684,13 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoBool:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoBool:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         BOOL arg_aBool = [GetNullableObjectAtIndex(args, 0) boolValue];
         FlutterError *error;
         NSNumber *output = [api echoBool:arg_aBool error:&error];
@@ -659,14 +708,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoString:error:)],
           @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoString:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoString:arg_aString error:&error];
@@ -684,14 +733,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoUint8List",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoUint8List:error:)],
           @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoUint8List:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aUint8List = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FlutterStandardTypedData *output = [api echoUint8List:arg_aUint8List error:&error];
@@ -709,14 +758,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoObject",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoObject:error:)],
           @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoObject:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_anObject = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         id output = [api echoObject:arg_anObject error:&error];
@@ -734,13 +783,13 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoList:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoList:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSArray<id> *output = [api echoList:arg_list error:&error];
@@ -758,13 +807,13 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoMap:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoMap:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSDictionary<NSString *, id> *output = [api echoMap:arg_aMap error:&error];
@@ -782,14 +831,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoClassWrapper",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoClassWrapper:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoClassWrapper:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllClassesWrapper *arg_wrapper = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FLTAllClassesWrapper *output = [api echoClassWrapper:arg_wrapper error:&error];
@@ -807,17 +856,17 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoEnum:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to @selector(echoEnum:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        FLTAnEnum arg_anEnum = [GetNullableObjectAtIndex(args, 0) integerValue];
+        NSArray<id> *args = message;
+        FLTAnEnumBox *enumBox = GetNullableObjectAtIndex(args, 0);
+        FLTAnEnum arg_anEnum = enumBox.value;
         FlutterError *error;
-        FLTAnEnumBox *enumBox = [api echoEnum:arg_anEnum error:&error];
-        NSNumber *output = enumBox == nil ? nil : [NSNumber numberWithInteger:enumBox.value];
+        FLTAnEnumBox *output = [api echoEnum:arg_anEnum error:&error];
         callback(wrapResult(output, error));
       }];
     } else {
@@ -832,14 +881,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNamedDefaultString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNamedDefaultString:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNamedDefaultString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoNamedDefaultString:arg_aString error:&error];
@@ -858,14 +907,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoOptionalDefaultDouble",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoOptionalDefaultDouble:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoOptionalDefaultDouble:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         FlutterError *error;
         NSNumber *output = [api echoOptionalDefaultDouble:arg_aDouble error:&error];
@@ -883,14 +932,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoRequiredInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoRequiredInt:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoRequiredInt:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         FlutterError *error;
         NSNumber *output = [api echoRequiredInt:arg_anInt error:&error];
@@ -908,14 +957,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAllNullableTypes",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAllNullableTypes:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAllNullableTypes:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllNullableTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FLTAllNullableTypes *output = [api echoAllNullableTypes:arg_everything error:&error];
@@ -935,14 +984,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                     @"HostIntegrationCoreApi.echoAllNullableTypesWithoutRecursion",
                                     messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAllNullableTypesWithoutRecursion:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAllNullableTypesWithoutRecursion:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllNullableTypesWithoutRecursion *arg_everything = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FLTAllNullableTypesWithoutRecursion *output =
@@ -963,14 +1012,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.extractNestedNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(extractNestedNullableStringFrom:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(extractNestedNullableStringFrom:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllClassesWrapper *arg_wrapper = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api extractNestedNullableStringFrom:arg_wrapper error:&error];
@@ -990,14 +1039,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.createNestedNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(createNestedObjectWithNullableString:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(createNestedObjectWithNullableString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_nullableString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FLTAllClassesWrapper *output = [api createNestedObjectWithNullableString:arg_nullableString
@@ -1017,7 +1066,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.sendMultipleNullableTypes",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(sendMultipleNullableTypesABool:
                                                                            anInt:aString:error:)],
@@ -1025,7 +1074,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                 @"@selector(sendMultipleNullableTypesABool:anInt:aString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -1050,7 +1099,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                 @"HostIntegrationCoreApi.sendMultipleNullableTypesWithoutRecursion",
                                 messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (sendMultipleNullableTypesWithoutRecursionABool:anInt:aString:error:)],
@@ -1058,7 +1107,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                 @"@selector(sendMultipleNullableTypesWithoutRecursionABool:anInt:aString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -1082,14 +1131,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableInt:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableInt:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoNullableInt:arg_aNullableInt error:&error];
@@ -1107,14 +1156,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableDouble:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableDouble:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableDouble = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoNullableDouble:arg_aNullableDouble error:&error];
@@ -1132,14 +1181,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableBool:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableBool:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoNullableBool:arg_aNullableBool error:&error];
@@ -1157,14 +1206,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableString:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoNullableString:arg_aNullableString error:&error];
@@ -1182,14 +1231,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableUint8List",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableUint8List:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableUint8List:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aNullableUint8List = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FlutterStandardTypedData *output = [api echoNullableUint8List:arg_aNullableUint8List
@@ -1208,14 +1257,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableObject",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableObject:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableObject:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_aNullableObject = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         id output = [api echoNullableObject:arg_aNullableObject error:&error];
@@ -1233,14 +1282,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableList:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableList:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_aNullableList = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSArray<id> *output = [api echoNullableList:arg_aNullableList error:&error];
@@ -1258,14 +1307,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableMap:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableMap:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aNullableMap = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSDictionary<NSString *, id> *output = [api echoNullableMap:arg_aNullableMap error:&error];
@@ -1282,22 +1331,17 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoNullableEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableEnum:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableEnum:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        NSNumber *arg_anEnumAsNumber = GetNullableObjectAtIndex(args, 0);
-        FLTAnEnumBox *arg_anEnum =
-            arg_anEnumAsNumber == nil
-                ? nil
-                : [[FLTAnEnumBox alloc] initWithValue:[arg_anEnumAsNumber integerValue]];
+        NSArray<id> *args = message;
+        FLTAnEnumBox *arg_anEnum = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
-        FLTAnEnumBox *enumBox = [api echoNullableEnum:arg_anEnum error:&error];
-        NSNumber *output = enumBox == nil ? nil : [NSNumber numberWithInteger:enumBox.value];
+        FLTAnEnumBox *output = [api echoNullableEnum:arg_anEnum error:&error];
         callback(wrapResult(output, error));
       }];
     } else {
@@ -1313,14 +1357,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoOptionalNullableInt",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoOptionalNullableInt:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoOptionalNullableInt:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoOptionalNullableInt:arg_aNullableInt error:&error];
@@ -1339,14 +1383,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoNamedNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNamedNullableString:error:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNamedNullableString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoNamedNullableString:arg_aNullableString error:&error];
@@ -1365,7 +1409,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.noopAsync",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(noopAsyncWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1388,14 +1432,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncInt:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         [api echoAsyncInt:arg_anInt
                completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1414,14 +1458,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncDouble:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         [api echoAsyncDouble:arg_aDouble
                   completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1440,14 +1484,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncBool:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         BOOL arg_aBool = [GetNullableObjectAtIndex(args, 0) boolValue];
         [api echoAsyncBool:arg_aBool
                 completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1466,14 +1510,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncString:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncString:arg_aString
                   completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -1492,14 +1536,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncUint8List",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncUint8List:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aUint8List = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncUint8List:arg_aUint8List
                      completion:^(FlutterStandardTypedData *_Nullable output,
@@ -1519,14 +1563,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncObject",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncObject:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncObject:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_anObject = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncObject:arg_anObject
                   completion:^(id _Nullable output, FlutterError *_Nullable error) {
@@ -1545,14 +1589,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncList:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncList:arg_list
                 completion:^(NSArray<id> *_Nullable output, FlutterError *_Nullable error) {
@@ -1571,14 +1615,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncMap:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncMap:arg_aMap
                completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -1598,19 +1642,18 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncEnum:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        FLTAnEnum arg_anEnum = [GetNullableObjectAtIndex(args, 0) integerValue];
+        NSArray<id> *args = message;
+        FLTAnEnumBox *enumBox = GetNullableObjectAtIndex(args, 0);
+        FLTAnEnum arg_anEnum = enumBox.value;
         [api echoAsyncEnum:arg_anEnum
-                completion:^(FLTAnEnumBox *_Nullable enumValue, FlutterError *_Nullable error) {
-                  NSNumber *output =
-                      enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];
+                completion:^(FLTAnEnumBox *_Nullable output, FlutterError *_Nullable error) {
                   callback(wrapResult(output, error));
                 }];
       }];
@@ -1626,7 +1669,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.throwAsyncError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwAsyncErrorWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1650,7 +1693,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.throwAsyncErrorFromVoid",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwAsyncErrorFromVoidWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1673,7 +1716,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.throwAsyncFlutterError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwAsyncFlutterErrorWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1697,14 +1740,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncAllTypes",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncAllTypes:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncAllTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncAllTypes:arg_everything
                     completion:^(FLTAllTypes *_Nullable output, FlutterError *_Nullable error) {
@@ -1724,14 +1767,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                       @"HostIntegrationCoreApi.echoAsyncNullableAllNullableTypes",
                                       messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableAllNullableTypes:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableAllNullableTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllNullableTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableAllNullableTypes:arg_everything
                                     completion:^(FLTAllNullableTypes *_Nullable output,
@@ -1753,7 +1796,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"echoAsyncNullableAllNullableTypesWithoutRecursion",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (echoAsyncNullableAllNullableTypesWithoutRecursion:completion:)],
@@ -1761,7 +1804,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                 @"@selector(echoAsyncNullableAllNullableTypesWithoutRecursion:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllNullableTypesWithoutRecursion *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableAllNullableTypesWithoutRecursion:arg_everything
                                                     completion:^(FLTAllNullableTypesWithoutRecursion
@@ -1782,14 +1825,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncNullableInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableInt:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_anInt = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableInt:arg_anInt
                        completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1809,14 +1852,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoAsyncNullableDouble",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableDouble:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aDouble = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableDouble:arg_aDouble
                           completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1835,14 +1878,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncNullableBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableBool:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aBool = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableBool:arg_aBool
                         completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1862,14 +1905,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoAsyncNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableString:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableString:arg_aString
                           completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -1889,14 +1932,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoAsyncNullableUint8List",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableUint8List:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aUint8List = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableUint8List:arg_aUint8List
                              completion:^(FlutterStandardTypedData *_Nullable output,
@@ -1917,14 +1960,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.echoAsyncNullableObject",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableObject:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableObject:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_anObject = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableObject:arg_anObject
                           completion:^(id _Nullable output, FlutterError *_Nullable error) {
@@ -1943,14 +1986,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncNullableList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableList:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableList:arg_list
                         completion:^(NSArray<id> *_Nullable output, FlutterError *_Nullable error) {
@@ -1969,14 +2012,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncNullableMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableMap:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableMap:arg_aMap
                        completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -1996,26 +2039,20 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.echoAsyncNullableEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableEnum:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        NSNumber *arg_anEnumAsNumber = GetNullableObjectAtIndex(args, 0);
-        FLTAnEnumBox *arg_anEnum =
-            arg_anEnumAsNumber == nil
-                ? nil
-                : [[FLTAnEnumBox alloc] initWithValue:[arg_anEnumAsNumber integerValue]];
-        [api echoAsyncNullableEnum:arg_anEnum
-                        completion:^(FLTAnEnumBox *_Nullable enumValue,
-                                     FlutterError *_Nullable error) {
-                          NSNumber *output =
-                              enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];
-                          callback(wrapResult(output, error));
-                        }];
+        NSArray<id> *args = message;
+        FLTAnEnumBox *arg_anEnum = GetNullableObjectAtIndex(args, 0);
+        [api
+            echoAsyncNullableEnum:arg_anEnum
+                       completion:^(FLTAnEnumBox *_Nullable output, FlutterError *_Nullable error) {
+                         callback(wrapResult(output, error));
+                       }];
       }];
     } else {
       [channel setMessageHandler:nil];
@@ -2028,7 +2065,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterNoop",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterNoopWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -2050,7 +2087,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterThrowError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterThrowErrorWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -2074,7 +2111,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                           @"HostIntegrationCoreApi.callFlutterThrowErrorFromVoid",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterThrowErrorFromVoidWithCompletion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
@@ -2097,14 +2134,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoAllTypes",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoAllTypes:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoAllTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoAllTypes:arg_everything
                           completion:^(FLTAllTypes *_Nullable output,
@@ -2124,14 +2161,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                           @"HostIntegrationCoreApi.callFlutterEchoAllNullableTypes",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoAllNullableTypes:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoAllNullableTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllNullableTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoAllNullableTypes:arg_everything
                                   completion:^(FLTAllNullableTypes *_Nullable output,
@@ -2152,7 +2189,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                     @"HostIntegrationCoreApi.callFlutterSendMultipleNullableTypes",
                                     messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (callFlutterSendMultipleNullableTypesABool:anInt:aString:completion:)],
@@ -2160,7 +2197,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                 @"@selector(callFlutterSendMultipleNullableTypesABool:anInt:aString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -2185,7 +2222,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"callFlutterEchoAllNullableTypesWithoutRecursion",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (callFlutterEchoAllNullableTypesWithoutRecursion:completion:)],
@@ -2193,7 +2230,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                 @"@selector(callFlutterEchoAllNullableTypesWithoutRecursion:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FLTAllNullableTypesWithoutRecursion *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoAllNullableTypesWithoutRecursion:arg_everything
                                                   completion:^(FLTAllNullableTypesWithoutRecursion
@@ -2215,7 +2252,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                              @"callFlutterSendMultipleNullableTypesWithoutRecursion",
                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector
@@ -2226,7 +2263,7 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
           @"completion:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -2251,14 +2288,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoBool:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         BOOL arg_aBool = [GetNullableObjectAtIndex(args, 0) boolValue];
         [api callFlutterEchoBool:arg_aBool
                       completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -2276,14 +2313,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoInt:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         [api callFlutterEchoInt:arg_anInt
                      completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -2301,14 +2338,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoDouble:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         [api callFlutterEchoDouble:arg_aDouble
                         completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -2326,14 +2363,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoString:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoString:arg_aString
                         completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -2352,14 +2389,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoUint8List",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoUint8List:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoUint8List:arg_list
                            completion:^(FlutterStandardTypedData *_Nullable output,
@@ -2378,14 +2415,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoList:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoList:arg_list
                       completion:^(NSArray<id> *_Nullable output, FlutterError *_Nullable error) {
@@ -2403,14 +2440,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoMap:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoMap:arg_aMap
                      completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -2429,20 +2466,18 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                                    @"HostIntegrationCoreApi.callFlutterEchoEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoEnum:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        FLTAnEnum arg_anEnum = [GetNullableObjectAtIndex(args, 0) integerValue];
+        NSArray<id> *args = message;
+        FLTAnEnumBox *enumBox = GetNullableObjectAtIndex(args, 0);
+        FLTAnEnum arg_anEnum = enumBox.value;
         [api callFlutterEchoEnum:arg_anEnum
-                      completion:^(FLTAnEnumBox *_Nullable enumValue,
-                                   FlutterError *_Nullable error) {
-                        NSNumber *output =
-                            enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];
+                      completion:^(FLTAnEnumBox *_Nullable output, FlutterError *_Nullable error) {
                         callback(wrapResult(output, error));
                       }];
       }];
@@ -2458,14 +2493,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableBool",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableBool:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aBool = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableBool:arg_aBool
                               completion:^(NSNumber *_Nullable output,
@@ -2485,14 +2520,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableInt",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableInt:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_anInt = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableInt:arg_anInt
                              completion:^(NSNumber *_Nullable output,
@@ -2512,14 +2547,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                           @"HostIntegrationCoreApi.callFlutterEchoNullableDouble",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableDouble:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aDouble = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableDouble:arg_aDouble
                                 completion:^(NSNumber *_Nullable output,
@@ -2539,14 +2574,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                           @"HostIntegrationCoreApi.callFlutterEchoNullableString",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableString:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableString:arg_aString
                                 completion:^(NSString *_Nullable output,
@@ -2566,14 +2601,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                       @"HostIntegrationCoreApi.callFlutterEchoNullableUint8List",
                                       messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableUint8List:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableUint8List:arg_list
                                    completion:^(FlutterStandardTypedData *_Nullable output,
@@ -2593,14 +2628,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableList",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableList:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableList:arg_list
                               completion:^(NSArray<id> *_Nullable output,
@@ -2620,14 +2655,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableMap",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableMap:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableMap:arg_aMap
                              completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -2647,25 +2682,18 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableEnum",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableEnum:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        NSNumber *arg_anEnumAsNumber = GetNullableObjectAtIndex(args, 0);
-        FLTAnEnumBox *arg_anEnum =
-            arg_anEnumAsNumber == nil
-                ? nil
-                : [[FLTAnEnumBox alloc] initWithValue:[arg_anEnumAsNumber integerValue]];
+        NSArray<id> *args = message;
+        FLTAnEnumBox *arg_anEnum = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableEnum:arg_anEnum
-                              completion:^(FLTAnEnumBox *_Nullable enumValue,
+                              completion:^(FLTAnEnumBox *_Nullable output,
                                            FlutterError *_Nullable error) {
-                                NSNumber *output =
-                                    enumValue == nil ? nil
-                                                     : [NSNumber numberWithInteger:enumValue.value];
                                 callback(wrapResult(output, error));
                               }];
       }];
@@ -2681,14 +2709,14 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
                                           @"HostIntegrationCoreApi.callFlutterSmallApiEchoString",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostIntegrationCoreApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterSmallApiEchoString:completion:)],
                 @"FLTHostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterSmallApiEchoString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api callFlutterSmallApiEchoString:arg_aString
                                 completion:^(NSString *_Nullable output,
@@ -2701,74 +2729,6 @@ void SetUpFLTHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryM
     }
   }
 }
-@interface FLTFlutterIntegrationCoreApiCodecReader : FlutterStandardReader
-@end
-@implementation FLTFlutterIntegrationCoreApiCodecReader
-- (nullable id)readValueOfType:(UInt8)type {
-  switch (type) {
-    case 128:
-      return [FLTAllClassesWrapper fromList:[self readValue]];
-    case 129:
-      return [FLTAllNullableTypes fromList:[self readValue]];
-    case 130:
-      return [FLTAllNullableTypesWithoutRecursion fromList:[self readValue]];
-    case 131:
-      return [FLTAllTypes fromList:[self readValue]];
-    case 132:
-      return [FLTTestMessage fromList:[self readValue]];
-    default:
-      return [super readValueOfType:type];
-  }
-}
-@end
-
-@interface FLTFlutterIntegrationCoreApiCodecWriter : FlutterStandardWriter
-@end
-@implementation FLTFlutterIntegrationCoreApiCodecWriter
-- (void)writeValue:(id)value {
-  if ([value isKindOfClass:[FLTAllClassesWrapper class]]) {
-    [self writeByte:128];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTAllNullableTypes class]]) {
-    [self writeByte:129];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTAllNullableTypesWithoutRecursion class]]) {
-    [self writeByte:130];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTAllTypes class]]) {
-    [self writeByte:131];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[FLTTestMessage class]]) {
-    [self writeByte:132];
-    [self writeValue:[value toList]];
-  } else {
-    [super writeValue:value];
-  }
-}
-@end
-
-@interface FLTFlutterIntegrationCoreApiCodecReaderWriter : FlutterStandardReaderWriter
-@end
-@implementation FLTFlutterIntegrationCoreApiCodecReaderWriter
-- (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[FLTFlutterIntegrationCoreApiCodecWriter alloc] initWithData:data];
-}
-- (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[FLTFlutterIntegrationCoreApiCodecReader alloc] initWithData:data];
-}
-@end
-
-NSObject<FlutterMessageCodec> *FLTFlutterIntegrationCoreApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  static dispatch_once_t sPred = 0;
-  dispatch_once(&sPred, ^{
-    FLTFlutterIntegrationCoreApiCodecReaderWriter *readerWriter =
-        [[FLTFlutterIntegrationCoreApiCodecReaderWriter alloc] init];
-    sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
-  });
-  return sSharedObject;
-}
-
 @interface FLTFlutterIntegrationCoreApi ()
 @property(nonatomic, strong) NSObject<FlutterBinaryMessenger> *binaryMessenger;
 @property(nonatomic, strong) NSString *messageChannelSuffix;
@@ -2798,7 +2758,7 @@ - (void)noopWithCompletion:(void (^)(FlutterError *_Nullable))completion {
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2823,7 +2783,7 @@ - (void)throwErrorWithCompletion:(void (^)(id _Nullable, FlutterError *_Nullable
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2849,7 +2809,7 @@ - (void)throwErrorFromVoidWithCompletion:(void (^)(FlutterError *_Nullable))comp
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2875,7 +2835,7 @@ - (void)echoAllTypes:(FLTAllTypes *)arg_everything
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_everything ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2903,7 +2863,7 @@ - (void)echoAllNullableTypes:(nullable FLTAllNullableTypes *)arg_everything
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_everything ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2933,7 +2893,7 @@ - (void)sendMultipleNullableTypesABool:(nullable NSNumber *)arg_aNullableBool
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[
     arg_aNullableBool ?: [NSNull null], arg_aNullableInt ?: [NSNull null],
     arg_aNullableString ?: [NSNull null]
@@ -2966,7 +2926,7 @@ - (void)echoAllNullableTypesWithoutRecursion:
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_everything ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2999,7 +2959,7 @@ - (void)sendMultipleNullableTypesWithoutRecursionABool:(nullable NSNumber *)arg_
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[
     arg_aNullableBool ?: [NSNull null], arg_aNullableInt ?: [NSNull null],
     arg_aNullableString ?: [NSNull null]
@@ -3030,7 +2990,7 @@ - (void)echoBool:(BOOL)arg_aBool
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ @(arg_aBool) ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3056,7 +3016,7 @@ - (void)echoInt:(NSInteger)arg_anInt
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ @(arg_anInt) ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3083,7 +3043,7 @@ - (void)echoDouble:(double)arg_aDouble
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ @(arg_aDouble) ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3110,7 +3070,7 @@ - (void)echoString:(NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3138,7 +3098,7 @@ - (void)echoUint8List:(FlutterStandardTypedData *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3166,7 +3126,7 @@ - (void)echoList:(NSArray<id> *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3193,7 +3153,7 @@ - (void)echoMap:(NSDictionary<NSString *, id> *)arg_aMap
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aMap ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3221,8 +3181,8 @@ - (void)echoEnum:(FLTAnEnum)arg_anEnum
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
-  [channel sendMessage:@[ [NSNumber numberWithInteger:arg_anEnum] ]
+                                                   codec:FLTGetCoreTestsCodec()];
+  [channel sendMessage:@[ [[FLTAnEnumBox alloc] initWithValue:arg_anEnum] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
                      if (reply.count > 1) {
@@ -3230,11 +3190,7 @@ - (void)echoEnum:(FLTAnEnum)arg_anEnum
                                                            message:reply[1]
                                                            details:reply[2]]);
                      } else {
-                       NSNumber *outputAsNumber = reply[0] == [NSNull null] ? nil : reply[0];
-                       FLTAnEnumBox *output =
-                           outputAsNumber == nil
-                               ? nil
-                               : [[FLTAnEnumBox alloc] initWithValue:[outputAsNumber integerValue]];
+                       FLTAnEnumBox *output = reply[0] == [NSNull null] ? nil : reply[0];
                        completion(output, nil);
                      }
                    } else {
@@ -3252,7 +3208,7 @@ - (void)echoNullableBool:(nullable NSNumber *)arg_aBool
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aBool ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3279,7 +3235,7 @@ - (void)echoNullableInt:(nullable NSNumber *)arg_anInt
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_anInt ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3306,7 +3262,7 @@ - (void)echoNullableDouble:(nullable NSNumber *)arg_aDouble
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aDouble ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3333,7 +3289,7 @@ - (void)echoNullableString:(nullable NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3361,7 +3317,7 @@ - (void)echoNullableUint8List:(nullable FlutterStandardTypedData *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3389,7 +3345,7 @@ - (void)echoNullableList:(nullable NSArray<id> *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3417,7 +3373,7 @@ - (void)echoNullableMap:(nullable NSDictionary<NSString *, id> *)arg_aMap
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aMap ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3445,9 +3401,8 @@ - (void)echoNullableEnum:(nullable FLTAnEnumBox *)arg_anEnum
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
-  [channel sendMessage:@[ arg_anEnum == nil ? [NSNull null]
-                                            : [NSNumber numberWithInteger:arg_anEnum.value] ]
+                                                   codec:FLTGetCoreTestsCodec()];
+  [channel sendMessage:@[ arg_anEnum == nil ? [NSNull null] : arg_anEnum ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
                      if (reply.count > 1) {
@@ -3455,11 +3410,7 @@ - (void)echoNullableEnum:(nullable FLTAnEnumBox *)arg_anEnum
                                                            message:reply[1]
                                                            details:reply[2]]);
                      } else {
-                       NSNumber *outputAsNumber = reply[0] == [NSNull null] ? nil : reply[0];
-                       FLTAnEnumBox *output =
-                           outputAsNumber == nil
-                               ? nil
-                               : [[FLTAnEnumBox alloc] initWithValue:[outputAsNumber integerValue]];
+                       FLTAnEnumBox *output = reply[0] == [NSNull null] ? nil : reply[0];
                        completion(output, nil);
                      }
                    } else {
@@ -3476,7 +3427,7 @@ - (void)noopAsyncWithCompletion:(void (^)(FlutterError *_Nullable))completion {
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3502,7 +3453,7 @@ - (void)echoAsyncString:(NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterIntegrationCoreApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3521,12 +3472,6 @@ - (void)echoAsyncString:(NSString *)arg_aString
 }
 @end
 
-NSObject<FlutterMessageCodec> *FLTHostTrivialApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  sSharedObject = [FlutterStandardMessageCodec sharedInstance];
-  return sSharedObject;
-}
-
 void SetUpFLTHostTrivialApi(id<FlutterBinaryMessenger> binaryMessenger,
                             NSObject<FLTHostTrivialApi> *api) {
   SetUpFLTHostTrivialApiWithSuffix(binaryMessenger, api, @"");
@@ -3546,7 +3491,7 @@ void SetUpFLTHostTrivialApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger
                                 @"dev.flutter.pigeon.pigeon_integration_tests.HostTrivialApi.noop",
                                 messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostTrivialApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(noopWithError:)],
                 @"FLTHostTrivialApi api (%@) doesn't respond to @selector(noopWithError:)", api);
@@ -3560,12 +3505,6 @@ void SetUpFLTHostTrivialApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger
     }
   }
 }
-NSObject<FlutterMessageCodec> *FLTHostSmallApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  sSharedObject = [FlutterStandardMessageCodec sharedInstance];
-  return sSharedObject;
-}
-
 void SetUpFLTHostSmallApi(id<FlutterBinaryMessenger> binaryMessenger,
                           NSObject<FLTHostSmallApi> *api) {
   SetUpFLTHostSmallApiWithSuffix(binaryMessenger, api, @"");
@@ -3585,13 +3524,13 @@ void SetUpFLTHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
                                 @"dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo",
                                 messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostSmallApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoString:completion:)],
                 @"FLTHostSmallApi api (%@) doesn't respond to @selector(echoString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api echoString:arg_aString
              completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -3609,7 +3548,7 @@ void SetUpFLTHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
                                                    @"HostSmallApi.voidVoid",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:FLTHostSmallApiGetCodec()];
+                  codec:FLTGetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(voidVoidWithCompletion:)],
                 @"FLTHostSmallApi api (%@) doesn't respond to @selector(voidVoidWithCompletion:)",
@@ -3624,54 +3563,6 @@ void SetUpFLTHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
     }
   }
 }
-@interface FLTFlutterSmallApiCodecReader : FlutterStandardReader
-@end
-@implementation FLTFlutterSmallApiCodecReader
-- (nullable id)readValueOfType:(UInt8)type {
-  switch (type) {
-    case 128:
-      return [FLTTestMessage fromList:[self readValue]];
-    default:
-      return [super readValueOfType:type];
-  }
-}
-@end
-
-@interface FLTFlutterSmallApiCodecWriter : FlutterStandardWriter
-@end
-@implementation FLTFlutterSmallApiCodecWriter
-- (void)writeValue:(id)value {
-  if ([value isKindOfClass:[FLTTestMessage class]]) {
-    [self writeByte:128];
-    [self writeValue:[value toList]];
-  } else {
-    [super writeValue:value];
-  }
-}
-@end
-
-@interface FLTFlutterSmallApiCodecReaderWriter : FlutterStandardReaderWriter
-@end
-@implementation FLTFlutterSmallApiCodecReaderWriter
-- (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[FLTFlutterSmallApiCodecWriter alloc] initWithData:data];
-}
-- (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[FLTFlutterSmallApiCodecReader alloc] initWithData:data];
-}
-@end
-
-NSObject<FlutterMessageCodec> *FLTFlutterSmallApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  static dispatch_once_t sPred = 0;
-  dispatch_once(&sPred, ^{
-    FLTFlutterSmallApiCodecReaderWriter *readerWriter =
-        [[FLTFlutterSmallApiCodecReaderWriter alloc] init];
-    sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
-  });
-  return sSharedObject;
-}
-
 @interface FLTFlutterSmallApi ()
 @property(nonatomic, strong) NSObject<FlutterBinaryMessenger> *binaryMessenger;
 @property(nonatomic, strong) NSString *messageChannelSuffix;
@@ -3702,7 +3593,7 @@ - (void)echoWrappedList:(FLTTestMessage *)arg_msg
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterSmallApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_msg ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3728,7 +3619,7 @@ - (void)echoString:(NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FLTFlutterSmallApiGetCodec()];
+                                                   codec:FLTGetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h
index ee54d035eb6..f2b2c074755 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h
@@ -46,11 +46,15 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
                   a4ByteArray:(FlutterStandardTypedData *)a4ByteArray
                   a8ByteArray:(FlutterStandardTypedData *)a8ByteArray
                   aFloatArray:(FlutterStandardTypedData *)aFloatArray
-                         list:(NSArray *)list
-                         aMap:(NSDictionary *)aMap
                        anEnum:(AnEnum)anEnum
                       aString:(NSString *)aString
-                     anObject:(id)anObject;
+                     anObject:(id)anObject
+                         list:(NSArray<id> *)list
+                   stringList:(NSArray<NSString *> *)stringList
+                      intList:(NSArray<NSNumber *> *)intList
+                   doubleList:(NSArray<NSNumber *> *)doubleList
+                     boolList:(NSArray<NSNumber *> *)boolList
+                          map:(NSDictionary *)map;
 @property(nonatomic, assign) BOOL aBool;
 @property(nonatomic, assign) NSInteger anInt;
 @property(nonatomic, assign) NSInteger anInt64;
@@ -59,11 +63,15 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
 @property(nonatomic, strong) FlutterStandardTypedData *a4ByteArray;
 @property(nonatomic, strong) FlutterStandardTypedData *a8ByteArray;
 @property(nonatomic, strong) FlutterStandardTypedData *aFloatArray;
-@property(nonatomic, copy) NSArray *list;
-@property(nonatomic, copy) NSDictionary *aMap;
 @property(nonatomic, assign) AnEnum anEnum;
 @property(nonatomic, copy) NSString *aString;
 @property(nonatomic, strong) id anObject;
+@property(nonatomic, copy) NSArray<id> *list;
+@property(nonatomic, copy) NSArray<NSString *> *stringList;
+@property(nonatomic, copy) NSArray<NSNumber *> *intList;
+@property(nonatomic, copy) NSArray<NSNumber *> *doubleList;
+@property(nonatomic, copy) NSArray<NSNumber *> *boolList;
+@property(nonatomic, copy) NSDictionary *map;
 @end
 
 /// A class containing all supported nullable types.
@@ -76,8 +84,6 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
@@ -85,7 +91,14 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
                         aNullableEnum:(nullable AnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
                       aNullableObject:(nullable id)aNullableObject
-                     allNullableTypes:(nullable AllNullableTypes *)allNullableTypes;
+                     allNullableTypes:(nullable AllNullableTypes *)allNullableTypes
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                      nestedClassList:(nullable NSArray<AllNullableTypes *> *)nestedClassList
+                                  map:(nullable NSDictionary *)map;
 @property(nonatomic, strong, nullable) NSNumber *aNullableBool;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt64;
@@ -94,8 +107,6 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable4ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable8ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullableFloatArray;
-@property(nonatomic, copy, nullable) NSArray *aNullableList;
-@property(nonatomic, copy, nullable) NSDictionary *aNullableMap;
 @property(nonatomic, copy, nullable) NSArray<NSArray<NSNumber *> *> *nullableNestedList;
 @property(nonatomic, copy, nullable)
     NSDictionary<NSString *, NSString *> *nullableMapWithAnnotations;
@@ -104,6 +115,13 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
 @property(nonatomic, copy, nullable) NSString *aNullableString;
 @property(nonatomic, strong, nullable) id aNullableObject;
 @property(nonatomic, strong, nullable) AllNullableTypes *allNullableTypes;
+@property(nonatomic, copy, nullable) NSArray<id> *list;
+@property(nonatomic, copy, nullable) NSArray<NSString *> *stringList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *intList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *doubleList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *boolList;
+@property(nonatomic, copy, nullable) NSArray<AllNullableTypes *> *nestedClassList;
+@property(nonatomic, copy, nullable) NSDictionary *map;
 @end
 
 /// The primary purpose for this class is to ensure coverage of Swift structs
@@ -118,15 +136,19 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
                 nullableMapWithObject:(nullable NSDictionary<NSString *, id> *)nullableMapWithObject
                         aNullableEnum:(nullable AnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
-                      aNullableObject:(nullable id)aNullableObject;
+                      aNullableObject:(nullable id)aNullableObject
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                                  map:(nullable NSDictionary *)map;
 @property(nonatomic, strong, nullable) NSNumber *aNullableBool;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt;
 @property(nonatomic, strong, nullable) NSNumber *aNullableInt64;
@@ -135,8 +157,6 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable4ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullable8ByteArray;
 @property(nonatomic, strong, nullable) FlutterStandardTypedData *aNullableFloatArray;
-@property(nonatomic, copy, nullable) NSArray *aNullableList;
-@property(nonatomic, copy, nullable) NSDictionary *aNullableMap;
 @property(nonatomic, copy, nullable) NSArray<NSArray<NSNumber *> *> *nullableNestedList;
 @property(nonatomic, copy, nullable)
     NSDictionary<NSString *, NSString *> *nullableMapWithAnnotations;
@@ -144,6 +164,12 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
 @property(nonatomic, strong, nullable) AnEnumBox *aNullableEnum;
 @property(nonatomic, copy, nullable) NSString *aNullableString;
 @property(nonatomic, strong, nullable) id aNullableObject;
+@property(nonatomic, copy, nullable) NSArray<id> *list;
+@property(nonatomic, copy, nullable) NSArray<NSString *> *stringList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *intList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *doubleList;
+@property(nonatomic, copy, nullable) NSArray<NSNumber *> *boolList;
+@property(nonatomic, copy, nullable) NSDictionary *map;
 @end
 
 /// A class for testing nested class handling.
@@ -166,12 +192,12 @@ typedef NS_ENUM(NSUInteger, AnEnum) {
 
 /// A data class containing a List, used in unit tests.
 @interface TestMessage : NSObject
-+ (instancetype)makeWithTestList:(nullable NSArray *)testList;
-@property(nonatomic, copy, nullable) NSArray *testList;
++ (instancetype)makeWithTestList:(nullable NSArray<id> *)testList;
+@property(nonatomic, copy, nullable) NSArray<id> *testList;
 @end
 
-/// The codec used by HostIntegrationCoreApi.
-NSObject<FlutterMessageCodec> *HostIntegrationCoreApiGetCodec(void);
+/// The codec used by all APIs.
+NSObject<FlutterMessageCodec> *GetCoreTestsCodec(void);
 
 /// The core interface that each host language plugin must implement in
 /// platform_test integration tests.
@@ -483,9 +509,6 @@ extern void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> bin
                                                   NSObject<HostIntegrationCoreApi> *_Nullable api,
                                                   NSString *messageChannelSuffix);
 
-/// The codec used by FlutterIntegrationCoreApi.
-NSObject<FlutterMessageCodec> *FlutterIntegrationCoreApiGetCodec(void);
-
 /// The core interface that the Dart platform_test code implements for host
 /// integration tests to call into.
 @interface FlutterIntegrationCoreApi : NSObject
@@ -588,9 +611,6 @@ NSObject<FlutterMessageCodec> *FlutterIntegrationCoreApiGetCodec(void);
              completion:(void (^)(NSString *_Nullable, FlutterError *_Nullable))completion;
 @end
 
-/// The codec used by HostTrivialApi.
-NSObject<FlutterMessageCodec> *HostTrivialApiGetCodec(void);
-
 /// An API that can be implemented for minimal, compile-only tests.
 @protocol HostTrivialApi
 - (void)noopWithError:(FlutterError *_Nullable *_Nonnull)error;
@@ -603,9 +623,6 @@ extern void SetUpHostTrivialApiWithSuffix(id<FlutterBinaryMessenger> binaryMesse
                                           NSObject<HostTrivialApi> *_Nullable api,
                                           NSString *messageChannelSuffix);
 
-/// The codec used by HostSmallApi.
-NSObject<FlutterMessageCodec> *HostSmallApiGetCodec(void);
-
 /// A simple API implemented in some unit tests.
 @protocol HostSmallApi
 - (void)echoString:(NSString *)aString
@@ -620,9 +637,6 @@ extern void SetUpHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMesseng
                                         NSObject<HostSmallApi> *_Nullable api,
                                         NSString *messageChannelSuffix);
 
-/// The codec used by FlutterSmallApi.
-NSObject<FlutterMessageCodec> *FlutterSmallApiGetCodec(void);
-
 /// A simple API called in some unit tests.
 @interface FlutterSmallApi : NSObject
 - (instancetype)initWithBinaryMessenger:(id<FlutterBinaryMessenger>)binaryMessenger;
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m
index fafcbcf7d73..be3810ceae8 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m
@@ -17,7 +17,7 @@
 #error File requires ARC to be enabled.
 #endif
 
-static NSArray *wrapResult(id result, FlutterError *error) {
+static NSArray<id> *wrapResult(id result, FlutterError *error) {
   if (error) {
     return @[
       error.code ?: [NSNull null], error.message ?: [NSNull null], error.details ?: [NSNull null]
@@ -35,7 +35,7 @@
             details:@""];
 }
 
-static id GetNullableObjectAtIndex(NSArray *array, NSInteger key) {
+static id GetNullableObjectAtIndex(NSArray<id> *array, NSInteger key) {
   id result = array[key];
   return (result == [NSNull null]) ? nil : result;
 }
@@ -51,33 +51,33 @@ - (instancetype)initWithValue:(AnEnum)value {
 @end
 
 @interface AllTypes ()
-+ (AllTypes *)fromList:(NSArray *)list;
-+ (nullable AllTypes *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (AllTypes *)fromList:(NSArray<id> *)list;
++ (nullable AllTypes *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface AllNullableTypes ()
-+ (AllNullableTypes *)fromList:(NSArray *)list;
-+ (nullable AllNullableTypes *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (AllNullableTypes *)fromList:(NSArray<id> *)list;
++ (nullable AllNullableTypes *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface AllNullableTypesWithoutRecursion ()
-+ (AllNullableTypesWithoutRecursion *)fromList:(NSArray *)list;
-+ (nullable AllNullableTypesWithoutRecursion *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (AllNullableTypesWithoutRecursion *)fromList:(NSArray<id> *)list;
++ (nullable AllNullableTypesWithoutRecursion *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface AllClassesWrapper ()
-+ (AllClassesWrapper *)fromList:(NSArray *)list;
-+ (nullable AllClassesWrapper *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (AllClassesWrapper *)fromList:(NSArray<id> *)list;
++ (nullable AllClassesWrapper *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @interface TestMessage ()
-+ (TestMessage *)fromList:(NSArray *)list;
-+ (nullable TestMessage *)nullableFromList:(NSArray *)list;
-- (NSArray *)toList;
++ (TestMessage *)fromList:(NSArray<id> *)list;
++ (nullable TestMessage *)nullableFromList:(NSArray<id> *)list;
+- (NSArray<id> *)toList;
 @end
 
