Error handling notification: notifications/initialized

[edouardouvrard]

Describe the bug
When using witsy-mcp-client, I'm having this error :

14:39:50.999 [DefaultDispatcher-worker-16] INFO io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPlugin -- New SSE connection established with sessionId: ec3fa6b0-d2d2-4485-845b-2bf75a3f3132
14:39:51.002 [DefaultDispatcher-worker-16] DEBUG io.modelcontextprotocol.kotlin.sdk.server.Server -- Initializing MCP server with capabilities: ServerCapabilities(experimental={}, sampling={}, logging={}, prompts=null, resources=null, tools=Tools(listChanged=true))
14:39:51.002 [DefaultDispatcher-worker-16] INFO io.modelcontextprotocol.kotlin.sdk.server.Server -- Registering tool: test
14:39:51.002 [DefaultDispatcher-worker-16] DEBUG io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPlugin -- Server instance created and stored for sessionId: ec3fa6b0-d2d2-4485-845b-2bf75a3f3132
14:39:51.006 [DefaultDispatcher-worker-18] DEBUG io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPlugin -- Received message for sessionId: ec3fa6b0-d2d2-4485-845b-2bf75a3f3132
14:39:51.036 [DefaultDispatcher-worker-18] INFO io.modelcontextprotocol.kotlin.sdk.server.Server -- Handling initialize request from client Implementation(name=witsy-mcp-client, version=1.0.0)
14:39:51.045 [DefaultDispatcher-worker-16] DEBUG io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPlugin -- Received message for sessionId: ec3fa6b0-d2d2-4485-845b-2bf75a3f3132
14:39:51.047 [DefaultDispatcher-worker-16] ERROR io.modelcontextprotocol.kotlin.sdk.shared.Protocol -- Error handling notification: notifications/initialized
java.util.NoSuchElementException: Key method is missing in the map.
	at kotlin.collections.MapsKt__MapWithDefaultKt.getOrImplicitDefaultNullable(MapWithDefault.kt:24)
	at kotlin.collections.MapsKt__MapsKt.getValue(Maps.kt:369)
	at io.modelcontextprotocol.kotlin.sdk.Types_utilKt.selectClientNotificationDeserializer(types.util.kt:141)
	at io.modelcontextprotocol.kotlin.sdk.Types_utilKt.access$selectClientNotificationDeserializer(types.util.kt:1)
	at io.modelcontextprotocol.kotlin.sdk.NotificationPolymorphicSerializer.selectDeserializer(types.util.kt:191)
	at kotlinx.serialization.json.JsonContentPolymorphicSerializer.deserialize(JsonContentPolymorphicSerializer.kt:93)
	at kotlinx.serialization.json.internal.AbstractJsonTreeDecoder.decodeSerializableValue(TreeJsonDecoder.kt:345)
	at kotlinx.serialization.json.internal.TreeJsonDecoderKt.readJson(TreeJsonDecoder.kt:25)
	at kotlinx.serialization.json.Json.decodeFromJsonElement(Json.kt:170)
	at io.modelcontextprotocol.kotlin.sdk.TypesKt.fromJSON(types.kt:1461)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol$setNotificationHandler$1.invokeSuspend(Protocol.kt:470)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol$setNotificationHandler$1.invoke(Protocol.kt)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol$setNotificationHandler$1.invoke(Protocol.kt)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol.onNotification(Protocol.kt:198)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol.access$onNotification(Protocol.kt:93)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol$connect$4.invokeSuspend(Protocol.kt:167)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol$connect$4.invoke(Protocol.kt)
	at io.modelcontextprotocol.kotlin.sdk.shared.Protocol$connect$4.invoke(Protocol.kt)
	at io.modelcontextprotocol.kotlin.sdk.server.SSEServerTransport.handleMessage(SSEServerTransport.kt:103)
	at io.modelcontextprotocol.kotlin.sdk.server.SSEServerTransport.handlePostMessage(SSEServerTransport.kt:87)
	at io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPluginKt$MCP$1$2.invokeSuspend(McpKtorServerPlugin.kt:50)
	at io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPluginKt$MCP$1$2.invoke(McpKtorServerPlugin.kt)
	at io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPluginKt$MCP$1$2.invoke(McpKtorServerPlugin.kt)
	at io.ktor.server.routing.RoutingNode$buildPipeline$1$1.invokeSuspend(RoutingNode.kt:127)
	at io.ktor.server.routing.RoutingNode$buildPipeline$1$1.invoke(RoutingNode.kt)
	at io.ktor.server.routing.RoutingNode$buildPipeline$1$1.invoke(RoutingNode.kt)
	at io.ktor.util.pipeline.PipelineJvmKt.pipelineStartCoroutineUninterceptedOrReturn(PipelineJvm.kt:15)
	at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
