diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index e5dcda5393c..66ef942dc5c 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -186,3 +186,15 @@ message = "Smithy IDL v2 mixins are now supported"
 references = ["smithy-rs#1680"]
 meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "all"}
 author = "ogudavid"
+
+[[smithy-rs]]
+message = "Upgrade Smithy to 1.25.0"
+references = ["smithy-rs#1725"]
+meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "all"}
+author = "sugmanue"
+
+[[smithy-rs]]
+message = "Correctly determine nullability of members in IDLv2 models"
+references = ["smithy-rs#1725"]
+meta = { "breaking" = false, "tada" = false, "bug" = true, "target" = "all"}
+author = "sugmanue"
diff --git a/aws/sdk-adhoc-test/build.gradle.kts b/aws/sdk-adhoc-test/build.gradle.kts
index b6d59ef47c8..9edc1aab731 100644
--- a/aws/sdk-adhoc-test/build.gradle.kts
+++ b/aws/sdk-adhoc-test/build.gradle.kts
@@ -25,6 +25,12 @@ configure<software.amazon.smithy.gradle.SmithyExtension> {
 }
 
 buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        google()
+    }
+
     val smithyVersion: String by project
     dependencies {
         classpath("software.amazon.smithy:smithy-cli:$smithyVersion")
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/BoxPrimitiveShapes.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/BoxPrimitiveShapes.kt
deleted file mode 100644
index 7f2cc008eff..00000000000
--- a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/BoxPrimitiveShapes.kt
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package software.amazon.smithy.rustsdk.customize.ec2
-
-import software.amazon.smithy.model.Model
-import software.amazon.smithy.model.shapes.AbstractShapeBuilder
-import software.amazon.smithy.model.shapes.BigDecimalShape
-import software.amazon.smithy.model.shapes.BigIntegerShape
-import software.amazon.smithy.model.shapes.BooleanShape
-import software.amazon.smithy.model.shapes.ByteShape
-import software.amazon.smithy.model.shapes.DoubleShape
-import software.amazon.smithy.model.shapes.FloatShape
-import software.amazon.smithy.model.shapes.IntegerShape
-import software.amazon.smithy.model.shapes.LongShape
-import software.amazon.smithy.model.shapes.NumberShape
-import software.amazon.smithy.model.shapes.Shape
-import software.amazon.smithy.model.shapes.ShortShape
-import software.amazon.smithy.model.traits.BoxTrait
-import software.amazon.smithy.model.transform.ModelTransformer
-import software.amazon.smithy.rust.codegen.util.UNREACHABLE
-import software.amazon.smithy.utils.ToSmithyBuilder
-
-object BoxPrimitiveShapes {
-    fun processModel(model: Model): Model {
-        val transformer = ModelTransformer.create()
-        return transformer.mapShapes(model, ::boxPrimitives)
-    }
-
-    private fun boxPrimitives(shape: Shape): Shape {
-        return when (shape) {
-            is NumberShape -> {
-                when (shape) {
-                    is ByteShape -> box(shape)
-                    is DoubleShape -> box(shape)
-                    is LongShape -> box(shape)
-                    is ShortShape -> box(shape)
-                    is FloatShape -> box(shape)
-                    is BigDecimalShape -> box(shape)
-                    is BigIntegerShape -> box(shape)
-                    is IntegerShape -> box(shape)
-                    else -> UNREACHABLE("unhandled numeric shape: $shape")
-                }
-            }
-            is BooleanShape -> box(shape)
-            else -> shape
-        }
-    }
-
-    private fun <T> box(shape: T): Shape where T : Shape, T : ToSmithyBuilder<T> {
-        return (shape.toBuilder() as AbstractShapeBuilder<*, T>).addTrait(BoxTrait()).build()
-    }
-}
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/EC2MakePrimitivesOptional.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/EC2MakePrimitivesOptional.kt
new file mode 100644
index 00000000000..bff87c0d5d5
--- /dev/null
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/EC2MakePrimitivesOptional.kt
@@ -0,0 +1,24 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rustsdk.customize.ec2
+
+import software.amazon.smithy.model.Model
+import software.amazon.smithy.model.shapes.Shape
+import software.amazon.smithy.model.traits.ClientOptionalTrait
+import software.amazon.smithy.model.transform.ModelTransformer
+
+object EC2MakePrimitivesOptional {
+    fun processModel(model: Model): Model {
+        val updates = arrayListOf<Shape>()
+        for (struct in model.structureShapes) {
+            for (member in struct.allMembers.values) {
+                updates.add(member.toBuilder().addTrait(ClientOptionalTrait()).build())
+            }
+
+        }
+        return ModelTransformer.create().replaceShapes(model, updates)
+    }
+}
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/Ec2Decorator.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/Ec2Decorator.kt
index d4152dc324d..784ed2c47a1 100644
--- a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/Ec2Decorator.kt
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ec2/Ec2Decorator.kt
@@ -26,7 +26,7 @@ class Ec2Decorator : RustCodegenDecorator<ClientCodegenContext> {
         // need to be boxed for the API to work properly
         return model.letIf(
             applies(service),
-            BoxPrimitiveShapes::processModel,
+            EC2MakePrimitivesOptional::processModel,
         )
     }
 