 @implementation AllTypes
@@ -89,11 +89,15 @@ + (instancetype)makeWithABool:(BOOL)aBool
                   a4ByteArray:(FlutterStandardTypedData *)a4ByteArray
                   a8ByteArray:(FlutterStandardTypedData *)a8ByteArray
                   aFloatArray:(FlutterStandardTypedData *)aFloatArray
-                         list:(NSArray *)list
-                         aMap:(NSDictionary *)aMap
                        anEnum:(AnEnum)anEnum
                       aString:(NSString *)aString
-                     anObject:(id)anObject {
+                     anObject:(id)anObject
+                         list:(NSArray<id> *)list
+                   stringList:(NSArray<NSString *> *)stringList
+                      intList:(NSArray<NSNumber *> *)intList
+                   doubleList:(NSArray<NSNumber *> *)doubleList
+                     boolList:(NSArray<NSNumber *> *)boolList
+                          map:(NSDictionary *)map {
   AllTypes *pigeonResult = [[AllTypes alloc] init];
   pigeonResult.aBool = aBool;
   pigeonResult.anInt = anInt;
@@ -103,14 +107,18 @@ + (instancetype)makeWithABool:(BOOL)aBool
   pigeonResult.a4ByteArray = a4ByteArray;
   pigeonResult.a8ByteArray = a8ByteArray;
   pigeonResult.aFloatArray = aFloatArray;
-  pigeonResult.list = list;
-  pigeonResult.aMap = aMap;
   pigeonResult.anEnum = anEnum;
   pigeonResult.aString = aString;
   pigeonResult.anObject = anObject;
+  pigeonResult.list = list;
+  pigeonResult.stringList = stringList;
+  pigeonResult.intList = intList;
+  pigeonResult.doubleList = doubleList;
+  pigeonResult.boolList = boolList;
+  pigeonResult.map = map;
   return pigeonResult;
 }
-+ (AllTypes *)fromList:(NSArray *)list {
++ (AllTypes *)fromList:(NSArray<id> *)list {
   AllTypes *pigeonResult = [[AllTypes alloc] init];
   pigeonResult.aBool = [GetNullableObjectAtIndex(list, 0) boolValue];
   pigeonResult.anInt = [GetNullableObjectAtIndex(list, 1) integerValue];
@@ -120,17 +128,22 @@ + (AllTypes *)fromList:(NSArray *)list {
   pigeonResult.a4ByteArray = GetNullableObjectAtIndex(list, 5);
   pigeonResult.a8ByteArray = GetNullableObjectAtIndex(list, 6);
   pigeonResult.aFloatArray = GetNullableObjectAtIndex(list, 7);
-  pigeonResult.list = GetNullableObjectAtIndex(list, 8);
-  pigeonResult.aMap = GetNullableObjectAtIndex(list, 9);
-  pigeonResult.anEnum = [GetNullableObjectAtIndex(list, 10) integerValue];
-  pigeonResult.aString = GetNullableObjectAtIndex(list, 11);
-  pigeonResult.anObject = GetNullableObjectAtIndex(list, 12);
+  AnEnumBox *enumBox = GetNullableObjectAtIndex(list, 8);
+  pigeonResult.anEnum = enumBox.value;
+  pigeonResult.aString = GetNullableObjectAtIndex(list, 9);
+  pigeonResult.anObject = GetNullableObjectAtIndex(list, 10);
+  pigeonResult.list = GetNullableObjectAtIndex(list, 11);
+  pigeonResult.stringList = GetNullableObjectAtIndex(list, 12);
+  pigeonResult.intList = GetNullableObjectAtIndex(list, 13);
+  pigeonResult.doubleList = GetNullableObjectAtIndex(list, 14);
+  pigeonResult.boolList = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.map = GetNullableObjectAtIndex(list, 16);
   return pigeonResult;
 }
-+ (nullable AllTypes *)nullableFromList:(NSArray *)list {
++ (nullable AllTypes *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [AllTypes fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     @(self.aBool),
     @(self.anInt),
@@ -140,11 +153,15 @@ - (NSArray *)toList {
     self.a4ByteArray ?: [NSNull null],
     self.a8ByteArray ?: [NSNull null],
     self.aFloatArray ?: [NSNull null],
-    self.list ?: [NSNull null],
-    self.aMap ?: [NSNull null],
-    @(self.anEnum),
+    [[AnEnumBox alloc] initWithValue:self.anEnum],
     self.aString ?: [NSNull null],
     self.anObject ?: [NSNull null],
+    self.list ?: [NSNull null],
+    self.stringList ?: [NSNull null],
+    self.intList ?: [NSNull null],
+    self.doubleList ?: [NSNull null],
+    self.boolList ?: [NSNull null],
+    self.map ?: [NSNull null],
   ];
 }
 @end
@@ -158,8 +175,6 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
@@ -167,7 +182,14 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
                         aNullableEnum:(nullable AnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
                       aNullableObject:(nullable id)aNullableObject
-                     allNullableTypes:(nullable AllNullableTypes *)allNullableTypes {
+                     allNullableTypes:(nullable AllNullableTypes *)allNullableTypes
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                      nestedClassList:(nullable NSArray<AllNullableTypes *> *)nestedClassList
+                                  map:(nullable NSDictionary *)map {
   AllNullableTypes *pigeonResult = [[AllNullableTypes alloc] init];
   pigeonResult.aNullableBool = aNullableBool;
   pigeonResult.aNullableInt = aNullableInt;
@@ -177,8 +199,6 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
   pigeonResult.aNullable4ByteArray = aNullable4ByteArray;
   pigeonResult.aNullable8ByteArray = aNullable8ByteArray;
   pigeonResult.aNullableFloatArray = aNullableFloatArray;
-  pigeonResult.aNullableList = aNullableList;
-  pigeonResult.aNullableMap = aNullableMap;
   pigeonResult.nullableNestedList = nullableNestedList;
   pigeonResult.nullableMapWithAnnotations = nullableMapWithAnnotations;
   pigeonResult.nullableMapWithObject = nullableMapWithObject;
@@ -186,9 +206,16 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
   pigeonResult.aNullableString = aNullableString;
   pigeonResult.aNullableObject = aNullableObject;
   pigeonResult.allNullableTypes = allNullableTypes;
+  pigeonResult.list = list;
+  pigeonResult.stringList = stringList;
+  pigeonResult.intList = intList;
+  pigeonResult.doubleList = doubleList;
+  pigeonResult.boolList = boolList;
+  pigeonResult.nestedClassList = nestedClassList;
+  pigeonResult.map = map;
   return pigeonResult;
 }
-+ (AllNullableTypes *)fromList:(NSArray *)list {
++ (AllNullableTypes *)fromList:(NSArray<id> *)list {
   AllNullableTypes *pigeonResult = [[AllNullableTypes alloc] init];
   pigeonResult.aNullableBool = GetNullableObjectAtIndex(list, 0);
   pigeonResult.aNullableInt = GetNullableObjectAtIndex(list, 1);
@@ -198,26 +225,26 @@ + (AllNullableTypes *)fromList:(NSArray *)list {
   pigeonResult.aNullable4ByteArray = GetNullableObjectAtIndex(list, 5);
   pigeonResult.aNullable8ByteArray = GetNullableObjectAtIndex(list, 6);
   pigeonResult.aNullableFloatArray = GetNullableObjectAtIndex(list, 7);
-  pigeonResult.aNullableList = GetNullableObjectAtIndex(list, 8);
-  pigeonResult.aNullableMap = GetNullableObjectAtIndex(list, 9);
-  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 10);
-  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 11);
-  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 12);
-  NSNumber *aNullableEnumAsNumber = GetNullableObjectAtIndex(list, 13);
-  AnEnumBox *aNullableEnum =
-      aNullableEnumAsNumber == nil
-          ? nil
-          : [[AnEnumBox alloc] initWithValue:[aNullableEnumAsNumber integerValue]];
-  pigeonResult.aNullableEnum = aNullableEnum;
-  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 14);
-  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 15);
-  pigeonResult.allNullableTypes = GetNullableObjectAtIndex(list, 16);
+  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 8);
+  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 9);
+  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 10);
+  pigeonResult.aNullableEnum = GetNullableObjectAtIndex(list, 11);
+  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 12);
+  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 13);
+  pigeonResult.allNullableTypes = GetNullableObjectAtIndex(list, 14);
+  pigeonResult.list = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.stringList = GetNullableObjectAtIndex(list, 16);
+  pigeonResult.intList = GetNullableObjectAtIndex(list, 17);
+  pigeonResult.doubleList = GetNullableObjectAtIndex(list, 18);
+  pigeonResult.boolList = GetNullableObjectAtIndex(list, 19);
+  pigeonResult.nestedClassList = GetNullableObjectAtIndex(list, 20);
+  pigeonResult.map = GetNullableObjectAtIndex(list, 21);
   return pigeonResult;
 }
-+ (nullable AllNullableTypes *)nullableFromList:(NSArray *)list {
++ (nullable AllNullableTypes *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [AllNullableTypes fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.aNullableBool ?: [NSNull null],
     self.aNullableInt ?: [NSNull null],
@@ -227,16 +254,20 @@ - (NSArray *)toList {
     self.aNullable4ByteArray ?: [NSNull null],
     self.aNullable8ByteArray ?: [NSNull null],
     self.aNullableFloatArray ?: [NSNull null],
-    self.aNullableList ?: [NSNull null],
-    self.aNullableMap ?: [NSNull null],
     self.nullableNestedList ?: [NSNull null],
     self.nullableMapWithAnnotations ?: [NSNull null],
     self.nullableMapWithObject ?: [NSNull null],
-    (self.aNullableEnum == nil ? [NSNull null]
-                               : [NSNumber numberWithInteger:self.aNullableEnum.value]),
+    self.aNullableEnum ?: [NSNull null],
     self.aNullableString ?: [NSNull null],
     self.aNullableObject ?: [NSNull null],
     self.allNullableTypes ?: [NSNull null],
+    self.list ?: [NSNull null],
+    self.stringList ?: [NSNull null],
+    self.intList ?: [NSNull null],
+    self.doubleList ?: [NSNull null],
+    self.boolList ?: [NSNull null],
+    self.nestedClassList ?: [NSNull null],
+    self.map ?: [NSNull null],
   ];
 }
 @end
@@ -250,15 +281,19 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
                   aNullable4ByteArray:(nullable FlutterStandardTypedData *)aNullable4ByteArray
                   aNullable8ByteArray:(nullable FlutterStandardTypedData *)aNullable8ByteArray
                   aNullableFloatArray:(nullable FlutterStandardTypedData *)aNullableFloatArray
-                        aNullableList:(nullable NSArray *)aNullableList
-                         aNullableMap:(nullable NSDictionary *)aNullableMap
                    nullableNestedList:(nullable NSArray<NSArray<NSNumber *> *> *)nullableNestedList
            nullableMapWithAnnotations:
                (nullable NSDictionary<NSString *, NSString *> *)nullableMapWithAnnotations
                 nullableMapWithObject:(nullable NSDictionary<NSString *, id> *)nullableMapWithObject
                         aNullableEnum:(nullable AnEnumBox *)aNullableEnum
                       aNullableString:(nullable NSString *)aNullableString
-                      aNullableObject:(nullable id)aNullableObject {
+                      aNullableObject:(nullable id)aNullableObject
+                                 list:(nullable NSArray<id> *)list
+                           stringList:(nullable NSArray<NSString *> *)stringList
+                              intList:(nullable NSArray<NSNumber *> *)intList
+                           doubleList:(nullable NSArray<NSNumber *> *)doubleList
+                             boolList:(nullable NSArray<NSNumber *> *)boolList
+                                  map:(nullable NSDictionary *)map {
   AllNullableTypesWithoutRecursion *pigeonResult = [[AllNullableTypesWithoutRecursion alloc] init];
   pigeonResult.aNullableBool = aNullableBool;
   pigeonResult.aNullableInt = aNullableInt;
@@ -268,17 +303,21 @@ + (instancetype)makeWithANullableBool:(nullable NSNumber *)aNullableBool
   pigeonResult.aNullable4ByteArray = aNullable4ByteArray;
   pigeonResult.aNullable8ByteArray = aNullable8ByteArray;
   pigeonResult.aNullableFloatArray = aNullableFloatArray;
-  pigeonResult.aNullableList = aNullableList;
-  pigeonResult.aNullableMap = aNullableMap;
   pigeonResult.nullableNestedList = nullableNestedList;
   pigeonResult.nullableMapWithAnnotations = nullableMapWithAnnotations;
   pigeonResult.nullableMapWithObject = nullableMapWithObject;
   pigeonResult.aNullableEnum = aNullableEnum;
   pigeonResult.aNullableString = aNullableString;
   pigeonResult.aNullableObject = aNullableObject;
+  pigeonResult.list = list;
+  pigeonResult.stringList = stringList;
+  pigeonResult.intList = intList;
+  pigeonResult.doubleList = doubleList;
+  pigeonResult.boolList = boolList;
+  pigeonResult.map = map;
   return pigeonResult;
 }
-+ (AllNullableTypesWithoutRecursion *)fromList:(NSArray *)list {
++ (AllNullableTypesWithoutRecursion *)fromList:(NSArray<id> *)list {
   AllNullableTypesWithoutRecursion *pigeonResult = [[AllNullableTypesWithoutRecursion alloc] init];
   pigeonResult.aNullableBool = GetNullableObjectAtIndex(list, 0);
   pigeonResult.aNullableInt = GetNullableObjectAtIndex(list, 1);
@@ -288,25 +327,24 @@ + (AllNullableTypesWithoutRecursion *)fromList:(NSArray *)list {
   pigeonResult.aNullable4ByteArray = GetNullableObjectAtIndex(list, 5);
   pigeonResult.aNullable8ByteArray = GetNullableObjectAtIndex(list, 6);
   pigeonResult.aNullableFloatArray = GetNullableObjectAtIndex(list, 7);
-  pigeonResult.aNullableList = GetNullableObjectAtIndex(list, 8);
-  pigeonResult.aNullableMap = GetNullableObjectAtIndex(list, 9);
-  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 10);
-  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 11);
-  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 12);
-  NSNumber *aNullableEnumAsNumber = GetNullableObjectAtIndex(list, 13);
-  AnEnumBox *aNullableEnum =
-      aNullableEnumAsNumber == nil
-          ? nil
-          : [[AnEnumBox alloc] initWithValue:[aNullableEnumAsNumber integerValue]];
-  pigeonResult.aNullableEnum = aNullableEnum;
-  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 14);
-  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.nullableNestedList = GetNullableObjectAtIndex(list, 8);
+  pigeonResult.nullableMapWithAnnotations = GetNullableObjectAtIndex(list, 9);
+  pigeonResult.nullableMapWithObject = GetNullableObjectAtIndex(list, 10);
+  pigeonResult.aNullableEnum = GetNullableObjectAtIndex(list, 11);
+  pigeonResult.aNullableString = GetNullableObjectAtIndex(list, 12);
+  pigeonResult.aNullableObject = GetNullableObjectAtIndex(list, 13);
+  pigeonResult.list = GetNullableObjectAtIndex(list, 14);
+  pigeonResult.stringList = GetNullableObjectAtIndex(list, 15);
+  pigeonResult.intList = GetNullableObjectAtIndex(list, 16);
+  pigeonResult.doubleList = GetNullableObjectAtIndex(list, 17);
+  pigeonResult.boolList = GetNullableObjectAtIndex(list, 18);
+  pigeonResult.map = GetNullableObjectAtIndex(list, 19);
   return pigeonResult;
 }
-+ (nullable AllNullableTypesWithoutRecursion *)nullableFromList:(NSArray *)list {
++ (nullable AllNullableTypesWithoutRecursion *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [AllNullableTypesWithoutRecursion fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.aNullableBool ?: [NSNull null],
     self.aNullableInt ?: [NSNull null],
@@ -316,15 +354,18 @@ - (NSArray *)toList {
     self.aNullable4ByteArray ?: [NSNull null],
     self.aNullable8ByteArray ?: [NSNull null],
     self.aNullableFloatArray ?: [NSNull null],
-    self.aNullableList ?: [NSNull null],
-    self.aNullableMap ?: [NSNull null],
     self.nullableNestedList ?: [NSNull null],
     self.nullableMapWithAnnotations ?: [NSNull null],
     self.nullableMapWithObject ?: [NSNull null],
-    (self.aNullableEnum == nil ? [NSNull null]
-                               : [NSNumber numberWithInteger:self.aNullableEnum.value]),
+    self.aNullableEnum ?: [NSNull null],
     self.aNullableString ?: [NSNull null],
     self.aNullableObject ?: [NSNull null],
+    self.list ?: [NSNull null],
+    self.stringList ?: [NSNull null],
+    self.intList ?: [NSNull null],
+    self.doubleList ?: [NSNull null],
+    self.boolList ?: [NSNull null],
+    self.map ?: [NSNull null],
   ];
 }
 @end
@@ -340,17 +381,17 @@ + (instancetype)makeWithAllNullableTypes:(AllNullableTypes *)allNullableTypes
   pigeonResult.allTypes = allTypes;
   return pigeonResult;
 }
-+ (AllClassesWrapper *)fromList:(NSArray *)list {
++ (AllClassesWrapper *)fromList:(NSArray<id> *)list {
   AllClassesWrapper *pigeonResult = [[AllClassesWrapper alloc] init];
   pigeonResult.allNullableTypes = GetNullableObjectAtIndex(list, 0);
   pigeonResult.allNullableTypesWithoutRecursion = GetNullableObjectAtIndex(list, 1);
   pigeonResult.allTypes = GetNullableObjectAtIndex(list, 2);
   return pigeonResult;
 }
-+ (nullable AllClassesWrapper *)nullableFromList:(NSArray *)list {
++ (nullable AllClassesWrapper *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [AllClassesWrapper fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.allNullableTypes ?: [NSNull null],
     self.allNullableTypesWithoutRecursion ?: [NSNull null],
@@ -360,94 +401,102 @@ - (NSArray *)toList {
 @end
 
 @implementation TestMessage
-+ (instancetype)makeWithTestList:(nullable NSArray *)testList {
++ (instancetype)makeWithTestList:(nullable NSArray<id> *)testList {
   TestMessage *pigeonResult = [[TestMessage alloc] init];
   pigeonResult.testList = testList;
   return pigeonResult;
 }
-+ (TestMessage *)fromList:(NSArray *)list {
++ (TestMessage *)fromList:(NSArray<id> *)list {
   TestMessage *pigeonResult = [[TestMessage alloc] init];
   pigeonResult.testList = GetNullableObjectAtIndex(list, 0);
   return pigeonResult;
 }
-+ (nullable TestMessage *)nullableFromList:(NSArray *)list {
++ (nullable TestMessage *)nullableFromList:(NSArray<id> *)list {
   return (list) ? [TestMessage fromList:list] : nil;
 }
-- (NSArray *)toList {
+- (NSArray<id> *)toList {
   return @[
     self.testList ?: [NSNull null],
   ];
 }
 @end
 
-@interface HostIntegrationCoreApiCodecReader : FlutterStandardReader
+@interface CoreTestsPigeonCodecReader : FlutterStandardReader
 @end
-@implementation HostIntegrationCoreApiCodecReader
+@implementation CoreTestsPigeonCodecReader
 - (nullable id)readValueOfType:(UInt8)type {
   switch (type) {
-    case 128:
-      return [AllClassesWrapper fromList:[self readValue]];
     case 129:
-      return [AllNullableTypes fromList:[self readValue]];
+      return [AllTypes fromList:[self readValue]];
     case 130:
-      return [AllNullableTypesWithoutRecursion fromList:[self readValue]];
+      return [AllNullableTypes fromList:[self readValue]];
     case 131:
-      return [AllTypes fromList:[self readValue]];
+      return [AllNullableTypesWithoutRecursion fromList:[self readValue]];
     case 132:
+      return [AllClassesWrapper fromList:[self readValue]];
+    case 133:
       return [TestMessage fromList:[self readValue]];
+    case 134: {
+      NSNumber *enumAsNumber = [self readValue];
+      return enumAsNumber == nil ? nil
+                                 : [[AnEnumBox alloc] initWithValue:[enumAsNumber integerValue]];
+    }
     default:
       return [super readValueOfType:type];
   }
 }
 @end
 
-@interface HostIntegrationCoreApiCodecWriter : FlutterStandardWriter
+@interface CoreTestsPigeonCodecWriter : FlutterStandardWriter
 @end
-@implementation HostIntegrationCoreApiCodecWriter
+@implementation CoreTestsPigeonCodecWriter
 - (void)writeValue:(id)value {
-  if ([value isKindOfClass:[AllClassesWrapper class]]) {
-    [self writeByte:128];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[AllNullableTypes class]]) {
+  if ([value isKindOfClass:[AllTypes class]]) {
     [self writeByte:129];
     [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[AllNullableTypesWithoutRecursion class]]) {
+  } else if ([value isKindOfClass:[AllNullableTypes class]]) {
     [self writeByte:130];
     [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[AllTypes class]]) {
+  } else if ([value isKindOfClass:[AllNullableTypesWithoutRecursion class]]) {
     [self writeByte:131];
     [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[TestMessage class]]) {
+  } else if ([value isKindOfClass:[AllClassesWrapper class]]) {
     [self writeByte:132];
     [self writeValue:[value toList]];
+  } else if ([value isKindOfClass:[TestMessage class]]) {
+    [self writeByte:133];
+    [self writeValue:[value toList]];
+  } else if ([value isKindOfClass:[AnEnumBox class]]) {
+    AnEnumBox *box = (AnEnumBox *)value;
+    [self writeByte:134];
+    [self writeValue:(value == nil ? [NSNull null] : [NSNumber numberWithInteger:box.value])];
   } else {
     [super writeValue:value];
   }
 }
 @end
 
-@interface HostIntegrationCoreApiCodecReaderWriter : FlutterStandardReaderWriter
+@interface CoreTestsPigeonCodecReaderWriter : FlutterStandardReaderWriter
 @end
-@implementation HostIntegrationCoreApiCodecReaderWriter
+@implementation CoreTestsPigeonCodecReaderWriter
 - (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[HostIntegrationCoreApiCodecWriter alloc] initWithData:data];
+  return [[CoreTestsPigeonCodecWriter alloc] initWithData:data];
 }
 - (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[HostIntegrationCoreApiCodecReader alloc] initWithData:data];
+  return [[CoreTestsPigeonCodecReader alloc] initWithData:data];
 }
 @end
 
-NSObject<FlutterMessageCodec> *HostIntegrationCoreApiGetCodec(void) {
+NSObject<FlutterMessageCodec> *GetCoreTestsCodec(void) {
   static FlutterStandardMessageCodec *sSharedObject = nil;
   static dispatch_once_t sPred = 0;
   dispatch_once(&sPred, ^{
-    HostIntegrationCoreApiCodecReaderWriter *readerWriter =
-        [[HostIntegrationCoreApiCodecReaderWriter alloc] init];
+    CoreTestsPigeonCodecReaderWriter *readerWriter =
+        [[CoreTestsPigeonCodecReaderWriter alloc] init];
     sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
   });
   return sSharedObject;
 }
-
 void SetUpHostIntegrationCoreApi(id<FlutterBinaryMessenger> binaryMessenger,
                                  NSObject<HostIntegrationCoreApi> *api) {
   SetUpHostIntegrationCoreApiWithSuffix(binaryMessenger, api, @"");
@@ -468,7 +517,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.noop",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(noopWithError:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(noopWithError:)",
@@ -490,14 +539,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAllTypes",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoAllTypes:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoAllTypes:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         AllTypes *output = [api echoAllTypes:arg_everything error:&error];
@@ -515,7 +564,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.throwError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(throwErrorWithError:)],
@@ -538,7 +587,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.throwErrorFromVoid",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwErrorFromVoidWithError:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -561,7 +610,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.throwFlutterError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwFlutterErrorWithError:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -584,13 +633,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoInt:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoInt:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         FlutterError *error;
         NSNumber *output = [api echoInt:arg_anInt error:&error];
@@ -608,13 +657,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoDouble:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoDouble:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         FlutterError *error;
         NSNumber *output = [api echoDouble:arg_aDouble error:&error];
@@ -632,13 +681,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoBool:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoBool:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         BOOL arg_aBool = [GetNullableObjectAtIndex(args, 0) boolValue];
         FlutterError *error;
         NSNumber *output = [api echoBool:arg_aBool error:&error];
@@ -656,13 +705,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoString:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoString:arg_aString error:&error];
@@ -680,14 +729,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoUint8List",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoUint8List:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoUint8List:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aUint8List = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FlutterStandardTypedData *output = [api echoUint8List:arg_aUint8List error:&error];
@@ -705,13 +754,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoObject",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoObject:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoObject:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_anObject = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         id output = [api echoObject:arg_anObject error:&error];
@@ -729,13 +778,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoList:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoList:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSArray<id> *output = [api echoList:arg_list error:&error];
@@ -753,13 +802,13 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoMap:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoMap:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSDictionary<NSString *, id> *output = [api echoMap:arg_aMap error:&error];
@@ -777,14 +826,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoClassWrapper",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoClassWrapper:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoClassWrapper:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllClassesWrapper *arg_wrapper = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         AllClassesWrapper *output = [api echoClassWrapper:arg_wrapper error:&error];
@@ -802,17 +851,17 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoEnum:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoEnum:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        AnEnum arg_anEnum = [GetNullableObjectAtIndex(args, 0) integerValue];
+        NSArray<id> *args = message;
+        AnEnumBox *enumBox = GetNullableObjectAtIndex(args, 0);
+        AnEnum arg_anEnum = enumBox.value;
         FlutterError *error;
-        AnEnumBox *enumBox = [api echoEnum:arg_anEnum error:&error];
-        NSNumber *output = enumBox == nil ? nil : [NSNumber numberWithInteger:enumBox.value];
+        AnEnumBox *output = [api echoEnum:arg_anEnum error:&error];
         callback(wrapResult(output, error));
       }];
     } else {
@@ -827,14 +876,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNamedDefaultString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNamedDefaultString:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNamedDefaultString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoNamedDefaultString:arg_aString error:&error];
@@ -853,14 +902,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoOptionalDefaultDouble",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoOptionalDefaultDouble:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoOptionalDefaultDouble:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         FlutterError *error;
         NSNumber *output = [api echoOptionalDefaultDouble:arg_aDouble error:&error];
@@ -878,14 +927,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoRequiredInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoRequiredInt:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoRequiredInt:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         FlutterError *error;
         NSNumber *output = [api echoRequiredInt:arg_anInt error:&error];
@@ -903,14 +952,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAllNullableTypes",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAllNullableTypes:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAllNullableTypes:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllNullableTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         AllNullableTypes *output = [api echoAllNullableTypes:arg_everything error:&error];
@@ -930,14 +979,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                     @"HostIntegrationCoreApi.echoAllNullableTypesWithoutRecursion",
                                     messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAllNullableTypesWithoutRecursion:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAllNullableTypesWithoutRecursion:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllNullableTypesWithoutRecursion *arg_everything = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         AllNullableTypesWithoutRecursion *output =
@@ -958,14 +1007,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.extractNestedNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(extractNestedNullableStringFrom:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(extractNestedNullableStringFrom:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllClassesWrapper *arg_wrapper = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api extractNestedNullableStringFrom:arg_wrapper error:&error];
@@ -985,14 +1034,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.createNestedNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(createNestedObjectWithNullableString:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(createNestedObjectWithNullableString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_nullableString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         AllClassesWrapper *output = [api createNestedObjectWithNullableString:arg_nullableString
@@ -1012,7 +1061,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.sendMultipleNullableTypes",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(sendMultipleNullableTypesABool:
                                                                            anInt:aString:error:)],
@@ -1020,7 +1069,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                 @"@selector(sendMultipleNullableTypesABool:anInt:aString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -1045,7 +1094,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                 @"HostIntegrationCoreApi.sendMultipleNullableTypesWithoutRecursion",
                                 messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (sendMultipleNullableTypesWithoutRecursionABool:anInt:aString:error:)],
@@ -1053,7 +1102,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                 @"@selector(sendMultipleNullableTypesWithoutRecursionABool:anInt:aString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -1077,14 +1126,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoNullableInt:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoNullableInt:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoNullableInt:arg_aNullableInt error:&error];
@@ -1102,14 +1151,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableDouble:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableDouble:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableDouble = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoNullableDouble:arg_aNullableDouble error:&error];
@@ -1127,14 +1176,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoNullableBool:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoNullableBool:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoNullableBool:arg_aNullableBool error:&error];
@@ -1152,14 +1201,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableString:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoNullableString:arg_aNullableString error:&error];
@@ -1177,14 +1226,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableUint8List",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableUint8List:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableUint8List:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aNullableUint8List = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         FlutterStandardTypedData *output = [api echoNullableUint8List:arg_aNullableUint8List
@@ -1203,14 +1252,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableObject",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNullableObject:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNullableObject:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_aNullableObject = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         id output = [api echoNullableObject:arg_aNullableObject error:&error];
@@ -1228,14 +1277,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoNullableList:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoNullableList:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_aNullableList = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSArray<id> *output = [api echoNullableList:arg_aNullableList error:&error];
@@ -1253,14 +1302,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoNullableMap:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoNullableMap:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aNullableMap = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSDictionary<NSString *, id> *output = [api echoNullableMap:arg_aNullableMap error:&error];
@@ -1277,22 +1326,17 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoNullableEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoNullableEnum:error:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoNullableEnum:error:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        NSNumber *arg_anEnumAsNumber = GetNullableObjectAtIndex(args, 0);
-        AnEnumBox *arg_anEnum =
-            arg_anEnumAsNumber == nil
-                ? nil
-                : [[AnEnumBox alloc] initWithValue:[arg_anEnumAsNumber integerValue]];
+        NSArray<id> *args = message;
+        AnEnumBox *arg_anEnum = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
-        AnEnumBox *enumBox = [api echoNullableEnum:arg_anEnum error:&error];
-        NSNumber *output = enumBox == nil ? nil : [NSNumber numberWithInteger:enumBox.value];
+        AnEnumBox *output = [api echoNullableEnum:arg_anEnum error:&error];
         callback(wrapResult(output, error));
       }];
     } else {
@@ -1308,14 +1352,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoOptionalNullableInt",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoOptionalNullableInt:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoOptionalNullableInt:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSNumber *output = [api echoOptionalNullableInt:arg_aNullableInt error:&error];
@@ -1334,14 +1378,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoNamedNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoNamedNullableString:error:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoNamedNullableString:error:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 0);
         FlutterError *error;
         NSString *output = [api echoNamedNullableString:arg_aNullableString error:&error];
@@ -1360,7 +1404,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.noopAsync",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(noopAsyncWithCompletion:)],
@@ -1383,14 +1427,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoAsyncInt:completion:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoAsyncInt:completion:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         [api echoAsyncInt:arg_anInt
                completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1409,14 +1453,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncDouble:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         [api echoAsyncDouble:arg_aDouble
                   completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1435,14 +1479,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncBool:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         BOOL arg_aBool = [GetNullableObjectAtIndex(args, 0) boolValue];
         [api echoAsyncBool:arg_aBool
                 completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1461,14 +1505,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncString:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncString:arg_aString
                   completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -1487,14 +1531,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncUint8List",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncUint8List:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aUint8List = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncUint8List:arg_aUint8List
                      completion:^(FlutterStandardTypedData *_Nullable output,
@@ -1514,14 +1558,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncObject",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncObject:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncObject:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_anObject = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncObject:arg_anObject
                   completion:^(id _Nullable output, FlutterError *_Nullable error) {
@@ -1540,14 +1584,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncList:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncList:arg_list
                 completion:^(NSArray<id> *_Nullable output, FlutterError *_Nullable error) {
@@ -1566,14 +1610,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector(echoAsyncMap:completion:)],
           @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoAsyncMap:completion:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncMap:arg_aMap
                completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -1593,19 +1637,18 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncEnum:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        AnEnum arg_anEnum = [GetNullableObjectAtIndex(args, 0) integerValue];
+        NSArray<id> *args = message;
+        AnEnumBox *enumBox = GetNullableObjectAtIndex(args, 0);
+        AnEnum arg_anEnum = enumBox.value;
         [api echoAsyncEnum:arg_anEnum
-                completion:^(AnEnumBox *_Nullable enumValue, FlutterError *_Nullable error) {
-                  NSNumber *output =
-                      enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];
+                completion:^(AnEnumBox *_Nullable output, FlutterError *_Nullable error) {
                   callback(wrapResult(output, error));
                 }];
       }];
@@ -1621,7 +1664,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.throwAsyncError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwAsyncErrorWithCompletion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1645,7 +1688,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.throwAsyncErrorFromVoid",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwAsyncErrorFromVoidWithCompletion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1668,7 +1711,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.throwAsyncFlutterError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(throwAsyncFlutterErrorWithCompletion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -1692,14 +1735,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncAllTypes",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncAllTypes:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncAllTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncAllTypes:arg_everything
                     completion:^(AllTypes *_Nullable output, FlutterError *_Nullable error) {
@@ -1719,14 +1762,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                       @"HostIntegrationCoreApi.echoAsyncNullableAllNullableTypes",
                                       messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableAllNullableTypes:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableAllNullableTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllNullableTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableAllNullableTypes:arg_everything
                                     completion:^(AllNullableTypes *_Nullable output,
@@ -1748,7 +1791,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"echoAsyncNullableAllNullableTypesWithoutRecursion",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (echoAsyncNullableAllNullableTypesWithoutRecursion:completion:)],
@@ -1756,7 +1799,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                 @"@selector(echoAsyncNullableAllNullableTypesWithoutRecursion:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllNullableTypesWithoutRecursion *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableAllNullableTypesWithoutRecursion:arg_everything
                                                     completion:^(AllNullableTypesWithoutRecursion
@@ -1777,14 +1820,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncNullableInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableInt:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_anInt = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableInt:arg_anInt
                        completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1804,14 +1847,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoAsyncNullableDouble",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableDouble:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aDouble = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableDouble:arg_aDouble
                           completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1830,14 +1873,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncNullableBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableBool:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aBool = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableBool:arg_aBool
                         completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -1857,14 +1900,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoAsyncNullableString",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableString:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableString:arg_aString
                           completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -1884,14 +1927,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoAsyncNullableUint8List",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableUint8List:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_aUint8List = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableUint8List:arg_aUint8List
                              completion:^(FlutterStandardTypedData *_Nullable output,
@@ -1912,14 +1955,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.echoAsyncNullableObject",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableObject:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableObject:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         id arg_anObject = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableObject:arg_anObject
                           completion:^(id _Nullable output, FlutterError *_Nullable error) {
@@ -1938,14 +1981,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncNullableList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableList:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableList:arg_list
                         completion:^(NSArray<id> *_Nullable output, FlutterError *_Nullable error) {
@@ -1964,14 +2007,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncNullableMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableMap:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api echoAsyncNullableMap:arg_aMap
                        completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -1991,26 +2034,19 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.echoAsyncNullableEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoAsyncNullableEnum:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(echoAsyncNullableEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        NSNumber *arg_anEnumAsNumber = GetNullableObjectAtIndex(args, 0);
-        AnEnumBox *arg_anEnum =
-            arg_anEnumAsNumber == nil
-                ? nil
-                : [[AnEnumBox alloc] initWithValue:[arg_anEnumAsNumber integerValue]];
-        [api
-            echoAsyncNullableEnum:arg_anEnum
-                       completion:^(AnEnumBox *_Nullable enumValue, FlutterError *_Nullable error) {
-                         NSNumber *output =
-                             enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];
-                         callback(wrapResult(output, error));
-                       }];
+        NSArray<id> *args = message;
+        AnEnumBox *arg_anEnum = GetNullableObjectAtIndex(args, 0);
+        [api echoAsyncNullableEnum:arg_anEnum
+                        completion:^(AnEnumBox *_Nullable output, FlutterError *_Nullable error) {
+                          callback(wrapResult(output, error));
+                        }];
       }];
     } else {
       [channel setMessageHandler:nil];
@@ -2023,7 +2059,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterNoop",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterNoopWithCompletion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -2045,7 +2081,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterThrowError",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterThrowErrorWithCompletion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -2069,7 +2105,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                           @"HostIntegrationCoreApi.callFlutterThrowErrorFromVoid",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterThrowErrorFromVoidWithCompletion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
@@ -2092,14 +2128,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoAllTypes",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoAllTypes:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoAllTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoAllTypes:arg_everything
                           completion:^(AllTypes *_Nullable output, FlutterError *_Nullable error) {
@@ -2118,14 +2154,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                           @"HostIntegrationCoreApi.callFlutterEchoAllNullableTypes",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoAllNullableTypes:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoAllNullableTypes:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllNullableTypes *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoAllNullableTypes:arg_everything
                                   completion:^(AllNullableTypes *_Nullable output,
@@ -2146,7 +2182,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                     @"HostIntegrationCoreApi.callFlutterSendMultipleNullableTypes",
                                     messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (callFlutterSendMultipleNullableTypesABool:anInt:aString:completion:)],
@@ -2154,7 +2190,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                 @"@selector(callFlutterSendMultipleNullableTypesABool:anInt:aString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -2179,7 +2215,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"callFlutterEchoAllNullableTypesWithoutRecursion",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector
                      (callFlutterEchoAllNullableTypesWithoutRecursion:completion:)],
@@ -2187,7 +2223,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                 @"@selector(callFlutterEchoAllNullableTypesWithoutRecursion:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         AllNullableTypesWithoutRecursion *arg_everything = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoAllNullableTypesWithoutRecursion:arg_everything
                                                   completion:^(AllNullableTypesWithoutRecursion
@@ -2209,7 +2245,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                              @"callFlutterSendMultipleNullableTypesWithoutRecursion",
                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert(
           [api respondsToSelector:@selector
@@ -2220,7 +2256,7 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
           @"completion:)",
           api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aNullableBool = GetNullableObjectAtIndex(args, 0);
         NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 1);
         NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 2);
@@ -2245,14 +2281,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoBool",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoBool:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         BOOL arg_aBool = [GetNullableObjectAtIndex(args, 0) boolValue];
         [api callFlutterEchoBool:arg_aBool
                       completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -2270,14 +2306,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoInt",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoInt:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
         [api callFlutterEchoInt:arg_anInt
                      completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -2295,14 +2331,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoDouble",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoDouble:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
         [api callFlutterEchoDouble:arg_aDouble
                         completion:^(NSNumber *_Nullable output, FlutterError *_Nullable error) {
@@ -2320,14 +2356,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoString",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoString:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoString:arg_aString
                         completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -2346,14 +2382,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoUint8List",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoUint8List:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoUint8List:arg_list
                            completion:^(FlutterStandardTypedData *_Nullable output,
@@ -2372,14 +2408,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoList",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoList:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoList:arg_list
                       completion:^(NSArray<id> *_Nullable output, FlutterError *_Nullable error) {
@@ -2397,14 +2433,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoMap",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoMap:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoMap:arg_aMap
                      completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -2423,19 +2459,18 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                                    @"HostIntegrationCoreApi.callFlutterEchoEnum",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoEnum:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        AnEnum arg_anEnum = [GetNullableObjectAtIndex(args, 0) integerValue];
+        NSArray<id> *args = message;
+        AnEnumBox *enumBox = GetNullableObjectAtIndex(args, 0);
+        AnEnum arg_anEnum = enumBox.value;
         [api callFlutterEchoEnum:arg_anEnum
-                      completion:^(AnEnumBox *_Nullable enumValue, FlutterError *_Nullable error) {
-                        NSNumber *output =
-                            enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];
+                      completion:^(AnEnumBox *_Nullable output, FlutterError *_Nullable error) {
                         callback(wrapResult(output, error));
                       }];
       }];
@@ -2451,14 +2486,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableBool",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableBool:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableBool:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aBool = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableBool:arg_aBool
                               completion:^(NSNumber *_Nullable output,
@@ -2478,14 +2513,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableInt",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableInt:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableInt:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_anInt = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableInt:arg_anInt
                              completion:^(NSNumber *_Nullable output,
@@ -2505,14 +2540,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                           @"HostIntegrationCoreApi.callFlutterEchoNullableDouble",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableDouble:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableDouble:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSNumber *arg_aDouble = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableDouble:arg_aDouble
                                 completion:^(NSNumber *_Nullable output,
@@ -2532,14 +2567,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                           @"HostIntegrationCoreApi.callFlutterEchoNullableString",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableString:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableString:arg_aString
                                 completion:^(NSString *_Nullable output,
@@ -2559,14 +2594,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                       @"HostIntegrationCoreApi.callFlutterEchoNullableUint8List",
                                       messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableUint8List:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableUint8List:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         FlutterStandardTypedData *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableUint8List:arg_list
                                    completion:^(FlutterStandardTypedData *_Nullable output,
@@ -2586,14 +2621,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableList",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableList:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableList:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSArray<id> *arg_list = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableList:arg_list
                               completion:^(NSArray<id> *_Nullable output,
@@ -2613,14 +2648,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableMap",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableMap:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableMap:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSDictionary<NSString *, id> *arg_aMap = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableMap:arg_aMap
                              completion:^(NSDictionary<NSString *, id> *_Nullable output,
@@ -2640,25 +2675,18 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                              @"HostIntegrationCoreApi.callFlutterEchoNullableEnum",
                                              messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterEchoNullableEnum:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterEchoNullableEnum:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
-        NSNumber *arg_anEnumAsNumber = GetNullableObjectAtIndex(args, 0);
-        AnEnumBox *arg_anEnum =
-            arg_anEnumAsNumber == nil
-                ? nil
-                : [[AnEnumBox alloc] initWithValue:[arg_anEnumAsNumber integerValue]];
+        NSArray<id> *args = message;
+        AnEnumBox *arg_anEnum = GetNullableObjectAtIndex(args, 0);
         [api callFlutterEchoNullableEnum:arg_anEnum
-                              completion:^(AnEnumBox *_Nullable enumValue,
+                              completion:^(AnEnumBox *_Nullable output,
                                            FlutterError *_Nullable error) {
-                                NSNumber *output =
-                                    enumValue == nil ? nil
-                                                     : [NSNumber numberWithInteger:enumValue.value];
                                 callback(wrapResult(output, error));
                               }];
       }];
@@ -2674,14 +2702,14 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
                                           @"HostIntegrationCoreApi.callFlutterSmallApiEchoString",
                                           messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostIntegrationCoreApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(callFlutterSmallApiEchoString:completion:)],
                 @"HostIntegrationCoreApi api (%@) doesn't respond to "
                 @"@selector(callFlutterSmallApiEchoString:completion:)",
                 api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api callFlutterSmallApiEchoString:arg_aString
                                 completion:^(NSString *_Nullable output,
@@ -2694,74 +2722,6 @@ void SetUpHostIntegrationCoreApiWithSuffix(id<FlutterBinaryMessenger> binaryMess
     }
   }
 }
-@interface FlutterIntegrationCoreApiCodecReader : FlutterStandardReader
-@end
-@implementation FlutterIntegrationCoreApiCodecReader
-- (nullable id)readValueOfType:(UInt8)type {
-  switch (type) {
-    case 128:
-      return [AllClassesWrapper fromList:[self readValue]];
-    case 129:
-      return [AllNullableTypes fromList:[self readValue]];
-    case 130:
-      return [AllNullableTypesWithoutRecursion fromList:[self readValue]];
-    case 131:
-      return [AllTypes fromList:[self readValue]];
-    case 132:
-      return [TestMessage fromList:[self readValue]];
-    default:
-      return [super readValueOfType:type];
-  }
-}
-@end
-
-@interface FlutterIntegrationCoreApiCodecWriter : FlutterStandardWriter
-@end
-@implementation FlutterIntegrationCoreApiCodecWriter
-- (void)writeValue:(id)value {
-  if ([value isKindOfClass:[AllClassesWrapper class]]) {
-    [self writeByte:128];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[AllNullableTypes class]]) {
-    [self writeByte:129];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[AllNullableTypesWithoutRecursion class]]) {
-    [self writeByte:130];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[AllTypes class]]) {
-    [self writeByte:131];
-    [self writeValue:[value toList]];
-  } else if ([value isKindOfClass:[TestMessage class]]) {
-    [self writeByte:132];
-    [self writeValue:[value toList]];
-  } else {
-    [super writeValue:value];
-  }
-}
-@end
-
-@interface FlutterIntegrationCoreApiCodecReaderWriter : FlutterStandardReaderWriter
-@end
-@implementation FlutterIntegrationCoreApiCodecReaderWriter
-- (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[FlutterIntegrationCoreApiCodecWriter alloc] initWithData:data];
-}
-- (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[FlutterIntegrationCoreApiCodecReader alloc] initWithData:data];
-}
-@end
-
-NSObject<FlutterMessageCodec> *FlutterIntegrationCoreApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  static dispatch_once_t sPred = 0;
-  dispatch_once(&sPred, ^{
-    FlutterIntegrationCoreApiCodecReaderWriter *readerWriter =
-        [[FlutterIntegrationCoreApiCodecReaderWriter alloc] init];
-    sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
-  });
-  return sSharedObject;
-}
-
 @interface FlutterIntegrationCoreApi ()
 @property(nonatomic, strong) NSObject<FlutterBinaryMessenger> *binaryMessenger;
 @property(nonatomic, strong) NSString *messageChannelSuffix;
@@ -2791,7 +2751,7 @@ - (void)noopWithCompletion:(void (^)(FlutterError *_Nullable))completion {
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2816,7 +2776,7 @@ - (void)throwErrorWithCompletion:(void (^)(id _Nullable, FlutterError *_Nullable
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2842,7 +2802,7 @@ - (void)throwErrorFromVoidWithCompletion:(void (^)(FlutterError *_Nullable))comp
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2868,7 +2828,7 @@ - (void)echoAllTypes:(AllTypes *)arg_everything
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_everything ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2896,7 +2856,7 @@ - (void)echoAllNullableTypes:(nullable AllNullableTypes *)arg_everything
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_everything ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2926,7 +2886,7 @@ - (void)sendMultipleNullableTypesABool:(nullable NSNumber *)arg_aNullableBool
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[
     arg_aNullableBool ?: [NSNull null], arg_aNullableInt ?: [NSNull null],
     arg_aNullableString ?: [NSNull null]
@@ -2958,7 +2918,7 @@ - (void)echoAllNullableTypesWithoutRecursion:
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_everything ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -2991,7 +2951,7 @@ - (void)echoAllNullableTypesWithoutRecursion:
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[
     arg_aNullableBool ?: [NSNull null], arg_aNullableInt ?: [NSNull null],
     arg_aNullableString ?: [NSNull null]
@@ -3022,7 +2982,7 @@ - (void)echoBool:(BOOL)arg_aBool
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ @(arg_aBool) ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3048,7 +3008,7 @@ - (void)echoInt:(NSInteger)arg_anInt
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ @(arg_anInt) ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3075,7 +3035,7 @@ - (void)echoDouble:(double)arg_aDouble
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ @(arg_aDouble) ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3102,7 +3062,7 @@ - (void)echoString:(NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3130,7 +3090,7 @@ - (void)echoUint8List:(FlutterStandardTypedData *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3158,7 +3118,7 @@ - (void)echoList:(NSArray<id> *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3185,7 +3145,7 @@ - (void)echoMap:(NSDictionary<NSString *, id> *)arg_aMap
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aMap ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3213,8 +3173,8 @@ - (void)echoEnum:(AnEnum)arg_anEnum
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
-  [channel sendMessage:@[ [NSNumber numberWithInteger:arg_anEnum] ]
+                                                   codec:GetCoreTestsCodec()];
+  [channel sendMessage:@[ [[AnEnumBox alloc] initWithValue:arg_anEnum] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
                      if (reply.count > 1) {
@@ -3222,11 +3182,7 @@ - (void)echoEnum:(AnEnum)arg_anEnum
                                                            message:reply[1]
                                                            details:reply[2]]);
                      } else {
-                       NSNumber *outputAsNumber = reply[0] == [NSNull null] ? nil : reply[0];
-                       AnEnumBox *output =
-                           outputAsNumber == nil
-                               ? nil
-                               : [[AnEnumBox alloc] initWithValue:[outputAsNumber integerValue]];
+                       AnEnumBox *output = reply[0] == [NSNull null] ? nil : reply[0];
                        completion(output, nil);
                      }
                    } else {
@@ -3244,7 +3200,7 @@ - (void)echoNullableBool:(nullable NSNumber *)arg_aBool
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aBool ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3271,7 +3227,7 @@ - (void)echoNullableInt:(nullable NSNumber *)arg_anInt
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_anInt ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3298,7 +3254,7 @@ - (void)echoNullableDouble:(nullable NSNumber *)arg_aDouble
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aDouble ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3325,7 +3281,7 @@ - (void)echoNullableString:(nullable NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3353,7 +3309,7 @@ - (void)echoNullableUint8List:(nullable FlutterStandardTypedData *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3381,7 +3337,7 @@ - (void)echoNullableList:(nullable NSArray<id> *)arg_list
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_list ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3409,7 +3365,7 @@ - (void)echoNullableMap:(nullable NSDictionary<NSString *, id> *)arg_aMap
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aMap ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3437,9 +3393,8 @@ - (void)echoNullableEnum:(nullable AnEnumBox *)arg_anEnum
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
-  [channel sendMessage:@[ arg_anEnum == nil ? [NSNull null]
-                                            : [NSNumber numberWithInteger:arg_anEnum.value] ]
+                                                   codec:GetCoreTestsCodec()];
+  [channel sendMessage:@[ arg_anEnum == nil ? [NSNull null] : arg_anEnum ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
                      if (reply.count > 1) {
@@ -3447,11 +3402,7 @@ - (void)echoNullableEnum:(nullable AnEnumBox *)arg_anEnum
                                                            message:reply[1]
                                                            details:reply[2]]);
                      } else {
-                       NSNumber *outputAsNumber = reply[0] == [NSNull null] ? nil : reply[0];
-                       AnEnumBox *output =
-                           outputAsNumber == nil
-                               ? nil
-                               : [[AnEnumBox alloc] initWithValue:[outputAsNumber integerValue]];
+                       AnEnumBox *output = reply[0] == [NSNull null] ? nil : reply[0];
                        completion(output, nil);
                      }
                    } else {
@@ -3468,7 +3419,7 @@ - (void)noopAsyncWithCompletion:(void (^)(FlutterError *_Nullable))completion {
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:nil
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3494,7 +3445,7 @@ - (void)echoAsyncString:(NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterIntegrationCoreApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3513,12 +3464,6 @@ - (void)echoAsyncString:(NSString *)arg_aString
 }
 @end
 
