feat!: add mcp conformance test infra (#585); add SSE reconnection with retry support (#596) (#585)

Adds a comprehensive conformance test suite for the Kotlin MCP SDK,
covering core protocol operations, tool calls, elicitation, resources,
prompts, and 20 OAuth/auth scenarios

- Conformance server and client implementations
- OAuth/auth test scenarios: JWT, authorization code flow, client
credentials, PKCE, scope handling, cross-app access, client registration
- CI workflow
- Baseline file for tracking expected failures
- Shell script

fixes:
- #592
- #593
- #596


## Remaining known failures (tracked issues, will be fixed directly in
`main`)

- [x] `tools-call-with-logging`, `tools-call-with-progress`,
`tools-call-sampling`, `tools-call-elicitation`,
`elicitation-sep1034-defaults`-  see #599,
- [x] `elicitation-sep1330-enums` - #587 #600
- [x] `initialize` - #588 
- [x] `tools_call`, `auth/scope-step-up`, `auth/scope-retry-limit` -
#589
- [ ] `elicitation-sep1034-client-defaults` - #414 
- [x] `sse-retry` - #590 
- [ ] `resources-templates-read` - #591 

## Breaking Changes
from #596 
- `StreamableHttpClientTransport` and
`mcpStreamableHttp`/`mcpStreamableHttpTransport`: old constructors
accepting `Duration` timeout are now `@Deprecated` — use the new
overloads with `ReconnectionOptions` instead
- `StreamableHttpClientTransport.close()` no longer calls
`terminateSession()` automatically

## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

---------

Co-authored-by: Konstantin Pavlov <1517853+kpavlov@users.noreply.github.com>

kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/common.kt

@@ -8,12 +8,13 @@ import kotlinx.serialization.json.JsonObject
 // Protocol Version Constants
 // ============================================================================
 
-public const val LATEST_PROTOCOL_VERSION: String = "2025-06-18"
+public const val LATEST_PROTOCOL_VERSION: String = "2025-11-25"
 
-public const val DEFAULT_NEGOTIATED_PROTOCOL_VERSION: String = "2025-03-26"
+public const val DEFAULT_NEGOTIATED_PROTOCOL_VERSION: String = "2025-06-18"
 
 public val SUPPORTED_PROTOCOL_VERSIONS: List<String> = listOf(
     LATEST_PROTOCOL_VERSION,
+    "2025-06-18",
     "2025-03-26",
     "2024-11-05",
 )

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}")
         }
     }
 }

kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/types/CommonTypeTest.kt

@@ -14,13 +14,14 @@ class CommonTypeTest {
 
     @Test
     fun `should have correct latest protocol version`() {
-        LATEST_PROTOCOL_VERSION shouldBe "2025-06-18"
+        LATEST_PROTOCOL_VERSION shouldBe "2025-11-25"
     }
 
     @Test
     fun `should have correct supported protocol versions`() {
         SUPPORTED_PROTOCOL_VERSIONS shouldContainExactlyInAnyOrder listOf(
             LATEST_PROTOCOL_VERSION,
+            "2025-06-18",
             "2025-03-26",
             "2024-11-05",
         )