diff --git a/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/ec2/BoxPrimitiveShapesTest.kt b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/ec2/AddClientOptionalToShapesTest.kt
similarity index 69%
rename from aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/ec2/BoxPrimitiveShapesTest.kt
rename to aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/ec2/AddClientOptionalToShapesTest.kt
index ff9a944c3df..2d5f7325a72 100644
--- a/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/ec2/BoxPrimitiveShapesTest.kt
+++ b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/ec2/AddClientOptionalToShapesTest.kt
@@ -7,13 +7,12 @@ package software.amazon.smithy.rustsdk.customize.ec2
 
 import io.kotest.matchers.shouldBe
 import org.junit.jupiter.api.Test
+import software.amazon.smithy.model.knowledge.NullableIndex
 import software.amazon.smithy.model.shapes.StructureShape
-import software.amazon.smithy.model.traits.BoxTrait
 import software.amazon.smithy.rust.codegen.testutil.asSmithyModel
-import software.amazon.smithy.rust.codegen.util.hasTrait
 import software.amazon.smithy.rust.codegen.util.lookup
 
-internal class BoxPrimitiveShapesTest {
+internal class AddClientOptionalToShapesTest {
     @Test
     fun `primitive shapes are boxed`() {
         val baseModel = """
@@ -33,15 +32,11 @@ internal class BoxPrimitiveShapesTest {
             structure Other {}
 
         """.asSmithyModel()
-        val model = BoxPrimitiveShapes.processModel(baseModel)
-
+        val model = EC2MakePrimitivesOptional.processModel(baseModel)
+        val nullableIndex = NullableIndex(model)
         val struct = model.lookup<StructureShape>("test#Primitives")
         struct.members().forEach {
-            val target = model.expectShape(it.target)
-            when (target) {
-                is StructureShape -> target.hasTrait<BoxTrait>() shouldBe false
-                else -> target.hasTrait<BoxTrait>() shouldBe true
-            }
+            nullableIndex.isMemberNullable(it, NullableIndex.CheckMode.CLIENT_ZERO_VALUE_V1) shouldBe true
         }
     }
 }
diff --git a/aws/sdk/build.gradle.kts b/aws/sdk/build.gradle.kts
index e09f62b44a3..be8857614ce 100644
--- a/aws/sdk/build.gradle.kts
+++ b/aws/sdk/build.gradle.kts
@@ -35,6 +35,12 @@ val sdkOutputDir = outputDir.resolve("sdk")
 val examplesOutputDir = outputDir.resolve("examples")
 
 buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        google()
+    }
+
     val smithyVersion: String by project
     dependencies {
         classpath("software.amazon.smithy:smithy-aws-traits:$smithyVersion")
diff --git a/build.gradle.kts b/build.gradle.kts
index c6ff9c783bb..dd0d11b1e9e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -4,6 +4,7 @@
  */
 buildscript {
     repositories {
+        mavenLocal()
         mavenCentral()
         google()
     }
diff --git a/buildSrc/build.gradle.kts b/buildSrc/build.gradle.kts
index b1d48a62e5c..85ddfe20412 100644
--- a/buildSrc/build.gradle.kts
+++ b/buildSrc/build.gradle.kts
@@ -11,6 +11,7 @@ plugins {
     jacoco
 }
 repositories {
+    mavenLocal()
     mavenCentral()
     google()
 }
diff --git a/codegen-client-test/build.gradle.kts b/codegen-client-test/build.gradle.kts
index 0fb9ea9482f..8155ebeda3e 100644
--- a/codegen-client-test/build.gradle.kts
+++ b/codegen-client-test/build.gradle.kts
@@ -21,6 +21,11 @@ val pluginName = "rust-codegen"
 val workingDirUnderBuildDir = "smithyprojections/codegen-client-test/"
 
 buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        google()
+    }
     val smithyVersion: String by project
     dependencies {
         classpath("software.amazon.smithy:smithy-cli:$smithyVersion")
diff --git a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/CodegenVisitor.kt b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/CodegenVisitor.kt
index 184b94581c3..834f6806e73 100644
--- a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/CodegenVisitor.kt
+++ b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/CodegenVisitor.kt
@@ -7,6 +7,7 @@ package software.amazon.smithy.rust.codegen.smithy
 
 import software.amazon.smithy.build.PluginContext
 import software.amazon.smithy.model.Model
+import software.amazon.smithy.model.knowledge.NullableIndex
 import software.amazon.smithy.model.neighbor.Walker
 import software.amazon.smithy.model.shapes.ServiceShape
 import software.amazon.smithy.model.shapes.Shape
@@ -62,6 +63,7 @@ class CodegenVisitor(context: PluginContext, private val codegenDecorator: RustC
                 renameExceptions = settings.codegenConfig.renameExceptions,
                 handleRequired = false,
                 handleRustBoxing = true,
+                nullabilityCheckMode = NullableIndex.CheckMode.CLIENT_ZERO_VALUE_V1_NO_INPUT,
             )
         val baseModel = baselineTransform(context.model)
         val service = settings.getService(baseModel)
diff --git a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt
index 4b49387c5cd..dda0d9b3def 100644
--- a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt
+++ b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt
@@ -65,6 +65,7 @@ data class SymbolVisitorConfig(
     val renameExceptions: Boolean,
     val handleRustBoxing: Boolean,
     val handleRequired: Boolean,
+    val nullabilityCheckMode: NullableIndex.CheckMode,
 )
 
 /**
@@ -211,7 +212,7 @@ open class SymbolVisitor(
     private fun handleOptionality(symbol: Symbol, member: MemberShape): Symbol =
         if (config.handleRequired && member.isRequired) {
             symbol
-        } else if (nullableIndex.isNullable(member)) {
+        } else if (nullableIndex.isMemberNullable(member, config.nullabilityCheckMode)) {
             symbol.makeOptional()
         } else {
             symbol
diff --git a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/testutil/TestHelpers.kt b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/testutil/TestHelpers.kt
index 55cc877c22a..3c2a3eff0ef 100644
--- a/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/testutil/TestHelpers.kt
+++ b/codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/testutil/TestHelpers.kt
@@ -94,6 +94,7 @@ fun String.asSmithyModel(sourceLocation: String? = null, smithyVersion: String =
         .unwrap()
 }
 