-NSObject<FlutterMessageCodec> *HostTrivialApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  sSharedObject = [FlutterStandardMessageCodec sharedInstance];
-  return sSharedObject;
-}
-
 void SetUpHostTrivialApi(id<FlutterBinaryMessenger> binaryMessenger,
                          NSObject<HostTrivialApi> *api) {
   SetUpHostTrivialApiWithSuffix(binaryMessenger, api, @"");
@@ -3537,7 +3482,7 @@ void SetUpHostTrivialApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
                                 @"dev.flutter.pigeon.pigeon_integration_tests.HostTrivialApi.noop",
                                 messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostTrivialApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(noopWithError:)],
                 @"HostTrivialApi api (%@) doesn't respond to @selector(noopWithError:)", api);
@@ -3551,12 +3496,6 @@ void SetUpHostTrivialApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
     }
   }
 }
-NSObject<FlutterMessageCodec> *HostSmallApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  sSharedObject = [FlutterStandardMessageCodec sharedInstance];
-  return sSharedObject;
-}
-
 void SetUpHostSmallApi(id<FlutterBinaryMessenger> binaryMessenger, NSObject<HostSmallApi> *api) {
   SetUpHostSmallApiWithSuffix(binaryMessenger, api, @"");
 }
@@ -3574,12 +3513,12 @@ void SetUpHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
                                 @"dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo",
                                 messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostSmallApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(echoString:completion:)],
                 @"HostSmallApi api (%@) doesn't respond to @selector(echoString:completion:)", api);
       [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
-        NSArray *args = message;
+        NSArray<id> *args = message;
         NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
         [api echoString:arg_aString
              completion:^(NSString *_Nullable output, FlutterError *_Nullable error) {
@@ -3597,7 +3536,7 @@ void SetUpHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
                                                    @"HostSmallApi.voidVoid",
                                                    messageChannelSuffix]
         binaryMessenger:binaryMessenger
-                  codec:HostSmallApiGetCodec()];
+                  codec:GetCoreTestsCodec()];
     if (api) {
       NSCAssert([api respondsToSelector:@selector(voidVoidWithCompletion:)],
                 @"HostSmallApi api (%@) doesn't respond to @selector(voidVoidWithCompletion:)",
@@ -3612,54 +3551,6 @@ void SetUpHostSmallApiWithSuffix(id<FlutterBinaryMessenger> binaryMessenger,
     }
   }
 }
-@interface FlutterSmallApiCodecReader : FlutterStandardReader
-@end
-@implementation FlutterSmallApiCodecReader
-- (nullable id)readValueOfType:(UInt8)type {
-  switch (type) {
-    case 128:
-      return [TestMessage fromList:[self readValue]];
-    default:
-      return [super readValueOfType:type];
-  }
-}
-@end
-
-@interface FlutterSmallApiCodecWriter : FlutterStandardWriter
-@end
-@implementation FlutterSmallApiCodecWriter
-- (void)writeValue:(id)value {
-  if ([value isKindOfClass:[TestMessage class]]) {
-    [self writeByte:128];
-    [self writeValue:[value toList]];
-  } else {
-    [super writeValue:value];
-  }
-}
-@end
-
-@interface FlutterSmallApiCodecReaderWriter : FlutterStandardReaderWriter
-@end
-@implementation FlutterSmallApiCodecReaderWriter
-- (FlutterStandardWriter *)writerWithData:(NSMutableData *)data {
-  return [[FlutterSmallApiCodecWriter alloc] initWithData:data];
-}
-- (FlutterStandardReader *)readerWithData:(NSData *)data {
-  return [[FlutterSmallApiCodecReader alloc] initWithData:data];
-}
-@end
-
-NSObject<FlutterMessageCodec> *FlutterSmallApiGetCodec(void) {
-  static FlutterStandardMessageCodec *sSharedObject = nil;
-  static dispatch_once_t sPred = 0;
-  dispatch_once(&sPred, ^{
-    FlutterSmallApiCodecReaderWriter *readerWriter =
-        [[FlutterSmallApiCodecReaderWriter alloc] init];
-    sSharedObject = [FlutterStandardMessageCodec codecWithReaderWriter:readerWriter];
-  });
-  return sSharedObject;
-}
-
 @interface FlutterSmallApi ()
 @property(nonatomic, strong) NSObject<FlutterBinaryMessenger> *binaryMessenger;
 @property(nonatomic, strong) NSString *messageChannelSuffix;
@@ -3690,7 +3581,7 @@ - (void)echoWrappedList:(TestMessage *)arg_msg
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterSmallApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_msg ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
@@ -3716,7 +3607,7 @@ - (void)echoString:(NSString *)arg_aString
   FlutterBasicMessageChannel *channel =
       [FlutterBasicMessageChannel messageChannelWithName:channelName
                                          binaryMessenger:self.binaryMessenger
-                                                   codec:FlutterSmallApiGetCodec()];
+                                                   codec:GetCoreTestsCodec()];
   [channel sendMessage:@[ arg_aString ?: [NSNull null] ]
                  reply:^(NSArray<id> *reply) {
                    if (reply != nil) {
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
index 85484362b3a..d108f4892f0 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
@@ -8,6 +8,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:integration_test/integration_test.dart';
 
 import 'generated.dart';
+import 'src/generated/core_tests.gen.dart';
 
 const int _biggerThanBigInt = 3000000000;
 const int _regularInt = 42;
@@ -49,10 +50,14 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     expect(allTypesOne.a4ByteArray, allTypesTwo.a4ByteArray);
     expect(allTypesOne.a8ByteArray, allTypesTwo.a8ByteArray);
     expect(allTypesOne.aFloatArray, allTypesTwo.aFloatArray);
-    expect(listEquals(allTypesOne.list, allTypesTwo.list), true);
-    expect(mapEquals(allTypesOne.aMap, allTypesTwo.aMap), true);
     expect(allTypesOne.anEnum, allTypesTwo.anEnum);
     expect(allTypesOne.anObject, allTypesTwo.anObject);
+    expect(listEquals(allTypesOne.list, allTypesTwo.list), true);
+    expect(listEquals(allTypesOne.stringList, allTypesTwo.stringList), true);
+    expect(listEquals(allTypesOne.boolList, allTypesTwo.boolList), true);
+    expect(listEquals(allTypesOne.doubleList, allTypesTwo.doubleList), true);
+    expect(listEquals(allTypesOne.intList, allTypesTwo.intList), true);
+    expect(mapEquals(allTypesOne.map, allTypesTwo.map), true);
   }
 
   void compareAllNullableTypes(AllNullableTypes? allNullableTypesOne,
@@ -78,14 +83,6 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
         allNullableTypesTwo.aNullable8ByteArray);
     expect(allNullableTypesOne.aNullableFloatArray,
         allNullableTypesTwo.aNullableFloatArray);
-    expect(
-        listEquals(allNullableTypesOne.aNullableList,
-            allNullableTypesTwo.aNullableList),
-        true);
-    expect(
-        mapEquals(
-            allNullableTypesOne.aNullableMap, allNullableTypesTwo.aNullableMap),
-        true);
     expect(allNullableTypesOne.nullableNestedList?.length,
         allNullableTypesTwo.nullableNestedList?.length);
     // TODO(stuartmorgan): Enable this once the Dart types are fixed; see
@@ -108,6 +105,30 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
         allNullableTypesOne.aNullableEnum, allNullableTypesTwo.aNullableEnum);
     compareAllNullableTypes(allNullableTypesOne.allNullableTypes,
         allNullableTypesTwo.allNullableTypes);
+    expect(
+        listEquals(allNullableTypesOne.list, allNullableTypesTwo.list), true);
+    expect(
+        listEquals(
+            allNullableTypesOne.stringList, allNullableTypesTwo.stringList),
+        true);
+    expect(
+        listEquals(allNullableTypesOne.boolList, allNullableTypesTwo.boolList),
+        true);
+    expect(
+        listEquals(
+            allNullableTypesOne.doubleList, allNullableTypesTwo.doubleList),
+        true);
+    expect(listEquals(allNullableTypesOne.intList, allNullableTypesTwo.intList),
+        true);
+    expect(allNullableTypesOne.nestedClassList?.length,
+        allNullableTypesTwo.nestedClassList?.length);
+    for (int i = 0;
+        i < (allNullableTypesOne.nestedClassList?.length ?? 0);
+        i++) {
+      compareAllNullableTypes(allNullableTypesOne.nestedClassList?[i],
+          allNullableTypesTwo.nestedClassList?[i]);
+    }
+    expect(mapEquals(allNullableTypesOne.map, allNullableTypesTwo.map), true);
   }
 
   void compareAllNullableTypesWithoutRecursion(
@@ -134,14 +155,6 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
         allNullableTypesTwo.aNullable8ByteArray);
     expect(allNullableTypesOne.aNullableFloatArray,
         allNullableTypesTwo.aNullableFloatArray);
-    expect(
-        listEquals(allNullableTypesOne.aNullableList,
-            allNullableTypesTwo.aNullableList),
-        true);
-    expect(
-        mapEquals(
-            allNullableTypesOne.aNullableMap, allNullableTypesTwo.aNullableMap),
-        true);
     expect(allNullableTypesOne.nullableNestedList?.length,
         allNullableTypesTwo.nullableNestedList?.length);
     // TODO(stuartmorgan): Enable this once the Dart types are fixed; see
@@ -162,6 +175,22 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
         allNullableTypesTwo.aNullableObject);
     expect(
         allNullableTypesOne.aNullableEnum, allNullableTypesTwo.aNullableEnum);
+    expect(
+        listEquals(allNullableTypesOne.list, allNullableTypesTwo.list), true);
+    expect(
+        listEquals(
+            allNullableTypesOne.stringList, allNullableTypesTwo.stringList),
+        true);
+    expect(
+        listEquals(allNullableTypesOne.boolList, allNullableTypesTwo.boolList),
+        true);
+    expect(
+        listEquals(
+            allNullableTypesOne.doubleList, allNullableTypesTwo.doubleList),
+        true);
+    expect(listEquals(allNullableTypesOne.intList, allNullableTypesTwo.intList),
+        true);
+    expect(mapEquals(allNullableTypesOne.map, allNullableTypesTwo.map), true);
   }
 
   void compareAllClassesWrapper(
@@ -180,6 +209,54 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     compareAllTypes(wrapperOne.allTypes, wrapperTwo.allTypes);
   }
 
+  final Map<Object?, Object?> map = <Object?, Object?>{
+    'a': 1,
+    'b': 2.0,
+    'c': 'three',
+    'd': false,
+    'e': null
+  };
+
+  final List<Object?> list = <Object?>[
+    'Thing 1',
+    2,
+    true,
+    3.14,
+    null,
+  ];
+
+  final List<String?> stringList = <String?>[
+    'Thing 1',
+    '2',
+    'true',
+    '3.14',
+    null,
+  ];
+
+  final List<int?> intList = <int?>[
+    1,
+    2,
+    3,
+    4,
+    null,
+  ];
+
+  final List<double?> doubleList = <double?>[
+    1,
+    2.99999,
+    3,
+    3.14,
+    null,
+  ];
+
+  final List<bool?> boolList = <bool?>[
+    true,
+    false,
+    true,
+    false,
+    null,
+  ];
+
   final AllTypes genericAllTypes = AllTypes(
     aBool: true,
     anInt: _regularInt,
@@ -190,16 +267,14 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     a4ByteArray: Int32List.fromList(<int>[4, 5, 6]),
     a8ByteArray: Int64List.fromList(<int>[7, 8, 9]),
     aFloatArray: Float64List.fromList(<double>[2.71828, _doublePi]),
-    list: <Object?>['Thing 1', 2, true, 3.14, null],
-    aMap: <Object?, Object?>{
-      'a': 1,
-      'b': 2.0,
-      'c': 'three',
-      'd': false,
-      'e': null
-    },
     anEnum: AnEnum.fortyTwo,
     anObject: 1,
+    list: list,
+    stringList: stringList,
+    intList: intList,
+    doubleList: doubleList,
+    boolList: boolList,
+    map: map,
   );
 
   final AllNullableTypes genericAllNullableTypes = AllNullableTypes(
@@ -212,14 +287,6 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     aNullable4ByteArray: Int32List.fromList(<int>[4, 5, 6]),
     aNullable8ByteArray: Int64List.fromList(<int>[7, 8, 9]),
     aNullableFloatArray: Float64List.fromList(<double>[2.71828, _doublePi]),
-    aNullableList: <Object?>['Thing 1', 2, true, 3.14, null],
-    aNullableMap: <Object?, Object?>{
-      'a': 1,
-      'b': 2.0,
-      'c': 'three',
-      'd': false,
-      'e': null
-    },
     nullableNestedList: <List<bool>>[
       <bool>[true, false],
       <bool>[false, true]
@@ -228,8 +295,20 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     nullableMapWithObject: <String?, Object?>{},
     aNullableEnum: AnEnum.fourHundredTwentyTwo,
     aNullableObject: 0,
+    list: list,
+    stringList: stringList,
+    intList: intList,
+    doubleList: doubleList,
+    boolList: boolList,
+    map: map,
   );
 
+  final List<AllNullableTypes?> allNullableTypesList = <AllNullableTypes?>[
+    genericAllNullableTypes,
+    AllNullableTypes(),
+    null,
+  ];
+
   final AllNullableTypes recursiveAllNullableTypes = AllNullableTypes(
     aNullableBool: true,
     aNullableInt: _regularInt,
@@ -240,14 +319,6 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     aNullable4ByteArray: Int32List.fromList(<int>[4, 5, 6]),
     aNullable8ByteArray: Int64List.fromList(<int>[7, 8, 9]),
     aNullableFloatArray: Float64List.fromList(<double>[2.71828, _doublePi]),
-    aNullableList: <Object?>['Thing 1', 2, true, 3.14, null],
-    aNullableMap: <Object?, Object?>{
-      'a': 1,
-      'b': 2.0,
-      'c': 'three',
-      'd': false,
-      'e': null
-    },
     nullableNestedList: <List<bool>>[
       <bool>[true, false],
       <bool>[false, true]
@@ -257,6 +328,13 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     aNullableEnum: AnEnum.fourHundredTwentyTwo,
     aNullableObject: 0,
     allNullableTypes: genericAllNullableTypes,
+    list: list,
+    stringList: stringList,
+    intList: intList,
+    doubleList: doubleList,
+    boolList: boolList,
+    nestedClassList: allNullableTypesList,
+    map: map,
   );
 
   final AllNullableTypesWithoutRecursion
@@ -271,14 +349,6 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     aNullable4ByteArray: Int32List.fromList(<int>[4, 5, 6]),
     aNullable8ByteArray: Int64List.fromList(<int>[7, 8, 9]),
     aNullableFloatArray: Float64List.fromList(<double>[2.71828, _doublePi]),
-    aNullableList: <Object?>['Thing 1', 2, true, 3.14, null],
-    aNullableMap: <Object?, Object?>{
-      'a': 1,
-      'b': 2.0,
-      'c': 'three',
-      'd': false,
-      'e': null
-    },
     nullableNestedList: <List<bool>>[
       <bool>[true, false],
       <bool>[false, true]
@@ -287,6 +357,12 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     nullableMapWithObject: <String?, Object?>{},
     aNullableEnum: AnEnum.fourHundredTwentyTwo,
     aNullableObject: 0,
+    list: list,
+    stringList: stringList,
+    intList: intList,
+    doubleList: doubleList,
+    boolList: boolList,
+    map: map,
   );
 
   group('Host sync API tests', () {
@@ -330,7 +406,7 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
       final HostIntegrationCoreApi api = HostIntegrationCoreApi();
 
       final AllNullableTypes nullableListTypes =
-          AllNullableTypes(aNullableList: <String?>['String', null]);
+          AllNullableTypes(list: <String?>['String', null]);
 
       final AllNullableTypes? echoNullFilledClass =
           await api.echoAllNullableTypes(nullableListTypes);
@@ -343,7 +419,7 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
       final HostIntegrationCoreApi api = HostIntegrationCoreApi();
 
       final AllNullableTypes nullableListTypes = AllNullableTypes(
-          aNullableMap: <String?, String?>{'String': 'string', 'null': null});
+          map: <String?, String?>{'String': 'string', 'null': null});
 
       final AllNullableTypes? echoNullFilledClass =
           await api.echoAllNullableTypes(nullableListTypes);
@@ -385,7 +461,8 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
 
       final AllNullableTypesWithoutRecursion nullableListTypes =
           AllNullableTypesWithoutRecursion(
-              aNullableList: <String?>['String', null]);
+        list: <String?>['String', null],
+      );
 
       final AllNullableTypesWithoutRecursion? echoNullFilledClass =
           await api.echoAllNullableTypesWithoutRecursion(nullableListTypes);
@@ -400,10 +477,9 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
       final HostIntegrationCoreApi api = HostIntegrationCoreApi();
 
       final AllNullableTypesWithoutRecursion nullableListTypes =
-          AllNullableTypesWithoutRecursion(aNullableMap: <String?, String?>{
-        'String': 'string',
-        'null': null
-      });
+          AllNullableTypesWithoutRecursion(
+        map: <String?, String?>{'String': 'string', 'null': null},
+      );
 
       final AllNullableTypesWithoutRecursion? echoNullFilledClass =
           await api.echoAllNullableTypesWithoutRecursion(nullableListTypes);
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
index 461683120ce..e9e063126c1 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
@@ -19,6 +19,10 @@ PlatformException _createConnectionError(String channelName) {
   );
 }
 
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
+}
+
 class BackgroundApi2Host {
   /// Constructor for [BackgroundApi2Host].  The [binaryMessenger] named argument is
   /// available for dependency injection.  If it is left null, the default
@@ -30,8 +34,7 @@ class BackgroundApi2Host {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
index 2f24cdcb2ca..e192a84ceea 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
@@ -49,11 +49,15 @@ class AllTypes {
     required this.a4ByteArray,
     required this.a8ByteArray,
     required this.aFloatArray,
-    this.list = const <Object?>[],
-    this.aMap = const <String?, Object?>{},
     this.anEnum = AnEnum.one,
     this.aString = '',
     this.anObject = 0,
+    required this.list,
+    required this.stringList,
+    required this.intList,
+    required this.doubleList,
+    required this.boolList,
+    required this.map,
   });
 
   bool aBool;
@@ -72,16 +76,24 @@ class AllTypes {
 
   Float64List aFloatArray;
 
-  List<Object?> list;
-
-  Map<Object?, Object?> aMap;
-
   AnEnum anEnum;
 
   String aString;
 
   Object anObject;
 
+  List<Object?> list;
+
+  List<String?> stringList;
+
+  List<int?> intList;
+
+  List<double?> doubleList;
+
+  List<bool?> boolList;
+
+  Map<Object?, Object?> map;
+
   Object encode() {
     return <Object?>[
       aBool,
@@ -92,11 +104,15 @@ class AllTypes {
       a4ByteArray,
       a8ByteArray,
       aFloatArray,
-      list,
-      aMap,
-      anEnum.index,
+      anEnum,
       aString,
       anObject,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      map,
     ];
   }
 
@@ -111,11 +127,15 @@ class AllTypes {
       a4ByteArray: result[5]! as Int32List,
       a8ByteArray: result[6]! as Int64List,
       aFloatArray: result[7]! as Float64List,
-      list: result[8]! as List<Object?>,
-      aMap: result[9]! as Map<Object?, Object?>,
-      anEnum: AnEnum.values[result[10]! as int],
-      aString: result[11]! as String,
-      anObject: result[12]!,
+      anEnum: result[8]! as AnEnum,
+      aString: result[9]! as String,
+      anObject: result[10]!,
+      list: result[11]! as List<Object?>,
+      stringList: (result[12] as List<Object?>?)!.cast<String?>(),
+      intList: (result[13] as List<Object?>?)!.cast<int?>(),
+      doubleList: (result[14] as List<Object?>?)!.cast<double?>(),
+      boolList: (result[15] as List<Object?>?)!.cast<bool?>(),
+      map: result[16]! as Map<Object?, Object?>,
     );
   }
 }
@@ -131,8 +151,6 @@ class AllNullableTypes {
     this.aNullable4ByteArray,
     this.aNullable8ByteArray,
     this.aNullableFloatArray,
-    this.aNullableList,
-    this.aNullableMap,
     this.nullableNestedList,
     this.nullableMapWithAnnotations,
     this.nullableMapWithObject,
@@ -140,6 +158,13 @@ class AllNullableTypes {
     this.aNullableString,
     this.aNullableObject,
     this.allNullableTypes,
+    this.list,
+    this.stringList,
+    this.intList,
+    this.doubleList,
+    this.boolList,
+    this.nestedClassList,
+    this.map,
   });
 
   bool? aNullableBool;
@@ -158,10 +183,6 @@ class AllNullableTypes {
 
   Float64List? aNullableFloatArray;
 
-  List<Object?>? aNullableList;
-
-  Map<Object?, Object?>? aNullableMap;
-
   List<List<bool?>?>? nullableNestedList;
 
   Map<String?, String?>? nullableMapWithAnnotations;
@@ -176,6 +197,20 @@ class AllNullableTypes {
 
   AllNullableTypes? allNullableTypes;
 
+  List<Object?>? list;
+
+  List<String?>? stringList;
+
+  List<int?>? intList;
+
+  List<double?>? doubleList;
+
+  List<bool?>? boolList;
+
+  List<AllNullableTypes?>? nestedClassList;
+
+  Map<Object?, Object?>? map;
+
   Object encode() {
     return <Object?>[
       aNullableBool,
@@ -186,15 +221,20 @@ class AllNullableTypes {
       aNullable4ByteArray,
       aNullable8ByteArray,
       aNullableFloatArray,
-      aNullableList,
-      aNullableMap,
       nullableNestedList,
       nullableMapWithAnnotations,
       nullableMapWithObject,
-      aNullableEnum?.index,
+      aNullableEnum,
       aNullableString,
       aNullableObject,
       allNullableTypes,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      nestedClassList,
+      map,
     ];
   }
 
@@ -209,18 +249,23 @@ class AllNullableTypes {
       aNullable4ByteArray: result[5] as Int32List?,
       aNullable8ByteArray: result[6] as Int64List?,
       aNullableFloatArray: result[7] as Float64List?,
-      aNullableList: result[8] as List<Object?>?,
-      aNullableMap: result[9] as Map<Object?, Object?>?,
-      nullableNestedList: (result[10] as List<Object?>?)?.cast<List<bool?>?>(),
+      nullableNestedList: (result[8] as List<Object?>?)?.cast<List<bool?>?>(),
       nullableMapWithAnnotations:
-          (result[11] as Map<Object?, Object?>?)?.cast<String?, String?>(),
+          (result[9] as Map<Object?, Object?>?)?.cast<String?, String?>(),
       nullableMapWithObject:
-          (result[12] as Map<Object?, Object?>?)?.cast<String?, Object?>(),
-      aNullableEnum:
-          result[13] != null ? AnEnum.values[result[13]! as int] : null,
-      aNullableString: result[14] as String?,
-      aNullableObject: result[15],
-      allNullableTypes: result[16] as AllNullableTypes?,
+          (result[10] as Map<Object?, Object?>?)?.cast<String?, Object?>(),
+      aNullableEnum: result[11] as AnEnum?,
+      aNullableString: result[12] as String?,
+      aNullableObject: result[13],
+      allNullableTypes: result[14] as AllNullableTypes?,
+      list: result[15] as List<Object?>?,
+      stringList: (result[16] as List<Object?>?)?.cast<String?>(),
+      intList: (result[17] as List<Object?>?)?.cast<int?>(),
+      doubleList: (result[18] as List<Object?>?)?.cast<double?>(),
+      boolList: (result[19] as List<Object?>?)?.cast<bool?>(),
+      nestedClassList:
+          (result[20] as List<Object?>?)?.cast<AllNullableTypes?>(),
+      map: result[21] as Map<Object?, Object?>?,
     );
   }
 }
@@ -238,14 +283,18 @@ class AllNullableTypesWithoutRecursion {
     this.aNullable4ByteArray,
     this.aNullable8ByteArray,
     this.aNullableFloatArray,
-    this.aNullableList,
-    this.aNullableMap,
     this.nullableNestedList,
     this.nullableMapWithAnnotations,
     this.nullableMapWithObject,
     this.aNullableEnum,
     this.aNullableString,
     this.aNullableObject,
+    this.list,
+    this.stringList,
+    this.intList,
+    this.doubleList,
+    this.boolList,
+    this.map,
   });
 
   bool? aNullableBool;
@@ -264,10 +313,6 @@ class AllNullableTypesWithoutRecursion {
 
   Float64List? aNullableFloatArray;
 
-  List<Object?>? aNullableList;
-
-  Map<Object?, Object?>? aNullableMap;
-
   List<List<bool?>?>? nullableNestedList;
 
   Map<String?, String?>? nullableMapWithAnnotations;
@@ -280,6 +325,18 @@ class AllNullableTypesWithoutRecursion {
 
   Object? aNullableObject;
 
+  List<Object?>? list;
+
+  List<String?>? stringList;
+
+  List<int?>? intList;
+
+  List<double?>? doubleList;
+
+  List<bool?>? boolList;
+
+  Map<Object?, Object?>? map;
+
   Object encode() {
     return <Object?>[
       aNullableBool,
@@ -290,14 +347,18 @@ class AllNullableTypesWithoutRecursion {
       aNullable4ByteArray,
       aNullable8ByteArray,
       aNullableFloatArray,
-      aNullableList,
-      aNullableMap,
       nullableNestedList,
       nullableMapWithAnnotations,
       nullableMapWithObject,
-      aNullableEnum?.index,
+      aNullableEnum,
       aNullableString,
       aNullableObject,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      map,
     ];
   }
 
@@ -312,17 +373,20 @@ class AllNullableTypesWithoutRecursion {
       aNullable4ByteArray: result[5] as Int32List?,
       aNullable8ByteArray: result[6] as Int64List?,
       aNullableFloatArray: result[7] as Float64List?,
-      aNullableList: result[8] as List<Object?>?,
-      aNullableMap: result[9] as Map<Object?, Object?>?,
-      nullableNestedList: (result[10] as List<Object?>?)?.cast<List<bool?>?>(),
+      nullableNestedList: (result[8] as List<Object?>?)?.cast<List<bool?>?>(),
       nullableMapWithAnnotations:
-          (result[11] as Map<Object?, Object?>?)?.cast<String?, String?>(),
+          (result[9] as Map<Object?, Object?>?)?.cast<String?, String?>(),
       nullableMapWithObject:
-          (result[12] as Map<Object?, Object?>?)?.cast<String?, Object?>(),
-      aNullableEnum:
-          result[13] != null ? AnEnum.values[result[13]! as int] : null,
-      aNullableString: result[14] as String?,
-      aNullableObject: result[15],
+          (result[10] as Map<Object?, Object?>?)?.cast<String?, Object?>(),
+      aNullableEnum: result[11] as AnEnum?,
+      aNullableString: result[12] as String?,
+      aNullableObject: result[13],
+      list: result[14] as List<Object?>?,
+      stringList: (result[15] as List<Object?>?)?.cast<String?>(),
+      intList: (result[16] as List<Object?>?)?.cast<int?>(),
+      doubleList: (result[17] as List<Object?>?)?.cast<double?>(),
+      boolList: (result[18] as List<Object?>?)?.cast<bool?>(),
+      map: result[19] as Map<Object?, Object?>?,
     );
   }
 }
@@ -386,25 +450,28 @@ class TestMessage {
   }
 }
 
-class _HostIntegrationCoreApiCodec extends StandardMessageCodec {
-  const _HostIntegrationCoreApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is AllClassesWrapper) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is AllNullableTypes) {
+    if (value is AllTypes) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
-    } else if (value is AllNullableTypesWithoutRecursion) {
+    } else if (value is AllNullableTypes) {
       buffer.putUint8(130);
       writeValue(buffer, value.encode());
-    } else if (value is AllTypes) {
+    } else if (value is AllNullableTypesWithoutRecursion) {
       buffer.putUint8(131);
       writeValue(buffer, value.encode());
-    } else if (value is TestMessage) {
+    } else if (value is AllClassesWrapper) {
       buffer.putUint8(132);
       writeValue(buffer, value.encode());
+    } else if (value is TestMessage) {
+      buffer.putUint8(133);
+      writeValue(buffer, value.encode());
+    } else if (value is AnEnum) {
+      buffer.putUint8(134);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -413,16 +480,19 @@ class _HostIntegrationCoreApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
-        return AllClassesWrapper.decode(readValue(buffer)!);
       case 129:
-        return AllNullableTypes.decode(readValue(buffer)!);
+        return AllTypes.decode(readValue(buffer)!);
       case 130:
-        return AllNullableTypesWithoutRecursion.decode(readValue(buffer)!);
+        return AllNullableTypes.decode(readValue(buffer)!);
       case 131:
-        return AllTypes.decode(readValue(buffer)!);
+        return AllNullableTypesWithoutRecursion.decode(readValue(buffer)!);
       case 132:
+        return AllClassesWrapper.decode(readValue(buffer)!);
+      case 133:
         return TestMessage.decode(readValue(buffer)!);
+      case 134:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : AnEnum.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -442,8 +512,7 @@ class HostIntegrationCoreApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _HostIntegrationCoreApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -860,7 +929,7 @@ class HostIntegrationCoreApi {
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList =
-        await __pigeon_channel.send(<Object?>[anEnum.index]) as List<Object?>?;
+        await __pigeon_channel.send(<Object?>[anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -875,7 +944,7 @@ class HostIntegrationCoreApi {
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return AnEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as AnEnum?)!;
     }
   }
 
@@ -1358,7 +1427,7 @@ class HostIntegrationCoreApi {
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList =
-        await __pigeon_channel.send(<Object?>[anEnum?.index]) as List<Object?>?;
+        await __pigeon_channel.send(<Object?>[anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -1368,9 +1437,7 @@ class HostIntegrationCoreApi {
         details: __pigeon_replyList[2],
       );
     } else {
-      return (__pigeon_replyList[0] as int?) == null
-          ? null
-          : AnEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as AnEnum?);
     }
   }
 
@@ -1702,7 +1769,7 @@ class HostIntegrationCoreApi {
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList =
-        await __pigeon_channel.send(<Object?>[anEnum.index]) as List<Object?>?;
+        await __pigeon_channel.send(<Object?>[anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -1717,7 +1784,7 @@ class HostIntegrationCoreApi {
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return AnEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as AnEnum?)!;
     }
   }
 
@@ -2092,7 +2159,7 @@ class HostIntegrationCoreApi {
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList =
-        await __pigeon_channel.send(<Object?>[anEnum?.index]) as List<Object?>?;
+        await __pigeon_channel.send(<Object?>[anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -2102,9 +2169,7 @@ class HostIntegrationCoreApi {
         details: __pigeon_replyList[2],
       );
     } else {
-      return (__pigeon_replyList[0] as int?) == null
-          ? null
-          : AnEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as AnEnum?);
     }
   }
 
@@ -2538,7 +2603,7 @@ class HostIntegrationCoreApi {
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList =
-        await __pigeon_channel.send(<Object?>[anEnum.index]) as List<Object?>?;
+        await __pigeon_channel.send(<Object?>[anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -2553,7 +2618,7 @@ class HostIntegrationCoreApi {
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return AnEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as AnEnum?)!;
     }
   }
 
@@ -2738,7 +2803,7 @@ class HostIntegrationCoreApi {
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList =
-        await __pigeon_channel.send(<Object?>[anEnum?.index]) as List<Object?>?;
+        await __pigeon_channel.send(<Object?>[anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -2748,9 +2813,7 @@ class HostIntegrationCoreApi {
         details: __pigeon_replyList[2],
       );
     } else {
-      return (__pigeon_replyList[0] as int?) == null
-          ? null
-          : AnEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as AnEnum?);
     }
   }
 
@@ -2784,54 +2847,10 @@ class HostIntegrationCoreApi {
   }
 }
 
-class _FlutterIntegrationCoreApiCodec extends StandardMessageCodec {
-  const _FlutterIntegrationCoreApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is AllClassesWrapper) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is AllNullableTypes) {
-      buffer.putUint8(129);
-      writeValue(buffer, value.encode());
-    } else if (value is AllNullableTypesWithoutRecursion) {
-      buffer.putUint8(130);
-      writeValue(buffer, value.encode());
-    } else if (value is AllTypes) {
-      buffer.putUint8(131);
-      writeValue(buffer, value.encode());
-    } else if (value is TestMessage) {
-      buffer.putUint8(132);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return AllClassesWrapper.decode(readValue(buffer)!);
-      case 129:
-        return AllNullableTypes.decode(readValue(buffer)!);
-      case 130:
-        return AllNullableTypesWithoutRecursion.decode(readValue(buffer)!);
-      case 131:
-        return AllTypes.decode(readValue(buffer)!);
-      case 132:
-        return TestMessage.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 /// The core interface that the Dart platform_test code implements for host
 /// integration tests to call into.
 abstract class FlutterIntegrationCoreApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _FlutterIntegrationCoreApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic calling.
@@ -3347,13 +3366,12 @@ abstract class FlutterIntegrationCoreApi {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum was null.');
           final List<Object?> args = (message as List<Object?>?)!;
-          final AnEnum? arg_anEnum =
-              args[0] == null ? null : AnEnum.values[args[0]! as int];
+          final AnEnum? arg_anEnum = (args[0] as AnEnum?);
           assert(arg_anEnum != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum was null, expected non-null AnEnum.');
           try {
             final AnEnum output = api.echoEnum(arg_anEnum!);
-            return wrapResponse(result: output.index);
+            return wrapResponse(result: output);
           } on PlatformException catch (e) {
             return wrapResponse(error: e);
           } catch (e) {
@@ -3560,11 +3578,10 @@ abstract class FlutterIntegrationCoreApi {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableEnum was null.');
           final List<Object?> args = (message as List<Object?>?)!;
-          final AnEnum? arg_anEnum =
-              args[0] == null ? null : AnEnum.values[args[0]! as int];
+          final AnEnum? arg_anEnum = (args[0] as AnEnum?);
           try {
             final AnEnum? output = api.echoNullableEnum(arg_anEnum);
-            return wrapResponse(result: output?.index);
+            return wrapResponse(result: output);
           } on PlatformException catch (e) {
             return wrapResponse(error: e);
           } catch (e) {
@@ -3639,8 +3656,7 @@ class HostTrivialApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -3681,8 +3697,7 @@ class HostSmallApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -3740,33 +3755,9 @@ class HostSmallApi {
   }
 }
 
-class _FlutterSmallApiCodec extends StandardMessageCodec {
-  const _FlutterSmallApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is TestMessage) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return TestMessage.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 /// A simple API called in some unit tests.
 abstract class FlutterSmallApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _FlutterSmallApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   TestMessage echoWrappedList(TestMessage msg);
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
index 374f272c358..e2ca92672ed 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
@@ -56,25 +56,28 @@ class DataWithEnum {
 
   Object encode() {
     return <Object?>[
-      state?.index,
+      state,
     ];
   }
 
   static DataWithEnum decode(Object result) {
     result as List<Object?>;
     return DataWithEnum(
-      state: result[0] != null ? EnumState.values[result[0]! as int] : null,
+      state: result[0] as EnumState?,
     );
   }
 }
 
-class _EnumApi2HostCodec extends StandardMessageCodec {
-  const _EnumApi2HostCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
     if (value is DataWithEnum) {
-      buffer.putUint8(128);
+      buffer.putUint8(129);
       writeValue(buffer, value.encode());
+    } else if (value is EnumState) {
+      buffer.putUint8(130);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -83,8 +86,11 @@ class _EnumApi2HostCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
+      case 129:
         return DataWithEnum.decode(readValue(buffer)!);
+      case 130:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : EnumState.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -103,7 +109,7 @@ class EnumApi2Host {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec = _EnumApi2HostCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -138,33 +144,9 @@ class EnumApi2Host {
   }
 }
 
-class _EnumApi2FlutterCodec extends StandardMessageCodec {
-  const _EnumApi2FlutterCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is DataWithEnum) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return DataWithEnum.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 /// This comment is to test api documentation comments.
 abstract class EnumApi2Flutter {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _EnumApi2FlutterCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   /// This comment is to test method documentation comments.
   DataWithEnum echo(DataWithEnum data);
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
index b37dffb2557..61e4b97a5fe 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
@@ -108,22 +108,22 @@ class FlutterSearchReplies {
   }
 }
 
-class _ApiCodec extends StandardMessageCodec {
-  const _ApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is FlutterSearchReplies) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is FlutterSearchReply) {
+    if (value is FlutterSearchRequest) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
-    } else if (value is FlutterSearchRequest) {
+    } else if (value is FlutterSearchReply) {
       buffer.putUint8(130);
       writeValue(buffer, value.encode());
     } else if (value is FlutterSearchRequests) {
       buffer.putUint8(131);
       writeValue(buffer, value.encode());
+    } else if (value is FlutterSearchReplies) {
+      buffer.putUint8(132);
+      writeValue(buffer, value.encode());
     } else {
       super.writeValue(buffer, value);
     }
@@ -132,14 +132,14 @@ class _ApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
-        return FlutterSearchReplies.decode(readValue(buffer)!);
       case 129:
-        return FlutterSearchReply.decode(readValue(buffer)!);
-      case 130:
         return FlutterSearchRequest.decode(readValue(buffer)!);
+      case 130:
+        return FlutterSearchReply.decode(readValue(buffer)!);
       case 131:
         return FlutterSearchRequests.decode(readValue(buffer)!);
+      case 132:
+        return FlutterSearchReplies.decode(readValue(buffer)!);
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -156,7 +156,7 @@ class Api {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec = _ApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
index c4f744b5fb8..fb7e65c9483 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
@@ -103,7 +103,7 @@ class MessageSearchReply {
     return <Object?>[
       result,
       error,
-      state?.index,
+      state,
     ];
   }
 
@@ -112,9 +112,7 @@ class MessageSearchReply {
     return MessageSearchReply(
       result: result[0] as String?,
       error: result[1] as String?,
-      state: result[2] != null
-          ? MessageRequestState.values[result[2]! as int]
-          : null,
+      state: result[2] as MessageRequestState?,
     );
   }
 }
@@ -142,16 +140,22 @@ class MessageNested {
   }
 }
 
-class _MessageApiCodec extends StandardMessageCodec {
-  const _MessageApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is MessageSearchReply) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchRequest) {
+    if (value is MessageSearchRequest) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
+    } else if (value is MessageSearchReply) {
+      buffer.putUint8(130);
+      writeValue(buffer, value.encode());
+    } else if (value is MessageNested) {
+      buffer.putUint8(131);
+      writeValue(buffer, value.encode());
+    } else if (value is MessageRequestState) {
+      buffer.putUint8(132);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -160,10 +164,15 @@ class _MessageApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
-        return MessageSearchReply.decode(readValue(buffer)!);
       case 129:
         return MessageSearchRequest.decode(readValue(buffer)!);
+      case 130:
+        return MessageSearchReply.decode(readValue(buffer)!);
+      case 131:
+        return MessageNested.decode(readValue(buffer)!);
+      case 132:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : MessageRequestState.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -184,7 +193,7 @@ class MessageApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec = _MessageApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -246,39 +255,6 @@ class MessageApi {
   }
 }
 
-class _MessageNestedApiCodec extends StandardMessageCodec {
-  const _MessageNestedApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is MessageNested) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchReply) {
-      buffer.putUint8(129);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchRequest) {
-      buffer.putUint8(130);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return MessageNested.decode(readValue(buffer)!);
-      case 129:
-        return MessageSearchReply.decode(readValue(buffer)!);
-      case 130:
-        return MessageSearchRequest.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 /// This comment is to test api documentation comments.
 class MessageNestedApi {
   /// Constructor for [MessageNestedApi].  The [binaryMessenger] named argument is
@@ -291,8 +267,7 @@ class MessageNestedApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _MessageNestedApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -329,38 +304,9 @@ class MessageNestedApi {
   }
 }
 
-class _MessageFlutterSearchApiCodec extends StandardMessageCodec {
-  const _MessageFlutterSearchApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is MessageSearchReply) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchRequest) {
-      buffer.putUint8(129);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return MessageSearchReply.decode(readValue(buffer)!);
-      case 129:
-        return MessageSearchRequest.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 /// This comment is to test api documentation comments.
 abstract class MessageFlutterSearchApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _MessageFlutterSearchApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   /// This comment is to test method documentation comments.
   MessageSearchReply search(MessageSearchRequest request);
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
index 61bd5d14094..33b984077af 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
@@ -30,6 +30,10 @@ List<Object?> wrapResponse(
   return <Object?>[error.code, error.message, error.details];
 }
 
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
+}
+
 class MultipleArityHostApi {
   /// Constructor for [MultipleArityHostApi].  The [binaryMessenger] named argument is
   /// available for dependency injection.  If it is left null, the default
@@ -41,8 +45,7 @@ class MultipleArityHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -77,8 +80,7 @@ class MultipleArityHostApi {
 }
 
 abstract class MultipleArityFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   int subtract(int x, int y);
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
index 8f3560363e0..c9c7fe5a638 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
@@ -107,7 +107,7 @@ class NonNullFieldSearchReply {
       error,
       indices,
       extraData,
-      type.index,
+      type,
     ];
   }
 
@@ -118,24 +118,27 @@ class NonNullFieldSearchReply {
       error: result[1]! as String,
       indices: (result[2] as List<Object?>?)!.cast<int?>(),
       extraData: result[3]! as ExtraData,
-      type: ReplyType.values[result[4]! as int],
+      type: result[4]! as ReplyType,
     );
   }
 }
 
-class _NonNullFieldHostApiCodec extends StandardMessageCodec {
-  const _NonNullFieldHostApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is ExtraData) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is NonNullFieldSearchReply) {
+    if (value is NonNullFieldSearchRequest) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
-    } else if (value is NonNullFieldSearchRequest) {
+    } else if (value is ExtraData) {
       buffer.putUint8(130);
       writeValue(buffer, value.encode());
+    } else if (value is NonNullFieldSearchReply) {
+      buffer.putUint8(131);
+      writeValue(buffer, value.encode());
+    } else if (value is ReplyType) {
+      buffer.putUint8(132);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -144,12 +147,15 @@ class _NonNullFieldHostApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
-        return ExtraData.decode(readValue(buffer)!);
       case 129:
-        return NonNullFieldSearchReply.decode(readValue(buffer)!);
-      case 130:
         return NonNullFieldSearchRequest.decode(readValue(buffer)!);
+      case 130:
+        return ExtraData.decode(readValue(buffer)!);
+      case 131:
+        return NonNullFieldSearchReply.decode(readValue(buffer)!);
+      case 132:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : ReplyType.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -167,8 +173,7 @@ class NonNullFieldHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _NonNullFieldHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -203,42 +208,8 @@ class NonNullFieldHostApi {
   }
 }
 
-class _NonNullFieldFlutterApiCodec extends StandardMessageCodec {
-  const _NonNullFieldFlutterApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is ExtraData) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is NonNullFieldSearchReply) {
-      buffer.putUint8(129);
-      writeValue(buffer, value.encode());
-    } else if (value is NonNullFieldSearchRequest) {
-      buffer.putUint8(130);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return ExtraData.decode(readValue(buffer)!);
-      case 129:
-        return NonNullFieldSearchReply.decode(readValue(buffer)!);
-      case 130:
-        return NonNullFieldSearchRequest.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 abstract class NonNullFieldFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _NonNullFieldFlutterApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   NonNullFieldSearchReply search(NonNullFieldSearchRequest request);
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
index 3af44e61683..578a7c28c31 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
@@ -86,7 +86,7 @@ class NullFieldsSearchReply {
       error,
       indices,
       request,
-      type?.index,
+      type,
     ];
   }
 
@@ -97,23 +97,24 @@ class NullFieldsSearchReply {
       error: result[1] as String?,
       indices: (result[2] as List<Object?>?)?.cast<int?>(),
       request: result[3] as NullFieldsSearchRequest?,
-      type: result[4] != null
-          ? NullFieldsSearchReplyType.values[result[4]! as int]
-          : null,
+      type: result[4] as NullFieldsSearchReplyType?,
     );
   }
 }
 
-class _NullFieldsHostApiCodec extends StandardMessageCodec {
-  const _NullFieldsHostApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is NullFieldsSearchReply) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is NullFieldsSearchRequest) {
+    if (value is NullFieldsSearchRequest) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
+    } else if (value is NullFieldsSearchReply) {
+      buffer.putUint8(130);
+      writeValue(buffer, value.encode());
+    } else if (value is NullFieldsSearchReplyType) {
+      buffer.putUint8(131);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -122,10 +123,13 @@ class _NullFieldsHostApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
-        return NullFieldsSearchReply.decode(readValue(buffer)!);
       case 129:
         return NullFieldsSearchRequest.decode(readValue(buffer)!);
+      case 130:
+        return NullFieldsSearchReply.decode(readValue(buffer)!);
+      case 131:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : NullFieldsSearchReplyType.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -143,8 +147,7 @@ class NullFieldsHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _NullFieldsHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -178,37 +181,8 @@ class NullFieldsHostApi {
   }
 }
 
-class _NullFieldsFlutterApiCodec extends StandardMessageCodec {
-  const _NullFieldsFlutterApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is NullFieldsSearchReply) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is NullFieldsSearchRequest) {
-      buffer.putUint8(129);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return NullFieldsSearchReply.decode(readValue(buffer)!);
-      case 129:
-        return NullFieldsSearchRequest.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 abstract class NullFieldsFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      _NullFieldsFlutterApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   NullFieldsSearchReply search(NullFieldsSearchRequest request);
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
index 39348701f18..72ea0ae7363 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
@@ -30,6 +30,10 @@ List<Object?> wrapResponse(
   return <Object?>[error.code, error.message, error.details];
 }
 
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
+}
+
 class NullableReturnHostApi {
   /// Constructor for [NullableReturnHostApi].  The [binaryMessenger] named argument is
   /// available for dependency injection.  If it is left null, the default
@@ -41,8 +45,7 @@ class NullableReturnHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -72,8 +75,7 @@ class NullableReturnHostApi {
 }
 
 abstract class NullableReturnFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   int? doit();
 
@@ -120,8 +122,7 @@ class NullableArgHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -156,8 +157,7 @@ class NullableArgHostApi {
 }
 
 abstract class NullableArgFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   int? doit(int? x);
 
@@ -208,8 +208,7 @@ class NullableCollectionReturnHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -239,8 +238,7 @@ class NullableCollectionReturnHostApi {
 }
 
 abstract class NullableCollectionReturnFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   List<String?>? doit();
 
@@ -287,8 +285,7 @@ class NullableCollectionArgHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -323,8 +320,7 @@ class NullableCollectionArgHostApi {
 }
 
 abstract class NullableCollectionArgFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   List<String?> doit(List<String?>? x);
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
index 846d67e6099..8ac914eb6fa 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
@@ -30,6 +30,10 @@ List<Object?> wrapResponse(
   return <Object?>[error.code, error.message, error.details];
 }
 
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
+}
+
 class PrimitiveHostApi {
   /// Constructor for [PrimitiveHostApi].  The [binaryMessenger] named argument is
   /// available for dependency injection.  If it is left null, the default
@@ -41,8 +45,7 @@ class PrimitiveHostApi {
             messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
   final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   final String __pigeon_messageChannelSuffix;
 
@@ -310,8 +313,7 @@ class PrimitiveHostApi {
 }
 
 abstract class PrimitiveFlutterApi {
-  static const MessageCodec<Object?> pigeonChannelCodec =
-      StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   int anInt(int value);
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/proxy_api_tests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/proxy_api_tests.gen.dart
index 3e3e4b51bc1..97dbbc67559 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/proxy_api_tests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/proxy_api_tests.gen.dart
@@ -379,7 +379,7 @@ class _PigeonInstanceManagerApi {
   }
 }
 
-class _PigeonProxyApiBaseCodec extends StandardMessageCodec {
+class _PigeonProxyApiBaseCodec extends _PigeonCodec {
   const _PigeonProxyApiBaseCodec(this.instanceManager);
   final PigeonInstanceManager instanceManager;
   @override
@@ -410,6 +410,30 @@ enum ProxyApiTestEnum {
   three,
 }
 
