From 1a1be69e3e94e98f392a99b46384a9385d52e48c Mon Sep 17 00:00:00 2001
From: devcrocod <devcrocod@gmail.com>
Date: Fri, 6 Mar 2026 17:40:21 +0100
Subject: [PATCH 1/2] update JSONRPCMessage serializer to handle
 JSONRPCEmptyMessage scenarios

---
 .../kotlin/sdk/types/serializers.kt            | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/serializers.kt b/kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/serializers.kt
index a00b26be4..4d5974d92 100644
--- a/kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/serializers.kt
+++ b/kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/serializers.kt
@@ -371,21 +371,23 @@ internal object ServerResultPolymorphicSerializer :
  * Polymorphic serializer for [JSONRPCMessage] types.
  * Determines the message type based on the presence of specific fields:
  * - "error" -> JSONRPCError
- * - "result" -> JSONRPCResponse
+ * - "result" + "id" -> JSONRPCResponse
+ * - "result" -> JSONRPCEmptyMessage
  * - "method" + "id" -> JSONRPCRequest
  * - "method" -> JSONRPCNotification
  */
 internal object JSONRPCMessagePolymorphicSerializer :
     JsonContentPolymorphicSerializer<JSONRPCMessage>(JSONRPCMessage::class) {
     override fun selectDeserializer(element: JsonElement): DeserializationStrategy<JSONRPCMessage> {
-        val jsonObject = element.jsonObject
+        val jsonObj = element.jsonObject
         return when {
-            "error" in jsonObject -> JSONRPCError.serializer()
-            "result" in jsonObject -> JSONRPCResponse.serializer()
-            "method" in jsonObject && "id" in jsonObject -> JSONRPCRequest.serializer()
-            "method" in jsonObject -> JSONRPCNotification.serializer()
-            jsonObject.isEmpty() || jsonObject.keys == setOf("jsonrpc") -> JSONRPCEmptyMessage.serializer()
-            else -> throw SerializationException("Invalid JSONRPCMessage type: ${jsonObject.keys}")
+            "error" in jsonObj -> JSONRPCError.serializer()
+            "result" in jsonObj && "id" in jsonObj -> JSONRPCResponse.serializer()
+            "result" in jsonObj && jsonObj["result"]?.jsonObject?.isEmpty() == true -> JSONRPCEmptyMessage.serializer()
+            "method" in jsonObj && "id" in jsonObj -> JSONRPCRequest.serializer()
+            "method" in jsonObj -> JSONRPCNotification.serializer()
+            jsonObj.isEmpty() || jsonObj.keys == setOf("jsonrpc") -> JSONRPCEmptyMessage.serializer()
+            else -> throw SerializationException("Invalid JSONRPCMessage type: ${jsonObj.keys}")
         }
     }
 }

From a00a71e01a9c4cdad0ff0891ac88e434a54f2331 Mon Sep 17 00:00:00 2001
From: devcrocod <devcrocod@gmail.com>
Date: Sat, 7 Mar 2026 02:32:36 +0100
Subject: [PATCH 2/2] reduce known SDK limitations to 12 scenarios and update
 conformance baseline

---
 conformance-test/README.md                | 3 +--
 conformance-test/conformance-baseline.yml | 1 -
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/conformance-test/README.md b/conformance-test/README.md
index b1ad35559..0f08d751f 100644
--- a/conformance-test/README.md
+++ b/conformance-test/README.md
@@ -110,7 +110,7 @@ Tests the conformance server against all server scenarios:
 
 ## Known SDK Limitations
 
-10 scenarios are expected to fail due to current SDK limitations (tracked in [
+9 scenarios are expected to fail due to current SDK limitations (tracked in [
 `conformance-baseline.yml`](conformance-baseline.yml).
 
 | Scenario                              | Suite  | Root Cause                                                                                                                                             |
@@ -122,7 +122,6 @@ Tests the conformance server against all server scenarios:
 | `elicitation-sep1034-defaults`        | server | *(same as above)*                                                                                                                                      |
 | `elicitation-sep1330-enums`           | server | *(same as above)*                                                                                                                                      |
 | `resources-templates-read`            | server | SDK does not implement `addResourceTemplate()` with URI pattern matching; resources are looked up by exact URI                                         |
-| `initialize`                          | client | Conformance server sends a JSON-RPC response without `id`; `JSONRPCResponse.id` is non-nullable so deserialization fails                               |
 | `elicitation-sep1034-client-defaults` | client | SDK does not fill in `default` values from the elicitation request schema before sending the response                                                  |
 | `sse-retry`                           | client | Transport does not respect the SSE `retry` field timing or send `Last-Event-ID` on reconnection                                                        |
 
diff --git a/conformance-test/conformance-baseline.yml b/conformance-test/conformance-baseline.yml
index 0c4cb234a..9126f0d34 100644
--- a/conformance-test/conformance-baseline.yml
+++ b/conformance-test/conformance-baseline.yml
@@ -10,6 +10,5 @@ server:
   - resources-templates-read
 
 client:
-  - initialize
   - elicitation-sep1034-client-defaults
   - sse-retry