+
 /**
  * In tests, we frequently need to generate a struct, a builder, and an impl block to access said builder.
  */
diff --git a/codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/SymbolBuilderTest.kt b/codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/SymbolBuilderTest.kt
index 951c389b047..f2c6e40b0cf 100644
--- a/codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/SymbolBuilderTest.kt
+++ b/codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/SymbolBuilderTest.kt
@@ -125,17 +125,13 @@ class SymbolBuilderTest {
         "PrimitiveBoolean, false, bool",
     )
     fun `creates primitives`(primitiveType: String, optional: Boolean, rustName: String) {
-        val memberBuilder = MemberShape.builder().id("foo.bar#MyStruct\$quux").target("smithy.api#$primitiveType")
-        val member = memberBuilder.build()
-        val struct = StructureShape.builder()
-            .id("foo.bar#MyStruct")
-            .addMember(member)
-            .build()
-        val model = Model.assembler()
-            .addShapes(struct, member)
-            .assemble()
-            .unwrap()
-
+        val model = """
+    namespace foo.bar
+    structure MyStruct {
+        quux: $primitiveType
+    }
+""".asSmithyModel()
+        var member = model.expectShape(ShapeId.from("foo.bar#MyStruct\$quux"))
         val provider: SymbolProvider = testSymbolProvider(model)
         val memberSymbol = provider.toSymbol(member)
         // builtins should not have a namespace set
diff --git a/codegen-server-test/build.gradle.kts b/codegen-server-test/build.gradle.kts
index 8912b9b35af..eb2430bdfc1 100644
--- a/codegen-server-test/build.gradle.kts
+++ b/codegen-server-test/build.gradle.kts
@@ -22,6 +22,11 @@ val pluginName = "rust-server-codegen"
 val workingDirUnderBuildDir = "smithyprojections/codegen-server-test/"
 
 buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        google()
+    }
     val smithyVersion: String by project
     dependencies {
         classpath("software.amazon.smithy:smithy-cli:$smithyVersion")
diff --git a/codegen-server-test/python/build.gradle.kts b/codegen-server-test/python/build.gradle.kts
index 004060e48fc..ddf15804ab1 100644
--- a/codegen-server-test/python/build.gradle.kts
+++ b/codegen-server-test/python/build.gradle.kts
@@ -26,6 +26,11 @@ configure<software.amazon.smithy.gradle.SmithyExtension> {
 }
 
 buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        google()
+    }
     val smithyVersion: String by project
     dependencies {
         classpath("software.amazon.smithy:smithy-cli:$smithyVersion")
diff --git a/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCodegenVisitor.kt b/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCodegenVisitor.kt
index 1b28ee8599a..0b0ba93a18e 100644
--- a/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCodegenVisitor.kt
+++ b/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ServerCodegenVisitor.kt
@@ -7,6 +7,7 @@ package software.amazon.smithy.rust.codegen.server.smithy
 
 import software.amazon.smithy.build.PluginContext
 import software.amazon.smithy.model.Model
+import software.amazon.smithy.model.knowledge.NullableIndex
 import software.amazon.smithy.model.neighbor.Walker
 import software.amazon.smithy.model.shapes.ServiceShape
 import software.amazon.smithy.model.shapes.Shape
@@ -70,6 +71,7 @@ open class ServerCodegenVisitor(
                 renameExceptions = false,
                 handleRequired = true,
                 handleRustBoxing = true,
+                nullabilityCheckMode = NullableIndex.CheckMode.SERVER,
             )
         val baseModel = baselineTransform(context.model)
         val service = settings.getService(baseModel)
diff --git a/gradle.properties b/gradle.properties
index a5e8c71f08f..9e739d51a7b 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -15,7 +15,7 @@ kotlin.code.style=official
 
 # codegen
 smithyGradlePluginVersion=0.6.0
-smithyVersion=1.23.1
+smithyVersion=1.25.0
 
 # kotlin
 kotlinVersion=1.6.21