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
+  @override
+  void writeValue(WriteBuffer buffer, Object? value) {
+    if (value is ProxyApiTestEnum) {
+      buffer.putUint8(129);
+      writeValue(buffer, value.index);
+    } else {
+      super.writeValue(buffer, value);
+    }
+  }
+
+  @override
+  Object? readValueOfType(int type, ReadBuffer buffer) {
+    switch (type) {
+      case 129:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : ProxyApiTestEnum.values[value];
+      default:
+        return super.readValueOfType(type, buffer);
+    }
+  }
+}
+
 /// The core ProxyApi test class that each supported host language must
 /// implement in platform_tests integration tests.
 class ProxyApiTestClass extends ProxyApiSuperClass
@@ -504,7 +528,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         aUint8List,
         aList,
         aMap,
-        anEnum.index,
+        anEnum,
         aProxyApi,
         aNullableBool,
         aNullableInt,
@@ -513,7 +537,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         aNullableUint8List,
         aNullableList,
         aNullableMap,
-        aNullableEnum?.index,
+        aNullableEnum,
         aNullableProxyApi,
         boolParam,
         intParam,
@@ -522,7 +546,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         aUint8ListParam,
         listParam,
         mapParam,
-        enumParam.index,
+        enumParam,
         proxyApiParam,
         nullableBoolParam,
         nullableIntParam,
@@ -531,7 +555,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         nullableUint8ListParam,
         nullableListParam,
         nullableMapParam,
-        nullableEnumParam?.index,
+        nullableEnumParam,
         nullableProxyApiParam
       ]) as List<Object?>?;
       if (__pigeon_replyList == null) {
@@ -1399,8 +1423,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
               (args[7] as Map<Object?, Object?>?)?.cast<String?, Object?>();
           assert(arg_aMap != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiTestClass.pigeon_newInstance was null, expected non-null Map<String?, Object?>.');
-          final ProxyApiTestEnum? arg_anEnum =
-              args[8] == null ? null : ProxyApiTestEnum.values[args[8]! as int];
+          final ProxyApiTestEnum? arg_anEnum = (args[8] as ProxyApiTestEnum?);
           assert(arg_anEnum != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiTestClass.pigeon_newInstance was null, expected non-null ProxyApiTestEnum.');
           final ProxyApiSuperClass? arg_aProxyApi =
@@ -1416,9 +1439,8 @@ class ProxyApiTestClass extends ProxyApiSuperClass
               (args[15] as List<Object?>?)?.cast<Object?>();
           final Map<String?, Object?>? arg_aNullableMap =
               (args[16] as Map<Object?, Object?>?)?.cast<String?, Object?>();
-          final ProxyApiTestEnum? arg_aNullableEnum = args[17] == null
-              ? null
-              : ProxyApiTestEnum.values[args[17]! as int];
+          final ProxyApiTestEnum? arg_aNullableEnum =
+              (args[17] as ProxyApiTestEnum?);
           final ProxyApiSuperClass? arg_aNullableProxyApi =
               (args[18] as ProxyApiSuperClass?);
           try {
@@ -1911,15 +1933,14 @@ class ProxyApiTestClass extends ProxyApiSuperClass
               (args[0] as ProxyApiTestClass?);
           assert(arg_pigeon_instance != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiTestClass.flutterEchoEnum was null, expected non-null ProxyApiTestClass.');
-          final ProxyApiTestEnum? arg_anEnum =
-              args[1] == null ? null : ProxyApiTestEnum.values[args[1]! as int];
+          final ProxyApiTestEnum? arg_anEnum = (args[1] as ProxyApiTestEnum?);
           assert(arg_anEnum != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiTestClass.flutterEchoEnum was null, expected non-null ProxyApiTestEnum.');
           try {
             final ProxyApiTestEnum? output =
                 (flutterEchoEnum ?? arg_pigeon_instance!.flutterEchoEnum)
                     ?.call(arg_pigeon_instance!, arg_anEnum!);
-            return wrapResponse(result: output?.index);
+            return wrapResponse(result: output);
           } on PlatformException catch (e) {
             return wrapResponse(error: e);
           } catch (e) {
@@ -2216,13 +2237,12 @@ class ProxyApiTestClass extends ProxyApiSuperClass
               (args[0] as ProxyApiTestClass?);
           assert(arg_pigeon_instance != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiTestClass.flutterEchoNullableEnum was null, expected non-null ProxyApiTestClass.');
-          final ProxyApiTestEnum? arg_anEnum =
-              args[1] == null ? null : ProxyApiTestEnum.values[args[1]! as int];
+          final ProxyApiTestEnum? arg_anEnum = (args[1] as ProxyApiTestEnum?);
           try {
             final ProxyApiTestEnum? output = (flutterEchoNullableEnum ??
                     arg_pigeon_instance!.flutterEchoNullableEnum)
                 ?.call(arg_pigeon_instance!, arg_anEnum);
-            return wrapResponse(result: output?.index);
+            return wrapResponse(result: output);
           } on PlatformException catch (e) {
             return wrapResponse(error: e);
           } catch (e) {
@@ -2869,8 +2889,8 @@ class ProxyApiTestClass extends ProxyApiSuperClass
       pigeonChannelCodec,
       binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? __pigeon_replyList = await __pigeon_channel
-        .send(<Object?>[this, anEnum.index]) as List<Object?>?;
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -2885,7 +2905,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return ProxyApiTestEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as ProxyApiTestEnum?)!;
     }
   }
 
@@ -3163,7 +3183,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
       binaryMessenger: __pigeon_binaryMessenger,
     );
     final List<Object?>? __pigeon_replyList = await __pigeon_channel
-        .send(<Object?>[this, aNullableEnum?.index]) as List<Object?>?;
+        .send(<Object?>[this, aNullableEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -3173,9 +3193,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         details: __pigeon_replyList[2],
       );
     } else {
-      return (__pigeon_replyList[0] as int?) == null
-          ? null
-          : ProxyApiTestEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as ProxyApiTestEnum?);
     }
   }
 
@@ -3515,8 +3533,8 @@ class ProxyApiTestClass extends ProxyApiSuperClass
       pigeonChannelCodec,
       binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? __pigeon_replyList = await __pigeon_channel
-        .send(<Object?>[this, anEnum.index]) as List<Object?>?;
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -3531,7 +3549,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return ProxyApiTestEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as ProxyApiTestEnum?)!;
     }
   }
 
@@ -3859,8 +3877,8 @@ class ProxyApiTestClass extends ProxyApiSuperClass
       pigeonChannelCodec,
       binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? __pigeon_replyList = await __pigeon_channel
-        .send(<Object?>[this, anEnum?.index]) as List<Object?>?;
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -3870,9 +3888,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         details: __pigeon_replyList[2],
       );
     } else {
-      return (__pigeon_replyList[0] as int?) == null
-          ? null
-          : ProxyApiTestEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as ProxyApiTestEnum?);
     }
   }
 
@@ -4362,8 +4378,8 @@ class ProxyApiTestClass extends ProxyApiSuperClass
       pigeonChannelCodec,
       binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? __pigeon_replyList = await __pigeon_channel
-        .send(<Object?>[this, anEnum.index]) as List<Object?>?;
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -4378,7 +4394,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return ProxyApiTestEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as ProxyApiTestEnum?)!;
     }
   }
 
@@ -4621,8 +4637,8 @@ class ProxyApiTestClass extends ProxyApiSuperClass
       pigeonChannelCodec,
       binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? __pigeon_replyList = await __pigeon_channel
-        .send(<Object?>[this, anEnum?.index]) as List<Object?>?;
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anEnum]) as List<Object?>?;
     if (__pigeon_replyList == null) {
       throw _createConnectionError(__pigeon_channelName);
     } else if (__pigeon_replyList.length > 1) {
@@ -4632,9 +4648,7 @@ class ProxyApiTestClass extends ProxyApiSuperClass
         details: __pigeon_replyList[2],
       );
     } else {
-      return (__pigeon_replyList[0] as int?) == null
-          ? null
-          : ProxyApiTestEnum.values[__pigeon_replyList[0]! as int];
+      return (__pigeon_replyList[0] as ProxyApiTestEnum?);
     }
   }
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/genered_dart_test_code_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/generated_dart_test_code_test.dart
similarity index 95%
rename from packages/pigeon/platform_tests/shared_test_plugin_code/test/genered_dart_test_code_test.dart
rename to packages/pigeon/platform_tests/shared_test_plugin_code/test/generated_dart_test_code_test.dart
index a0632cf3486..27e622c597e 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/genered_dart_test_code_test.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/generated_dart_test_code_test.dart
@@ -44,7 +44,7 @@ void main() {
   test('simple', () async {
     final MessageNestedApi api = MessageNestedApi();
     final MockNested mock = MockNested();
-    TestNestedApi.setup(mock);
+    TestNestedApi.setUp(mock);
     final MessageSearchReply reply =
         await api.search(MessageNested()..request = null);
     expect(mock.didCall, true);
@@ -54,7 +54,7 @@ void main() {
   test('nested', () async {
     final MessageApi api = MessageApi();
     final Mock mock = Mock();
-    TestHostApi.setup(mock);
+    TestHostApi.setUp(mock);
     final MessageSearchReply reply =
         await api.search(MessageSearchRequest()..query = 'foo');
     expect(mock.log, <String>['search']);
@@ -64,7 +64,7 @@ void main() {
   test('no-arg calls', () async {
     final MessageApi api = MessageApi();
     final Mock mock = Mock();
-    TestHostApi.setup(mock);
+    TestHostApi.setUp(mock);
     await api.initialize();
     expect(mock.log, <String>['initialize']);
   });
@@ -73,7 +73,7 @@ void main() {
     'calling methods with null',
     () async {
       final Mock mock = Mock();
-      TestHostApi.setup(mock);
+      TestHostApi.setUp(mock);
       expect(
         await const BasicMessageChannel<Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.initialize',
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_fields_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_fields_test.dart
index aa0ecb02424..5192bebc3f1 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_fields_test.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_fields_test.dart
@@ -134,7 +134,7 @@ void main() {
       'error',
       <int>[1, 2, 3],
       request,
-      NullFieldsSearchReplyType.success.index,
+      NullFieldsSearchReplyType.success,
     ]);
   });
 
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/test_message.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/test_message.gen.dart
index ff3a3d9c89a..27add325337 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/test_message.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/test_message.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, unnecessary_import, no_leading_underscores_for_local_identifiers
 // ignore_for_file: avoid_relative_lib_imports
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -14,16 +14,22 @@ import 'package:flutter_test/flutter_test.dart';
 
 import 'package:shared_test_plugin_code/src/generated/message.gen.dart';
 
-class _TestHostApiCodec extends StandardMessageCodec {
-  const _TestHostApiCodec();
+class _PigeonCodec extends StandardMessageCodec {
+  const _PigeonCodec();
   @override
   void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is MessageSearchReply) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchRequest) {
+    if (value is MessageSearchRequest) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
+    } else if (value is MessageSearchReply) {
+      buffer.putUint8(130);
+      writeValue(buffer, value.encode());
+    } else if (value is MessageNested) {
+      buffer.putUint8(131);
+      writeValue(buffer, value.encode());
+    } else if (value is MessageRequestState) {
+      buffer.putUint8(132);
+      writeValue(buffer, value.index);
     } else {
       super.writeValue(buffer, value);
     }
@@ -32,10 +38,15 @@ class _TestHostApiCodec extends StandardMessageCodec {
   @override
   Object? readValueOfType(int type, ReadBuffer buffer) {
     switch (type) {
-      case 128:
-        return MessageSearchReply.decode(readValue(buffer)!);
       case 129:
         return MessageSearchRequest.decode(readValue(buffer)!);
+      case 130:
+        return MessageSearchReply.decode(readValue(buffer)!);
+      case 131:
+        return MessageNested.decode(readValue(buffer)!);
+      case 132:
+        final int? value = readValue(buffer) as int?;
+        return value == null ? null : MessageRequestState.values[value];
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -48,7 +59,7 @@ class _TestHostApiCodec extends StandardMessageCodec {
 abstract class TestHostApi {
   static TestDefaultBinaryMessengerBinding? get _testBinaryMessengerBinding =>
       TestDefaultBinaryMessengerBinding.instance;
-  static const MessageCodec<Object?> codec = _TestHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   /// This comment is to test documentation comments.
   ///
@@ -58,36 +69,50 @@ abstract class TestHostApi {
   /// This comment is to test method documentation comments.
   MessageSearchReply search(MessageSearchRequest request);
 
-  static void setup(TestHostApi? api, {BinaryMessenger? binaryMessenger}) {
+  static void setUp(
+    TestHostApi? api, {
+    BinaryMessenger? binaryMessenger,
+    String messageChannelSuffix = '',
+  }) {
+    messageChannelSuffix =
+        messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-          'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.initialize',
-          codec,
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.initialize$messageChannelSuffix',
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
         _testBinaryMessengerBinding!.defaultBinaryMessenger
-            .setMockDecodedMessageHandler<Object?>(channel, null);
+            .setMockDecodedMessageHandler<Object?>(__pigeon_channel, null);
       } else {
         _testBinaryMessengerBinding!.defaultBinaryMessenger
-            .setMockDecodedMessageHandler<Object?>(channel,
+            .setMockDecodedMessageHandler<Object?>(__pigeon_channel,
                 (Object? message) async {
-          // ignore message
-          api.initialize();
-          return <Object?>[];
+          try {
+            api.initialize();
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
         });
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-          'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.search',
-          codec,
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.search$messageChannelSuffix',
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
         _testBinaryMessengerBinding!.defaultBinaryMessenger
-            .setMockDecodedMessageHandler<Object?>(channel, null);
+            .setMockDecodedMessageHandler<Object?>(__pigeon_channel, null);
       } else {
         _testBinaryMessengerBinding!.defaultBinaryMessenger
-            .setMockDecodedMessageHandler<Object?>(channel,
+            .setMockDecodedMessageHandler<Object?>(__pigeon_channel,
                 (Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.MessageApi.search was null.');
@@ -96,70 +121,51 @@ abstract class TestHostApi {
               (args[0] as MessageSearchRequest?);
           assert(arg_request != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.MessageApi.search was null, expected non-null MessageSearchRequest.');
-          final MessageSearchReply output = api.search(arg_request!);
-          return <Object?>[output];
+          try {
+            final MessageSearchReply output = api.search(arg_request!);
+            return <Object?>[output];
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
         });
       }
     }
   }
 }
 
-class _TestNestedApiCodec extends StandardMessageCodec {
-  const _TestNestedApiCodec();
-  @override
-  void writeValue(WriteBuffer buffer, Object? value) {
-    if (value is MessageNested) {
-      buffer.putUint8(128);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchReply) {
-      buffer.putUint8(129);
-      writeValue(buffer, value.encode());
-    } else if (value is MessageSearchRequest) {
-      buffer.putUint8(130);
-      writeValue(buffer, value.encode());
-    } else {
-      super.writeValue(buffer, value);
-    }
-  }
-
-  @override
-  Object? readValueOfType(int type, ReadBuffer buffer) {
-    switch (type) {
-      case 128:
-        return MessageNested.decode(readValue(buffer)!);
-      case 129:
-        return MessageSearchReply.decode(readValue(buffer)!);
-      case 130:
-        return MessageSearchRequest.decode(readValue(buffer)!);
-      default:
-        return super.readValueOfType(type, buffer);
-    }
-  }
-}
-
 /// This comment is to test api documentation comments.
 abstract class TestNestedApi {
   static TestDefaultBinaryMessengerBinding? get _testBinaryMessengerBinding =>
       TestDefaultBinaryMessengerBinding.instance;
-  static const MessageCodec<Object?> codec = _TestNestedApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _PigeonCodec();
 
   /// This comment is to test method documentation comments.
   ///
   /// This comment also tests multiple line comments.
   MessageSearchReply search(MessageNested nested);
 
-  static void setup(TestNestedApi? api, {BinaryMessenger? binaryMessenger}) {
+  static void setUp(
+    TestNestedApi? api, {
+    BinaryMessenger? binaryMessenger,
+    String messageChannelSuffix = '',
+  }) {
+    messageChannelSuffix =
+        messageChannelSuffix.isNotEmpty ? '.$messageChannelSuffix' : '';
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-          'dev.flutter.pigeon.pigeon_integration_tests.MessageNestedApi.search',
-          codec,
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.MessageNestedApi.search$messageChannelSuffix',
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
         _testBinaryMessengerBinding!.defaultBinaryMessenger
-            .setMockDecodedMessageHandler<Object?>(channel, null);
+            .setMockDecodedMessageHandler<Object?>(__pigeon_channel, null);
       } else {
         _testBinaryMessengerBinding!.defaultBinaryMessenger
-            .setMockDecodedMessageHandler<Object?>(channel,
+            .setMockDecodedMessageHandler<Object?>(__pigeon_channel,
                 (Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.MessageNestedApi.search was null.');
@@ -167,8 +173,15 @@ abstract class TestNestedApi {
           final MessageNested? arg_nested = (args[0] as MessageNested?);
           assert(arg_nested != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.MessageNestedApi.search was null, expected non-null MessageNested.');
-          final MessageSearchReply output = api.search(arg_nested!);
-          return <Object?>[output];
+          try {
+            final MessageSearchReply output = api.search(arg_nested!);
+            return <Object?>[output];
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
         });
       }
     }
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
index 3668ec94738..f90b5119611 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
@@ -64,11 +64,15 @@ data class AllTypes(
     val a4ByteArray: IntArray,
     val a8ByteArray: LongArray,
     val aFloatArray: DoubleArray,
-    val list: List<Any?>,
-    val aMap: Map<Any, Any?>,
     val anEnum: AnEnum,
     val aString: String,
-    val anObject: Any
+    val anObject: Any,
+    val list: List<Any?>,
+    val stringList: List<String?>,
+    val intList: List<Long?>,
+    val doubleList: List<Double?>,
+    val boolList: List<Boolean?>,
+    val map: Map<Any, Any?>
 ) {
   companion object {
     @Suppress("LocalVariableName")
@@ -81,11 +85,15 @@ data class AllTypes(
       val a4ByteArray = __pigeon_list[5] as IntArray
       val a8ByteArray = __pigeon_list[6] as LongArray
       val aFloatArray = __pigeon_list[7] as DoubleArray
-      val list = __pigeon_list[8] as List<Any?>
-      val aMap = __pigeon_list[9] as Map<Any, Any?>
-      val anEnum = AnEnum.ofRaw(__pigeon_list[10] as Int)!!
-      val aString = __pigeon_list[11] as String
-      val anObject = __pigeon_list[12] as Any
+      val anEnum = __pigeon_list[8] as AnEnum
+      val aString = __pigeon_list[9] as String
+      val anObject = __pigeon_list[10] as Any
+      val list = __pigeon_list[11] as List<Any?>
+      val stringList = __pigeon_list[12] as List<String?>
+      val intList = __pigeon_list[13] as List<Long?>
+      val doubleList = __pigeon_list[14] as List<Double?>
+      val boolList = __pigeon_list[15] as List<Boolean?>
+      val map = __pigeon_list[16] as Map<Any, Any?>
       return AllTypes(
           aBool,
           anInt,
@@ -95,16 +103,20 @@ data class AllTypes(
           a4ByteArray,
           a8ByteArray,
           aFloatArray,
-          list,
-          aMap,
           anEnum,
           aString,
-          anObject)
+          anObject,
+          list,
+          stringList,
+          intList,
+          doubleList,
+          boolList,
+          map)
     }
   }
 
   fun toList(): List<Any?> {
-    return listOf<Any?>(
+    return listOf(
         aBool,
         anInt,
         anInt64,
@@ -113,11 +125,15 @@ data class AllTypes(
         a4ByteArray,
         a8ByteArray,
         aFloatArray,
-        list,
-        aMap,
-        anEnum.raw,
+        anEnum,
         aString,
         anObject,
+        list,
+        stringList,
+        intList,
+        doubleList,
+        boolList,
+        map,
     )
   }
 }
@@ -136,15 +152,20 @@ data class AllNullableTypes(
     val aNullable4ByteArray: IntArray? = null,
     val aNullable8ByteArray: LongArray? = null,
     val aNullableFloatArray: DoubleArray? = null,
-    val aNullableList: List<Any?>? = null,
-    val aNullableMap: Map<Any, Any?>? = null,
     val nullableNestedList: List<List<Boolean?>?>? = null,
     val nullableMapWithAnnotations: Map<String?, String?>? = null,
     val nullableMapWithObject: Map<String?, Any?>? = null,
     val aNullableEnum: AnEnum? = null,
     val aNullableString: String? = null,
     val aNullableObject: Any? = null,
-    val allNullableTypes: AllNullableTypes? = null
+    val allNullableTypes: AllNullableTypes? = null,
+    val list: List<Any?>? = null,
+    val stringList: List<String?>? = null,
+    val intList: List<Long?>? = null,
+    val doubleList: List<Double?>? = null,
+    val boolList: List<Boolean?>? = null,
+    val nestedClassList: List<AllNullableTypes?>? = null,
+    val map: Map<Any, Any?>? = null
 ) {
   companion object {
     @Suppress("LocalVariableName")
@@ -159,15 +180,20 @@ data class AllNullableTypes(
       val aNullable4ByteArray = __pigeon_list[5] as IntArray?
       val aNullable8ByteArray = __pigeon_list[6] as LongArray?
       val aNullableFloatArray = __pigeon_list[7] as DoubleArray?
-      val aNullableList = __pigeon_list[8] as List<Any?>?
-      val aNullableMap = __pigeon_list[9] as Map<Any, Any?>?
-      val nullableNestedList = __pigeon_list[10] as List<List<Boolean?>?>?
-      val nullableMapWithAnnotations = __pigeon_list[11] as Map<String?, String?>?
-      val nullableMapWithObject = __pigeon_list[12] as Map<String?, Any?>?
-      val aNullableEnum: AnEnum? = (__pigeon_list[13] as Int?)?.let { num -> AnEnum.ofRaw(num) }
-      val aNullableString = __pigeon_list[14] as String?
-      val aNullableObject = __pigeon_list[15]
-      val allNullableTypes = __pigeon_list[16] as AllNullableTypes?
+      val nullableNestedList = __pigeon_list[8] as List<List<Boolean?>?>?
+      val nullableMapWithAnnotations = __pigeon_list[9] as Map<String?, String?>?
+      val nullableMapWithObject = __pigeon_list[10] as Map<String?, Any?>?
+      val aNullableEnum = __pigeon_list[11] as AnEnum?
+      val aNullableString = __pigeon_list[12] as String?
+      val aNullableObject = __pigeon_list[13]
+      val allNullableTypes = __pigeon_list[14] as AllNullableTypes?
+      val list = __pigeon_list[15] as List<Any?>?
+      val stringList = __pigeon_list[16] as List<String?>?
+      val intList = __pigeon_list[17] as List<Long?>?
+      val doubleList = __pigeon_list[18] as List<Double?>?
+      val boolList = __pigeon_list[19] as List<Boolean?>?
+      val nestedClassList = __pigeon_list[20] as List<AllNullableTypes?>?
+      val map = __pigeon_list[21] as Map<Any, Any?>?
       return AllNullableTypes(
           aNullableBool,
           aNullableInt,
@@ -177,20 +203,25 @@ data class AllNullableTypes(
           aNullable4ByteArray,
           aNullable8ByteArray,
           aNullableFloatArray,
-          aNullableList,
-          aNullableMap,
           nullableNestedList,
           nullableMapWithAnnotations,
           nullableMapWithObject,
           aNullableEnum,
           aNullableString,
           aNullableObject,
-          allNullableTypes)
+          allNullableTypes,
+          list,
+          stringList,
+          intList,
+          doubleList,
+          boolList,
+          nestedClassList,
+          map)
     }
   }
 
   fun toList(): List<Any?> {
-    return listOf<Any?>(
+    return listOf(
         aNullableBool,
         aNullableInt,
         aNullableInt64,
@@ -199,15 +230,20 @@ data class AllNullableTypes(
         aNullable4ByteArray,
         aNullable8ByteArray,
         aNullableFloatArray,
-        aNullableList,
-        aNullableMap,
         nullableNestedList,
         nullableMapWithAnnotations,
         nullableMapWithObject,
-        aNullableEnum?.raw,
+        aNullableEnum,
         aNullableString,
         aNullableObject,
         allNullableTypes,
+        list,
+        stringList,
+        intList,
+        doubleList,
+        boolList,
+        nestedClassList,
+        map,
     )
   }
 }
@@ -227,14 +263,18 @@ data class AllNullableTypesWithoutRecursion(
     val aNullable4ByteArray: IntArray? = null,
     val aNullable8ByteArray: LongArray? = null,
     val aNullableFloatArray: DoubleArray? = null,
-    val aNullableList: List<Any?>? = null,
-    val aNullableMap: Map<Any, Any?>? = null,
     val nullableNestedList: List<List<Boolean?>?>? = null,
     val nullableMapWithAnnotations: Map<String?, String?>? = null,
     val nullableMapWithObject: Map<String?, Any?>? = null,
     val aNullableEnum: AnEnum? = null,
     val aNullableString: String? = null,
-    val aNullableObject: Any? = null
+    val aNullableObject: Any? = null,
+    val list: List<Any?>? = null,
+    val stringList: List<String?>? = null,
+    val intList: List<Long?>? = null,
+    val doubleList: List<Double?>? = null,
+    val boolList: List<Boolean?>? = null,
+    val map: Map<Any, Any?>? = null
 ) {
   companion object {
     @Suppress("LocalVariableName")
@@ -249,14 +289,18 @@ data class AllNullableTypesWithoutRecursion(
       val aNullable4ByteArray = __pigeon_list[5] as IntArray?
       val aNullable8ByteArray = __pigeon_list[6] as LongArray?
       val aNullableFloatArray = __pigeon_list[7] as DoubleArray?
-      val aNullableList = __pigeon_list[8] as List<Any?>?
-      val aNullableMap = __pigeon_list[9] as Map<Any, Any?>?
-      val nullableNestedList = __pigeon_list[10] as List<List<Boolean?>?>?
-      val nullableMapWithAnnotations = __pigeon_list[11] as Map<String?, String?>?
-      val nullableMapWithObject = __pigeon_list[12] as Map<String?, Any?>?
-      val aNullableEnum: AnEnum? = (__pigeon_list[13] as Int?)?.let { num -> AnEnum.ofRaw(num) }
-      val aNullableString = __pigeon_list[14] as String?
-      val aNullableObject = __pigeon_list[15]
+      val nullableNestedList = __pigeon_list[8] as List<List<Boolean?>?>?
+      val nullableMapWithAnnotations = __pigeon_list[9] as Map<String?, String?>?
+      val nullableMapWithObject = __pigeon_list[10] as Map<String?, Any?>?
+      val aNullableEnum = __pigeon_list[11] as AnEnum?
+      val aNullableString = __pigeon_list[12] as String?
+      val aNullableObject = __pigeon_list[13]
+      val list = __pigeon_list[14] as List<Any?>?
+      val stringList = __pigeon_list[15] as List<String?>?
+      val intList = __pigeon_list[16] as List<Long?>?
+      val doubleList = __pigeon_list[17] as List<Double?>?
+      val boolList = __pigeon_list[18] as List<Boolean?>?
+      val map = __pigeon_list[19] as Map<Any, Any?>?
       return AllNullableTypesWithoutRecursion(
           aNullableBool,
           aNullableInt,
@@ -266,19 +310,23 @@ data class AllNullableTypesWithoutRecursion(
           aNullable4ByteArray,
           aNullable8ByteArray,
           aNullableFloatArray,
-          aNullableList,
-          aNullableMap,
           nullableNestedList,
           nullableMapWithAnnotations,
           nullableMapWithObject,
           aNullableEnum,
           aNullableString,
-          aNullableObject)
+          aNullableObject,
+          list,
+          stringList,
+          intList,
+          doubleList,
+          boolList,
+          map)
     }
   }
 
   fun toList(): List<Any?> {
-    return listOf<Any?>(
+    return listOf(
         aNullableBool,
         aNullableInt,
         aNullableInt64,
@@ -287,14 +335,18 @@ data class AllNullableTypesWithoutRecursion(
         aNullable4ByteArray,
         aNullable8ByteArray,
         aNullableFloatArray,
-        aNullableList,
-        aNullableMap,
         nullableNestedList,
         nullableMapWithAnnotations,
         nullableMapWithObject,
-        aNullableEnum?.raw,
+        aNullableEnum,
         aNullableString,
         aNullableObject,
+        list,
+        stringList,
+        intList,
+        doubleList,
+        boolList,
+        map,
     )
   }
 }
@@ -324,7 +376,7 @@ data class AllClassesWrapper(
   }
 
   fun toList(): List<Any?> {
-    return listOf<Any?>(
+    return listOf(
         allNullableTypes,
         allNullableTypesWithoutRecursion,
         allTypes,
@@ -348,58 +400,65 @@ data class TestMessage(val testList: List<Any?>? = null) {
   }
 
   fun toList(): List<Any?> {
-    return listOf<Any?>(
+    return listOf(
         testList,
     )
   }
 }
 
-private object HostIntegrationCoreApiCodec : StandardMessageCodec() {
+private object CoreTestsPigeonCodec : StandardMessageCodec() {
   override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
     return when (type) {
-      128.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { AllClassesWrapper.fromList(it) }
-      }
       129.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { AllNullableTypes.fromList(it) }
+        return (readValue(buffer) as? List<Any?>)?.let { AllTypes.fromList(it) }
       }
       130.toByte() -> {
+        return (readValue(buffer) as? List<Any?>)?.let { AllNullableTypes.fromList(it) }
+      }
+      131.toByte() -> {
         return (readValue(buffer) as? List<Any?>)?.let {
           AllNullableTypesWithoutRecursion.fromList(it)
         }
       }
-      131.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { AllTypes.fromList(it) }
-      }
       132.toByte() -> {
+        return (readValue(buffer) as? List<Any?>)?.let { AllClassesWrapper.fromList(it) }
+      }
+      133.toByte() -> {
         return (readValue(buffer) as? List<Any?>)?.let { TestMessage.fromList(it) }
       }
+      134.toByte() -> {
+        return (readValue(buffer) as Int?)?.let { AnEnum.ofRaw(it) }
+      }
       else -> super.readValueOfType(type, buffer)
     }
   }
 
   override fun writeValue(stream: ByteArrayOutputStream, value: Any?) {
     when (value) {
-      is AllClassesWrapper -> {
-        stream.write(128)
+      is AllTypes -> {
+        stream.write(129)
         writeValue(stream, value.toList())
       }
       is AllNullableTypes -> {
-        stream.write(129)
+        stream.write(130)
         writeValue(stream, value.toList())
       }
       is AllNullableTypesWithoutRecursion -> {
-        stream.write(130)
+        stream.write(131)
         writeValue(stream, value.toList())
       }
-      is AllTypes -> {
-        stream.write(131)
+      is AllClassesWrapper -> {
+        stream.write(132)
         writeValue(stream, value.toList())
       }
       is TestMessage -> {
-        stream.write(132)
+        stream.write(133)
         writeValue(stream, value.toList())
       }
+      is AnEnum -> {
+        stream.write(134)
+        writeValue(stream, value.raw)
+      }
       else -> super.writeValue(stream, value)
     }
   }
@@ -630,11 +689,12 @@ interface HostIntegrationCoreApi {
 
   companion object {
     /** The codec used by HostIntegrationCoreApi. */
-    val codec: MessageCodec<Any?> by lazy { HostIntegrationCoreApiCodec }
+    val codec: MessageCodec<Any?> by lazy { CoreTestsPigeonCodec }
     /**
      * Sets up an instance of `HostIntegrationCoreApi` to handle messages through the
      * `binaryMessenger`.
      */
+    @JvmOverloads
     fun setUp(
         binaryMessenger: BinaryMessenger,
         api: HostIntegrationCoreApi?,
@@ -653,7 +713,7 @@ interface HostIntegrationCoreApi {
             val wrapped: List<Any?> =
                 try {
                   api.noop()
-                  listOf<Any?>(null)
+                  listOf(null)
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -675,7 +735,7 @@ interface HostIntegrationCoreApi {
             val everythingArg = args[0] as AllTypes
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoAllTypes(everythingArg))
+                  listOf(api.echoAllTypes(everythingArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -695,7 +755,7 @@ interface HostIntegrationCoreApi {
           channel.setMessageHandler { _, reply ->
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.throwError())
+                  listOf(api.throwError())
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -716,7 +776,7 @@ interface HostIntegrationCoreApi {
             val wrapped: List<Any?> =
                 try {
                   api.throwErrorFromVoid()
-                  listOf<Any?>(null)
+                  listOf(null)
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -736,7 +796,7 @@ interface HostIntegrationCoreApi {
           channel.setMessageHandler { _, reply ->
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.throwFlutterError())
+                  listOf(api.throwFlutterError())
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -758,7 +818,7 @@ interface HostIntegrationCoreApi {
             val anIntArg = args[0].let { num -> if (num is Int) num.toLong() else num as Long }
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoInt(anIntArg))
+                  listOf(api.echoInt(anIntArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -780,7 +840,7 @@ interface HostIntegrationCoreApi {
             val aDoubleArg = args[0] as Double
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoDouble(aDoubleArg))
+                  listOf(api.echoDouble(aDoubleArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -802,7 +862,7 @@ interface HostIntegrationCoreApi {
             val aBoolArg = args[0] as Boolean
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoBool(aBoolArg))
+                  listOf(api.echoBool(aBoolArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -824,7 +884,7 @@ interface HostIntegrationCoreApi {
             val aStringArg = args[0] as String
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoString(aStringArg))
+                  listOf(api.echoString(aStringArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -846,7 +906,7 @@ interface HostIntegrationCoreApi {
             val aUint8ListArg = args[0] as ByteArray
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoUint8List(aUint8ListArg))
+                  listOf(api.echoUint8List(aUint8ListArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -868,7 +928,7 @@ interface HostIntegrationCoreApi {
             val anObjectArg = args[0] as Any
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoObject(anObjectArg))
+                  listOf(api.echoObject(anObjectArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -890,7 +950,7 @@ interface HostIntegrationCoreApi {
             val listArg = args[0] as List<Any?>
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoList(listArg))
+                  listOf(api.echoList(listArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -912,7 +972,7 @@ interface HostIntegrationCoreApi {
             val aMapArg = args[0] as Map<String?, Any?>
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoMap(aMapArg))
+                  listOf(api.echoMap(aMapArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -934,7 +994,7 @@ interface HostIntegrationCoreApi {
             val wrapperArg = args[0] as AllClassesWrapper
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoClassWrapper(wrapperArg))
+                  listOf(api.echoClassWrapper(wrapperArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -953,10 +1013,10 @@ interface HostIntegrationCoreApi {
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
-            val anEnumArg = AnEnum.ofRaw(args[0] as Int)!!
+            val anEnumArg = args[0] as AnEnum
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoEnum(anEnumArg).raw)
+                  listOf(api.echoEnum(anEnumArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -978,7 +1038,7 @@ interface HostIntegrationCoreApi {
             val aStringArg = args[0] as String
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNamedDefaultString(aStringArg))
+                  listOf(api.echoNamedDefaultString(aStringArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1000,7 +1060,7 @@ interface HostIntegrationCoreApi {
             val aDoubleArg = args[0] as Double
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoOptionalDefaultDouble(aDoubleArg))
+                  listOf(api.echoOptionalDefaultDouble(aDoubleArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1022,7 +1082,7 @@ interface HostIntegrationCoreApi {
             val anIntArg = args[0].let { num -> if (num is Int) num.toLong() else num as Long }
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoRequiredInt(anIntArg))
+                  listOf(api.echoRequiredInt(anIntArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1044,7 +1104,7 @@ interface HostIntegrationCoreApi {
             val everythingArg = args[0] as AllNullableTypes?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoAllNullableTypes(everythingArg))
+                  listOf(api.echoAllNullableTypes(everythingArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1066,7 +1126,7 @@ interface HostIntegrationCoreApi {
             val everythingArg = args[0] as AllNullableTypesWithoutRecursion?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoAllNullableTypesWithoutRecursion(everythingArg))
+                  listOf(api.echoAllNullableTypesWithoutRecursion(everythingArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1088,7 +1148,7 @@ interface HostIntegrationCoreApi {
             val wrapperArg = args[0] as AllClassesWrapper
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.extractNestedNullableString(wrapperArg))
+                  listOf(api.extractNestedNullableString(wrapperArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1110,7 +1170,7 @@ interface HostIntegrationCoreApi {
             val nullableStringArg = args[0] as String?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.createNestedNullableString(nullableStringArg))
+                  listOf(api.createNestedNullableString(nullableStringArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1135,7 +1195,7 @@ interface HostIntegrationCoreApi {
             val aNullableStringArg = args[2] as String?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(
+                  listOf(
                       api.sendMultipleNullableTypes(
                           aNullableBoolArg, aNullableIntArg, aNullableStringArg))
                 } catch (exception: Throwable) {
@@ -1162,7 +1222,7 @@ interface HostIntegrationCoreApi {
             val aNullableStringArg = args[2] as String?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(
+                  listOf(
                       api.sendMultipleNullableTypesWithoutRecursion(
                           aNullableBoolArg, aNullableIntArg, aNullableStringArg))
                 } catch (exception: Throwable) {
@@ -1187,7 +1247,7 @@ interface HostIntegrationCoreApi {
                 args[0].let { num -> if (num is Int) num.toLong() else num as Long? }
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableInt(aNullableIntArg))
+                  listOf(api.echoNullableInt(aNullableIntArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1209,7 +1269,7 @@ interface HostIntegrationCoreApi {
             val aNullableDoubleArg = args[0] as Double?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableDouble(aNullableDoubleArg))
+                  listOf(api.echoNullableDouble(aNullableDoubleArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1231,7 +1291,7 @@ interface HostIntegrationCoreApi {
             val aNullableBoolArg = args[0] as Boolean?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableBool(aNullableBoolArg))
+                  listOf(api.echoNullableBool(aNullableBoolArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1253,7 +1313,7 @@ interface HostIntegrationCoreApi {
             val aNullableStringArg = args[0] as String?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableString(aNullableStringArg))
+                  listOf(api.echoNullableString(aNullableStringArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1275,7 +1335,7 @@ interface HostIntegrationCoreApi {
             val aNullableUint8ListArg = args[0] as ByteArray?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableUint8List(aNullableUint8ListArg))
+                  listOf(api.echoNullableUint8List(aNullableUint8ListArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1297,7 +1357,7 @@ interface HostIntegrationCoreApi {
             val aNullableObjectArg = args[0]
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableObject(aNullableObjectArg))
+                  listOf(api.echoNullableObject(aNullableObjectArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1319,7 +1379,7 @@ interface HostIntegrationCoreApi {
             val aNullableListArg = args[0] as List<Any?>?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableList(aNullableListArg))
+                  listOf(api.echoNullableList(aNullableListArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1341,7 +1401,7 @@ interface HostIntegrationCoreApi {
             val aNullableMapArg = args[0] as Map<String?, Any?>?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableMap(aNullableMapArg))
+                  listOf(api.echoNullableMap(aNullableMapArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1360,10 +1420,10 @@ interface HostIntegrationCoreApi {
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
-            val anEnumArg = if (args[0] == null) null else AnEnum.ofRaw(args[0] as Int)
+            val anEnumArg = args[0] as AnEnum?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNullableEnum(anEnumArg)?.raw)
+                  listOf(api.echoNullableEnum(anEnumArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1386,7 +1446,7 @@ interface HostIntegrationCoreApi {
                 args[0].let { num -> if (num is Int) num.toLong() else num as Long? }
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoOptionalNullableInt(aNullableIntArg))
+                  listOf(api.echoOptionalNullableInt(aNullableIntArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1408,7 +1468,7 @@ interface HostIntegrationCoreApi {
             val aNullableStringArg = args[0] as String?
             val wrapped: List<Any?> =
                 try {
-                  listOf<Any?>(api.echoNamedNullableString(aNullableStringArg))
+                  listOf(api.echoNamedNullableString(aNullableStringArg))
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -1426,7 +1486,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.noopAsync() { result: Result<Unit> ->
+            api.noopAsync { result: Result<Unit> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -1640,14 +1700,14 @@ interface HostIntegrationCoreApi {
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
-            val anEnumArg = AnEnum.ofRaw(args[0] as Int)!!
+            val anEnumArg = args[0] as AnEnum
             api.echoAsyncEnum(anEnumArg) { result: Result<AnEnum> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
               } else {
                 val data = result.getOrNull()
-                reply.reply(wrapResult(data!!.raw))
+                reply.reply(wrapResult(data))
               }
             }
           }
@@ -1663,7 +1723,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.throwAsyncError() { result: Result<Any?> ->
+            api.throwAsyncError { result: Result<Any?> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -1685,7 +1745,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.throwAsyncErrorFromVoid() { result: Result<Unit> ->
+            api.throwAsyncErrorFromVoid { result: Result<Unit> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -1706,7 +1766,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.throwAsyncFlutterError() { result: Result<Any?> ->
+            api.throwAsyncFlutterError { result: Result<Any?> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -1995,14 +2055,14 @@ interface HostIntegrationCoreApi {
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
-            val anEnumArg = if (args[0] == null) null else AnEnum.ofRaw(args[0] as Int)
+            val anEnumArg = args[0] as AnEnum?
             api.echoAsyncNullableEnum(anEnumArg) { result: Result<AnEnum?> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
               } else {
                 val data = result.getOrNull()
-                reply.reply(wrapResult(data?.raw))
+                reply.reply(wrapResult(data))
               }
             }
           }
@@ -2018,7 +2078,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.callFlutterNoop() { result: Result<Unit> ->
+            api.callFlutterNoop { result: Result<Unit> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -2039,7 +2099,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.callFlutterThrowError() { result: Result<Any?> ->
+            api.callFlutterThrowError { result: Result<Any?> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -2061,7 +2121,7 @@ interface HostIntegrationCoreApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.callFlutterThrowErrorFromVoid() { result: Result<Unit> ->
+            api.callFlutterThrowErrorFromVoid { result: Result<Unit> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -2383,14 +2443,14 @@ interface HostIntegrationCoreApi {
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
-            val anEnumArg = AnEnum.ofRaw(args[0] as Int)!!
+            val anEnumArg = args[0] as AnEnum
             api.callFlutterEchoEnum(anEnumArg) { result: Result<AnEnum> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
               } else {
                 val data = result.getOrNull()
-                reply.reply(wrapResult(data!!.raw))
+                reply.reply(wrapResult(data))
               }
             }
           }
@@ -2575,14 +2635,14 @@ interface HostIntegrationCoreApi {
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
-            val anEnumArg = if (args[0] == null) null else AnEnum.ofRaw(args[0] as Int)
+            val anEnumArg = args[0] as AnEnum?
             api.callFlutterEchoNullableEnum(anEnumArg) { result: Result<AnEnum?> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
               } else {
                 val data = result.getOrNull()
-                reply.reply(wrapResult(data?.raw))
+                reply.reply(wrapResult(data))
               }
             }
           }
@@ -2617,58 +2677,6 @@ interface HostIntegrationCoreApi {
     }
   }
 }
-
-private object FlutterIntegrationCoreApiCodec : StandardMessageCodec() {
-  override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
-    return when (type) {
-      128.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { AllClassesWrapper.fromList(it) }
-      }
-      129.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { AllNullableTypes.fromList(it) }
-      }
-      130.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let {
-          AllNullableTypesWithoutRecursion.fromList(it)
-        }
-      }
-      131.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { AllTypes.fromList(it) }
-      }
-      132.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { TestMessage.fromList(it) }
-      }
-      else -> super.readValueOfType(type, buffer)
-    }
-  }
-
-  override fun writeValue(stream: ByteArrayOutputStream, value: Any?) {
-    when (value) {
-      is AllClassesWrapper -> {
-        stream.write(128)
-        writeValue(stream, value.toList())
-      }
-      is AllNullableTypes -> {
-        stream.write(129)
-        writeValue(stream, value.toList())
-      }
-      is AllNullableTypesWithoutRecursion -> {
-        stream.write(130)
-        writeValue(stream, value.toList())
-      }
-      is AllTypes -> {
-        stream.write(131)
-        writeValue(stream, value.toList())
-      }
-      is TestMessage -> {
-        stream.write(132)
-        writeValue(stream, value.toList())
-      }
-      else -> super.writeValue(stream, value)
-    }
-  }
-}
-
 /**
  * The core interface that the Dart platform_test code implements for host integration tests to call
  * into.
@@ -2681,7 +2689,7 @@ class FlutterIntegrationCoreApi(
 ) {
   companion object {
     /** The codec used by FlutterIntegrationCoreApi. */
-    val codec: MessageCodec<Any?> by lazy { FlutterIntegrationCoreApiCodec }
+    val codec: MessageCodec<Any?> by lazy { CoreTestsPigeonCodec }
   }
   /** A no-op function taking no arguments and returning no value, to sanity test basic calling. */
   fun noop(callback: (Result<Unit>) -> Unit) {
@@ -3082,7 +3090,7 @@ class FlutterIntegrationCoreApi(
     val channelName =
         "dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum$separatedMessageChannelSuffix"
     val channel = BasicMessageChannel<Any?>(binaryMessenger, channelName, codec)
-    channel.send(listOf(anEnumArg.raw)) {
+    channel.send(listOf(anEnumArg)) {
       if (it is List<*>) {
         if (it.size > 1) {
           callback(Result.failure(FlutterError(it[0] as String, it[1] as String, it[2] as String?)))
@@ -3094,7 +3102,7 @@ class FlutterIntegrationCoreApi(
                       "Flutter api returned null value for non-null return value.",
                       "")))
         } else {
-          val output = AnEnum.ofRaw(it[0] as Int)!!
+          val output = it[0] as AnEnum
           callback(Result.success(output))
         }
       } else {
@@ -3252,12 +3260,12 @@ class FlutterIntegrationCoreApi(
     val channelName =
         "dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableEnum$separatedMessageChannelSuffix"
     val channel = BasicMessageChannel<Any?>(binaryMessenger, channelName, codec)
-    channel.send(listOf(anEnumArg?.raw)) {
+    channel.send(listOf(anEnumArg)) {
       if (it is List<*>) {
         if (it.size > 1) {
           callback(Result.failure(FlutterError(it[0] as String, it[1] as String, it[2] as String?)))
         } else {
-          val output = (it[0] as Int?)?.let { num -> AnEnum.ofRaw(num) }
+          val output = it[0] as AnEnum?
           callback(Result.success(output))
         }
       } else {
@@ -3325,8 +3333,9 @@ interface HostTrivialApi {
 
   companion object {
     /** The codec used by HostTrivialApi. */
-    val codec: MessageCodec<Any?> by lazy { StandardMessageCodec() }
+    val codec: MessageCodec<Any?> by lazy { CoreTestsPigeonCodec }
     /** Sets up an instance of `HostTrivialApi` to handle messages through the `binaryMessenger`. */
+    @JvmOverloads
     fun setUp(
         binaryMessenger: BinaryMessenger,
         api: HostTrivialApi?,
@@ -3345,7 +3354,7 @@ interface HostTrivialApi {
             val wrapped: List<Any?> =
                 try {
                   api.noop()
-                  listOf<Any?>(null)
+                  listOf(null)
                 } catch (exception: Throwable) {
                   wrapError(exception)
                 }
@@ -3370,8 +3379,9 @@ interface HostSmallApi {
 
   companion object {
     /** The codec used by HostSmallApi. */
-    val codec: MessageCodec<Any?> by lazy { StandardMessageCodec() }
+    val codec: MessageCodec<Any?> by lazy { CoreTestsPigeonCodec }
     /** Sets up an instance of `HostSmallApi` to handle messages through the `binaryMessenger`. */
+    @JvmOverloads
     fun setUp(
         binaryMessenger: BinaryMessenger,
         api: HostSmallApi?,
@@ -3411,7 +3421,7 @@ interface HostSmallApi {
                 codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            api.voidVoid() { result: Result<Unit> ->
+            api.voidVoid { result: Result<Unit> ->
               val error = result.exceptionOrNull()
               if (error != null) {
                 reply.reply(wrapError(error))
@@ -3427,28 +3437,6 @@ interface HostSmallApi {
     }
   }
 }
-
-private object FlutterSmallApiCodec : StandardMessageCodec() {
-  override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
-    return when (type) {
-      128.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let { TestMessage.fromList(it) }
-      }
-      else -> super.readValueOfType(type, buffer)
-    }
-  }
-
-  override fun writeValue(stream: ByteArrayOutputStream, value: Any?) {
-    when (value) {
-      is TestMessage -> {
-        stream.write(128)
-        writeValue(stream, value.toList())
-      }
-      else -> super.writeValue(stream, value)
-    }
-  }
-}
-
 /**
  * A simple API called in some unit tests.
  *
@@ -3460,7 +3448,7 @@ class FlutterSmallApi(
 ) {
   companion object {
     /** The codec used by FlutterSmallApi. */
-    val codec: MessageCodec<Any?> by lazy { FlutterSmallApiCodec }
+    val codec: MessageCodec<Any?> by lazy { CoreTestsPigeonCodec }
   }
 
   fun echoWrappedList(msgArg: TestMessage, callback: (Result<TestMessage>) -> Unit) {
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt
index 97236e316bb..43ed1282d12 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt
@@ -13,18 +13,18 @@ class TestPlugin : FlutterPlugin, HostIntegrationCoreApi {
   private var flutterSmallApiOne: FlutterSmallApi? = null
   private var flutterSmallApiTwo: FlutterSmallApi? = null
 