	at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
	at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:109)
	at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:92)
	at io.ktor.server.routing.RoutingRoot$executeResult$$inlined$execute$1.invokeSuspend(Pipeline.kt:510)
	at io.ktor.server.routing.RoutingRoot$executeResult$$inlined$execute$1.invoke(Pipeline.kt)
	at io.ktor.server.routing.RoutingRoot$executeResult$$inlined$execute$1.invoke(Pipeline.kt)
	at io.ktor.util.debug.ContextUtilsKt.initContextInDebugMode(ContextUtils.kt:19)
	at io.ktor.server.routing.RoutingRoot.executeResult(RoutingRoot.kt:208)
	at io.ktor.server.routing.RoutingRoot.interceptor(RoutingRoot.kt:71)
	at io.ktor.server.routing.RoutingRoot$Plugin$install$1.invokeSuspend(RoutingRoot.kt:154)
	at io.ktor.server.routing.RoutingRoot$Plugin$install$1.invoke(RoutingRoot.kt)
	at io.ktor.server.routing.RoutingRoot$Plugin$install$1.invoke(RoutingRoot.kt)
	at io.ktor.util.pipeline.PipelineJvmKt.pipelineStartCoroutineUninterceptedOrReturn(PipelineJvm.kt:15)
	at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
	at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
	at io.ktor.server.engine.BaseApplicationEngineKt$installDefaultTransformationChecker$1.invokeSuspend(BaseApplicationEngine.kt:117)
	at io.ktor.server.engine.BaseApplicationEngineKt$installDefaultTransformationChecker$1.invoke(BaseApplicationEngine.kt)
	at io.ktor.server.engine.BaseApplicationEngineKt$installDefaultTransformationChecker$1.invoke(BaseApplicationEngine.kt)
	at io.ktor.util.pipeline.PipelineJvmKt.pipelineStartCoroutineUninterceptedOrReturn(PipelineJvm.kt:15)
	at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
	at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
	at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:109)
	at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:92)
	at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1$invokeSuspend$$inlined$execute$1.invokeSuspend(Pipeline.kt:510)
	at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt)
	at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt)
	at io.ktor.util.debug.ContextUtilsKt.initContextInDebugMode(ContextUtils.kt:19)
	at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invokeSuspend(DefaultEnginePipeline.kt:131)
	at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invoke(DefaultEnginePipeline.kt)
	at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invoke(DefaultEnginePipeline.kt)
	at io.ktor.util.pipeline.PipelineJvmKt.pipelineStartCoroutineUninterceptedOrReturn(PipelineJvm.kt:15)
	at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
	at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
	at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:109)
	at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:92)
	at io.ktor.server.cio.CIOApplicationEngine$handleRequest$2$invokeSuspend$$inlined$execute$1.invokeSuspend(Pipeline.kt:488)
	at io.ktor.server.cio.CIOApplicationEngine$handleRequest$2$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt)
	at io.ktor.server.cio.CIOApplicationEngine$handleRequest$2$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt)
	at io.ktor.util.debug.ContextUtilsKt.initContextInDebugMode(ContextUtils.kt:19)
	at io.ktor.server.cio.CIOApplicationEngine$handleRequest$2.invokeSuspend(CIOApplicationEngine.kt:229)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
	at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:113)
	at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:89)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:586)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:820)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:717)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:704)
14:39:51.050 [DefaultDispatcher-worker-24] DEBUG io.modelcontextprotocol.kotlin.sdk.server.McpKtorServerPlugin -- Received message for sessionId: ec3fa6b0-d2d2-4485-845b-2bf75a3f3132

[tomakehurst]

I've also encountered this when Cursor is the client.

It looks like the server is expecting method to be present in the params map in the RPC event, whereas Cursor (and presumably other clients) only send it in the parent object.

[adamglin0]

This error will also occur when using the inspector connection. and cherry-studio, chatwise. This issue prevents all mcp-clients from using the server.
https://github.com/modelcontextprotocol/inspector