-  override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+  override fun onAttachedToEngine(binding: FlutterPluginBinding) {
     HostIntegrationCoreApi.setUp(binding.binaryMessenger, this)
-    val testSuffixApiOne: TestPluginWithSuffix = TestPluginWithSuffix()
+    val testSuffixApiOne = TestPluginWithSuffix()
     testSuffixApiOne.setUp(binding, "suffixOne")
-    val testSuffixApiTwo: TestPluginWithSuffix = TestPluginWithSuffix()
+    val testSuffixApiTwo = TestPluginWithSuffix()
     testSuffixApiTwo.setUp(binding, "suffixTwo")
     flutterApi = FlutterIntegrationCoreApi(binding.binaryMessenger)
     flutterSmallApiOne = FlutterSmallApi(binding.binaryMessenger, "suffixOne")
     flutterSmallApiTwo = FlutterSmallApi(binding.binaryMessenger, "suffixTwo")
   }
 
-  override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {}
+  override fun onDetachedFromEngine(binding: FlutterPluginBinding) {}
 
   // HostIntegrationCoreApi
 
@@ -298,15 +298,15 @@ class TestPlugin : FlutterPlugin, HostIntegrationCoreApi {
   }
 
   override fun callFlutterNoop(callback: (Result<Unit>) -> Unit) {
-    flutterApi!!.noop() { callback(Result.success(Unit)) }
+    flutterApi!!.noop { callback(Result.success(Unit)) }
   }
 
   override fun callFlutterThrowError(callback: (Result<Any?>) -> Unit) {
-    flutterApi!!.throwError() { result -> callback(result) }
+    flutterApi!!.throwError { result -> callback(result) }
   }
 
   override fun callFlutterThrowErrorFromVoid(callback: (Result<Unit>) -> Unit) {
-    flutterApi!!.throwErrorFromVoid() { result -> callback(result) }
+    flutterApi!!.throwErrorFromVoid { result -> callback(result) }
   }
 
   override fun callFlutterEchoAllTypes(everything: AllTypes, callback: (Result<AllTypes>) -> Unit) {
@@ -375,6 +375,7 @@ class TestPlugin : FlutterPlugin, HostIntegrationCoreApi {
   }
 
   override fun callFlutterEchoEnum(anEnum: AnEnum, callback: (Result<AnEnum>) -> Unit) {
+    //    callback(Result.success(anEnum))
     flutterApi!!.echoEnum(anEnum) { echo -> callback(echo) }
   }
 
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AllDatatypesTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AllDatatypesTest.kt
index 2560efb65b2..56e0111d63f 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AllDatatypesTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AllDatatypesTest.kt
@@ -9,10 +9,14 @@ import io.mockk.every
 import io.mockk.mockk
 import java.nio.ByteBuffer
 import java.util.ArrayList
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-internal class AllDatatypesTest : TestCase() {
+internal class AllDatatypesTest {
+
   fun compareAllTypes(firstTypes: AllTypes?, secondTypes: AllTypes?) {
     assertEquals(firstTypes == null, secondTypes == null)
     if (firstTypes == null || secondTypes == null) {
@@ -21,19 +25,26 @@ internal class AllDatatypesTest : TestCase() {
     assertEquals(firstTypes.aBool, secondTypes.aBool)
     assertEquals(firstTypes.anInt, secondTypes.anInt)
     assertEquals(firstTypes.anInt64, secondTypes.anInt64)
-    assertEquals(firstTypes.aDouble, secondTypes.aDouble)
+    assertEquals(firstTypes.aDouble, secondTypes.aDouble, 0.0)
     assertEquals(firstTypes.aString, secondTypes.aString)
     assertTrue(firstTypes.aByteArray.contentEquals(secondTypes.aByteArray))
     assertTrue(firstTypes.a4ByteArray.contentEquals(secondTypes.a4ByteArray))
     assertTrue(firstTypes.a8ByteArray.contentEquals(secondTypes.a8ByteArray))
     assertTrue(firstTypes.aFloatArray.contentEquals(secondTypes.aFloatArray))
-    assertEquals(firstTypes.list, secondTypes.list)
-    assertEquals(firstTypes.aMap, secondTypes.aMap)
     assertEquals(firstTypes.anEnum, secondTypes.anEnum)
     assertEquals(firstTypes.anObject, secondTypes.anObject)
+    assertEquals(firstTypes.list, secondTypes.list)
+    assertEquals(firstTypes.boolList, secondTypes.boolList)
+    assertEquals(firstTypes.doubleList, secondTypes.doubleList)
+    assertEquals(firstTypes.intList, secondTypes.intList)
+    assertEquals(firstTypes.stringList, secondTypes.stringList)
+    assertEquals(firstTypes.map, secondTypes.map)
   }
 
-  fun compareAllNullableTypes(firstTypes: AllNullableTypes?, secondTypes: AllNullableTypes?) {
+  private fun compareAllNullableTypes(
+      firstTypes: AllNullableTypes?,
+      secondTypes: AllNullableTypes?
+  ) {
     assertEquals(firstTypes == null, secondTypes == null)
     if (firstTypes == null || secondTypes == null) {
       return
@@ -46,10 +57,14 @@ internal class AllDatatypesTest : TestCase() {
     assertTrue(firstTypes.aNullable4ByteArray.contentEquals(secondTypes.aNullable4ByteArray))
     assertTrue(firstTypes.aNullable8ByteArray.contentEquals(secondTypes.aNullable8ByteArray))
     assertTrue(firstTypes.aNullableFloatArray.contentEquals(secondTypes.aNullableFloatArray))
-    assertEquals(firstTypes.aNullableList, secondTypes.aNullableList)
-    assertEquals(firstTypes.aNullableMap, secondTypes.aNullableMap)
     assertEquals(firstTypes.nullableMapWithObject, secondTypes.nullableMapWithObject)
     assertEquals(firstTypes.aNullableObject, secondTypes.aNullableObject)
+    assertEquals(firstTypes.list, secondTypes.list)
+    assertEquals(firstTypes.boolList, secondTypes.boolList)
+    assertEquals(firstTypes.doubleList, secondTypes.doubleList)
+    assertEquals(firstTypes.intList, secondTypes.intList)
+    assertEquals(firstTypes.stringList, secondTypes.stringList)
+    assertEquals(firstTypes.map, secondTypes.map)
   }
 
   @Test
@@ -71,22 +86,9 @@ internal class AllDatatypesTest : TestCase() {
         }
 
     var didCall = false
-    api.echoAllNullableTypes(everything) {
+    api.echoAllNullableTypes(everything) { result ->
       didCall = true
-      val output =
-          (it.getOrNull())?.let {
-            assertNull(it.aNullableBool)
-            assertNull(it.aNullableInt)
-            assertNull(it.aNullableDouble)
-            assertNull(it.aNullableString)
-            assertNull(it.aNullableByteArray)
-            assertNull(it.aNullable4ByteArray)
-            assertNull(it.aNullable8ByteArray)
-            assertNull(it.aNullableFloatArray)
-            assertNull(it.aNullableList)
-            assertNull(it.aNullableMap)
-            assertNull(it.nullableMapWithObject)
-          }
+      val output = (result.getOrNull())?.let { compareAllNullableTypes(it, everything) }
       assertNotNull(output)
     }
 
@@ -105,11 +107,14 @@ internal class AllDatatypesTest : TestCase() {
             aNullable4ByteArray = intArrayOf(1, 2, 3, 4),
             aNullable8ByteArray = longArrayOf(1, 2, 3, 4),
             aNullableFloatArray = doubleArrayOf(0.5, 0.25, 1.5, 1.25),
-            aNullableList = listOf(1, 2, 3),
-            aNullableMap = mapOf("hello" to 1234),
             nullableMapWithObject = mapOf("hello" to 1234),
             aNullableObject = 0,
-        )
+            list = listOf(1, 2, 3),
+            stringList = listOf("string", "another one"),
+            boolList = listOf(true, false),
+            intList = listOf(1, 2),
+            doubleList = listOf(1.1, 2.2),
+            map = mapOf("hello" to 1234))
     val binaryMessenger = mockk<BinaryMessenger>()
     val api = FlutterIntegrationCoreApi(binaryMessenger)
 
@@ -161,6 +166,11 @@ internal class AllDatatypesTest : TestCase() {
             null,
             null,
             null,
+            null,
+            null,
+            null,
+            null,
+            null,
             null)
     val everything2 = AllNullableTypes.fromList(list2)
 
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AsyncHandlersTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AsyncHandlersTest.kt
index d42c62fefcb..8de43ad15fb 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AsyncHandlersTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/AsyncHandlersTest.kt
@@ -10,10 +10,14 @@ import io.mockk.mockk
 import io.mockk.slot
 import io.mockk.verify
 import java.nio.ByteBuffer
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-internal class AsyncHandlersTest : TestCase() {
+internal class AsyncHandlersTest {
+
   @Test
   fun testAsyncHost2Flutter() {
     val binaryMessenger = mockk<BinaryMessenger>()
@@ -56,7 +60,6 @@ internal class AsyncHandlersTest : TestCase() {
     val handlerSlot = slot<BinaryMessenger.BinaryMessageHandler>()
 
     val input = "Test"
-    val output = input
     val channelName = "dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo"
 
     every {
@@ -67,7 +70,7 @@ internal class AsyncHandlersTest : TestCase() {
     every { api.echo(any(), any()) } answers
         {
           val callback = arg<(Result<String>) -> Unit>(1)
-          callback(Result.success(output))
+          callback(Result.success(input))
         }
 
     HostSmallApi.setUp(binaryMessenger, api)
@@ -80,7 +83,7 @@ internal class AsyncHandlersTest : TestCase() {
       it?.rewind()
       @Suppress("UNCHECKED_CAST") val wrapped = codec.decodeMessage(it) as MutableList<Any>?
       assertNotNull(wrapped)
-      wrapped?.let { assertEquals(output, wrapped.first()) }
+      wrapped?.let { assertEquals(input, wrapped.first()) }
     }
 
     verify { binaryMessenger.setMessageHandler(channelName, handlerSlot.captured) }
@@ -88,7 +91,7 @@ internal class AsyncHandlersTest : TestCase() {
   }
 
   @Test
-  fun asyncFlutter2HostVoidVoid() {
+  fun testAsyncFlutter2HostVoidVoid() {
     val binaryMessenger = mockk<BinaryMessenger>()
     val api = mockk<HostSmallApi>()
 
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/EnumTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/EnumTest.kt
index 1117a8a3a1e..acdc6192c01 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/EnumTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/EnumTest.kt
@@ -11,10 +11,13 @@ import io.mockk.slot
 import io.mockk.verify
 import java.nio.ByteBuffer
 import java.util.ArrayList
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-internal class EnumTest : TestCase() {
+internal class EnumTest {
+
   @Test
   fun testEchoHost() {
     val binaryMessenger = mockk<BinaryMessenger>()
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/ListTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/ListTest.kt
index 923cc3b90e6..cab26d56a52 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/ListTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/ListTest.kt
@@ -9,10 +9,12 @@ import io.mockk.every
 import io.mockk.mockk
 import java.nio.ByteBuffer
 import java.util.ArrayList
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-class ListTest : TestCase() {
+class ListTest {
+
   @Test
   fun testListInList() {
     val binaryMessenger = mockk<BinaryMessenger>()
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/MultipleArityTests.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/MultipleArityTests.kt
index 27925a308ae..789c944eb48 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/MultipleArityTests.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/MultipleArityTests.kt
@@ -10,10 +10,13 @@ import io.mockk.mockk
 import io.mockk.slot
 import java.nio.ByteBuffer
 import java.util.ArrayList
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-class MultipleArityTests : TestCase() {
+class MultipleArityTests {
+
   @Test
   fun testSimpleHost() {
     val binaryMessenger = mockk<BinaryMessenger>()
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NonNullFieldsTests.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NonNullFieldsTests.kt
index c5357af1b72..6e867760a08 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NonNullFieldsTests.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NonNullFieldsTests.kt
@@ -4,10 +4,11 @@
 
 package com.example.test_plugin
 
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
 import org.junit.Test
 
-class NonNullFieldsTests : TestCase() {
+class NonNullFieldsTests {
+
   @Test
   fun testMake() {
     val request = NonNullFieldSearchRequest("hello")
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NullableReturnsTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NullableReturnsTest.kt
index a1f6b52558b..78c85ba91d8 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NullableReturnsTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/NullableReturnsTest.kt
@@ -9,10 +9,13 @@ import io.mockk.every
 import io.mockk.mockk
 import io.mockk.slot
 import io.mockk.verify
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-class NullableReturnsTest : TestCase() {
+class NullableReturnsTest {
+
   @Test
   fun testNullableParameterHost() {
     val binaryMessenger = mockk<BinaryMessenger>(relaxed = true)
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/PrimitiveTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/PrimitiveTest.kt
index a883b6b0325..047c5b3c219 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/PrimitiveTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/PrimitiveTest.kt
@@ -9,10 +9,13 @@ import io.mockk.every
 import io.mockk.mockk
 import io.mockk.slot
 import io.mockk.verify
-import junit.framework.TestCase
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 
-class PrimitiveTest : TestCase() {
+class PrimitiveTest {
+
   @Test
   fun testIntPrimitiveHost() {
     val binaryMessenger = mockk<BinaryMessenger>(relaxed = true)
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme b/packages/pigeon/platform_tests/test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
index 7e1380f00a5..58761a450d7 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1430"
+   LastUpgradeVersion = "1510"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AllDatatypesTests.swift b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AllDatatypesTests.swift
index 7e7266940f5..76877a80978 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AllDatatypesTests.swift
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AllDatatypesTests.swift
@@ -11,7 +11,7 @@ class AllDatatypesTests: XCTestCase {
 
   func testAllNull() throws {
     let everything = AllNullableTypes()
-    let binaryMessenger = EchoBinaryMessenger(codec: FlutterIntegrationCoreApiCodec.shared)
+    let binaryMessenger = EchoBinaryMessenger(codec: CoreTestsPigeonCodec.shared)
     let api = FlutterIntegrationCoreApi(binaryMessenger: binaryMessenger)
 
     let expectation = XCTestExpectation(description: "callback")
@@ -28,11 +28,15 @@ class AllDatatypesTests: XCTestCase {
         XCTAssertNil(res!.aNullable4ByteArray)
         XCTAssertNil(res!.aNullable8ByteArray)
         XCTAssertNil(res!.aNullableFloatArray)
-        XCTAssertNil(res!.aNullableList)
-        XCTAssertNil(res!.aNullableMap)
         XCTAssertNil(res!.nullableNestedList)
         XCTAssertNil(res!.nullableMapWithAnnotations)
         XCTAssertNil(res!.nullableMapWithObject)
+        XCTAssertNil(res!.map)
+        XCTAssertNil(res!.list)
+        XCTAssertNil(res!.boolList)
+        XCTAssertNil(res!.intList)
+        XCTAssertNil(res!.doubleList)
+        XCTAssertNil(res!.stringList)
         expectation.fulfill()
       case .failure(_):
         return
@@ -52,15 +56,19 @@ class AllDatatypesTests: XCTestCase {
       aNullable4ByteArray: FlutterStandardTypedData(int32: "1234".data(using: .utf8)!),
       aNullable8ByteArray: FlutterStandardTypedData(int64: "12345678".data(using: .utf8)!),
       aNullableFloatArray: FlutterStandardTypedData(float64: "12345678".data(using: .utf8)!),
-      aNullableList: [1, 2],
-      aNullableMap: ["hello": 1234],
       nullableNestedList: [[true, false], [true]],
       nullableMapWithAnnotations: ["hello": "world"],
       nullableMapWithObject: ["hello": 1234, "goodbye": "world"],
-      aNullableString: "123"
+      aNullableString: "123",
+      list: ["string", 2],
+      stringList: ["string", "another one"],
+      intList: [1, 2],
+      doubleList: [1.1, 2.2],
+      boolList: [true, false],
+      map: ["hello": 1234]
     )
 
-    let binaryMessenger = EchoBinaryMessenger(codec: FlutterIntegrationCoreApiCodec.shared)
+    let binaryMessenger = EchoBinaryMessenger(codec: CoreTestsPigeonCodec.shared)
     let api = FlutterIntegrationCoreApi(binaryMessenger: binaryMessenger)
 
     let expectation = XCTestExpectation(description: "callback")
@@ -77,11 +85,15 @@ class AllDatatypesTests: XCTestCase {
         XCTAssertEqual(res!.aNullable4ByteArray, everything.aNullable4ByteArray)
         XCTAssertEqual(res!.aNullable8ByteArray, everything.aNullable8ByteArray)
         XCTAssertEqual(res!.aNullableFloatArray, everything.aNullableFloatArray)
-        XCTAssert(equalsList(res!.aNullableList, everything.aNullableList))
-        XCTAssert(equalsDictionary(res!.aNullableMap, everything.aNullableMap))
         XCTAssertEqual(res!.nullableNestedList, everything.nullableNestedList)
         XCTAssertEqual(res!.nullableMapWithAnnotations, everything.nullableMapWithAnnotations)
         XCTAssert(equalsDictionary(res!.nullableMapWithObject, everything.nullableMapWithObject))
+        XCTAssert(equalsList(res!.list, everything.list))
+        XCTAssert(equalsList(res!.stringList, everything.stringList))
+        XCTAssert(equalsList(res!.intList, everything.intList))
+        XCTAssert(equalsList(res!.doubleList, everything.doubleList))
+        XCTAssert(equalsList(res!.boolList, everything.boolList))
+        XCTAssert(equalsDictionary(res!.map, everything.map))
         expectation.fulfill()
         return
       case .failure(_):
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AsyncHandlersTest.swift b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AsyncHandlersTest.swift
index f7e8db59606..cd69b08a9b6 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AsyncHandlersTest.swift
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/AsyncHandlersTest.swift
@@ -22,7 +22,7 @@ class AsyncHandlersTest: XCTestCase {
 
   func testAsyncHost2Flutter() throws {
     let value = "Test"
-    let binaryMessenger = MockBinaryMessenger<String>(codec: FlutterIntegrationCoreApiCodec.shared)
+    let binaryMessenger = MockBinaryMessenger<String>(codec: CoreTestsPigeonCodec.shared)
     binaryMessenger.result = value
     let flutterApi = FlutterIntegrationCoreApi(binaryMessenger: binaryMessenger)
 
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/EnumTests.swift b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/EnumTests.swift
index 391ace5d914..60683ff236f 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/EnumTests.swift
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/EnumTests.swift
@@ -21,7 +21,7 @@ extension DataWithEnum: Equatable {
 class EnumTests: XCTestCase {
 
   func testEchoHost() throws {
-    let binaryMessenger = MockBinaryMessenger<DataWithEnum>(codec: EnumApi2HostCodec.shared)
+    let binaryMessenger = MockBinaryMessenger<DataWithEnum>(codec: EnumPigeonCodec.shared)
     EnumApi2HostSetup.setUp(binaryMessenger: binaryMessenger, api: MockEnumApi2Host())
     let channelName = "dev.flutter.pigeon.pigeon_integration_tests.EnumApi2Host.echo"
     XCTAssertNotNil(binaryMessenger.handlers[channelName])
@@ -44,7 +44,7 @@ class EnumTests: XCTestCase {
 
   func testEchoFlutter() throws {
     let data = DataWithEnum(state: .error)
-    let binaryMessenger = EchoBinaryMessenger(codec: EnumApi2HostCodec.shared)
+    let binaryMessenger = EchoBinaryMessenger(codec: EnumPigeonCodec.shared)
     let api = EnumApi2Flutter(binaryMessenger: binaryMessenger)
 
     let expectation = XCTestExpectation(description: "callback")
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/ListTests.swift b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/ListTests.swift
index 4fc7de6b96e..fa56f7231ff 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/ListTests.swift
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/ListTests.swift
@@ -11,7 +11,7 @@ class ListTests: XCTestCase {
   func testListInList() throws {
     let inside = TestMessage(testList: [1, 2, 3])
     let top = TestMessage(testList: [inside])
-    let binaryMessenger = EchoBinaryMessenger(codec: FlutterSmallApiCodec.shared)
+    let binaryMessenger = EchoBinaryMessenger(codec: CoreTestsPigeonCodec.shared)
     let api = FlutterSmallApi(binaryMessenger: binaryMessenger)
 
     let expectation = XCTestExpectation(description: "callback")
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/MultipleArityTests.swift b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/MultipleArityTests.swift
index f42933b2391..6994a6703bf 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/MultipleArityTests.swift
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/MultipleArityTests.swift
@@ -16,7 +16,7 @@ class MockMultipleArityHostApi: MultipleArityHostApi {
 class MultipleArityTests: XCTestCase {
   var codec = FlutterStandardMessageCodec.sharedInstance()
   func testSimpleHost() throws {
-    let binaryMessenger = MockBinaryMessenger<Int64>(codec: EnumApi2HostCodec.shared)
+    let binaryMessenger = MockBinaryMessenger<Int64>(codec: EnumPigeonCodec.shared)
     MultipleArityHostApiSetup.setUp(
       binaryMessenger: binaryMessenger, api: MockMultipleArityHostApi())
     let channelName = "dev.flutter.pigeon.pigeon_integration_tests.MultipleArityHostApi.subtract"
diff --git a/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift b/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift
index c54100d2db4..2b95f040b48 100644
--- a/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift
+++ b/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift
@@ -94,11 +94,15 @@ struct AllTypes {
   var a4ByteArray: FlutterStandardTypedData
   var a8ByteArray: FlutterStandardTypedData
   var aFloatArray: FlutterStandardTypedData
-  var list: [Any?]
-  var aMap: [AnyHashable: Any?]
   var anEnum: AnEnum
   var aString: String
   var anObject: Any
+  var list: [Any?]
+  var stringList: [String?]
+  var intList: [Int64?]
+  var doubleList: [Double?]
+  var boolList: [Bool?]
+  var map: [AnyHashable: Any?]
 
   // swift-format-ignore: AlwaysUseLowerCamelCase
   static func fromList(_ __pigeon_list: [Any?]) -> AllTypes? {
@@ -112,11 +116,15 @@ struct AllTypes {
     let a4ByteArray = __pigeon_list[5] as! FlutterStandardTypedData
     let a8ByteArray = __pigeon_list[6] as! FlutterStandardTypedData
     let aFloatArray = __pigeon_list[7] as! FlutterStandardTypedData
-    let list = __pigeon_list[8] as! [Any?]
-    let aMap = __pigeon_list[9] as! [AnyHashable: Any?]
-    let anEnum = AnEnum(rawValue: __pigeon_list[10] as! Int)!
-    let aString = __pigeon_list[11] as! String
-    let anObject = __pigeon_list[12]!
+    let anEnum = __pigeon_list[8] as! AnEnum
+    let aString = __pigeon_list[9] as! String
+    let anObject = __pigeon_list[10]!
+    let list = __pigeon_list[11] as! [Any?]
+    let stringList = __pigeon_list[12] as! [String?]
+    let intList = __pigeon_list[13] as! [Int64?]
+    let doubleList = __pigeon_list[14] as! [Double?]
+    let boolList = __pigeon_list[15] as! [Bool?]
+    let map = __pigeon_list[16] as! [AnyHashable: Any?]
 
     return AllTypes(
       aBool: aBool,
@@ -127,11 +135,15 @@ struct AllTypes {
       a4ByteArray: a4ByteArray,
       a8ByteArray: a8ByteArray,
       aFloatArray: aFloatArray,
-      list: list,
-      aMap: aMap,
       anEnum: anEnum,
       aString: aString,
-      anObject: anObject
+      anObject: anObject,
+      list: list,
+      stringList: stringList,
+      intList: intList,
+      doubleList: doubleList,
+      boolList: boolList,
+      map: map
     )
   }
   func toList() -> [Any?] {
@@ -144,11 +156,15 @@ struct AllTypes {
       a4ByteArray,
       a8ByteArray,
       aFloatArray,
-      list,
-      aMap,
-      anEnum.rawValue,
+      anEnum,
       aString,
       anObject,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      map,
     ]
   }
 }
@@ -166,15 +182,20 @@ class AllNullableTypes {
     aNullable4ByteArray: FlutterStandardTypedData? = nil,
     aNullable8ByteArray: FlutterStandardTypedData? = nil,
     aNullableFloatArray: FlutterStandardTypedData? = nil,
-    aNullableList: [Any?]? = nil,
-    aNullableMap: [AnyHashable: Any?]? = nil,
     nullableNestedList: [[Bool?]?]? = nil,
     nullableMapWithAnnotations: [String?: String?]? = nil,
     nullableMapWithObject: [String?: Any?]? = nil,
     aNullableEnum: AnEnum? = nil,
     aNullableString: String? = nil,
     aNullableObject: Any? = nil,
-    allNullableTypes: AllNullableTypes? = nil
+    allNullableTypes: AllNullableTypes? = nil,
+    list: [Any?]? = nil,
+    stringList: [String?]? = nil,
+    intList: [Int64?]? = nil,
+    doubleList: [Double?]? = nil,
+    boolList: [Bool?]? = nil,
+    nestedClassList: [AllNullableTypes?]? = nil,
+    map: [AnyHashable: Any?]? = nil
   ) {
     self.aNullableBool = aNullableBool
     self.aNullableInt = aNullableInt
@@ -184,8 +205,6 @@ class AllNullableTypes {
     self.aNullable4ByteArray = aNullable4ByteArray
     self.aNullable8ByteArray = aNullable8ByteArray
     self.aNullableFloatArray = aNullableFloatArray
-    self.aNullableList = aNullableList
-    self.aNullableMap = aNullableMap
     self.nullableNestedList = nullableNestedList
     self.nullableMapWithAnnotations = nullableMapWithAnnotations
     self.nullableMapWithObject = nullableMapWithObject
@@ -193,6 +212,13 @@ class AllNullableTypes {
     self.aNullableString = aNullableString
     self.aNullableObject = aNullableObject
     self.allNullableTypes = allNullableTypes
+    self.list = list
+    self.stringList = stringList
+    self.intList = intList
+    self.doubleList = doubleList
+    self.boolList = boolList
+    self.nestedClassList = nestedClassList
+    self.map = map
   }
   var aNullableBool: Bool?
   var aNullableInt: Int64?
@@ -202,8 +228,6 @@ class AllNullableTypes {
   var aNullable4ByteArray: FlutterStandardTypedData?
   var aNullable8ByteArray: FlutterStandardTypedData?
   var aNullableFloatArray: FlutterStandardTypedData?
-  var aNullableList: [Any?]?
-  var aNullableMap: [AnyHashable: Any?]?
   var nullableNestedList: [[Bool?]?]?
   var nullableMapWithAnnotations: [String?: String?]?
   var nullableMapWithObject: [String?: Any?]?
@@ -211,6 +235,13 @@ class AllNullableTypes {
   var aNullableString: String?
   var aNullableObject: Any?
   var allNullableTypes: AllNullableTypes?
+  var list: [Any?]?
+  var stringList: [String?]?
+  var intList: [Int64?]?
+  var doubleList: [Double?]?
+  var boolList: [Bool?]?
+  var nestedClassList: [AllNullableTypes?]?
+  var map: [AnyHashable: Any?]?
 
   // swift-format-ignore: AlwaysUseLowerCamelCase
   static func fromList(_ __pigeon_list: [Any?]) -> AllNullableTypes? {
@@ -230,19 +261,20 @@ class AllNullableTypes {
     let aNullable4ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[5])
     let aNullable8ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[6])
     let aNullableFloatArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[7])
-    let aNullableList: [Any?]? = nilOrValue(__pigeon_list[8])
-    let aNullableMap: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[9])
-    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[10])
-    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[11])
-    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[12])
-    var aNullableEnum: AnEnum? = nil
-    let aNullableEnumEnumVal: Int? = nilOrValue(__pigeon_list[13])
-    if let aNullableEnumRawValue = aNullableEnumEnumVal {
-      aNullableEnum = AnEnum(rawValue: aNullableEnumRawValue)!
-    }
-    let aNullableString: String? = nilOrValue(__pigeon_list[14])
-    let aNullableObject: Any? = __pigeon_list[15]
-    let allNullableTypes: AllNullableTypes? = nilOrValue(__pigeon_list[16])
+    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[8])
+    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[9])
+    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[10])
+    let aNullableEnum: AnEnum? = nilOrValue(__pigeon_list[11])
+    let aNullableString: String? = nilOrValue(__pigeon_list[12])
+    let aNullableObject: Any? = __pigeon_list[13]
+    let allNullableTypes: AllNullableTypes? = nilOrValue(__pigeon_list[14])
+    let list: [Any?]? = nilOrValue(__pigeon_list[15])
+    let stringList: [String?]? = nilOrValue(__pigeon_list[16])
+    let intList: [Int64?]? = nilOrValue(__pigeon_list[17])
+    let doubleList: [Double?]? = nilOrValue(__pigeon_list[18])
+    let boolList: [Bool?]? = nilOrValue(__pigeon_list[19])
+    let nestedClassList: [AllNullableTypes?]? = nilOrValue(__pigeon_list[20])
+    let map: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[21])
 
     return AllNullableTypes(
       aNullableBool: aNullableBool,
@@ -253,15 +285,20 @@ class AllNullableTypes {
       aNullable4ByteArray: aNullable4ByteArray,
       aNullable8ByteArray: aNullable8ByteArray,
       aNullableFloatArray: aNullableFloatArray,
-      aNullableList: aNullableList,
-      aNullableMap: aNullableMap,
       nullableNestedList: nullableNestedList,
       nullableMapWithAnnotations: nullableMapWithAnnotations,
       nullableMapWithObject: nullableMapWithObject,
       aNullableEnum: aNullableEnum,
       aNullableString: aNullableString,
       aNullableObject: aNullableObject,
-      allNullableTypes: allNullableTypes
+      allNullableTypes: allNullableTypes,
+      list: list,
+      stringList: stringList,
+      intList: intList,
+      doubleList: doubleList,
+      boolList: boolList,
+      nestedClassList: nestedClassList,
+      map: map
     )
   }
   func toList() -> [Any?] {
@@ -274,15 +311,20 @@ class AllNullableTypes {
       aNullable4ByteArray,
       aNullable8ByteArray,
       aNullableFloatArray,
-      aNullableList,
-      aNullableMap,
       nullableNestedList,
       nullableMapWithAnnotations,
       nullableMapWithObject,
-      aNullableEnum?.rawValue,
+      aNullableEnum,
       aNullableString,
       aNullableObject,
       allNullableTypes,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      nestedClassList,
+      map,
     ]
   }
 }
@@ -301,14 +343,18 @@ struct AllNullableTypesWithoutRecursion {
   var aNullable4ByteArray: FlutterStandardTypedData? = nil
   var aNullable8ByteArray: FlutterStandardTypedData? = nil
   var aNullableFloatArray: FlutterStandardTypedData? = nil
-  var aNullableList: [Any?]? = nil
-  var aNullableMap: [AnyHashable: Any?]? = nil
   var nullableNestedList: [[Bool?]?]? = nil
   var nullableMapWithAnnotations: [String?: String?]? = nil
   var nullableMapWithObject: [String?: Any?]? = nil
   var aNullableEnum: AnEnum? = nil
   var aNullableString: String? = nil
   var aNullableObject: Any? = nil
+  var list: [Any?]? = nil
+  var stringList: [String?]? = nil
+  var intList: [Int64?]? = nil
+  var doubleList: [Double?]? = nil
+  var boolList: [Bool?]? = nil
+  var map: [AnyHashable: Any?]? = nil
 
   // swift-format-ignore: AlwaysUseLowerCamelCase
   static func fromList(_ __pigeon_list: [Any?]) -> AllNullableTypesWithoutRecursion? {
@@ -328,18 +374,18 @@ struct AllNullableTypesWithoutRecursion {
     let aNullable4ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[5])
     let aNullable8ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[6])
     let aNullableFloatArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[7])
-    let aNullableList: [Any?]? = nilOrValue(__pigeon_list[8])
-    let aNullableMap: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[9])
-    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[10])
-    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[11])
-    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[12])
-    var aNullableEnum: AnEnum? = nil
-    let aNullableEnumEnumVal: Int? = nilOrValue(__pigeon_list[13])
-    if let aNullableEnumRawValue = aNullableEnumEnumVal {
-      aNullableEnum = AnEnum(rawValue: aNullableEnumRawValue)!
-    }
-    let aNullableString: String? = nilOrValue(__pigeon_list[14])
-    let aNullableObject: Any? = __pigeon_list[15]
+    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[8])
+    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[9])
+    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[10])
+    let aNullableEnum: AnEnum? = nilOrValue(__pigeon_list[11])
+    let aNullableString: String? = nilOrValue(__pigeon_list[12])
+    let aNullableObject: Any? = __pigeon_list[13]
+    let list: [Any?]? = nilOrValue(__pigeon_list[14])
+    let stringList: [String?]? = nilOrValue(__pigeon_list[15])
+    let intList: [Int64?]? = nilOrValue(__pigeon_list[16])
+    let doubleList: [Double?]? = nilOrValue(__pigeon_list[17])
+    let boolList: [Bool?]? = nilOrValue(__pigeon_list[18])
+    let map: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[19])
 
     return AllNullableTypesWithoutRecursion(
       aNullableBool: aNullableBool,
@@ -350,14 +396,18 @@ struct AllNullableTypesWithoutRecursion {
       aNullable4ByteArray: aNullable4ByteArray,
       aNullable8ByteArray: aNullable8ByteArray,
       aNullableFloatArray: aNullableFloatArray,
-      aNullableList: aNullableList,
-      aNullableMap: aNullableMap,
       nullableNestedList: nullableNestedList,
       nullableMapWithAnnotations: nullableMapWithAnnotations,
       nullableMapWithObject: nullableMapWithObject,
       aNullableEnum: aNullableEnum,
       aNullableString: aNullableString,
-      aNullableObject: aNullableObject
+      aNullableObject: aNullableObject,
+      list: list,
+      stringList: stringList,
+      intList: intList,
+      doubleList: doubleList,
+      boolList: boolList,
+      map: map
     )
   }
   func toList() -> [Any?] {
@@ -370,14 +420,18 @@ struct AllNullableTypesWithoutRecursion {
       aNullable4ByteArray,
       aNullable8ByteArray,
       aNullableFloatArray,
-      aNullableList,
-      aNullableMap,
       nullableNestedList,
       nullableMapWithAnnotations,
       nullableMapWithObject,
-      aNullableEnum?.rawValue,
+      aNullableEnum,
       aNullableString,
       aNullableObject,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      map,
     ]
   }
 }
@@ -436,62 +490,70 @@ struct TestMessage {
     ]
   }
 }
-
-private class HostIntegrationCoreApiCodecReader: FlutterStandardReader {
+private class CoreTestsPigeonCodecReader: FlutterStandardReader {
   override func readValue(ofType type: UInt8) -> Any? {
     switch type {
-    case 128:
-      return AllClassesWrapper.fromList(self.readValue() as! [Any?])
     case 129:
-      return AllNullableTypes.fromList(self.readValue() as! [Any?])
+      return AllTypes.fromList(self.readValue() as! [Any?])
     case 130:
-      return AllNullableTypesWithoutRecursion.fromList(self.readValue() as! [Any?])
+      return AllNullableTypes.fromList(self.readValue() as! [Any?])
     case 131:
-      return AllTypes.fromList(self.readValue() as! [Any?])
+      return AllNullableTypesWithoutRecursion.fromList(self.readValue() as! [Any?])
     case 132:
+      return AllClassesWrapper.fromList(self.readValue() as! [Any?])
+    case 133:
       return TestMessage.fromList(self.readValue() as! [Any?])
+    case 134:
+      var enumResult: AnEnum? = nil
+      let enumResultAsInt: Int? = nilOrValue(self.readValue() as? Int)
+      if let enumResultAsInt = enumResultAsInt {
+        enumResult = AnEnum(rawValue: enumResultAsInt)
+      }
+      return enumResult
     default:
       return super.readValue(ofType: type)
     }
   }
 }
 
-private class HostIntegrationCoreApiCodecWriter: FlutterStandardWriter {
+private class CoreTestsPigeonCodecWriter: FlutterStandardWriter {
   override func writeValue(_ value: Any) {
-    if let value = value as? AllClassesWrapper {
-      super.writeByte(128)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypes {
+    if let value = value as? AllTypes {
       super.writeByte(129)
       super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypesWithoutRecursion {
+    } else if let value = value as? AllNullableTypes {
       super.writeByte(130)
       super.writeValue(value.toList())
-    } else if let value = value as? AllTypes {
+    } else if let value = value as? AllNullableTypesWithoutRecursion {
       super.writeByte(131)
       super.writeValue(value.toList())
-    } else if let value = value as? TestMessage {
+    } else if let value = value as? AllClassesWrapper {
       super.writeByte(132)
       super.writeValue(value.toList())
+    } else if let value = value as? TestMessage {
+      super.writeByte(133)
+      super.writeValue(value.toList())
+    } else if let value = value as? AnEnum {
+      super.writeByte(134)
+      super.writeValue(value.rawValue)
     } else {
       super.writeValue(value)
     }
   }
 }
 
-private class HostIntegrationCoreApiCodecReaderWriter: FlutterStandardReaderWriter {
+private class CoreTestsPigeonCodecReaderWriter: FlutterStandardReaderWriter {
   override func reader(with data: Data) -> FlutterStandardReader {
-    return HostIntegrationCoreApiCodecReader(data: data)
+    return CoreTestsPigeonCodecReader(data: data)
   }
 
   override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return HostIntegrationCoreApiCodecWriter(data: data)
+    return CoreTestsPigeonCodecWriter(data: data)
   }
 }
 
-class HostIntegrationCoreApiCodec: FlutterStandardMessageCodec {
-  static let shared = HostIntegrationCoreApiCodec(
-    readerWriter: HostIntegrationCoreApiCodecReaderWriter())
+class CoreTestsPigeonCodec: FlutterStandardMessageCodec, @unchecked Sendable {
+  static let shared = CoreTestsPigeonCodec(readerWriter: CoreTestsPigeonCodecReaderWriter())
 }
 
 /// The core interface that each host language plugin must implement in
@@ -687,8 +749,7 @@ protocol HostIntegrationCoreApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class HostIntegrationCoreApiSetup {
-  /// The codec used by HostIntegrationCoreApi.
-  static var codec: FlutterStandardMessageCodec { HostIntegrationCoreApiCodec.shared }
+  static var codec: FlutterStandardMessageCodec { CoreTestsPigeonCodec.shared }
   /// Sets up an instance of `HostIntegrationCoreApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: HostIntegrationCoreApi?,
@@ -962,10 +1023,10 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg = AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg = args[0] as! AnEnum
         do {
           let result = try api.echo(anEnumArg)
-          reply(wrapResult(result.rawValue))
+          reply(wrapResult(result))
         } catch {
           reply(wrapError(error))
         }
@@ -1317,10 +1378,10 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoNullableEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg: AnEnum? = isNullish(args[0]) ? nil : AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg: AnEnum? = nilOrValue(args[0])
         do {
           let result = try api.echoNullable(anEnumArg)
-          reply(wrapResult(result?.rawValue))
+          reply(wrapResult(result))
         } catch {
           reply(wrapError(error))
         }
@@ -1564,11 +1625,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoAsyncEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg = AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg = args[0] as! AnEnum
         api.echoAsync(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -1875,11 +1936,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoAsyncNullableEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg: AnEnum? = isNullish(args[0]) ? nil : AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg: AnEnum? = nilOrValue(args[0])
         api.echoAsyncNullable(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res?.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -2202,11 +2263,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       callFlutterEchoEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg = AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg = args[0] as! AnEnum
         api.callFlutterEcho(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -2364,11 +2425,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       callFlutterEchoNullableEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg: AnEnum? = isNullish(args[0]) ? nil : AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg: AnEnum? = nilOrValue(args[0])
         api.callFlutterNullableEcho(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res?.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -2399,63 +2460,6 @@ class HostIntegrationCoreApiSetup {
     }
   }
 }
-private class FlutterIntegrationCoreApiCodecReader: FlutterStandardReader {
-  override func readValue(ofType type: UInt8) -> Any? {
-    switch type {
-    case 128:
-      return AllClassesWrapper.fromList(self.readValue() as! [Any?])
-    case 129:
-      return AllNullableTypes.fromList(self.readValue() as! [Any?])
-    case 130:
-      return AllNullableTypesWithoutRecursion.fromList(self.readValue() as! [Any?])
-    case 131:
-      return AllTypes.fromList(self.readValue() as! [Any?])
-    case 132:
-      return TestMessage.fromList(self.readValue() as! [Any?])
-    default:
-      return super.readValue(ofType: type)
-    }
-  }
-}
-
-private class FlutterIntegrationCoreApiCodecWriter: FlutterStandardWriter {
-  override func writeValue(_ value: Any) {
-    if let value = value as? AllClassesWrapper {
-      super.writeByte(128)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypes {
-      super.writeByte(129)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypesWithoutRecursion {
-      super.writeByte(130)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllTypes {
-      super.writeByte(131)
-      super.writeValue(value.toList())
-    } else if let value = value as? TestMessage {
-      super.writeByte(132)
-      super.writeValue(value.toList())
-    } else {
-      super.writeValue(value)
-    }
-  }
-}
-
-private class FlutterIntegrationCoreApiCodecReaderWriter: FlutterStandardReaderWriter {
-  override func reader(with data: Data) -> FlutterStandardReader {
-    return FlutterIntegrationCoreApiCodecReader(data: data)
-  }
-
-  override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return FlutterIntegrationCoreApiCodecWriter(data: data)
-  }
-}
-
-class FlutterIntegrationCoreApiCodec: FlutterStandardMessageCodec {
-  static let shared = FlutterIntegrationCoreApiCodec(
-    readerWriter: FlutterIntegrationCoreApiCodecReaderWriter())
-}
-
 /// The core interface that the Dart platform_test code implements for host
 /// integration tests to call into.
 ///
@@ -2550,8 +2554,8 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
     self.binaryMessenger = binaryMessenger
     self.messageChannelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
   }
-  var codec: FlutterStandardMessageCodec {
-    return FlutterIntegrationCoreApiCodec.shared
+  var codec: CoreTestsPigeonCodec {
+    return CoreTestsPigeonCodec.shared
   }
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic calling.
@@ -2976,7 +2980,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
       "dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum\(messageChannelSuffix)"
     let channel = FlutterBasicMessageChannel(
       name: channelName, binaryMessenger: binaryMessenger, codec: codec)
-    channel.sendMessage([anEnumArg.rawValue] as [Any?]) { response in
+    channel.sendMessage([anEnumArg] as [Any?]) { response in
       guard let listResponse = response as? [Any?] else {
         completion(.failure(createConnectionError(withChannelName: channelName)))
         return
@@ -2993,7 +2997,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
               code: "null-error",
               message: "Flutter api returned null value for non-null return value.", details: "")))
       } else {
-        let result = AnEnum(rawValue: listResponse[0] as! Int)!
+        let result = listResponse[0] as! AnEnum
         completion(.success(result))
       }
     }
@@ -3177,7 +3181,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
       "dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableEnum\(messageChannelSuffix)"
     let channel = FlutterBasicMessageChannel(
       name: channelName, binaryMessenger: binaryMessenger, codec: codec)
-    channel.sendMessage([anEnumArg?.rawValue] as [Any?]) { response in
+    channel.sendMessage([anEnumArg] as [Any?]) { response in
       guard let listResponse = response as? [Any?] else {
         completion(.failure(createConnectionError(withChannelName: channelName)))
         return
@@ -3188,8 +3192,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
         let details: String? = nilOrValue(listResponse[2])
         completion(.failure(PigeonError(code: code, message: message, details: details)))
       } else {
-        let result: AnEnum? =
-          isNullish(listResponse[0]) ? nil : AnEnum(rawValue: listResponse[0] as! Int)!
+        let result: AnEnum? = nilOrValue(listResponse[0])
         completion(.success(result))
       }
     }
@@ -3255,7 +3258,7 @@ protocol HostTrivialApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class HostTrivialApiSetup {
-  /// The codec used by HostTrivialApi.
+  static var codec: FlutterStandardMessageCodec { CoreTestsPigeonCodec.shared }
   /// Sets up an instance of `HostTrivialApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: HostTrivialApi?, messageChannelSuffix: String = ""
@@ -3263,7 +3266,7 @@ class HostTrivialApiSetup {
     let channelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
     let noopChannel = FlutterBasicMessageChannel(
       name: "dev.flutter.pigeon.pigeon_integration_tests.HostTrivialApi.noop\(channelSuffix)",
-      binaryMessenger: binaryMessenger)
+      binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       noopChannel.setMessageHandler { _, reply in
         do {
@@ -3288,7 +3291,7 @@ protocol HostSmallApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class HostSmallApiSetup {
-  /// The codec used by HostSmallApi.
+  static var codec: FlutterStandardMessageCodec { CoreTestsPigeonCodec.shared }
   /// Sets up an instance of `HostSmallApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: HostSmallApi?, messageChannelSuffix: String = ""
@@ -3296,7 +3299,7 @@ class HostSmallApiSetup {
     let channelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
     let echoChannel = FlutterBasicMessageChannel(
       name: "dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo\(channelSuffix)",
-      binaryMessenger: binaryMessenger)
+      binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       echoChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
@@ -3315,7 +3318,7 @@ class HostSmallApiSetup {
     }
     let voidVoidChannel = FlutterBasicMessageChannel(
       name: "dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.voidVoid\(channelSuffix)",
-      binaryMessenger: binaryMessenger)
+      binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       voidVoidChannel.setMessageHandler { _, reply in
         api.voidVoid { result in
@@ -3332,42 +3335,6 @@ class HostSmallApiSetup {
     }
   }
 }
-private class FlutterSmallApiCodecReader: FlutterStandardReader {
-  override func readValue(ofType type: UInt8) -> Any? {
-    switch type {
-    case 128:
-      return TestMessage.fromList(self.readValue() as! [Any?])
-    default:
-      return super.readValue(ofType: type)
-    }
-  }
-}
-
-private class FlutterSmallApiCodecWriter: FlutterStandardWriter {
-  override func writeValue(_ value: Any) {
-    if let value = value as? TestMessage {
-      super.writeByte(128)
-      super.writeValue(value.toList())
-    } else {
-      super.writeValue(value)
-    }
-  }
-}
-
-private class FlutterSmallApiCodecReaderWriter: FlutterStandardReaderWriter {
-  override func reader(with data: Data) -> FlutterStandardReader {
-    return FlutterSmallApiCodecReader(data: data)
-  }
-
-  override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return FlutterSmallApiCodecWriter(data: data)
-  }
-}
-
-class FlutterSmallApiCodec: FlutterStandardMessageCodec {
-  static let shared = FlutterSmallApiCodec(readerWriter: FlutterSmallApiCodecReaderWriter())
-}
-
 /// A simple API called in some unit tests.
 ///
 /// Generated protocol from Pigeon that represents Flutter messages that can be called from Swift.
@@ -3382,8 +3349,8 @@ class FlutterSmallApi: FlutterSmallApiProtocol {
     self.binaryMessenger = binaryMessenger
     self.messageChannelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
   }
-  var codec: FlutterStandardMessageCodec {
-    return FlutterSmallApiCodec.shared
+  var codec: CoreTestsPigeonCodec {
+    return CoreTestsPigeonCodec.shared
   }
   func echo(_ msgArg: TestMessage, completion: @escaping (Result<TestMessage, PigeonError>) -> Void)
   {
diff --git a/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift b/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift
index c54100d2db4..2b95f040b48 100644
--- a/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift
+++ b/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift
@@ -94,11 +94,15 @@ struct AllTypes {
   var a4ByteArray: FlutterStandardTypedData
   var a8ByteArray: FlutterStandardTypedData
   var aFloatArray: FlutterStandardTypedData
-  var list: [Any?]
-  var aMap: [AnyHashable: Any?]
   var anEnum: AnEnum
   var aString: String
   var anObject: Any
+  var list: [Any?]
+  var stringList: [String?]
+  var intList: [Int64?]
+  var doubleList: [Double?]
+  var boolList: [Bool?]
+  var map: [AnyHashable: Any?]
 
   // swift-format-ignore: AlwaysUseLowerCamelCase
   static func fromList(_ __pigeon_list: [Any?]) -> AllTypes? {
@@ -112,11 +116,15 @@ struct AllTypes {
     let a4ByteArray = __pigeon_list[5] as! FlutterStandardTypedData
     let a8ByteArray = __pigeon_list[6] as! FlutterStandardTypedData
     let aFloatArray = __pigeon_list[7] as! FlutterStandardTypedData
-    let list = __pigeon_list[8] as! [Any?]
-    let aMap = __pigeon_list[9] as! [AnyHashable: Any?]
-    let anEnum = AnEnum(rawValue: __pigeon_list[10] as! Int)!
-    let aString = __pigeon_list[11] as! String
-    let anObject = __pigeon_list[12]!
+    let anEnum = __pigeon_list[8] as! AnEnum
+    let aString = __pigeon_list[9] as! String
+    let anObject = __pigeon_list[10]!
+    let list = __pigeon_list[11] as! [Any?]
+    let stringList = __pigeon_list[12] as! [String?]
+    let intList = __pigeon_list[13] as! [Int64?]
+    let doubleList = __pigeon_list[14] as! [Double?]
+    let boolList = __pigeon_list[15] as! [Bool?]
+    let map = __pigeon_list[16] as! [AnyHashable: Any?]
 
     return AllTypes(
       aBool: aBool,
@@ -127,11 +135,15 @@ struct AllTypes {
       a4ByteArray: a4ByteArray,
       a8ByteArray: a8ByteArray,
       aFloatArray: aFloatArray,
-      list: list,
-      aMap: aMap,
       anEnum: anEnum,
       aString: aString,
-      anObject: anObject
+      anObject: anObject,
+      list: list,
+      stringList: stringList,
+      intList: intList,
+      doubleList: doubleList,
+      boolList: boolList,
+      map: map
     )
   }
   func toList() -> [Any?] {
@@ -144,11 +156,15 @@ struct AllTypes {
       a4ByteArray,
       a8ByteArray,
       aFloatArray,
-      list,
-      aMap,
-      anEnum.rawValue,
+      anEnum,
       aString,
       anObject,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      map,
     ]
   }
 }
@@ -166,15 +182,20 @@ class AllNullableTypes {
     aNullable4ByteArray: FlutterStandardTypedData? = nil,
     aNullable8ByteArray: FlutterStandardTypedData? = nil,
     aNullableFloatArray: FlutterStandardTypedData? = nil,
-    aNullableList: [Any?]? = nil,
-    aNullableMap: [AnyHashable: Any?]? = nil,
     nullableNestedList: [[Bool?]?]? = nil,
     nullableMapWithAnnotations: [String?: String?]? = nil,
     nullableMapWithObject: [String?: Any?]? = nil,
     aNullableEnum: AnEnum? = nil,
     aNullableString: String? = nil,
     aNullableObject: Any? = nil,
-    allNullableTypes: AllNullableTypes? = nil
+    allNullableTypes: AllNullableTypes? = nil,
+    list: [Any?]? = nil,
+    stringList: [String?]? = nil,
+    intList: [Int64?]? = nil,
+    doubleList: [Double?]? = nil,
+    boolList: [Bool?]? = nil,
+    nestedClassList: [AllNullableTypes?]? = nil,
+    map: [AnyHashable: Any?]? = nil
   ) {
     self.aNullableBool = aNullableBool
     self.aNullableInt = aNullableInt
@@ -184,8 +205,6 @@ class AllNullableTypes {
     self.aNullable4ByteArray = aNullable4ByteArray
     self.aNullable8ByteArray = aNullable8ByteArray
     self.aNullableFloatArray = aNullableFloatArray
-    self.aNullableList = aNullableList
-    self.aNullableMap = aNullableMap
     self.nullableNestedList = nullableNestedList
     self.nullableMapWithAnnotations = nullableMapWithAnnotations
     self.nullableMapWithObject = nullableMapWithObject
@@ -193,6 +212,13 @@ class AllNullableTypes {
     self.aNullableString = aNullableString
     self.aNullableObject = aNullableObject
     self.allNullableTypes = allNullableTypes
+    self.list = list
+    self.stringList = stringList
+    self.intList = intList
+    self.doubleList = doubleList
+    self.boolList = boolList
+    self.nestedClassList = nestedClassList
+    self.map = map
   }
   var aNullableBool: Bool?
   var aNullableInt: Int64?
@@ -202,8 +228,6 @@ class AllNullableTypes {
   var aNullable4ByteArray: FlutterStandardTypedData?
   var aNullable8ByteArray: FlutterStandardTypedData?
   var aNullableFloatArray: FlutterStandardTypedData?
-  var aNullableList: [Any?]?
-  var aNullableMap: [AnyHashable: Any?]?
   var nullableNestedList: [[Bool?]?]?
   var nullableMapWithAnnotations: [String?: String?]?
   var nullableMapWithObject: [String?: Any?]?
@@ -211,6 +235,13 @@ class AllNullableTypes {
   var aNullableString: String?
   var aNullableObject: Any?
   var allNullableTypes: AllNullableTypes?
+  var list: [Any?]?
+  var stringList: [String?]?
+  var intList: [Int64?]?
+  var doubleList: [Double?]?
+  var boolList: [Bool?]?
+  var nestedClassList: [AllNullableTypes?]?
+  var map: [AnyHashable: Any?]?
 
   // swift-format-ignore: AlwaysUseLowerCamelCase
   static func fromList(_ __pigeon_list: [Any?]) -> AllNullableTypes? {
@@ -230,19 +261,20 @@ class AllNullableTypes {
     let aNullable4ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[5])
     let aNullable8ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[6])
     let aNullableFloatArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[7])
-    let aNullableList: [Any?]? = nilOrValue(__pigeon_list[8])
-    let aNullableMap: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[9])
-    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[10])
-    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[11])
-    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[12])
-    var aNullableEnum: AnEnum? = nil
-    let aNullableEnumEnumVal: Int? = nilOrValue(__pigeon_list[13])
-    if let aNullableEnumRawValue = aNullableEnumEnumVal {
-      aNullableEnum = AnEnum(rawValue: aNullableEnumRawValue)!
-    }
-    let aNullableString: String? = nilOrValue(__pigeon_list[14])
-    let aNullableObject: Any? = __pigeon_list[15]
-    let allNullableTypes: AllNullableTypes? = nilOrValue(__pigeon_list[16])
+    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[8])
+    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[9])
+    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[10])
+    let aNullableEnum: AnEnum? = nilOrValue(__pigeon_list[11])
+    let aNullableString: String? = nilOrValue(__pigeon_list[12])
+    let aNullableObject: Any? = __pigeon_list[13]
+    let allNullableTypes: AllNullableTypes? = nilOrValue(__pigeon_list[14])
+    let list: [Any?]? = nilOrValue(__pigeon_list[15])
+    let stringList: [String?]? = nilOrValue(__pigeon_list[16])
+    let intList: [Int64?]? = nilOrValue(__pigeon_list[17])
+    let doubleList: [Double?]? = nilOrValue(__pigeon_list[18])
+    let boolList: [Bool?]? = nilOrValue(__pigeon_list[19])
+    let nestedClassList: [AllNullableTypes?]? = nilOrValue(__pigeon_list[20])
+    let map: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[21])
 
     return AllNullableTypes(
       aNullableBool: aNullableBool,
@@ -253,15 +285,20 @@ class AllNullableTypes {
       aNullable4ByteArray: aNullable4ByteArray,
       aNullable8ByteArray: aNullable8ByteArray,
       aNullableFloatArray: aNullableFloatArray,
-      aNullableList: aNullableList,
-      aNullableMap: aNullableMap,
       nullableNestedList: nullableNestedList,
       nullableMapWithAnnotations: nullableMapWithAnnotations,
       nullableMapWithObject: nullableMapWithObject,
       aNullableEnum: aNullableEnum,
       aNullableString: aNullableString,
       aNullableObject: aNullableObject,
-      allNullableTypes: allNullableTypes
+      allNullableTypes: allNullableTypes,
+      list: list,
+      stringList: stringList,
+      intList: intList,
+      doubleList: doubleList,
+      boolList: boolList,
+      nestedClassList: nestedClassList,
+      map: map
     )
   }
   func toList() -> [Any?] {
@@ -274,15 +311,20 @@ class AllNullableTypes {
       aNullable4ByteArray,
       aNullable8ByteArray,
       aNullableFloatArray,
-      aNullableList,
-      aNullableMap,
       nullableNestedList,
       nullableMapWithAnnotations,
       nullableMapWithObject,
-      aNullableEnum?.rawValue,
+      aNullableEnum,
       aNullableString,
       aNullableObject,
       allNullableTypes,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      nestedClassList,
+      map,
     ]
   }
 }
@@ -301,14 +343,18 @@ struct AllNullableTypesWithoutRecursion {
   var aNullable4ByteArray: FlutterStandardTypedData? = nil
   var aNullable8ByteArray: FlutterStandardTypedData? = nil
   var aNullableFloatArray: FlutterStandardTypedData? = nil
-  var aNullableList: [Any?]? = nil
-  var aNullableMap: [AnyHashable: Any?]? = nil
   var nullableNestedList: [[Bool?]?]? = nil
   var nullableMapWithAnnotations: [String?: String?]? = nil
   var nullableMapWithObject: [String?: Any?]? = nil
   var aNullableEnum: AnEnum? = nil
   var aNullableString: String? = nil
   var aNullableObject: Any? = nil
+  var list: [Any?]? = nil
+  var stringList: [String?]? = nil
+  var intList: [Int64?]? = nil
+  var doubleList: [Double?]? = nil
+  var boolList: [Bool?]? = nil
+  var map: [AnyHashable: Any?]? = nil
 
   // swift-format-ignore: AlwaysUseLowerCamelCase
   static func fromList(_ __pigeon_list: [Any?]) -> AllNullableTypesWithoutRecursion? {
@@ -328,18 +374,18 @@ struct AllNullableTypesWithoutRecursion {
     let aNullable4ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[5])
     let aNullable8ByteArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[6])
     let aNullableFloatArray: FlutterStandardTypedData? = nilOrValue(__pigeon_list[7])
-    let aNullableList: [Any?]? = nilOrValue(__pigeon_list[8])
-    let aNullableMap: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[9])
-    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[10])
-    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[11])
-    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[12])
-    var aNullableEnum: AnEnum? = nil
-    let aNullableEnumEnumVal: Int? = nilOrValue(__pigeon_list[13])
-    if let aNullableEnumRawValue = aNullableEnumEnumVal {
-      aNullableEnum = AnEnum(rawValue: aNullableEnumRawValue)!
-    }
-    let aNullableString: String? = nilOrValue(__pigeon_list[14])
-    let aNullableObject: Any? = __pigeon_list[15]
+    let nullableNestedList: [[Bool?]?]? = nilOrValue(__pigeon_list[8])
+    let nullableMapWithAnnotations: [String?: String?]? = nilOrValue(__pigeon_list[9])
+    let nullableMapWithObject: [String?: Any?]? = nilOrValue(__pigeon_list[10])
+    let aNullableEnum: AnEnum? = nilOrValue(__pigeon_list[11])
+    let aNullableString: String? = nilOrValue(__pigeon_list[12])
+    let aNullableObject: Any? = __pigeon_list[13]
+    let list: [Any?]? = nilOrValue(__pigeon_list[14])
+    let stringList: [String?]? = nilOrValue(__pigeon_list[15])
+    let intList: [Int64?]? = nilOrValue(__pigeon_list[16])
+    let doubleList: [Double?]? = nilOrValue(__pigeon_list[17])
+    let boolList: [Bool?]? = nilOrValue(__pigeon_list[18])
+    let map: [AnyHashable: Any?]? = nilOrValue(__pigeon_list[19])
 
     return AllNullableTypesWithoutRecursion(
       aNullableBool: aNullableBool,
@@ -350,14 +396,18 @@ struct AllNullableTypesWithoutRecursion {
       aNullable4ByteArray: aNullable4ByteArray,
       aNullable8ByteArray: aNullable8ByteArray,
       aNullableFloatArray: aNullableFloatArray,
-      aNullableList: aNullableList,
-      aNullableMap: aNullableMap,
       nullableNestedList: nullableNestedList,
       nullableMapWithAnnotations: nullableMapWithAnnotations,
       nullableMapWithObject: nullableMapWithObject,
       aNullableEnum: aNullableEnum,
       aNullableString: aNullableString,
-      aNullableObject: aNullableObject
+      aNullableObject: aNullableObject,
+      list: list,
+      stringList: stringList,
+      intList: intList,
+      doubleList: doubleList,
+      boolList: boolList,
+      map: map
     )
   }
   func toList() -> [Any?] {
@@ -370,14 +420,18 @@ struct AllNullableTypesWithoutRecursion {
       aNullable4ByteArray,
       aNullable8ByteArray,
       aNullableFloatArray,
-      aNullableList,
-      aNullableMap,
       nullableNestedList,
       nullableMapWithAnnotations,
       nullableMapWithObject,
-      aNullableEnum?.rawValue,
+      aNullableEnum,
       aNullableString,
       aNullableObject,
+      list,
+      stringList,
+      intList,
+      doubleList,
+      boolList,
+      map,
     ]
   }
 }
@@ -436,62 +490,70 @@ struct TestMessage {
     ]
   }
 }
-
-private class HostIntegrationCoreApiCodecReader: FlutterStandardReader {
+private class CoreTestsPigeonCodecReader: FlutterStandardReader {
   override func readValue(ofType type: UInt8) -> Any? {
     switch type {
-    case 128:
-      return AllClassesWrapper.fromList(self.readValue() as! [Any?])
     case 129:
-      return AllNullableTypes.fromList(self.readValue() as! [Any?])
+      return AllTypes.fromList(self.readValue() as! [Any?])
     case 130:
-      return AllNullableTypesWithoutRecursion.fromList(self.readValue() as! [Any?])
+      return AllNullableTypes.fromList(self.readValue() as! [Any?])
     case 131:
-      return AllTypes.fromList(self.readValue() as! [Any?])
+      return AllNullableTypesWithoutRecursion.fromList(self.readValue() as! [Any?])
     case 132:
+      return AllClassesWrapper.fromList(self.readValue() as! [Any?])
+    case 133:
       return TestMessage.fromList(self.readValue() as! [Any?])
+    case 134:
+      var enumResult: AnEnum? = nil
+      let enumResultAsInt: Int? = nilOrValue(self.readValue() as? Int)
+      if let enumResultAsInt = enumResultAsInt {
+        enumResult = AnEnum(rawValue: enumResultAsInt)
+      }
+      return enumResult
     default:
       return super.readValue(ofType: type)
     }
   }
 }
 
-private class HostIntegrationCoreApiCodecWriter: FlutterStandardWriter {
+private class CoreTestsPigeonCodecWriter: FlutterStandardWriter {
   override func writeValue(_ value: Any) {
-    if let value = value as? AllClassesWrapper {
-      super.writeByte(128)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypes {
+    if let value = value as? AllTypes {
       super.writeByte(129)
       super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypesWithoutRecursion {
+    } else if let value = value as? AllNullableTypes {
       super.writeByte(130)
       super.writeValue(value.toList())
-    } else if let value = value as? AllTypes {
+    } else if let value = value as? AllNullableTypesWithoutRecursion {
       super.writeByte(131)
       super.writeValue(value.toList())
-    } else if let value = value as? TestMessage {
+    } else if let value = value as? AllClassesWrapper {
       super.writeByte(132)
       super.writeValue(value.toList())
+    } else if let value = value as? TestMessage {
+      super.writeByte(133)
+      super.writeValue(value.toList())
+    } else if let value = value as? AnEnum {
+      super.writeByte(134)
+      super.writeValue(value.rawValue)
     } else {
       super.writeValue(value)
     }
   }
 }
 
-private class HostIntegrationCoreApiCodecReaderWriter: FlutterStandardReaderWriter {
+private class CoreTestsPigeonCodecReaderWriter: FlutterStandardReaderWriter {
   override func reader(with data: Data) -> FlutterStandardReader {
-    return HostIntegrationCoreApiCodecReader(data: data)
+    return CoreTestsPigeonCodecReader(data: data)
   }
 
   override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return HostIntegrationCoreApiCodecWriter(data: data)
+    return CoreTestsPigeonCodecWriter(data: data)
   }
 }
 
-class HostIntegrationCoreApiCodec: FlutterStandardMessageCodec {
-  static let shared = HostIntegrationCoreApiCodec(
-    readerWriter: HostIntegrationCoreApiCodecReaderWriter())
+class CoreTestsPigeonCodec: FlutterStandardMessageCodec, @unchecked Sendable {
+  static let shared = CoreTestsPigeonCodec(readerWriter: CoreTestsPigeonCodecReaderWriter())
 }
 
 /// The core interface that each host language plugin must implement in
@@ -687,8 +749,7 @@ protocol HostIntegrationCoreApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class HostIntegrationCoreApiSetup {
-  /// The codec used by HostIntegrationCoreApi.
-  static var codec: FlutterStandardMessageCodec { HostIntegrationCoreApiCodec.shared }
+  static var codec: FlutterStandardMessageCodec { CoreTestsPigeonCodec.shared }
   /// Sets up an instance of `HostIntegrationCoreApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: HostIntegrationCoreApi?,
@@ -962,10 +1023,10 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg = AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg = args[0] as! AnEnum
         do {
           let result = try api.echo(anEnumArg)
-          reply(wrapResult(result.rawValue))
+          reply(wrapResult(result))
         } catch {
           reply(wrapError(error))
         }
@@ -1317,10 +1378,10 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoNullableEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg: AnEnum? = isNullish(args[0]) ? nil : AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg: AnEnum? = nilOrValue(args[0])
         do {
           let result = try api.echoNullable(anEnumArg)
-          reply(wrapResult(result?.rawValue))
+          reply(wrapResult(result))
         } catch {
           reply(wrapError(error))
         }
@@ -1564,11 +1625,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoAsyncEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg = AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg = args[0] as! AnEnum
         api.echoAsync(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -1875,11 +1936,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       echoAsyncNullableEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg: AnEnum? = isNullish(args[0]) ? nil : AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg: AnEnum? = nilOrValue(args[0])
         api.echoAsyncNullable(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res?.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -2202,11 +2263,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       callFlutterEchoEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg = AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg = args[0] as! AnEnum
         api.callFlutterEcho(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -2364,11 +2425,11 @@ class HostIntegrationCoreApiSetup {
     if let api = api {
       callFlutterEchoNullableEnumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
-        let anEnumArg: AnEnum? = isNullish(args[0]) ? nil : AnEnum(rawValue: args[0] as! Int)!
+        let anEnumArg: AnEnum? = nilOrValue(args[0])
         api.callFlutterNullableEcho(anEnumArg) { result in
           switch result {
           case .success(let res):
-            reply(wrapResult(res?.rawValue))
+            reply(wrapResult(res))
           case .failure(let error):
             reply(wrapError(error))
           }
@@ -2399,63 +2460,6 @@ class HostIntegrationCoreApiSetup {
     }
   }
 }
-private class FlutterIntegrationCoreApiCodecReader: FlutterStandardReader {
-  override func readValue(ofType type: UInt8) -> Any? {
-    switch type {
-    case 128:
-      return AllClassesWrapper.fromList(self.readValue() as! [Any?])
-    case 129:
-      return AllNullableTypes.fromList(self.readValue() as! [Any?])
-    case 130:
-      return AllNullableTypesWithoutRecursion.fromList(self.readValue() as! [Any?])
-    case 131:
-      return AllTypes.fromList(self.readValue() as! [Any?])
-    case 132:
-      return TestMessage.fromList(self.readValue() as! [Any?])
-    default:
-      return super.readValue(ofType: type)
-    }
-  }
-}
-
-private class FlutterIntegrationCoreApiCodecWriter: FlutterStandardWriter {
-  override func writeValue(_ value: Any) {
-    if let value = value as? AllClassesWrapper {
-      super.writeByte(128)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypes {
-      super.writeByte(129)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllNullableTypesWithoutRecursion {
-      super.writeByte(130)
-      super.writeValue(value.toList())
-    } else if let value = value as? AllTypes {
-      super.writeByte(131)
-      super.writeValue(value.toList())
-    } else if let value = value as? TestMessage {
-      super.writeByte(132)
-      super.writeValue(value.toList())
-    } else {
-      super.writeValue(value)
-    }
-  }
-}
-
-private class FlutterIntegrationCoreApiCodecReaderWriter: FlutterStandardReaderWriter {
-  override func reader(with data: Data) -> FlutterStandardReader {
-    return FlutterIntegrationCoreApiCodecReader(data: data)
-  }
-
-  override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return FlutterIntegrationCoreApiCodecWriter(data: data)
-  }
-}
-
-class FlutterIntegrationCoreApiCodec: FlutterStandardMessageCodec {
-  static let shared = FlutterIntegrationCoreApiCodec(
-    readerWriter: FlutterIntegrationCoreApiCodecReaderWriter())
-}
-
 /// The core interface that the Dart platform_test code implements for host
 /// integration tests to call into.
 ///
@@ -2550,8 +2554,8 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
     self.binaryMessenger = binaryMessenger
     self.messageChannelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
   }
-  var codec: FlutterStandardMessageCodec {
-    return FlutterIntegrationCoreApiCodec.shared
+  var codec: CoreTestsPigeonCodec {
+    return CoreTestsPigeonCodec.shared
   }
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic calling.
@@ -2976,7 +2980,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
       "dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum\(messageChannelSuffix)"
     let channel = FlutterBasicMessageChannel(
       name: channelName, binaryMessenger: binaryMessenger, codec: codec)
-    channel.sendMessage([anEnumArg.rawValue] as [Any?]) { response in
+    channel.sendMessage([anEnumArg] as [Any?]) { response in
       guard let listResponse = response as? [Any?] else {
         completion(.failure(createConnectionError(withChannelName: channelName)))
         return
@@ -2993,7 +2997,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
               code: "null-error",
               message: "Flutter api returned null value for non-null return value.", details: "")))
       } else {
-        let result = AnEnum(rawValue: listResponse[0] as! Int)!
+        let result = listResponse[0] as! AnEnum
         completion(.success(result))
       }
     }
@@ -3177,7 +3181,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
       "dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableEnum\(messageChannelSuffix)"
     let channel = FlutterBasicMessageChannel(
       name: channelName, binaryMessenger: binaryMessenger, codec: codec)
-    channel.sendMessage([anEnumArg?.rawValue] as [Any?]) { response in
+    channel.sendMessage([anEnumArg] as [Any?]) { response in
       guard let listResponse = response as? [Any?] else {
         completion(.failure(createConnectionError(withChannelName: channelName)))
         return
@@ -3188,8 +3192,7 @@ class FlutterIntegrationCoreApi: FlutterIntegrationCoreApiProtocol {
         let details: String? = nilOrValue(listResponse[2])
         completion(.failure(PigeonError(code: code, message: message, details: details)))
       } else {
-        let result: AnEnum? =
-          isNullish(listResponse[0]) ? nil : AnEnum(rawValue: listResponse[0] as! Int)!
+        let result: AnEnum? = nilOrValue(listResponse[0])
         completion(.success(result))
       }
     }
@@ -3255,7 +3258,7 @@ protocol HostTrivialApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class HostTrivialApiSetup {
-  /// The codec used by HostTrivialApi.
+  static var codec: FlutterStandardMessageCodec { CoreTestsPigeonCodec.shared }
   /// Sets up an instance of `HostTrivialApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: HostTrivialApi?, messageChannelSuffix: String = ""
@@ -3263,7 +3266,7 @@ class HostTrivialApiSetup {
     let channelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
     let noopChannel = FlutterBasicMessageChannel(
       name: "dev.flutter.pigeon.pigeon_integration_tests.HostTrivialApi.noop\(channelSuffix)",
-      binaryMessenger: binaryMessenger)
+      binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       noopChannel.setMessageHandler { _, reply in
         do {
@@ -3288,7 +3291,7 @@ protocol HostSmallApi {
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
 class HostSmallApiSetup {
-  /// The codec used by HostSmallApi.
+  static var codec: FlutterStandardMessageCodec { CoreTestsPigeonCodec.shared }
   /// Sets up an instance of `HostSmallApi` to handle messages through the `binaryMessenger`.
   static func setUp(
     binaryMessenger: FlutterBinaryMessenger, api: HostSmallApi?, messageChannelSuffix: String = ""
@@ -3296,7 +3299,7 @@ class HostSmallApiSetup {
     let channelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
     let echoChannel = FlutterBasicMessageChannel(
       name: "dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo\(channelSuffix)",
-      binaryMessenger: binaryMessenger)
+      binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       echoChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
@@ -3315,7 +3318,7 @@ class HostSmallApiSetup {
     }
     let voidVoidChannel = FlutterBasicMessageChannel(
       name: "dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.voidVoid\(channelSuffix)",
-      binaryMessenger: binaryMessenger)
+      binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       voidVoidChannel.setMessageHandler { _, reply in
         api.voidVoid { result in
@@ -3332,42 +3335,6 @@ class HostSmallApiSetup {
     }
   }
 }
-private class FlutterSmallApiCodecReader: FlutterStandardReader {
-  override func readValue(ofType type: UInt8) -> Any? {
-    switch type {
-    case 128:
-      return TestMessage.fromList(self.readValue() as! [Any?])
-    default:
-      return super.readValue(ofType: type)
-    }
-  }
-}
-
-private class FlutterSmallApiCodecWriter: FlutterStandardWriter {
-  override func writeValue(_ value: Any) {
-    if let value = value as? TestMessage {
-      super.writeByte(128)
-      super.writeValue(value.toList())
-    } else {
-      super.writeValue(value)
-    }
-  }
-}
-
-private class FlutterSmallApiCodecReaderWriter: FlutterStandardReaderWriter {
-  override func reader(with data: Data) -> FlutterStandardReader {
-    return FlutterSmallApiCodecReader(data: data)
-  }
-
-  override func writer(with data: NSMutableData) -> FlutterStandardWriter {
-    return FlutterSmallApiCodecWriter(data: data)
-  }
-}
-
-class FlutterSmallApiCodec: FlutterStandardMessageCodec {
-  static let shared = FlutterSmallApiCodec(readerWriter: FlutterSmallApiCodecReaderWriter())
-}
-
 /// A simple API called in some unit tests.
 ///
 /// Generated protocol from Pigeon that represents Flutter messages that can be called from Swift.
@@ -3382,8 +3349,8 @@ class FlutterSmallApi: FlutterSmallApiProtocol {
     self.binaryMessenger = binaryMessenger
     self.messageChannelSuffix = messageChannelSuffix.count > 0 ? ".\(messageChannelSuffix)" : ""
   }
-  var codec: FlutterStandardMessageCodec {
-    return FlutterSmallApiCodec.shared
+  var codec: CoreTestsPigeonCodec {
+    return CoreTestsPigeonCodec.shared
   }
   func echo(_ msgArg: TestMessage, completion: @escaping (Result<TestMessage, PigeonError>) -> Void)
   {
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp
index c4e74f45119..ec06637957d 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp
+++ b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp
@@ -39,9 +39,12 @@ AllTypes::AllTypes(bool a_bool, int64_t an_int, int64_t an_int64,
                    const std::vector<int32_t>& a4_byte_array,
                    const std::vector<int64_t>& a8_byte_array,
                    const std::vector<double>& a_float_array,
-                   const EncodableList& list, const EncodableMap& a_map,
                    const AnEnum& an_enum, const std::string& a_string,
-                   const EncodableValue& an_object)
+                   const EncodableValue& an_object, const EncodableList& list,
+                   const EncodableList& string_list,
+                   const EncodableList& int_list,
+                   const EncodableList& double_list,
+                   const EncodableList& bool_list, const EncodableMap& map)
     : a_bool_(a_bool),
       an_int_(an_int),
       an_int64_(an_int64),
@@ -50,11 +53,15 @@ AllTypes::AllTypes(bool a_bool, int64_t an_int, int64_t an_int64,
       a4_byte_array_(a4_byte_array),
       a8_byte_array_(a8_byte_array),
       a_float_array_(a_float_array),
-      list_(list),
-      a_map_(a_map),
       an_enum_(an_enum),
       a_string_(a_string),
-      an_object_(an_object) {}
+      an_object_(an_object),
+      list_(list),
+      string_list_(string_list),
+      int_list_(int_list),
+      double_list_(double_list),
+      bool_list_(bool_list),
+      map_(map) {}
 
 bool AllTypes::a_bool() const { return a_bool_; }
 
@@ -104,14 +111,6 @@ void AllTypes::set_a_float_array(const std::vector<double>& value_arg) {
   a_float_array_ = value_arg;
 }
 
-const EncodableList& AllTypes::list() const { return list_; }
-
-void AllTypes::set_list(const EncodableList& value_arg) { list_ = value_arg; }
-
-const EncodableMap& AllTypes::a_map() const { return a_map_; }
-
-void AllTypes::set_a_map(const EncodableMap& value_arg) { a_map_ = value_arg; }
-
 const AnEnum& AllTypes::an_enum() const { return an_enum_; }
 
 void AllTypes::set_an_enum(const AnEnum& value_arg) { an_enum_ = value_arg; }
@@ -128,9 +127,41 @@ void AllTypes::set_an_object(const EncodableValue& value_arg) {
   an_object_ = value_arg;
 }
 
+const EncodableList& AllTypes::list() const { return list_; }
+
+void AllTypes::set_list(const EncodableList& value_arg) { list_ = value_arg; }
+
+const EncodableList& AllTypes::string_list() const { return string_list_; }
+
+void AllTypes::set_string_list(const EncodableList& value_arg) {
+  string_list_ = value_arg;
+}
+
+const EncodableList& AllTypes::int_list() const { return int_list_; }
+
+void AllTypes::set_int_list(const EncodableList& value_arg) {
+  int_list_ = value_arg;
+}
+
+const EncodableList& AllTypes::double_list() const { return double_list_; }
+
+void AllTypes::set_double_list(const EncodableList& value_arg) {
+  double_list_ = value_arg;
+}
+
+const EncodableList& AllTypes::bool_list() const { return bool_list_; }
+
+void AllTypes::set_bool_list(const EncodableList& value_arg) {
+  bool_list_ = value_arg;
+}
+
+const EncodableMap& AllTypes::map() const { return map_; }
+
+void AllTypes::set_map(const EncodableMap& value_arg) { map_ = value_arg; }
+
 EncodableList AllTypes::ToEncodableList() const {
   EncodableList list;
-  list.reserve(13);
+  list.reserve(17);
   list.push_back(EncodableValue(a_bool_));
   list.push_back(EncodableValue(an_int_));
   list.push_back(EncodableValue(an_int64_));
@@ -139,11 +170,15 @@ EncodableList AllTypes::ToEncodableList() const {
   list.push_back(EncodableValue(a4_byte_array_));
   list.push_back(EncodableValue(a8_byte_array_));
   list.push_back(EncodableValue(a_float_array_));
-  list.push_back(EncodableValue(list_));
-  list.push_back(EncodableValue(a_map_));
-  list.push_back(EncodableValue((int)an_enum_));
+  list.push_back(CustomEncodableValue(an_enum_));
   list.push_back(EncodableValue(a_string_));
   list.push_back(an_object_);
+  list.push_back(EncodableValue(list_));
+  list.push_back(EncodableValue(string_list_));
+  list.push_back(EncodableValue(int_list_));
+  list.push_back(EncodableValue(double_list_));
+  list.push_back(EncodableValue(bool_list_));
+  list.push_back(EncodableValue(map_));
   return list;
 }
 
@@ -153,9 +188,12 @@ AllTypes AllTypes::FromEncodableList(const EncodableList& list) {
       std::get<double>(list[3]), std::get<std::vector<uint8_t>>(list[4]),
       std::get<std::vector<int32_t>>(list[5]),
       std::get<std::vector<int64_t>>(list[6]),
-      std::get<std::vector<double>>(list[7]), std::get<EncodableList>(list[8]),
-      std::get<EncodableMap>(list[9]), (AnEnum)(std::get<int32_t>(list[10])),
-      std::get<std::string>(list[11]), list[12]);
+      std::get<std::vector<double>>(list[7]),
+      std::any_cast<const AnEnum&>(std::get<CustomEncodableValue>(list[8])),
+      std::get<std::string>(list[9]), list[10],
+      std::get<EncodableList>(list[11]), std::get<EncodableList>(list[12]),
+      std::get<EncodableList>(list[13]), std::get<EncodableList>(list[14]),
+      std::get<EncodableList>(list[15]), std::get<EncodableMap>(list[16]));
   return decoded;
 }
 
@@ -170,13 +208,15 @@ AllNullableTypes::AllNullableTypes(
     const std::vector<int32_t>* a_nullable4_byte_array,
     const std::vector<int64_t>* a_nullable8_byte_array,
     const std::vector<double>* a_nullable_float_array,
-    const EncodableList* a_nullable_list, const EncodableMap* a_nullable_map,
     const EncodableList* nullable_nested_list,
     const EncodableMap* nullable_map_with_annotations,
     const EncodableMap* nullable_map_with_object, const AnEnum* a_nullable_enum,
     const std::string* a_nullable_string,
     const EncodableValue* a_nullable_object,
-    const AllNullableTypes* all_nullable_types)
+    const AllNullableTypes* all_nullable_types, const EncodableList* list,
+    const EncodableList* string_list, const EncodableList* int_list,
+    const EncodableList* double_list, const EncodableList* bool_list,
+    const EncodableList* nested_class_list, const EncodableMap* map)
     : a_nullable_bool_(a_nullable_bool ? std::optional<bool>(*a_nullable_bool)
                                        : std::nullopt),
       a_nullable_int_(a_nullable_int ? std::optional<int64_t>(*a_nullable_int)
@@ -203,12 +243,6 @@ AllNullableTypes::AllNullableTypes(
           a_nullable_float_array
               ? std::optional<std::vector<double>>(*a_nullable_float_array)
               : std::nullopt),
-      a_nullable_list_(a_nullable_list
-                           ? std::optional<EncodableList>(*a_nullable_list)
-                           : std::nullopt),
-      a_nullable_map_(a_nullable_map
-                          ? std::optional<EncodableMap>(*a_nullable_map)
-                          : std::nullopt),
       nullable_nested_list_(nullable_nested_list ? std::optional<EncodableList>(
                                                        *nullable_nested_list)
                                                  : std::nullopt),
@@ -231,7 +265,20 @@ AllNullableTypes::AllNullableTypes(
       all_nullable_types_(
           all_nullable_types
               ? std::make_unique<AllNullableTypes>(*all_nullable_types)
-              : nullptr) {}
+              : nullptr),
+      list_(list ? std::optional<EncodableList>(*list) : std::nullopt),
+      string_list_(string_list ? std::optional<EncodableList>(*string_list)
+                               : std::nullopt),
+      int_list_(int_list ? std::optional<EncodableList>(*int_list)
+                         : std::nullopt),
+      double_list_(double_list ? std::optional<EncodableList>(*double_list)
+                               : std::nullopt),
+      bool_list_(bool_list ? std::optional<EncodableList>(*bool_list)
+                           : std::nullopt),
+      nested_class_list_(nested_class_list
+                             ? std::optional<EncodableList>(*nested_class_list)
+                             : std::nullopt),
+      map_(map ? std::optional<EncodableMap>(*map) : std::nullopt) {}
 
 AllNullableTypes::AllNullableTypes(const AllNullableTypes& other)
     : a_nullable_bool_(other.a_nullable_bool_
@@ -262,12 +309,6 @@ AllNullableTypes::AllNullableTypes(const AllNullableTypes& other)
                                   ? std::optional<std::vector<double>>(
                                         *other.a_nullable_float_array_)
                                   : std::nullopt),
-      a_nullable_list_(other.a_nullable_list_ ? std::optional<EncodableList>(
-                                                    *other.a_nullable_list_)
-                                              : std::nullopt),
-      a_nullable_map_(other.a_nullable_map_
-                          ? std::optional<EncodableMap>(*other.a_nullable_map_)
-                          : std::nullopt),
       nullable_nested_list_(
           other.nullable_nested_list_
               ? std::optional<EncodableList>(*other.nullable_nested_list_)
@@ -295,7 +336,26 @@ AllNullableTypes::AllNullableTypes(const AllNullableTypes& other)
       all_nullable_types_(
           other.all_nullable_types_
               ? std::make_unique<AllNullableTypes>(*other.all_nullable_types_)
-              : nullptr) {}
+              : nullptr),
+      list_(other.list_ ? std::optional<EncodableList>(*other.list_)
+                        : std::nullopt),
+      string_list_(other.string_list_
+                       ? std::optional<EncodableList>(*other.string_list_)
+                       : std::nullopt),
+      int_list_(other.int_list_ ? std::optional<EncodableList>(*other.int_list_)
+                                : std::nullopt),
+      double_list_(other.double_list_
+                       ? std::optional<EncodableList>(*other.double_list_)
+                       : std::nullopt),
+      bool_list_(other.bool_list_
+                     ? std::optional<EncodableList>(*other.bool_list_)
+                     : std::nullopt),
+      nested_class_list_(
+          other.nested_class_list_
+              ? std::optional<EncodableList>(*other.nested_class_list_)
+              : std::nullopt),
+      map_(other.map_ ? std::optional<EncodableMap>(*other.map_)
+                      : std::nullopt) {}
 
 AllNullableTypes& AllNullableTypes::operator=(const AllNullableTypes& other) {
   a_nullable_bool_ = other.a_nullable_bool_;
@@ -306,8 +366,6 @@ AllNullableTypes& AllNullableTypes::operator=(const AllNullableTypes& other) {
   a_nullable4_byte_array_ = other.a_nullable4_byte_array_;
   a_nullable8_byte_array_ = other.a_nullable8_byte_array_;
   a_nullable_float_array_ = other.a_nullable_float_array_;
-  a_nullable_list_ = other.a_nullable_list_;
-  a_nullable_map_ = other.a_nullable_map_;
   nullable_nested_list_ = other.nullable_nested_list_;
   nullable_map_with_annotations_ = other.nullable_map_with_annotations_;
   nullable_map_with_object_ = other.nullable_map_with_object_;
@@ -318,6 +376,13 @@ AllNullableTypes& AllNullableTypes::operator=(const AllNullableTypes& other) {
       other.all_nullable_types_
           ? std::make_unique<AllNullableTypes>(*other.all_nullable_types_)
           : nullptr;
+  list_ = other.list_;
+  string_list_ = other.string_list_;
+  int_list_ = other.int_list_;
+  double_list_ = other.double_list_;
+  bool_list_ = other.bool_list_;
+  nested_class_list_ = other.nested_class_list_;
+  map_ = other.map_;
   return *this;
 }
 
@@ -435,32 +500,6 @@ void AllNullableTypes::set_a_nullable_float_array(
   a_nullable_float_array_ = value_arg;
 }
 
-const EncodableList* AllNullableTypes::a_nullable_list() const {
-  return a_nullable_list_ ? &(*a_nullable_list_) : nullptr;
-}
-
-void AllNullableTypes::set_a_nullable_list(const EncodableList* value_arg) {
-  a_nullable_list_ =
-      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
-}
-
-void AllNullableTypes::set_a_nullable_list(const EncodableList& value_arg) {
-  a_nullable_list_ = value_arg;
-}
-
-const EncodableMap* AllNullableTypes::a_nullable_map() const {
-  return a_nullable_map_ ? &(*a_nullable_map_) : nullptr;
-}
-
-void AllNullableTypes::set_a_nullable_map(const EncodableMap* value_arg) {
-  a_nullable_map_ =
-      value_arg ? std::optional<EncodableMap>(*value_arg) : std::nullopt;
-}
-
-void AllNullableTypes::set_a_nullable_map(const EncodableMap& value_arg) {
-  a_nullable_map_ = value_arg;
-}
-
 const EncodableList* AllNullableTypes::nullable_nested_list() const {
   return nullable_nested_list_ ? &(*nullable_nested_list_) : nullptr;
 }
@@ -562,9 +601,98 @@ void AllNullableTypes::set_all_nullable_types(
   all_nullable_types_ = std::make_unique<AllNullableTypes>(value_arg);
 }
 
+const EncodableList* AllNullableTypes::list() const {
+  return list_ ? &(*list_) : nullptr;
+}
+
+void AllNullableTypes::set_list(const EncodableList* value_arg) {
+  list_ = value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_list(const EncodableList& value_arg) {
+  list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypes::string_list() const {
+  return string_list_ ? &(*string_list_) : nullptr;
+}
+
+void AllNullableTypes::set_string_list(const EncodableList* value_arg) {
+  string_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_string_list(const EncodableList& value_arg) {
+  string_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypes::int_list() const {
+  return int_list_ ? &(*int_list_) : nullptr;
+}
+
+void AllNullableTypes::set_int_list(const EncodableList* value_arg) {
+  int_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_int_list(const EncodableList& value_arg) {
+  int_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypes::double_list() const {
+  return double_list_ ? &(*double_list_) : nullptr;
+}
+
+void AllNullableTypes::set_double_list(const EncodableList* value_arg) {
+  double_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_double_list(const EncodableList& value_arg) {
+  double_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypes::bool_list() const {
+  return bool_list_ ? &(*bool_list_) : nullptr;
+}
+
+void AllNullableTypes::set_bool_list(const EncodableList* value_arg) {
+  bool_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_bool_list(const EncodableList& value_arg) {
+  bool_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypes::nested_class_list() const {
+  return nested_class_list_ ? &(*nested_class_list_) : nullptr;
+}
+
+void AllNullableTypes::set_nested_class_list(const EncodableList* value_arg) {
+  nested_class_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_nested_class_list(const EncodableList& value_arg) {
+  nested_class_list_ = value_arg;
+}
+
+const EncodableMap* AllNullableTypes::map() const {
+  return map_ ? &(*map_) : nullptr;
+}
+
+void AllNullableTypes::set_map(const EncodableMap* value_arg) {
+  map_ = value_arg ? std::optional<EncodableMap>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypes::set_map(const EncodableMap& value_arg) {
+  map_ = value_arg;
+}
+
 EncodableList AllNullableTypes::ToEncodableList() const {
   EncodableList list;
-  list.reserve(17);
+  list.reserve(22);
   list.push_back(a_nullable_bool_ ? EncodableValue(*a_nullable_bool_)
                                   : EncodableValue());
   list.push_back(a_nullable_int_ ? EncodableValue(*a_nullable_int_)
@@ -585,10 +713,6 @@ EncodableList AllNullableTypes::ToEncodableList() const {
   list.push_back(a_nullable_float_array_
                      ? EncodableValue(*a_nullable_float_array_)
                      : EncodableValue());
-  list.push_back(a_nullable_list_ ? EncodableValue(*a_nullable_list_)
-                                  : EncodableValue());
-  list.push_back(a_nullable_map_ ? EncodableValue(*a_nullable_map_)
-                                 : EncodableValue());
   list.push_back(nullable_nested_list_ ? EncodableValue(*nullable_nested_list_)
                                        : EncodableValue());
   list.push_back(nullable_map_with_annotations_
@@ -597,7 +721,7 @@ EncodableList AllNullableTypes::ToEncodableList() const {
   list.push_back(nullable_map_with_object_
                      ? EncodableValue(*nullable_map_with_object_)
                      : EncodableValue());
-  list.push_back(a_nullable_enum_ ? EncodableValue((int)(*a_nullable_enum_))
+  list.push_back(a_nullable_enum_ ? CustomEncodableValue(*a_nullable_enum_)
                                   : EncodableValue());
   list.push_back(a_nullable_string_ ? EncodableValue(*a_nullable_string_)
                                     : EncodableValue());
@@ -605,6 +729,16 @@ EncodableList AllNullableTypes::ToEncodableList() const {
   list.push_back(all_nullable_types_
                      ? CustomEncodableValue(*all_nullable_types_)
                      : EncodableValue());
+  list.push_back(list_ ? EncodableValue(*list_) : EncodableValue());
+  list.push_back(string_list_ ? EncodableValue(*string_list_)
+                              : EncodableValue());
+  list.push_back(int_list_ ? EncodableValue(*int_list_) : EncodableValue());
+  list.push_back(double_list_ ? EncodableValue(*double_list_)
+                              : EncodableValue());
+  list.push_back(bool_list_ ? EncodableValue(*bool_list_) : EncodableValue());
+  list.push_back(nested_class_list_ ? EncodableValue(*nested_class_list_)
+                                    : EncodableValue());
+  list.push_back(map_ ? EncodableValue(*map_) : EncodableValue());
   return list;
 }
 
@@ -648,50 +782,69 @@ AllNullableTypes AllNullableTypes::FromEncodableList(
     decoded.set_a_nullable_float_array(
         std::get<std::vector<double>>(encodable_a_nullable_float_array));
   }
-  auto& encodable_a_nullable_list = list[8];
-  if (!encodable_a_nullable_list.IsNull()) {
-    decoded.set_a_nullable_list(
-        std::get<EncodableList>(encodable_a_nullable_list));
-  }
-  auto& encodable_a_nullable_map = list[9];
-  if (!encodable_a_nullable_map.IsNull()) {
-    decoded.set_a_nullable_map(
-        std::get<EncodableMap>(encodable_a_nullable_map));
-  }
-  auto& encodable_nullable_nested_list = list[10];
+  auto& encodable_nullable_nested_list = list[8];
   if (!encodable_nullable_nested_list.IsNull()) {
     decoded.set_nullable_nested_list(
         std::get<EncodableList>(encodable_nullable_nested_list));
   }
-  auto& encodable_nullable_map_with_annotations = list[11];
+  auto& encodable_nullable_map_with_annotations = list[9];
   if (!encodable_nullable_map_with_annotations.IsNull()) {
     decoded.set_nullable_map_with_annotations(
         std::get<EncodableMap>(encodable_nullable_map_with_annotations));
   }
-  auto& encodable_nullable_map_with_object = list[12];
+  auto& encodable_nullable_map_with_object = list[10];
   if (!encodable_nullable_map_with_object.IsNull()) {
     decoded.set_nullable_map_with_object(
         std::get<EncodableMap>(encodable_nullable_map_with_object));
   }
-  auto& encodable_a_nullable_enum = list[13];
+  auto& encodable_a_nullable_enum = list[11];
   if (!encodable_a_nullable_enum.IsNull()) {
-    decoded.set_a_nullable_enum(
-        (AnEnum)(std::get<int32_t>(encodable_a_nullable_enum)));
+    decoded.set_a_nullable_enum(std::any_cast<const AnEnum&>(
+        std::get<CustomEncodableValue>(encodable_a_nullable_enum)));
   }
-  auto& encodable_a_nullable_string = list[14];
+  auto& encodable_a_nullable_string = list[12];
   if (!encodable_a_nullable_string.IsNull()) {
     decoded.set_a_nullable_string(
         std::get<std::string>(encodable_a_nullable_string));
   }
-  auto& encodable_a_nullable_object = list[15];
+  auto& encodable_a_nullable_object = list[13];
   if (!encodable_a_nullable_object.IsNull()) {
     decoded.set_a_nullable_object(encodable_a_nullable_object);
   }
-  auto& encodable_all_nullable_types = list[16];
+  auto& encodable_all_nullable_types = list[14];
   if (!encodable_all_nullable_types.IsNull()) {
     decoded.set_all_nullable_types(std::any_cast<const AllNullableTypes&>(
         std::get<CustomEncodableValue>(encodable_all_nullable_types)));
   }
+  auto& encodable_list = list[15];
+  if (!encodable_list.IsNull()) {
+    decoded.set_list(std::get<EncodableList>(encodable_list));
+  }
+  auto& encodable_string_list = list[16];
+  if (!encodable_string_list.IsNull()) {
+    decoded.set_string_list(std::get<EncodableList>(encodable_string_list));
+  }
+  auto& encodable_int_list = list[17];
+  if (!encodable_int_list.IsNull()) {
+    decoded.set_int_list(std::get<EncodableList>(encodable_int_list));
+  }
+  auto& encodable_double_list = list[18];
+  if (!encodable_double_list.IsNull()) {
+    decoded.set_double_list(std::get<EncodableList>(encodable_double_list));
+  }
+  auto& encodable_bool_list = list[19];
+  if (!encodable_bool_list.IsNull()) {
+    decoded.set_bool_list(std::get<EncodableList>(encodable_bool_list));
+  }
+  auto& encodable_nested_class_list = list[20];
+  if (!encodable_nested_class_list.IsNull()) {
+    decoded.set_nested_class_list(
+        std::get<EncodableList>(encodable_nested_class_list));
+  }
+  auto& encodable_map = list[21];
+  if (!encodable_map.IsNull()) {
+    decoded.set_map(std::get<EncodableMap>(encodable_map));
+  }
   return decoded;
 }
 
@@ -706,12 +859,14 @@ AllNullableTypesWithoutRecursion::AllNullableTypesWithoutRecursion(
     const std::vector<int32_t>* a_nullable4_byte_array,
     const std::vector<int64_t>* a_nullable8_byte_array,
     const std::vector<double>* a_nullable_float_array,
-    const EncodableList* a_nullable_list, const EncodableMap* a_nullable_map,
     const EncodableList* nullable_nested_list,
     const EncodableMap* nullable_map_with_annotations,
     const EncodableMap* nullable_map_with_object, const AnEnum* a_nullable_enum,
     const std::string* a_nullable_string,
-    const EncodableValue* a_nullable_object)
+    const EncodableValue* a_nullable_object, const EncodableList* list,
+    const EncodableList* string_list, const EncodableList* int_list,
+    const EncodableList* double_list, const EncodableList* bool_list,
+    const EncodableMap* map)
     : a_nullable_bool_(a_nullable_bool ? std::optional<bool>(*a_nullable_bool)
                                        : std::nullopt),
       a_nullable_int_(a_nullable_int ? std::optional<int64_t>(*a_nullable_int)
@@ -738,12 +893,6 @@ AllNullableTypesWithoutRecursion::AllNullableTypesWithoutRecursion(
           a_nullable_float_array
               ? std::optional<std::vector<double>>(*a_nullable_float_array)
               : std::nullopt),
-      a_nullable_list_(a_nullable_list
-                           ? std::optional<EncodableList>(*a_nullable_list)
-                           : std::nullopt),
-      a_nullable_map_(a_nullable_map
-                          ? std::optional<EncodableMap>(*a_nullable_map)
-                          : std::nullopt),
       nullable_nested_list_(nullable_nested_list ? std::optional<EncodableList>(
                                                        *nullable_nested_list)
                                                  : std::nullopt),
@@ -762,7 +911,17 @@ AllNullableTypesWithoutRecursion::AllNullableTypesWithoutRecursion(
                              : std::nullopt),
       a_nullable_object_(a_nullable_object
                              ? std::optional<EncodableValue>(*a_nullable_object)
-                             : std::nullopt) {}
+                             : std::nullopt),
+      list_(list ? std::optional<EncodableList>(*list) : std::nullopt),
+      string_list_(string_list ? std::optional<EncodableList>(*string_list)
+                               : std::nullopt),
+      int_list_(int_list ? std::optional<EncodableList>(*int_list)
+                         : std::nullopt),
+      double_list_(double_list ? std::optional<EncodableList>(*double_list)
+                               : std::nullopt),
+      bool_list_(bool_list ? std::optional<EncodableList>(*bool_list)
+                           : std::nullopt),
+      map_(map ? std::optional<EncodableMap>(*map) : std::nullopt) {}
 
 const bool* AllNullableTypesWithoutRecursion::a_nullable_bool() const {
   return a_nullable_bool_ ? &(*a_nullable_bool_) : nullptr;
@@ -886,36 +1045,6 @@ void AllNullableTypesWithoutRecursion::set_a_nullable_float_array(
   a_nullable_float_array_ = value_arg;
 }
 
-const EncodableList* AllNullableTypesWithoutRecursion::a_nullable_list() const {
-  return a_nullable_list_ ? &(*a_nullable_list_) : nullptr;
-}
-
-void AllNullableTypesWithoutRecursion::set_a_nullable_list(
-    const EncodableList* value_arg) {
-  a_nullable_list_ =
-      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
-}
-
-void AllNullableTypesWithoutRecursion::set_a_nullable_list(
-    const EncodableList& value_arg) {
-  a_nullable_list_ = value_arg;
-}
-
-const EncodableMap* AllNullableTypesWithoutRecursion::a_nullable_map() const {
-  return a_nullable_map_ ? &(*a_nullable_map_) : nullptr;
-}
-
-void AllNullableTypesWithoutRecursion::set_a_nullable_map(
-    const EncodableMap* value_arg) {
-  a_nullable_map_ =
-      value_arg ? std::optional<EncodableMap>(*value_arg) : std::nullopt;
-}
-
-void AllNullableTypesWithoutRecursion::set_a_nullable_map(
-    const EncodableMap& value_arg) {
-  a_nullable_map_ = value_arg;
-}
-
 const EncodableList* AllNullableTypesWithoutRecursion::nullable_nested_list()
     const {
   return nullable_nested_list_ ? &(*nullable_nested_list_) : nullptr;
@@ -1011,9 +1140,95 @@ void AllNullableTypesWithoutRecursion::set_a_nullable_object(
   a_nullable_object_ = value_arg;
 }
 
+const EncodableList* AllNullableTypesWithoutRecursion::list() const {
+  return list_ ? &(*list_) : nullptr;
+}
+
+void AllNullableTypesWithoutRecursion::set_list(
+    const EncodableList* value_arg) {
+  list_ = value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypesWithoutRecursion::set_list(
+    const EncodableList& value_arg) {
+  list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypesWithoutRecursion::string_list() const {
+  return string_list_ ? &(*string_list_) : nullptr;
+}
+
+void AllNullableTypesWithoutRecursion::set_string_list(
+    const EncodableList* value_arg) {
+  string_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypesWithoutRecursion::set_string_list(
+    const EncodableList& value_arg) {
+  string_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypesWithoutRecursion::int_list() const {
+  return int_list_ ? &(*int_list_) : nullptr;
+}
+
+void AllNullableTypesWithoutRecursion::set_int_list(
+    const EncodableList* value_arg) {
+  int_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypesWithoutRecursion::set_int_list(
+    const EncodableList& value_arg) {
+  int_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypesWithoutRecursion::double_list() const {
+  return double_list_ ? &(*double_list_) : nullptr;
+}
+
+void AllNullableTypesWithoutRecursion::set_double_list(
+    const EncodableList* value_arg) {
+  double_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypesWithoutRecursion::set_double_list(
+    const EncodableList& value_arg) {
+  double_list_ = value_arg;
+}
+
+const EncodableList* AllNullableTypesWithoutRecursion::bool_list() const {
+  return bool_list_ ? &(*bool_list_) : nullptr;
+}
+
+void AllNullableTypesWithoutRecursion::set_bool_list(
+    const EncodableList* value_arg) {
+  bool_list_ =
+      value_arg ? std::optional<EncodableList>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypesWithoutRecursion::set_bool_list(
+    const EncodableList& value_arg) {
+  bool_list_ = value_arg;
+}
+
+const EncodableMap* AllNullableTypesWithoutRecursion::map() const {
+  return map_ ? &(*map_) : nullptr;
+}
+
+void AllNullableTypesWithoutRecursion::set_map(const EncodableMap* value_arg) {
+  map_ = value_arg ? std::optional<EncodableMap>(*value_arg) : std::nullopt;
+}
+
+void AllNullableTypesWithoutRecursion::set_map(const EncodableMap& value_arg) {
+  map_ = value_arg;
+}
+
 EncodableList AllNullableTypesWithoutRecursion::ToEncodableList() const {
   EncodableList list;
-  list.reserve(16);
+  list.reserve(20);
   list.push_back(a_nullable_bool_ ? EncodableValue(*a_nullable_bool_)
                                   : EncodableValue());
   list.push_back(a_nullable_int_ ? EncodableValue(*a_nullable_int_)
@@ -1034,10 +1249,6 @@ EncodableList AllNullableTypesWithoutRecursion::ToEncodableList() const {
   list.push_back(a_nullable_float_array_
                      ? EncodableValue(*a_nullable_float_array_)
                      : EncodableValue());
-  list.push_back(a_nullable_list_ ? EncodableValue(*a_nullable_list_)
-                                  : EncodableValue());
-  list.push_back(a_nullable_map_ ? EncodableValue(*a_nullable_map_)
-                                 : EncodableValue());
   list.push_back(nullable_nested_list_ ? EncodableValue(*nullable_nested_list_)
                                        : EncodableValue());
   list.push_back(nullable_map_with_annotations_
@@ -1046,11 +1257,19 @@ EncodableList AllNullableTypesWithoutRecursion::ToEncodableList() const {
   list.push_back(nullable_map_with_object_
                      ? EncodableValue(*nullable_map_with_object_)
                      : EncodableValue());
-  list.push_back(a_nullable_enum_ ? EncodableValue((int)(*a_nullable_enum_))
+  list.push_back(a_nullable_enum_ ? CustomEncodableValue(*a_nullable_enum_)
                                   : EncodableValue());
   list.push_back(a_nullable_string_ ? EncodableValue(*a_nullable_string_)
                                     : EncodableValue());
   list.push_back(a_nullable_object_ ? *a_nullable_object_ : EncodableValue());
+  list.push_back(list_ ? EncodableValue(*list_) : EncodableValue());
+  list.push_back(string_list_ ? EncodableValue(*string_list_)
+                              : EncodableValue());
+  list.push_back(int_list_ ? EncodableValue(*int_list_) : EncodableValue());
+  list.push_back(double_list_ ? EncodableValue(*double_list_)
+                              : EncodableValue());
+  list.push_back(bool_list_ ? EncodableValue(*bool_list_) : EncodableValue());
+  list.push_back(map_ ? EncodableValue(*map_) : EncodableValue());
   return list;
 }
 
@@ -1094,45 +1313,59 @@ AllNullableTypesWithoutRecursion::FromEncodableList(const EncodableList& list) {
     decoded.set_a_nullable_float_array(
         std::get<std::vector<double>>(encodable_a_nullable_float_array));
   }
-  auto& encodable_a_nullable_list = list[8];
-  if (!encodable_a_nullable_list.IsNull()) {
-    decoded.set_a_nullable_list(
-        std::get<EncodableList>(encodable_a_nullable_list));
-  }
-  auto& encodable_a_nullable_map = list[9];
-  if (!encodable_a_nullable_map.IsNull()) {
-    decoded.set_a_nullable_map(
-        std::get<EncodableMap>(encodable_a_nullable_map));
-  }
-  auto& encodable_nullable_nested_list = list[10];
+  auto& encodable_nullable_nested_list = list[8];
   if (!encodable_nullable_nested_list.IsNull()) {
     decoded.set_nullable_nested_list(
         std::get<EncodableList>(encodable_nullable_nested_list));
   }
-  auto& encodable_nullable_map_with_annotations = list[11];
+  auto& encodable_nullable_map_with_annotations = list[9];
   if (!encodable_nullable_map_with_annotations.IsNull()) {
     decoded.set_nullable_map_with_annotations(
         std::get<EncodableMap>(encodable_nullable_map_with_annotations));
   }
-  auto& encodable_nullable_map_with_object = list[12];
+  auto& encodable_nullable_map_with_object = list[10];
   if (!encodable_nullable_map_with_object.IsNull()) {
     decoded.set_nullable_map_with_object(
         std::get<EncodableMap>(encodable_nullable_map_with_object));
   }
-  auto& encodable_a_nullable_enum = list[13];
+  auto& encodable_a_nullable_enum = list[11];
   if (!encodable_a_nullable_enum.IsNull()) {
-    decoded.set_a_nullable_enum(
-        (AnEnum)(std::get<int32_t>(encodable_a_nullable_enum)));
+    decoded.set_a_nullable_enum(std::any_cast<const AnEnum&>(
+        std::get<CustomEncodableValue>(encodable_a_nullable_enum)));
   }
-  auto& encodable_a_nullable_string = list[14];
+  auto& encodable_a_nullable_string = list[12];
   if (!encodable_a_nullable_string.IsNull()) {
     decoded.set_a_nullable_string(
         std::get<std::string>(encodable_a_nullable_string));
   }
-  auto& encodable_a_nullable_object = list[15];
+  auto& encodable_a_nullable_object = list[13];
   if (!encodable_a_nullable_object.IsNull()) {
     decoded.set_a_nullable_object(encodable_a_nullable_object);
   }
+  auto& encodable_list = list[14];
+  if (!encodable_list.IsNull()) {
+    decoded.set_list(std::get<EncodableList>(encodable_list));
+  }
+  auto& encodable_string_list = list[15];
+  if (!encodable_string_list.IsNull()) {
+    decoded.set_string_list(std::get<EncodableList>(encodable_string_list));
+  }
+  auto& encodable_int_list = list[16];
+  if (!encodable_int_list.IsNull()) {
+    decoded.set_int_list(std::get<EncodableList>(encodable_int_list));
+  }
+  auto& encodable_double_list = list[17];
+  if (!encodable_double_list.IsNull()) {
+    decoded.set_double_list(std::get<EncodableList>(encodable_double_list));
+  }
+  auto& encodable_bool_list = list[18];
+  if (!encodable_bool_list.IsNull()) {
+    decoded.set_bool_list(std::get<EncodableList>(encodable_bool_list));
+  }
+  auto& encodable_map = list[19];
+  if (!encodable_map.IsNull()) {
+    decoded.set_map(std::get<EncodableMap>(encodable_map));
+  }
   return decoded;
 }
 
@@ -1290,46 +1523,53 @@ TestMessage TestMessage::FromEncodableList(const EncodableList& list) {
   return decoded;
 }
 
-HostIntegrationCoreApiCodecSerializer::HostIntegrationCoreApiCodecSerializer() {
-}
+PigeonCodecSerializer::PigeonCodecSerializer() {}
 
-EncodableValue HostIntegrationCoreApiCodecSerializer::ReadValueOfType(
+EncodableValue PigeonCodecSerializer::ReadValueOfType(
     uint8_t type, flutter::ByteStreamReader* stream) const {
   switch (type) {
-    case 128:
-      return CustomEncodableValue(AllClassesWrapper::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
     case 129:
-      return CustomEncodableValue(AllNullableTypes::FromEncodableList(
+      return CustomEncodableValue(AllTypes::FromEncodableList(
           std::get<EncodableList>(ReadValue(stream))));
     case 130:
+      return CustomEncodableValue(AllNullableTypes::FromEncodableList(
+          std::get<EncodableList>(ReadValue(stream))));
+    case 131:
       return CustomEncodableValue(
           AllNullableTypesWithoutRecursion::FromEncodableList(
               std::get<EncodableList>(ReadValue(stream))));
-    case 131:
-      return CustomEncodableValue(AllTypes::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
     case 132:
+      return CustomEncodableValue(AllClassesWrapper::FromEncodableList(
+          std::get<EncodableList>(ReadValue(stream))));
+    case 133:
       return CustomEncodableValue(TestMessage::FromEncodableList(
           std::get<EncodableList>(ReadValue(stream))));
+    case 134: {
+      const auto& encodable_enum_arg = ReadValue(stream);
+      const int64_t enum_arg_value =
+          encodable_enum_arg.IsNull() ? 0 : encodable_enum_arg.LongValue();
+      return encodable_enum_arg.IsNull()
+                 ? EncodableValue()
+                 : CustomEncodableValue(static_cast<AnEnum>(enum_arg_value));
+    }
     default:
       return flutter::StandardCodecSerializer::ReadValueOfType(type, stream);
   }
 }
 
-void HostIntegrationCoreApiCodecSerializer::WriteValue(
+void PigeonCodecSerializer::WriteValue(
     const EncodableValue& value, flutter::ByteStreamWriter* stream) const {
   if (const CustomEncodableValue* custom_value =
           std::get_if<CustomEncodableValue>(&value)) {
-    if (custom_value->type() == typeid(AllClassesWrapper)) {
-      stream->WriteByte(128);
-      WriteValue(EncodableValue(std::any_cast<AllClassesWrapper>(*custom_value)
-                                    .ToEncodableList()),
+    if (custom_value->type() == typeid(AllTypes)) {
+      stream->WriteByte(129);
+      WriteValue(EncodableValue(
+                     std::any_cast<AllTypes>(*custom_value).ToEncodableList()),
                  stream);
       return;
     }
     if (custom_value->type() == typeid(AllNullableTypes)) {
-      stream->WriteByte(129);
+      stream->WriteByte(130);
       WriteValue(
           EncodableValue(
               std::any_cast<AllNullableTypes>(*custom_value).ToEncodableList()),
@@ -1337,28 +1577,35 @@ void HostIntegrationCoreApiCodecSerializer::WriteValue(
       return;
     }
     if (custom_value->type() == typeid(AllNullableTypesWithoutRecursion)) {
-      stream->WriteByte(130);
+      stream->WriteByte(131);
       WriteValue(EncodableValue(std::any_cast<AllNullableTypesWithoutRecursion>(
                                     *custom_value)
                                     .ToEncodableList()),
                  stream);
       return;
     }
-    if (custom_value->type() == typeid(AllTypes)) {
-      stream->WriteByte(131);
-      WriteValue(EncodableValue(
-                     std::any_cast<AllTypes>(*custom_value).ToEncodableList()),
+    if (custom_value->type() == typeid(AllClassesWrapper)) {
+      stream->WriteByte(132);
+      WriteValue(EncodableValue(std::any_cast<AllClassesWrapper>(*custom_value)
+                                    .ToEncodableList()),
                  stream);
       return;
     }
     if (custom_value->type() == typeid(TestMessage)) {
-      stream->WriteByte(132);
+      stream->WriteByte(133);
       WriteValue(
           EncodableValue(
               std::any_cast<TestMessage>(*custom_value).ToEncodableList()),
           stream);
       return;
     }
+    if (custom_value->type() == typeid(AnEnum)) {
+      stream->WriteByte(134);
+      WriteValue(EncodableValue(
+                     static_cast<int>(std::any_cast<AnEnum>(*custom_value))),
+                 stream);
+      return;
+    }
   }
   flutter::StandardCodecSerializer::WriteValue(value, stream);
 }
@@ -1366,7 +1613,7 @@ void HostIntegrationCoreApiCodecSerializer::WriteValue(
 /// The codec used by HostIntegrationCoreApi.
 const flutter::StandardMessageCodec& HostIntegrationCoreApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &HostIntegrationCoreApiCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 // Sets up an instance of `HostIntegrationCoreApi` to handle messages through
@@ -1872,8 +2119,8 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                 reply(WrapError("an_enum_arg unexpectedly null."));
                 return;
               }
-              const AnEnum& an_enum_arg =
-                  (AnEnum)encodable_an_enum_arg.LongValue();
+              const auto& an_enum_arg = std::any_cast<const AnEnum&>(
+                  std::get<CustomEncodableValue>(encodable_an_enum_arg));
               ErrorOr<AnEnum> output = api->EchoEnum(an_enum_arg);
               if (output.has_error()) {
                 reply(WrapError(output.error()));
@@ -1881,7 +2128,7 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
               }
               EncodableList wrapped;
               wrapped.push_back(
-                  EncodableValue((int)std::move(output).TakeValue()));
+                  CustomEncodableValue(std::move(output).TakeValue()));
               reply(EncodableValue(std::move(wrapped)));
             } catch (const std::exception& exception) {
               reply(WrapError(exception.what()));
@@ -2578,15 +2825,13 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
             try {
               const auto& args = std::get<EncodableList>(message);
               const auto& encodable_an_enum_arg = args.at(0);
-              const int64_t an_enum_arg_value =
-                  encodable_an_enum_arg.IsNull()
-                      ? 0
-                      : encodable_an_enum_arg.LongValue();
-              const auto an_enum_arg =
-                  encodable_an_enum_arg.IsNull()
-                      ? std::nullopt
-                      : std::make_optional<AnEnum>(
-                            static_cast<AnEnum>(an_enum_arg_value));
+              AnEnum an_enum_arg_value;
+              const AnEnum* an_enum_arg = nullptr;
+              if (!encodable_an_enum_arg.IsNull()) {
+                an_enum_arg_value = std::any_cast<const AnEnum&>(
+                    std::get<CustomEncodableValue>(encodable_an_enum_arg));
+                an_enum_arg = &an_enum_arg_value;
+              }
               ErrorOr<std::optional<AnEnum>> output = api->EchoNullableEnum(
                   an_enum_arg ? &(*an_enum_arg) : nullptr);
               if (output.has_error()) {
@@ -2597,7 +2842,7 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
               auto output_optional = std::move(output).TakeValue();
               if (output_optional) {
                 wrapped.push_back(
-                    EncodableValue((int)std::move(output_optional).value()));
+                    CustomEncodableValue(std::move(output_optional).value()));
               } else {
                 wrapped.push_back(EncodableValue());
               }
@@ -3039,8 +3284,8 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                 reply(WrapError("an_enum_arg unexpectedly null."));
                 return;
               }
-              const AnEnum& an_enum_arg =
-                  (AnEnum)encodable_an_enum_arg.LongValue();
+              const auto& an_enum_arg = std::any_cast<const AnEnum&>(
+                  std::get<CustomEncodableValue>(encodable_an_enum_arg));
               api->EchoAsyncEnum(
                   an_enum_arg, [reply](ErrorOr<AnEnum>&& output) {
                     if (output.has_error()) {
@@ -3049,7 +3294,7 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                     }
                     EncodableList wrapped;
                     wrapped.push_back(
-                        EncodableValue((int)std::move(output).TakeValue()));
+                        CustomEncodableValue(std::move(output).TakeValue()));
                     reply(EncodableValue(std::move(wrapped)));
                   });
             } catch (const std::exception& exception) {
@@ -3631,15 +3876,13 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
             try {
               const auto& args = std::get<EncodableList>(message);
               const auto& encodable_an_enum_arg = args.at(0);
-              const int64_t an_enum_arg_value =
-                  encodable_an_enum_arg.IsNull()
-                      ? 0
-                      : encodable_an_enum_arg.LongValue();
-              const auto an_enum_arg =
-                  encodable_an_enum_arg.IsNull()
-                      ? std::nullopt
-                      : std::make_optional<AnEnum>(
-                            static_cast<AnEnum>(an_enum_arg_value));
+              AnEnum an_enum_arg_value;
+              const AnEnum* an_enum_arg = nullptr;
+              if (!encodable_an_enum_arg.IsNull()) {
+                an_enum_arg_value = std::any_cast<const AnEnum&>(
+                    std::get<CustomEncodableValue>(encodable_an_enum_arg));
+                an_enum_arg = &an_enum_arg_value;
+              }
               api->EchoAsyncNullableEnum(
                   an_enum_arg ? &(*an_enum_arg) : nullptr,
                   [reply](ErrorOr<std::optional<AnEnum>>&& output) {
@@ -3650,8 +3893,8 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                     EncodableList wrapped;
                     auto output_optional = std::move(output).TakeValue();
                     if (output_optional) {
-                      wrapped.push_back(EncodableValue(
-                          (int)std::move(output_optional).value()));
+                      wrapped.push_back(CustomEncodableValue(
+                          std::move(output_optional).value()));
                     } else {
                       wrapped.push_back(EncodableValue());
                     }
@@ -4269,8 +4512,8 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                 reply(WrapError("an_enum_arg unexpectedly null."));
                 return;
               }
-              const AnEnum& an_enum_arg =
-                  (AnEnum)encodable_an_enum_arg.LongValue();
+              const auto& an_enum_arg = std::any_cast<const AnEnum&>(
+                  std::get<CustomEncodableValue>(encodable_an_enum_arg));
               api->CallFlutterEchoEnum(
                   an_enum_arg, [reply](ErrorOr<AnEnum>&& output) {
                     if (output.has_error()) {
@@ -4279,7 +4522,7 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                     }
                     EncodableList wrapped;
                     wrapped.push_back(
-                        EncodableValue((int)std::move(output).TakeValue()));
+                        CustomEncodableValue(std::move(output).TakeValue()));
                     reply(EncodableValue(std::move(wrapped)));
                   });
             } catch (const std::exception& exception) {
@@ -4594,15 +4837,13 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
             try {
               const auto& args = std::get<EncodableList>(message);
               const auto& encodable_an_enum_arg = args.at(0);
-              const int64_t an_enum_arg_value =
-                  encodable_an_enum_arg.IsNull()
-                      ? 0
-                      : encodable_an_enum_arg.LongValue();
-              const auto an_enum_arg =
-                  encodable_an_enum_arg.IsNull()
-                      ? std::nullopt
-                      : std::make_optional<AnEnum>(
-                            static_cast<AnEnum>(an_enum_arg_value));
+              AnEnum an_enum_arg_value;
+              const AnEnum* an_enum_arg = nullptr;
+              if (!encodable_an_enum_arg.IsNull()) {
+                an_enum_arg_value = std::any_cast<const AnEnum&>(
+                    std::get<CustomEncodableValue>(encodable_an_enum_arg));
+                an_enum_arg = &an_enum_arg_value;
+              }
               api->CallFlutterEchoNullableEnum(
                   an_enum_arg ? &(*an_enum_arg) : nullptr,
                   [reply](ErrorOr<std::optional<AnEnum>>&& output) {
@@ -4613,8 +4854,8 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
                     EncodableList wrapped;
                     auto output_optional = std::move(output).TakeValue();
                     if (output_optional) {
-                      wrapped.push_back(EncodableValue(
-                          (int)std::move(output_optional).value()));
+                      wrapped.push_back(CustomEncodableValue(
+                          std::move(output_optional).value()));
                     } else {
                       wrapped.push_back(EncodableValue());
                     }
@@ -4682,79 +4923,6 @@ EncodableValue HostIntegrationCoreApi::WrapError(const FlutterError& error) {
                                       error.details()});
 }
 
-FlutterIntegrationCoreApiCodecSerializer::
-    FlutterIntegrationCoreApiCodecSerializer() {}
-
-EncodableValue FlutterIntegrationCoreApiCodecSerializer::ReadValueOfType(
-    uint8_t type, flutter::ByteStreamReader* stream) const {
-  switch (type) {
-    case 128:
-      return CustomEncodableValue(AllClassesWrapper::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
-    case 129:
-      return CustomEncodableValue(AllNullableTypes::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
-    case 130:
-      return CustomEncodableValue(
-          AllNullableTypesWithoutRecursion::FromEncodableList(
-              std::get<EncodableList>(ReadValue(stream))));
-    case 131:
-      return CustomEncodableValue(AllTypes::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
-    case 132:
-      return CustomEncodableValue(TestMessage::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
-    default:
-      return flutter::StandardCodecSerializer::ReadValueOfType(type, stream);
-  }
-}
-
-void FlutterIntegrationCoreApiCodecSerializer::WriteValue(
-    const EncodableValue& value, flutter::ByteStreamWriter* stream) const {
-  if (const CustomEncodableValue* custom_value =
-          std::get_if<CustomEncodableValue>(&value)) {
-    if (custom_value->type() == typeid(AllClassesWrapper)) {
-      stream->WriteByte(128);
-      WriteValue(EncodableValue(std::any_cast<AllClassesWrapper>(*custom_value)
-                                    .ToEncodableList()),
-                 stream);
-      return;
-    }
-    if (custom_value->type() == typeid(AllNullableTypes)) {
-      stream->WriteByte(129);
-      WriteValue(
-          EncodableValue(
-              std::any_cast<AllNullableTypes>(*custom_value).ToEncodableList()),
-          stream);
-      return;
-    }
-    if (custom_value->type() == typeid(AllNullableTypesWithoutRecursion)) {
-      stream->WriteByte(130);
-      WriteValue(EncodableValue(std::any_cast<AllNullableTypesWithoutRecursion>(
-                                    *custom_value)
-                                    .ToEncodableList()),
-                 stream);
-      return;
-    }
-    if (custom_value->type() == typeid(AllTypes)) {
-      stream->WriteByte(131);
-      WriteValue(EncodableValue(
-                     std::any_cast<AllTypes>(*custom_value).ToEncodableList()),
-                 stream);
-      return;
-    }
-    if (custom_value->type() == typeid(TestMessage)) {
-      stream->WriteByte(132);
-      WriteValue(
-          EncodableValue(
-              std::any_cast<TestMessage>(*custom_value).ToEncodableList()),
-          stream);
-      return;
-    }
-  }
-  flutter::StandardCodecSerializer::WriteValue(value, stream);
-}
-
 // Generated class from Pigeon that represents Flutter messages that can be
 // called from C++.
 FlutterIntegrationCoreApi::FlutterIntegrationCoreApi(
@@ -4771,7 +4939,7 @@ FlutterIntegrationCoreApi::FlutterIntegrationCoreApi(
 
 const flutter::StandardMessageCodec& FlutterIntegrationCoreApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &FlutterIntegrationCoreApiCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 void FlutterIntegrationCoreApi::Noop(
@@ -5347,7 +5515,7 @@ void FlutterIntegrationCoreApi::EchoEnum(
       message_channel_suffix_;
   BasicMessageChannel<> channel(binary_messenger_, channel_name, &GetCodec());
   EncodableValue encoded_api_arguments = EncodableValue(EncodableList{
-      EncodableValue((int)an_enum_arg),
+      CustomEncodableValue(an_enum_arg),
   });
   channel.Send(
       encoded_api_arguments, [channel_name, on_success = std::move(on_success),
@@ -5365,8 +5533,8 @@ void FlutterIntegrationCoreApi::EchoEnum(
                              std::get<std::string>(list_return_value->at(1)),
                              list_return_value->at(2)));
           } else {
-            const AnEnum& return_value =
-                (AnEnum)list_return_value->at(0).LongValue();
+            const auto& return_value = std::any_cast<const AnEnum&>(
+                std::get<CustomEncodableValue>(list_return_value->at(0)));
             on_success(return_value);
           }
         } else {
@@ -5650,37 +5818,37 @@ void FlutterIntegrationCoreApi::EchoNullableEnum(
       message_channel_suffix_;
   BasicMessageChannel<> channel(binary_messenger_, channel_name, &GetCodec());
   EncodableValue encoded_api_arguments = EncodableValue(EncodableList{
-      an_enum_arg ? EncodableValue((int)(*an_enum_arg)) : EncodableValue(),
-  });
-  channel.Send(encoded_api_arguments, [channel_name,
-                                       on_success = std::move(on_success),
-                                       on_error = std::move(on_error)](
-                                          const uint8_t* reply,
-                                          size_t reply_size) {
-    std::unique_ptr<EncodableValue> response =
-        GetCodec().DecodeMessage(reply, reply_size);
-    const auto& encodable_return_value = *response;
-    const auto* list_return_value =
-        std::get_if<EncodableList>(&encodable_return_value);
-    if (list_return_value) {
-      if (list_return_value->size() > 1) {
-        on_error(FlutterError(std::get<std::string>(list_return_value->at(0)),
-                              std::get<std::string>(list_return_value->at(1)),
-                              list_return_value->at(2)));
-      } else {
-        const int64_t return_value_value =
-            list_return_value->at(0).IsNull()
-                ? 0
-                : list_return_value->at(0).LongValue();
-        const AnEnum enum_return_value = (AnEnum)return_value_value;
-        const auto* return_value =
-            list_return_value->at(0).IsNull() ? nullptr : &enum_return_value;
-        on_success(return_value);
-      }
-    } else {
-      on_error(CreateConnectionError(channel_name));
-    }
+      an_enum_arg ? CustomEncodableValue(*an_enum_arg) : EncodableValue(),
   });
+  channel.Send(
+      encoded_api_arguments, [channel_name, on_success = std::move(on_success),
+                              on_error = std::move(on_error)](
+                                 const uint8_t* reply, size_t reply_size) {
+        std::unique_ptr<EncodableValue> response =
+            GetCodec().DecodeMessage(reply, reply_size);
+        const auto& encodable_return_value = *response;
+        const auto* list_return_value =
+            std::get_if<EncodableList>(&encodable_return_value);
+        if (list_return_value) {
+          if (list_return_value->size() > 1) {
+            on_error(
+                FlutterError(std::get<std::string>(list_return_value->at(0)),
+                             std::get<std::string>(list_return_value->at(1)),
+                             list_return_value->at(2)));
+          } else {
+            AnEnum return_value_value;
+            const AnEnum* return_value = nullptr;
+            if (!list_return_value->at(0).IsNull()) {
+              return_value_value = std::any_cast<const AnEnum&>(
+                  std::get<CustomEncodableValue>(list_return_value->at(0)));
+              return_value = &return_value_value;
+            }
+            on_success(return_value);
+          }
+        } else {
+          on_error(CreateConnectionError(channel_name));
+        }
+      });
 }
 
 void FlutterIntegrationCoreApi::NoopAsync(
@@ -5757,7 +5925,7 @@ void FlutterIntegrationCoreApi::EchoAsyncString(
 /// The codec used by HostTrivialApi.
 const flutter::StandardMessageCodec& HostTrivialApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &flutter::StandardCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 // Sets up an instance of `HostTrivialApi` to handle messages through the
@@ -5818,7 +5986,7 @@ EncodableValue HostTrivialApi::WrapError(const FlutterError& error) {
 /// The codec used by HostSmallApi.
 const flutter::StandardMessageCodec& HostSmallApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &flutter::StandardCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 // Sets up an instance of `HostSmallApi` to handle messages through the
@@ -5914,35 +6082,6 @@ EncodableValue HostSmallApi::WrapError(const FlutterError& error) {
                                       error.details()});
 }
 
-FlutterSmallApiCodecSerializer::FlutterSmallApiCodecSerializer() {}
-
-EncodableValue FlutterSmallApiCodecSerializer::ReadValueOfType(
-    uint8_t type, flutter::ByteStreamReader* stream) const {
-  switch (type) {
-    case 128:
-      return CustomEncodableValue(TestMessage::FromEncodableList(
-          std::get<EncodableList>(ReadValue(stream))));
-    default:
-      return flutter::StandardCodecSerializer::ReadValueOfType(type, stream);
-  }
-}
-
-void FlutterSmallApiCodecSerializer::WriteValue(
-    const EncodableValue& value, flutter::ByteStreamWriter* stream) const {
-  if (const CustomEncodableValue* custom_value =
-          std::get_if<CustomEncodableValue>(&value)) {
-    if (custom_value->type() == typeid(TestMessage)) {
-      stream->WriteByte(128);
-      WriteValue(
-          EncodableValue(
-              std::any_cast<TestMessage>(*custom_value).ToEncodableList()),
-          stream);
-      return;
-    }
-  }
-  flutter::StandardCodecSerializer::WriteValue(value, stream);
-}
-
 // Generated class from Pigeon that represents Flutter messages that can be
 // called from C++.
 FlutterSmallApi::FlutterSmallApi(flutter::BinaryMessenger* binary_messenger)
@@ -5957,7 +6096,7 @@ FlutterSmallApi::FlutterSmallApi(flutter::BinaryMessenger* binary_messenger,
 
 const flutter::StandardMessageCodec& FlutterSmallApi::GetCodec() {
   return flutter::StandardMessageCodec::GetInstance(
-      &FlutterSmallApiCodecSerializer::GetInstance());
+      &PigeonCodecSerializer::GetInstance());
 }
 
 void FlutterSmallApi::EchoWrappedList(
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
index 7ee94453826..ceed1b08727 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
+++ b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
@@ -84,10 +84,14 @@ class AllTypes {
                     const std::vector<int32_t>& a4_byte_array,
                     const std::vector<int64_t>& a8_byte_array,
                     const std::vector<double>& a_float_array,
+                    const AnEnum& an_enum, const std::string& a_string,
+                    const flutter::EncodableValue& an_object,
                     const flutter::EncodableList& list,
-                    const flutter::EncodableMap& a_map, const AnEnum& an_enum,
-                    const std::string& a_string,
-                    const flutter::EncodableValue& an_object);
+                    const flutter::EncodableList& string_list,
+                    const flutter::EncodableList& int_list,
+                    const flutter::EncodableList& double_list,
+                    const flutter::EncodableList& bool_list,
+                    const flutter::EncodableMap& map);
 
   bool a_bool() const;
   void set_a_bool(bool value_arg);
@@ -113,12 +117,6 @@ class AllTypes {
   const std::vector<double>& a_float_array() const;
   void set_a_float_array(const std::vector<double>& value_arg);
 
-  const flutter::EncodableList& list() const;
-  void set_list(const flutter::EncodableList& value_arg);
-
-  const flutter::EncodableMap& a_map() const;
-  void set_a_map(const flutter::EncodableMap& value_arg);
-
   const AnEnum& an_enum() const;
   void set_an_enum(const AnEnum& value_arg);
 
@@ -128,20 +126,34 @@ class AllTypes {
   const flutter::EncodableValue& an_object() const;
   void set_an_object(const flutter::EncodableValue& value_arg);
 
+  const flutter::EncodableList& list() const;
+  void set_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList& string_list() const;
+  void set_string_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList& int_list() const;
+  void set_int_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList& double_list() const;
+  void set_double_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList& bool_list() const;
+  void set_bool_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableMap& map() const;
+  void set_map(const flutter::EncodableMap& value_arg);
+
  private:
   static AllTypes FromEncodableList(const flutter::EncodableList& list);
   flutter::EncodableList ToEncodableList() const;
   friend class AllClassesWrapper;
   friend class HostIntegrationCoreApi;
-  friend class HostIntegrationCoreApiCodecSerializer;
   friend class FlutterIntegrationCoreApi;
-  friend class FlutterIntegrationCoreApiCodecSerializer;
   friend class HostTrivialApi;
-  friend class HostTrivialApiCodecSerializer;
   friend class HostSmallApi;
-  friend class HostSmallApiCodecSerializer;
   friend class FlutterSmallApi;
-  friend class FlutterSmallApiCodecSerializer;
+  friend class PigeonCodecSerializer;
   friend class CoreTestsTest;
   bool a_bool_;
   int64_t an_int_;
@@ -151,11 +163,15 @@ class AllTypes {
   std::vector<int32_t> a4_byte_array_;
   std::vector<int64_t> a8_byte_array_;
   std::vector<double> a_float_array_;
-  flutter::EncodableList list_;
-  flutter::EncodableMap a_map_;
   AnEnum an_enum_;
   std::string a_string_;
   flutter::EncodableValue an_object_;
+  flutter::EncodableList list_;
+  flutter::EncodableList string_list_;
+  flutter::EncodableList int_list_;
+  flutter::EncodableList double_list_;
+  flutter::EncodableList bool_list_;
+  flutter::EncodableMap map_;
 };
 
 // A class containing all supported nullable types.
@@ -174,14 +190,19 @@ class AllNullableTypes {
       const std::vector<int32_t>* a_nullable4_byte_array,
       const std::vector<int64_t>* a_nullable8_byte_array,
       const std::vector<double>* a_nullable_float_array,
-      const flutter::EncodableList* a_nullable_list,
-      const flutter::EncodableMap* a_nullable_map,
       const flutter::EncodableList* nullable_nested_list,
       const flutter::EncodableMap* nullable_map_with_annotations,
       const flutter::EncodableMap* nullable_map_with_object,
       const AnEnum* a_nullable_enum, const std::string* a_nullable_string,
       const flutter::EncodableValue* a_nullable_object,
-      const AllNullableTypes* all_nullable_types);
+      const AllNullableTypes* all_nullable_types,
+      const flutter::EncodableList* list,
+      const flutter::EncodableList* string_list,
+      const flutter::EncodableList* int_list,
+      const flutter::EncodableList* double_list,
+      const flutter::EncodableList* bool_list,
+      const flutter::EncodableList* nested_class_list,
+      const flutter::EncodableMap* map);
 
   ~AllNullableTypes() = default;
   AllNullableTypes(const AllNullableTypes& other);
@@ -220,14 +241,6 @@ class AllNullableTypes {
   void set_a_nullable_float_array(const std::vector<double>* value_arg);
   void set_a_nullable_float_array(const std::vector<double>& value_arg);
 
-  const flutter::EncodableList* a_nullable_list() const;
-  void set_a_nullable_list(const flutter::EncodableList* value_arg);
-  void set_a_nullable_list(const flutter::EncodableList& value_arg);
-
-  const flutter::EncodableMap* a_nullable_map() const;
-  void set_a_nullable_map(const flutter::EncodableMap* value_arg);
-  void set_a_nullable_map(const flutter::EncodableMap& value_arg);
-
   const flutter::EncodableList* nullable_nested_list() const;
   void set_nullable_nested_list(const flutter::EncodableList* value_arg);
   void set_nullable_nested_list(const flutter::EncodableList& value_arg);
@@ -258,20 +271,44 @@ class AllNullableTypes {
   void set_all_nullable_types(const AllNullableTypes* value_arg);
   void set_all_nullable_types(const AllNullableTypes& value_arg);
 
+  const flutter::EncodableList* list() const;
+  void set_list(const flutter::EncodableList* value_arg);
+  void set_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* string_list() const;
+  void set_string_list(const flutter::EncodableList* value_arg);
+  void set_string_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* int_list() const;
+  void set_int_list(const flutter::EncodableList* value_arg);
+  void set_int_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* double_list() const;
+  void set_double_list(const flutter::EncodableList* value_arg);
+  void set_double_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* bool_list() const;
+  void set_bool_list(const flutter::EncodableList* value_arg);
+  void set_bool_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* nested_class_list() const;
+  void set_nested_class_list(const flutter::EncodableList* value_arg);
+  void set_nested_class_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableMap* map() const;
+  void set_map(const flutter::EncodableMap* value_arg);
+  void set_map(const flutter::EncodableMap& value_arg);
+
  private:
   static AllNullableTypes FromEncodableList(const flutter::EncodableList& list);
   flutter::EncodableList ToEncodableList() const;
   friend class AllClassesWrapper;
   friend class HostIntegrationCoreApi;
-  friend class HostIntegrationCoreApiCodecSerializer;
   friend class FlutterIntegrationCoreApi;
-  friend class FlutterIntegrationCoreApiCodecSerializer;
   friend class HostTrivialApi;
-  friend class HostTrivialApiCodecSerializer;
   friend class HostSmallApi;
-  friend class HostSmallApiCodecSerializer;
   friend class FlutterSmallApi;
-  friend class FlutterSmallApiCodecSerializer;
+  friend class PigeonCodecSerializer;
   friend class CoreTestsTest;
   std::optional<bool> a_nullable_bool_;
   std::optional<int64_t> a_nullable_int_;
@@ -281,8 +318,6 @@ class AllNullableTypes {
   std::optional<std::vector<int32_t>> a_nullable4_byte_array_;
   std::optional<std::vector<int64_t>> a_nullable8_byte_array_;
   std::optional<std::vector<double>> a_nullable_float_array_;
-  std::optional<flutter::EncodableList> a_nullable_list_;
-  std::optional<flutter::EncodableMap> a_nullable_map_;
   std::optional<flutter::EncodableList> nullable_nested_list_;
   std::optional<flutter::EncodableMap> nullable_map_with_annotations_;
   std::optional<flutter::EncodableMap> nullable_map_with_object_;
@@ -290,6 +325,13 @@ class AllNullableTypes {
   std::optional<std::string> a_nullable_string_;
   std::optional<flutter::EncodableValue> a_nullable_object_;
   std::unique_ptr<AllNullableTypes> all_nullable_types_;
+  std::optional<flutter::EncodableList> list_;
+  std::optional<flutter::EncodableList> string_list_;
+  std::optional<flutter::EncodableList> int_list_;
+  std::optional<flutter::EncodableList> double_list_;
+  std::optional<flutter::EncodableList> bool_list_;
+  std::optional<flutter::EncodableList> nested_class_list_;
+  std::optional<flutter::EncodableMap> map_;
 };
 
 // The primary purpose for this class is to ensure coverage of Swift structs
@@ -310,13 +352,17 @@ class AllNullableTypesWithoutRecursion {
       const std::vector<int32_t>* a_nullable4_byte_array,
       const std::vector<int64_t>* a_nullable8_byte_array,
       const std::vector<double>* a_nullable_float_array,
-      const flutter::EncodableList* a_nullable_list,
-      const flutter::EncodableMap* a_nullable_map,
       const flutter::EncodableList* nullable_nested_list,
       const flutter::EncodableMap* nullable_map_with_annotations,
       const flutter::EncodableMap* nullable_map_with_object,
       const AnEnum* a_nullable_enum, const std::string* a_nullable_string,
-      const flutter::EncodableValue* a_nullable_object);
+      const flutter::EncodableValue* a_nullable_object,
+      const flutter::EncodableList* list,
+      const flutter::EncodableList* string_list,
+      const flutter::EncodableList* int_list,
+      const flutter::EncodableList* double_list,
+      const flutter::EncodableList* bool_list,
+      const flutter::EncodableMap* map);
 
   const bool* a_nullable_bool() const;
   void set_a_nullable_bool(const bool* value_arg);
@@ -350,14 +396,6 @@ class AllNullableTypesWithoutRecursion {
   void set_a_nullable_float_array(const std::vector<double>* value_arg);
   void set_a_nullable_float_array(const std::vector<double>& value_arg);
 
-  const flutter::EncodableList* a_nullable_list() const;
-  void set_a_nullable_list(const flutter::EncodableList* value_arg);
-  void set_a_nullable_list(const flutter::EncodableList& value_arg);
-
-  const flutter::EncodableMap* a_nullable_map() const;
-  void set_a_nullable_map(const flutter::EncodableMap* value_arg);
-  void set_a_nullable_map(const flutter::EncodableMap& value_arg);
-
   const flutter::EncodableList* nullable_nested_list() const;
   void set_nullable_nested_list(const flutter::EncodableList* value_arg);
   void set_nullable_nested_list(const flutter::EncodableList& value_arg);
@@ -384,21 +422,41 @@ class AllNullableTypesWithoutRecursion {
   void set_a_nullable_object(const flutter::EncodableValue* value_arg);
   void set_a_nullable_object(const flutter::EncodableValue& value_arg);
 
+  const flutter::EncodableList* list() const;
+  void set_list(const flutter::EncodableList* value_arg);
+  void set_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* string_list() const;
+  void set_string_list(const flutter::EncodableList* value_arg);
+  void set_string_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* int_list() const;
+  void set_int_list(const flutter::EncodableList* value_arg);
+  void set_int_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* double_list() const;
+  void set_double_list(const flutter::EncodableList* value_arg);
+  void set_double_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableList* bool_list() const;
+  void set_bool_list(const flutter::EncodableList* value_arg);
+  void set_bool_list(const flutter::EncodableList& value_arg);
+
+  const flutter::EncodableMap* map() const;
+  void set_map(const flutter::EncodableMap* value_arg);
+  void set_map(const flutter::EncodableMap& value_arg);
+
  private:
   static AllNullableTypesWithoutRecursion FromEncodableList(
       const flutter::EncodableList& list);
   flutter::EncodableList ToEncodableList() const;
   friend class AllClassesWrapper;
   friend class HostIntegrationCoreApi;
-  friend class HostIntegrationCoreApiCodecSerializer;
   friend class FlutterIntegrationCoreApi;
-  friend class FlutterIntegrationCoreApiCodecSerializer;
   friend class HostTrivialApi;
-  friend class HostTrivialApiCodecSerializer;
   friend class HostSmallApi;
-  friend class HostSmallApiCodecSerializer;
   friend class FlutterSmallApi;
-  friend class FlutterSmallApiCodecSerializer;
+  friend class PigeonCodecSerializer;
   friend class CoreTestsTest;
   std::optional<bool> a_nullable_bool_;
   std::optional<int64_t> a_nullable_int_;
@@ -408,14 +466,18 @@ class AllNullableTypesWithoutRecursion {
   std::optional<std::vector<int32_t>> a_nullable4_byte_array_;
   std::optional<std::vector<int64_t>> a_nullable8_byte_array_;
   std::optional<std::vector<double>> a_nullable_float_array_;
-  std::optional<flutter::EncodableList> a_nullable_list_;
-  std::optional<flutter::EncodableMap> a_nullable_map_;
   std::optional<flutter::EncodableList> nullable_nested_list_;
   std::optional<flutter::EncodableMap> nullable_map_with_annotations_;
   std::optional<flutter::EncodableMap> nullable_map_with_object_;
   std::optional<AnEnum> a_nullable_enum_;
   std::optional<std::string> a_nullable_string_;
   std::optional<flutter::EncodableValue> a_nullable_object_;
+  std::optional<flutter::EncodableList> list_;
+  std::optional<flutter::EncodableList> string_list_;
+  std::optional<flutter::EncodableList> int_list_;
+  std::optional<flutter::EncodableList> double_list_;
+  std::optional<flutter::EncodableList> bool_list_;
+  std::optional<flutter::EncodableMap> map_;
 };
 
 // A class for testing nested class handling.
@@ -460,15 +522,11 @@ class AllClassesWrapper {
       const flutter::EncodableList& list);
   flutter::EncodableList ToEncodableList() const;
   friend class HostIntegrationCoreApi;
-  friend class HostIntegrationCoreApiCodecSerializer;
   friend class FlutterIntegrationCoreApi;
-  friend class FlutterIntegrationCoreApiCodecSerializer;
   friend class HostTrivialApi;
-  friend class HostTrivialApiCodecSerializer;
   friend class HostSmallApi;
-  friend class HostSmallApiCodecSerializer;
   friend class FlutterSmallApi;
-  friend class FlutterSmallApiCodecSerializer;
+  friend class PigeonCodecSerializer;
   friend class CoreTestsTest;
   std::unique_ptr<AllNullableTypes> all_nullable_types_;
   std::unique_ptr<AllNullableTypesWithoutRecursion>
@@ -495,25 +553,20 @@ class TestMessage {
   static TestMessage FromEncodableList(const flutter::EncodableList& list);
   flutter::EncodableList ToEncodableList() const;
   friend class HostIntegrationCoreApi;
-  friend class HostIntegrationCoreApiCodecSerializer;
   friend class FlutterIntegrationCoreApi;
-  friend class FlutterIntegrationCoreApiCodecSerializer;
   friend class HostTrivialApi;
-  friend class HostTrivialApiCodecSerializer;
   friend class HostSmallApi;
-  friend class HostSmallApiCodecSerializer;
   friend class FlutterSmallApi;
-  friend class FlutterSmallApiCodecSerializer;
+  friend class PigeonCodecSerializer;
   friend class CoreTestsTest;
   std::optional<flutter::EncodableList> test_list_;
 };
 
-class HostIntegrationCoreApiCodecSerializer
-    : public flutter::StandardCodecSerializer {
+class PigeonCodecSerializer : public flutter::StandardCodecSerializer {
  public:
-  HostIntegrationCoreApiCodecSerializer();
-  inline static HostIntegrationCoreApiCodecSerializer& GetInstance() {
-    static HostIntegrationCoreApiCodecSerializer sInstance;
+  PigeonCodecSerializer();
+  inline static PigeonCodecSerializer& GetInstance() {
+    static PigeonCodecSerializer sInstance;
     return sInstance;
   }
 
@@ -842,23 +895,6 @@ class HostIntegrationCoreApi {
  protected:
   HostIntegrationCoreApi() = default;
 };
-class FlutterIntegrationCoreApiCodecSerializer
-    : public flutter::StandardCodecSerializer {
- public:
-  FlutterIntegrationCoreApiCodecSerializer();
-  inline static FlutterIntegrationCoreApiCodecSerializer& GetInstance() {
-    static FlutterIntegrationCoreApiCodecSerializer sInstance;
-    return sInstance;
-  }
-
-  void WriteValue(const flutter::EncodableValue& value,
-                  flutter::ByteStreamWriter* stream) const override;
-
- protected:
-  flutter::EncodableValue ReadValueOfType(
-      uint8_t type, flutter::ByteStreamReader* stream) const override;
-};
-
 // The core interface that the Dart platform_test code implements for host
 // integration tests to call into.
 //
@@ -1045,22 +1081,6 @@ class HostSmallApi {
  protected:
   HostSmallApi() = default;
 };
-class FlutterSmallApiCodecSerializer : public flutter::StandardCodecSerializer {
- public:
-  FlutterSmallApiCodecSerializer();
-  inline static FlutterSmallApiCodecSerializer& GetInstance() {
-    static FlutterSmallApiCodecSerializer sInstance;
-    return sInstance;
-  }
-
-  void WriteValue(const flutter::EncodableValue& value,
-                  flutter::ByteStreamWriter* stream) const override;
-
- protected:
-  flutter::EncodableValue ReadValueOfType(
-      uint8_t type, flutter::ByteStreamReader* stream) const override;
-};
-
 // A simple API called in some unit tests.
 //
 // Generated class from Pigeon that represents Flutter messages that can be
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/test/null_fields_test.cpp b/packages/pigeon/platform_tests/test_plugin/windows/test/null_fields_test.cpp
index d0c04561882..e6a366248f0 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/test/null_fields_test.cpp
+++ b/packages/pigeon/platform_tests/test_plugin/windows/test/null_fields_test.cpp
@@ -119,13 +119,9 @@ TEST_F(NullFieldsTest, ReplyFromListWithValues) {
   EncodableList list{
       EncodableValue("result"),
       EncodableValue("error"),
-      EncodableValue(EncodableList{
-          EncodableValue(1),
-          EncodableValue(2),
-          EncodableValue(3),
-      }),
+      EncodableValue(EncodableList({1, 2, 3})),
       CustomEncodableValue(request),
-      EncodableValue(0),
+      CustomEncodableValue(NullFieldsSearchReplyType::success),
   };
   NullFieldsSearchReply reply = ReplyFromList(list);
 
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/test/pigeon_test.cpp b/packages/pigeon/platform_tests/test_plugin/windows/test/pigeon_test.cpp
index 89118efc10d..427a62f06c6 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/test/pigeon_test.cpp
+++ b/packages/pigeon/platform_tests/test_plugin/windows/test/pigeon_test.cpp
@@ -137,7 +137,7 @@ TEST(PigeonTests, CallSearch) {
   Writer writer;
   flutter::EncodableList args;
   args.push_back(flutter::CustomEncodableValue(request));
-  MessageApiCodecSerializer::GetInstance().WriteValue(args, &writer);
+  PigeonCodecSerializer::GetInstance().WriteValue(args, &writer);
   handler(writer.data_.data(), writer.data_.size(), reply);
   EXPECT_TRUE(did_call_reply);
 }
diff --git a/packages/pigeon/pubspec.yaml b/packages/pigeon/pubspec.yaml
index edbba1f4027..0281b15cba3 100644
--- a/packages/pigeon/pubspec.yaml
+++ b/packages/pigeon/pubspec.yaml
@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 19.0.2 # This must match the version in lib/generator_tools.dart
+version: 20.0.0 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: ^3.2.0
diff --git a/packages/pigeon/test/cpp_generator_test.dart b/packages/pigeon/test/cpp_generator_test.dart
index 8695ae45e96..ecdb0ab33d2 100644
--- a/packages/pigeon/test/cpp_generator_test.dart
+++ b/packages/pigeon/test/cpp_generator_test.dart
@@ -1814,50 +1814,7 @@ void main() {
     expect(code, contains('// ///'));
   });
 
-  test("doesn't create codecs if no custom datatypes", () {
-    final Root root = Root(
-      apis: <Api>[
-        AstFlutterApi(
-          name: 'Api',
-          methods: <Method>[
-            Method(
-              name: 'method',
-              location: ApiLocation.flutter,
-              returnType: const TypeDeclaration.voidDeclaration(),
-              parameters: <Parameter>[
-                Parameter(
-                  name: 'field',
-                  type: const TypeDeclaration(
-                    baseName: 'int',
-                    isNullable: true,
-                  ),
-                ),
-              ],
-            )
-          ],
-        )
-      ],
-      classes: <Class>[],
-      enums: <Enum>[],
-    );
-    final StringBuffer sink = StringBuffer();
-    const CppGenerator generator = CppGenerator();
-    final OutputFileOptions<CppOptions> generatorOptions =
-        OutputFileOptions<CppOptions>(
-      fileType: FileType.header,
-      languageOptions: const CppOptions(),
-    );
-    generator.generate(
-      generatorOptions,
-      root,
-      sink,
-      dartPackageName: DEFAULT_PACKAGE_NAME,
-    );
-    final String code = sink.toString();
-    expect(code, isNot(contains(' : public flutter::StandardCodecSerializer')));
-  });
-
-  test('creates custom codecs if custom datatypes present', () {
+  test('creates custom codecs', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
diff --git a/packages/pigeon/test/dart/proxy_api_test.dart b/packages/pigeon/test/dart/proxy_api_test.dart
index 95c4f90da75..a8b3a5a9eb0 100644
--- a/packages/pigeon/test/dart/proxy_api_test.dart
+++ b/packages/pigeon/test/dart/proxy_api_test.dart
@@ -517,8 +517,8 @@ void main() {
           contains(
             r'__pigeon_channel.send(<Object?>[ '
             r'__pigeon_instanceIdentifier, '
-            r'validType, enumType.index, proxyApiType, '
-            r'nullableValidType, nullableEnumType?.index, nullableProxyApiType ])',
+            r'validType, enumType, proxyApiType, '
+            r'nullableValidType, nullableEnumType, nullableProxyApiType ])',
           ),
         );
       });
@@ -627,8 +627,8 @@ void main() {
           contains(
             r'__pigeon_channel.send(<Object?>[ '
             r'__pigeon_instanceIdentifier, '
-            r'validType, enumType.index, proxyApiType, '
-            r'nullableValidType, nullableEnumType?.index, nullableProxyApiType ])',
+            r'validType, enumType, proxyApiType, '
+            r'nullableValidType, nullableEnumType, nullableProxyApiType ])',
           ),
         );
         expect(
@@ -847,8 +847,8 @@ void main() {
           collapsedCode,
           contains(
             r'await __pigeon_channel.send(<Object?>[ this, validType, '
-            r'enumType.index, proxyApiType, nullableValidType, '
-            r'nullableEnumType?.index, nullableProxyApiType ])',
+            r'enumType, proxyApiType, nullableValidType, '
+            r'nullableEnumType, nullableProxyApiType ])',
           ),
         );
       });
@@ -1004,10 +1004,9 @@ void main() {
           contains(r'final int? arg_validType = (args[1] as int?);'),
         );
         expect(
-          collapsedCode,
+          code,
           contains(
-            r'final AnEnum? arg_enumType = args[2] == null ? '
-            r'null : AnEnum.values[args[2]! as int];',
+            r'final AnEnum? arg_enumType = (args[2] as AnEnum?);',
           ),
         );
         expect(
@@ -1019,10 +1018,9 @@ void main() {
           contains(r'final int? arg_nullableValidType = (args[4] as int?);'),
         );
         expect(
-          collapsedCode,
+          code,
           contains(
-            r'final AnEnum? arg_nullableEnumType = args[5] == null ? '
-            r'null : AnEnum.values[args[5]! as int];',
+            r'final AnEnum? arg_nullableEnumType = (args[5] as AnEnum?);',
           ),
         );
         expect(
diff --git a/packages/pigeon/test/dart_generator_test.dart b/packages/pigeon/test/dart_generator_test.dart
index a1470427c7f..944c6e334ce 100644
--- a/packages/pigeon/test/dart_generator_test.dart
+++ b/packages/pigeon/test/dart_generator_test.dart
@@ -532,8 +532,10 @@ void main() {
       dartPackageName: DEFAULT_PACKAGE_NAME,
     );
     final String code = sink.toString();
-    expect(code, contains('enum1?.index,'));
-    expect(code, contains('? Enum.values[result[0]! as int]'));
+    expect(code, contains('return value == null ? null : Enum.values[value];'));
+    expect(code, contains('writeValue(buffer, value.index);'));
+    expect(code,
+        contains('final EnumClass? arg_enumClass = (args[0] as EnumClass?);'));
     expect(code, contains('EnumClass doSomething(EnumClass enumClass);'));
   });
 
@@ -571,7 +573,7 @@ void main() {
     final String code = sink.toString();
     expect(code, contains('enum Foo {'));
     expect(code, contains('Future<void> bar(Foo? foo) async'));
-    expect(code, contains('__pigeon_channel.send(<Object?>[foo?.index])'));
+    expect(code, contains('__pigeon_channel.send(<Object?>[foo])'));
   });
 
   test('flutter non-nullable enum argument with enum class', () {
@@ -624,8 +626,9 @@ void main() {
       dartPackageName: DEFAULT_PACKAGE_NAME,
     );
     final String code = sink.toString();
-    expect(code, contains('enum1.index,'));
-    expect(code, contains('enum1: Enum.values[result[0]! as int]'));
+    expect(code, contains('writeValue(buffer, value.index)'));
+    expect(code, contains('return value == null ? null : Enum.values[value];'));
+    expect(code, contains('enum1: result[0]! as Enum,'));
   });
 
   test('host void argument', () {
@@ -1600,46 +1603,7 @@ name: foobar
     expect(code, contains('/// ///'));
   });
 
-  test("doesn't create codecs if no custom datatypes", () {
-    final Root root = Root(
-      apis: <Api>[
-        AstFlutterApi(
-          name: 'Api',
-          methods: <Method>[
-            Method(
-              name: 'method',
-              location: ApiLocation.flutter,
-              returnType: const TypeDeclaration.voidDeclaration(),
-              parameters: <Parameter>[
-                Parameter(
-                  name: 'field',
-                  type: const TypeDeclaration(
-                    baseName: 'int',
-                    isNullable: true,
-                  ),
-                ),
-              ],
-            )
-          ],
-        )
-      ],
-      classes: <Class>[],
-      enums: <Enum>[],
-    );
-    final StringBuffer sink = StringBuffer();
-    const DartGenerator generator = DartGenerator();
-    generator.generate(
-      const DartOptions(),
-      root,
-      sink,
-      dartPackageName: DEFAULT_PACKAGE_NAME,
-    );
-    final String code = sink.toString();
-    expect(code, isNot(contains('extends StandardMessageCodec')));
-    expect(code, contains('StandardMessageCodec'));
-  });
-
-  test('creates custom codecs if custom datatypes present', () {
+  test('creates custom codecs', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
@@ -1740,10 +1704,10 @@ name: foobar
     );
 
     final String testCode = sink.toString();
-    expect(
-        testCode,
-        contains(
-            'final Enum? arg_anEnum = args[0] == null ? null : Enum.values[args[0]! as int]'));
+    expect(testCode, contains('final Enum? arg_anEnum = (args[0] as Enum?);'));
+    expect(testCode,
+        contains('return value == null ? null : Enum.values[value];'));
+    expect(testCode, contains('writeValue(buffer, value.index);'));
   });
 
   test('connection error contains channel name', () {
diff --git a/packages/pigeon/test/generator_tools_test.dart b/packages/pigeon/test/generator_tools_test.dart
index e68bb96239c..d7c49e37154 100644
--- a/packages/pigeon/test/generator_tools_test.dart
+++ b/packages/pigeon/test/generator_tools_test.dart
@@ -44,11 +44,6 @@ final Class emptyClass = Class(name: 'className', fields: <NamedType>[
   )
 ]);
 
-final Enum emptyEnum = Enum(
-  name: 'enumName',
-  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
-);
-
 void main() {
   test('test merge maps', () {
     final Map<String, Object> source = <String, Object>{
@@ -77,144 +72,26 @@ void main() {
     expect(_equalMaps(expected, mergeMaps(source, modification)), isTrue);
   });
 
-  test('get codec classes from argument type arguments', () {
-    final AstFlutterApi api = AstFlutterApi(name: 'Api', methods: <Method>[
-      Method(
-        name: 'doSomething',
-        location: ApiLocation.flutter,
-        parameters: <Parameter>[
-          Parameter(
-            type: TypeDeclaration(
-              baseName: 'List',
-              isNullable: false,
-              typeArguments: <TypeDeclaration>[
-                TypeDeclaration(
-                  baseName: 'Input',
-                  isNullable: true,
-                  associatedClass: emptyClass,
-                )
-              ],
-            ),
-            name: '',
-          )
-        ],
-        returnType: TypeDeclaration(
-          baseName: 'Output',
-          isNullable: false,
-          associatedClass: emptyClass,
-        ),
-        isAsynchronous: true,
-      )
-    ]);
-    final Root root =
-        Root(classes: <Class>[], apis: <Api>[api], enums: <Enum>[]);
-    final List<EnumeratedClass> classes = getCodecClasses(api, root).toList();
-    expect(classes.length, 2);
-    expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Input')
-            .length,
-        1);
-    expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Output')
-            .length,
-        1);
-  });
-
-  test('get codec classes from return value type arguments', () {
-    final AstFlutterApi api = AstFlutterApi(name: 'Api', methods: <Method>[
-      Method(
-        name: 'doSomething',
-        location: ApiLocation.flutter,
-        parameters: <Parameter>[
-          Parameter(
-            type: TypeDeclaration(
-              baseName: 'Output',
-              isNullable: false,
-              associatedClass: emptyClass,
-            ),
-            name: '',
-          )
-        ],
-        returnType: TypeDeclaration(
-          baseName: 'List',
-          isNullable: false,
-          typeArguments: <TypeDeclaration>[
-            TypeDeclaration(
-              baseName: 'Input',
+  test('get codec types from all classes and enums', () {
+    final Root root = Root(classes: <Class>[
+      Class(name: 'name', fields: <NamedType>[
+        NamedType(
+            name: 'name',
+            type: const TypeDeclaration(
+              baseName: 'name',
               isNullable: true,
-              associatedClass: emptyClass,
-            )
-          ],
-        ),
-        isAsynchronous: true,
-      )
-    ]);
-    final Root root =
-        Root(classes: <Class>[], apis: <Api>[api], enums: <Enum>[]);
-    final List<EnumeratedClass> classes = getCodecClasses(api, root).toList();
-    expect(classes.length, 2);
-    expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Input')
-            .length,
-        1);
-    expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Output')
-            .length,
-        1);
-  });
-
-  test('get codec classes from all arguments', () {
-    final AstFlutterApi api = AstFlutterApi(name: 'Api', methods: <Method>[
-      Method(
-        name: 'doSomething',
-        location: ApiLocation.flutter,
-        parameters: <Parameter>[
-          Parameter(
-            type: TypeDeclaration(
-              baseName: 'Foo',
-              isNullable: false,
-              associatedClass: emptyClass,
-            ),
-            name: '',
-          ),
-          Parameter(
-            type: TypeDeclaration(
-              baseName: 'Bar',
-              isNullable: false,
-              associatedEnum: emptyEnum,
-            ),
-            name: '',
-          ),
-        ],
-        returnType: const TypeDeclaration(
-          baseName: 'List',
-          isNullable: false,
-          typeArguments: <TypeDeclaration>[TypeDeclaration.voidDeclaration()],
-        ),
-        isAsynchronous: true,
-      )
+            ))
+      ])
+    ], apis: <Api>[], enums: <Enum>[
+      Enum(name: 'enum', members: <EnumMember>[
+        EnumMember(name: 'enumMember'),
+      ])
     ]);
-    final Root root =
-        Root(classes: <Class>[], apis: <Api>[api], enums: <Enum>[]);
-    final List<EnumeratedClass> classes = getCodecClasses(api, root).toList();
-    expect(classes.length, 2);
-    expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Foo')
-            .length,
-        1);
-    expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Bar')
-            .length,
-        1);
+    final List<EnumeratedType> types = getEnumeratedTypes(root).toList();
+    expect(types.length, 2);
   });
 
-  test('getCodecClasses: nested type arguments', () {
+  test('getEnumeratedTypes:ed type arguments', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
@@ -256,22 +133,17 @@ void main() {
             ))
       ])
     ], enums: <Enum>[]);
-    final List<EnumeratedClass> classes =
-        getCodecClasses(root.apis[0], root).toList();
+    final List<EnumeratedType> classes = getEnumeratedTypes(root).toList();
     expect(classes.length, 2);
     expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Foo')
-            .length,
+        classes.where((EnumeratedType element) => element.name == 'Foo').length,
         1);
     expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Bar')
-            .length,
+        classes.where((EnumeratedType element) => element.name == 'Bar').length,
         1);
   });
 
-  test('getCodecClasses: with Object', () {
+  test('getEnumeratedTypes: Object', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(
         name: 'Api1',
@@ -300,17 +172,14 @@ void main() {
             type: const TypeDeclaration(baseName: 'int', isNullable: true)),
       ]),
     ], enums: <Enum>[]);
-    final List<EnumeratedClass> classes =
-        getCodecClasses(root.apis[0], root).toList();
+    final List<EnumeratedType> classes = getEnumeratedTypes(root).toList();
     expect(classes.length, 1);
     expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Foo')
-            .length,
+        classes.where((EnumeratedType element) => element.name == 'Foo').length,
         1);
   });
 
-  test('getCodecClasses: unique entries', () {
+  test('getEnumeratedTypes:ue entries', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(
         name: 'Api1',
@@ -357,13 +226,10 @@ void main() {
             type: const TypeDeclaration(baseName: 'int', isNullable: true)),
       ]),
     ], enums: <Enum>[]);
-    final List<EnumeratedClass> classes =
-        getCodecClasses(root.apis[0], root).toList();
+    final List<EnumeratedType> classes = getEnumeratedTypes(root).toList();
     expect(classes.length, 1);
     expect(
-        classes
-            .where((EnumeratedClass element) => element.name == 'Foo')
-            .length,
+        classes.where((EnumeratedType element) => element.name == 'Foo').length,
         1);
   });
 
diff --git a/packages/pigeon/test/java_generator_test.dart b/packages/pigeon/test/java_generator_test.dart
index c3bb560279d..3982c25150b 100644
--- a/packages/pigeon/test/java_generator_test.dart
+++ b/packages/pigeon/test/java_generator_test.dart
@@ -739,12 +739,8 @@ void main() {
     expect(code, contains('private Enum1(final int index) {'));
     expect(code, contains('      this.index = index;'));
 
-    expect(code,
-        contains('toListResult.add(enum1 == null ? null : enum1.index);'));
-    expect(
-        code,
-        contains(
-            'pigeonResult.setEnum1(enum1 == null ? null : Enum1.values()[(int) enum1])'));
+    expect(code, contains('toListResult.add(enum1);'));
+    expect(code, contains('pigeonResult.setEnum1((Enum1) enum1);'));
   });
 
   test('primitive enum host', () {
@@ -782,10 +778,13 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('public enum Foo'));
+    expect(code,
+        contains('return value == null ? null : Foo.values()[(int) value];'));
     expect(
         code,
         contains(
-            'Foo fooArg = args.get(0) == null ? null : Foo.values()[(int) args.get(0)];'));
+            'writeValue(stream, value == null ? null : ((Foo) value).index);'));
+    expect(code, contains('Foo fooArg = (Foo) args.get(0);'));
   });
 
   Iterable<String> makeIterable(String string) sync* {
@@ -1512,47 +1511,7 @@ void main() {
     expect(code, isNot(contains('*//')));
   });
 
-  test("doesn't create codecs if no custom datatypes", () {
-    final Root root = Root(
-      apis: <Api>[
-        AstFlutterApi(
-          name: 'Api',
-          methods: <Method>[
-            Method(
-              name: 'method',
-              location: ApiLocation.flutter,
-              returnType: const TypeDeclaration.voidDeclaration(),
-              parameters: <Parameter>[
-                Parameter(
-                  name: 'field',
-                  type: const TypeDeclaration(
-                    baseName: 'int',
-                    isNullable: true,
-                  ),
-                ),
-              ],
-            )
-          ],
-        )
-      ],
-      classes: <Class>[],
-      enums: <Enum>[],
-    );
-    final StringBuffer sink = StringBuffer();
-    const JavaOptions javaOptions = JavaOptions(className: 'Messages');
-    const JavaGenerator generator = JavaGenerator();
-    generator.generate(
-      javaOptions,
-      root,
-      sink,
-      dartPackageName: DEFAULT_PACKAGE_NAME,
-    );
-    final String code = sink.toString();
-    expect(code, isNot(contains(' extends StandardMessageCodec')));
-    expect(code, contains('StandardMessageCodec'));
-  });
-
-  test('creates custom codecs if custom datatypes present', () {
+  test('creates custom codecs', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
diff --git a/packages/pigeon/test/kotlin_generator_test.dart b/packages/pigeon/test/kotlin_generator_test.dart
index 40c1e75c3aa..ea87f508ca1 100644
--- a/packages/pigeon/test/kotlin_generator_test.dart
+++ b/packages/pigeon/test/kotlin_generator_test.dart
@@ -133,8 +133,8 @@ void main() {
     expect(code, contains('val field1: Foo,'));
     expect(code, contains('val field2: String'));
     expect(code, contains('fun fromList(__pigeon_list: List<Any?>): Bar'));
-    expect(
-        code, contains('val field1 = Foo.ofRaw(__pigeon_list[0] as Int)!!\n'));
+    expect(code, contains('Foo.ofRaw(it)'));
+    expect(code, contains('val field1 = __pigeon_list[0] as Foo'));
     expect(code, contains('val field2 = __pigeon_list[1] as String\n'));
     expect(code, contains('fun toList(): List<Any?>'));
   });
@@ -173,7 +173,7 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('enum class Foo(val raw: Int) {'));
-    expect(code, contains('val fooArg = Foo.ofRaw(args[0] as Int)'));
+    expect(code, contains('Foo.ofRaw(it)'));
   });
 
   test('gen one host api', () {
@@ -242,7 +242,7 @@ void main() {
             val args = message as List<Any?>
             val inputArg = args[0] as Input
             val wrapped: List<Any?> = try {
-              listOf<Any?>(api.doSomething(inputArg))
+              listOf(api.doSomething(inputArg))
             } catch (exception: Throwable) {
               wrapError(exception)
             }
@@ -595,7 +595,7 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('fun doSomething(): Output'));
-    expect(code, contains('listOf<Any?>(api.doSomething())'));
+    expect(code, contains('listOf(api.doSomething())'));
     expect(code, contains('wrapError(exception)'));
     expect(code, contains('reply(wrapped)'));
   });
@@ -1093,7 +1093,7 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('fun doit(): List<Long?>'));
-    expect(code, contains('listOf<Any?>(api.doit())'));
+    expect(code, contains('listOf(api.doit())'));
     expect(code, contains('reply.reply(wrapped)'));
   });
 
@@ -1171,7 +1171,7 @@ void main() {
         code,
         contains(
             'val yArg = args[1].let { num -> if (num is Int) num.toLong() else num as Long }'));
-    expect(code, contains('listOf<Any?>(api.add(xArg, yArg))'));
+    expect(code, contains('listOf(api.add(xArg, yArg))'));
     expect(code, contains('reply.reply(wrapped)'));
   });
 
@@ -1491,47 +1491,7 @@ void main() {
     expect(code, isNot(contains('*//')));
   });
 
-  test("doesn't create codecs if no custom datatypes", () {
-    final Root root = Root(
-      apis: <Api>[
-        AstFlutterApi(
-          name: 'Api',
-          methods: <Method>[
-            Method(
-              name: 'method',
-              location: ApiLocation.flutter,
-              returnType: const TypeDeclaration.voidDeclaration(),
-              parameters: <Parameter>[
-                Parameter(
-                  name: 'field',
-                  type: const TypeDeclaration(
-                    baseName: 'int',
-                    isNullable: true,
-                  ),
-                ),
-              ],
-            )
-          ],
-        )
-      ],
-      classes: <Class>[],
-      enums: <Enum>[],
-    );
-    final StringBuffer sink = StringBuffer();
-    const KotlinOptions kotlinOptions = KotlinOptions();
-    const KotlinGenerator generator = KotlinGenerator();
-    generator.generate(
-      kotlinOptions,
-      root,
-      sink,
-      dartPackageName: DEFAULT_PACKAGE_NAME,
-    );
-    final String code = sink.toString();
-    expect(code, isNot(contains(' : StandardMessageCodec() ')));
-    expect(code, contains('StandardMessageCodec'));
-  });
-
-  test('creates custom codecs if custom datatypes present', () {
+  test('creates custom codecs', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
@@ -1823,4 +1783,99 @@ void main() {
     expect(code, contains(errorClassName));
     expect(code, isNot(contains('FlutterError')));
   });
+
+  test('do not generate duplicated entries in writeValue', () {
+    final Root root = Root(
+      apis: <Api>[
+        AstHostApi(
+          name: 'FooBar',
+          methods: <Method>[
+            Method(
+              name: 'fooBar',
+              location: ApiLocation.host,
+              returnType: const TypeDeclaration.voidDeclaration(),
+              parameters: <Parameter>[
+                Parameter(
+                  name: 'bar',
+                  type: const TypeDeclaration(
+                    baseName: 'Bar',
+                    isNullable: false,
+                  ),
+                ),
+              ],
+            )
+          ],
+        )
+      ],
+      classes: <Class>[
+        Class(
+          name: 'Foo',
+          fields: <NamedType>[
+            NamedType(
+              type: const TypeDeclaration(
+                baseName: 'int',
+                isNullable: false,
+              ),
+              name: 'foo',
+            ),
+          ],
+        ),
+        Class(
+          name: 'Bar',
+          fields: <NamedType>[
+            NamedType(
+              type: const TypeDeclaration(
+                baseName: 'Foo',
+                isNullable: false,
+              ),
+              name: 'foo',
+            ),
+            NamedType(
+              type: const TypeDeclaration(
+                baseName: 'Foo',
+                isNullable: true,
+              ),
+              name: 'foo2',
+            ),
+          ],
+        ),
+      ],
+      enums: <Enum>[],
+    );
+
+    final StringBuffer sink = StringBuffer();
+    const String errorClassName = 'FooError';
+    const KotlinOptions kotlinOptions =
+        KotlinOptions(errorClassName: errorClassName);
+    const KotlinGenerator generator = KotlinGenerator();
+    generator.generate(
+      kotlinOptions,
+      root,
+      sink,
+      dartPackageName: DEFAULT_PACKAGE_NAME,
+    );
+
+    final String code = sink.toString();
+
+    // Extract override fun writeValue block
+    final int blockStart = code.indexOf('override fun writeValue');
+    expect(blockStart, isNot(-1));
+    final int blockEnd = code.indexOf('super.writeValue', blockStart);
+    expect(blockEnd, isNot(-1));
+    final String writeValueBlock = code.substring(blockStart, blockEnd);
+
+    // Count the occurrence of 'is Foo' in the block
+    int count = 0;
+    int index = 0;
+    while (index != -1) {
+      index = writeValueBlock.indexOf('is Foo', index);
+      if (index != -1) {
+        count++;
+        index += 'is Foo'.length;
+      }
+    }
+
+    // There should be only one occurrence of 'is Foo' in the block
+    expect(count, 1);
+  });
 }
diff --git a/packages/pigeon/test/objc_generator_test.dart b/packages/pigeon/test/objc_generator_test.dart
index 49ab94b78bc..84146be42db 100644
--- a/packages/pigeon/test/objc_generator_test.dart
+++ b/packages/pigeon/test/objc_generator_test.dart
@@ -183,7 +183,7 @@ void main() {
     expect(
         code,
         contains(
-            'Enum1Box *enum1 = enum1AsNumber == nil ? nil : [[Enum1Box alloc] initWithValue:[enum1AsNumber integerValue]];'));
+            'return enumAsNumber == nil ? nil : [[Enum1Box alloc] initWithValue:[enumAsNumber integerValue]];'));
   });
 
   test('primitive enum host', () {
@@ -246,7 +246,9 @@ void main() {
       expect(
           code,
           contains(
-              'ACFoo arg_foo = [GetNullableObjectAtIndex(args, 0) integerValue];'));
+              'return enumAsNumber == nil ? nil : [[ACFooBox alloc] initWithValue:[enumAsNumber integerValue]];'));
+
+      expect(code, contains('ACFooBox * box = (ACFooBox *)value;'));
     }
   });
 
@@ -381,7 +383,6 @@ void main() {
     expect(code, contains('/// @return `nil` only when `error != nil`.'));
     expect(code, matches('nullable Output.*doSomething.*Input.*FlutterError'));
     expect(code, matches('SetUpApi.*<Api>.*_Nullable'));
-    expect(code, contains('ApiGetCodec(void)'));
   });
 
   test('gen one api source', () {
@@ -439,7 +440,6 @@ void main() {
         code,
         contains(
             'NSCAssert([api respondsToSelector:@selector(doSomething:error:)'));
-    expect(code, contains('ApiGetCodec(void) {'));
   });
 
   test('all the simple datatypes header', () {
@@ -819,7 +819,6 @@ void main() {
         contains(
             'initWithBinaryMessenger:(id<FlutterBinaryMessenger>)binaryMessenger;'));
     expect(code, matches('void.*doSomething.*Input.*Output'));
-    expect(code, contains('ApiGetCodec(void)'));
   });
 
   test('gen flutter api source', () {
@@ -871,7 +870,6 @@ void main() {
     final String code = sink.toString();
     expect(code, contains('@implementation Api'));
     expect(code, matches('void.*doSomething.*Input.*Output.*{'));
-    expect(code, contains('ApiGetCodec(void) {'));
   });
 
   test('gen host void header', () {
@@ -2121,7 +2119,7 @@ void main() {
         dartPackageName: DEFAULT_PACKAGE_NAME,
       );
       final String code = sink.toString();
-      expect(code, contains('NSArray *args = message;'));
+      expect(code, contains('NSArray<id> *args = message;'));
       expect(
           code,
           contains(
@@ -2193,7 +2191,7 @@ void main() {
         dartPackageName: DEFAULT_PACKAGE_NAME,
       );
       final String code = sink.toString();
-      expect(code, contains('NSArray *args = message;'));
+      expect(code, contains('NSArray<id> *args = message;'));
       expect(
           code,
           contains(
@@ -2780,50 +2778,7 @@ void main() {
     expect(code, contains('/// ///'));
   });
 
-  test("doesn't create codecs if no custom datatypes", () {
-    final Root root = Root(
-      apis: <Api>[
-        AstFlutterApi(
-          name: 'Api',
-          methods: <Method>[
-            Method(
-              name: 'method',
-              location: ApiLocation.flutter,
-              returnType: const TypeDeclaration.voidDeclaration(),
-              parameters: <Parameter>[
-                Parameter(
-                  name: 'field',
-                  type: const TypeDeclaration(
-                    baseName: 'int',
-                    isNullable: true,
-                  ),
-                ),
-              ],
-            )
-          ],
-        )
-      ],
-      classes: <Class>[],
-      enums: <Enum>[],
-    );
-    final StringBuffer sink = StringBuffer();
-    const ObjcGenerator generator = ObjcGenerator();
-    final OutputFileOptions<ObjcOptions> generatorOptions =
-        OutputFileOptions<ObjcOptions>(
-      fileType: FileType.source,
-      languageOptions: const ObjcOptions(),
-    );
-    generator.generate(
-      generatorOptions,
-      root,
-      sink,
-      dartPackageName: DEFAULT_PACKAGE_NAME,
-    );
-    final String code = sink.toString();
-    expect(code, isNot(contains(' : FlutterStandardReader')));
-  });
-
-  test('creates custom codecs if custom datatypes present', () {
+  test('creates custom codecs', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
diff --git a/packages/pigeon/test/pigeon_lib_test.dart b/packages/pigeon/test/pigeon_lib_test.dart
index 34516e8c0de..8d56fa9d66f 100644
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@@ -1123,28 +1123,6 @@ abstract class Api {
     expect(results.errors.length, 0);
   });
 
-  test('Enum key not supported', () {
-    const String code = '''
-enum MessageKey {
-  title,
-  subtitle,
-  description,
-}
-
-class Message {
-  int? id;
-  Map<MessageKey?, String?>? additionalProperties;
-}
-
-@HostApi()
-abstract class HostApiBridge {
-  void sendMessage(Message message);
-}
-''';
-    final ParseResults results = parseSource(code);
-    expect(results.errors.length, 1);
-  });
-
   test('Export unreferenced enums', () {
     const String code = '''
 enum MessageKey {
@@ -1213,6 +1191,36 @@ class Message {
     expect(options.objcOptions!.copyrightHeader, <String>['A', 'Header']);
   });
 
+  test('@ConfigurePigeon ObjcOptions.headerIncludePath', () {
+    const String code = '''
+@ConfigurePigeon(PigeonOptions(
+  objcOptions: ObjcOptions(headerIncludePath: 'Header.path'),
+))
+class Message {
+  int? id;
+}
+''';
+
+    final ParseResults results = parseSource(code);
+    final PigeonOptions options = PigeonOptions.fromMap(results.pigeonOptions!);
+    expect(options.objcOptions?.headerIncludePath, 'Header.path');
+  });
+
+  test('@ConfigurePigeon CppOptions.headerIncludePath', () {
+    const String code = '''
+@ConfigurePigeon(PigeonOptions(
+  cppOptions: CppOptions(headerIncludePath: 'Header.path'),
+))
+class Message {
+  int? id;
+}
+''';
+
+    final ParseResults results = parseSource(code);
+    final PigeonOptions options = PigeonOptions.fromMap(results.pigeonOptions!);
+    expect(options.cppOptions?.headerIncludePath, 'Header.path');
+  });
+
   test('return nullable', () {
     const String code = '''
 @HostApi()
diff --git a/packages/pigeon/test/swift_generator_test.dart b/packages/pigeon/test/swift_generator_test.dart
index 780736c03b5..6ffe4f4d9d7 100644
--- a/packages/pigeon/test/swift_generator_test.dart
+++ b/packages/pigeon/test/swift_generator_test.dart
@@ -119,7 +119,12 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('enum Foo: Int'));
-    expect(code, contains('let fooArg = Foo(rawValue: args[0] as! Int)!'));
+    expect(
+        code,
+        contains(
+            'let enumResultAsInt: Int? = nilOrValue(self.readValue() as? Int)'));
+    expect(code, contains('enumResult = Foo(rawValue: enumResultAsInt)'));
+    expect(code, contains('let fooArg = args[0] as! Foo'));
     expect(code, isNot(contains('if (')));
   });
 
@@ -1326,46 +1331,7 @@ void main() {
     expect(code, contains('/// ///'));
   });
 
-  test("doesn't create codecs if no custom datatypes", () {
-    final Root root = Root(
-      apis: <Api>[
-        AstFlutterApi(
-          name: 'Api',
-          methods: <Method>[
-            Method(
-              name: 'method',
-              location: ApiLocation.flutter,
-              returnType: const TypeDeclaration.voidDeclaration(),
-              parameters: <Parameter>[
-                Parameter(
-                  name: 'field',
-                  type: const TypeDeclaration(
-                    baseName: 'int',
-                    isNullable: true,
-                  ),
-                ),
-              ],
-            )
-          ],
-        )
-      ],
-      classes: <Class>[],
-      enums: <Enum>[],
-    );
-    final StringBuffer sink = StringBuffer();
-    const SwiftOptions swiftOptions = SwiftOptions();
-    const SwiftGenerator generator = SwiftGenerator();
-    generator.generate(
-      swiftOptions,
-      root,
-      sink,
-      dartPackageName: DEFAULT_PACKAGE_NAME,
-    );
-    final String code = sink.toString();
-    expect(code, isNot(contains(': FlutterStandardReader ')));
-  });
-
-  test('creates custom codecs if custom datatypes present', () {
+  test('creates custom codecs', () {
     final Root root = Root(apis: <Api>[
       AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
diff --git a/packages/pigeon/tool/shared/generation.dart b/packages/pigeon/tool/shared/generation.dart
index c4cf84582f1..8166e49d73f 100644
--- a/packages/pigeon/tool/shared/generation.dart
+++ b/packages/pigeon/tool/shared/generation.dart
@@ -98,6 +98,9 @@ Future<int> generateTestPigeons({required String baseDir}) async {
     int generateCode = await runPigeon(
       input: './pigeons/$input.dart',
       dartOut: '$sharedDartOutputBase/lib/src/generated/$input.gen.dart',
+      dartTestOut: input == 'message'
+          ? '$sharedDartOutputBase/test/test_message.gen.dart'
+          : null,
       // Android
       kotlinOut: skipLanguages.contains(GeneratorLanguage.kotlin)
           ? null