Closed
Description
Describe the bug
When connected to src/server/simpleStreamableHttp.ts, src/client/simpleStreamableHttp.ts will hang on the second tool call.
The proximate cause is the global notificationsToolLastEventId not being reset between tool calls, and can be fixed by adding the following to src/client/simpleStreamableHttp.ts:
diff --git a/src/examples/client/simpleStreamableHttp.ts b/src/examples/client/simpleStreamableHttp.ts
index 4bcaf94..353e952 100644
--- a/src/examples/client/simpleStreamableHttp.ts
+++ b/src/examples/client/simpleStreamableHttp.ts
@@ -552,6 +552,9 @@ async function callTool(name: string, args: Record<string, unknown>): Promise<vo
console.log(` ${item.type} content:`, item);
}
});
+
+ notificationCount = 0;
+ notificationsToolLastEventId = undefined;
} catch (error) {
console.log(`Error calling tool ${name}: ${error}`);
}
But the real fix is properly handling the client mistakenly sending a resumption token on a fresh tool request.
To Reproduce
Steps to reproduce the behavior:
in terminal 1 (server):
$ npx tsx src/examples/server/simpleStreamableHttp.ts
in terminal 2 (client):
$ npx tsx src/examples/client/simpleStreamableHttp.ts
> greet me
Calling tool 'greet' with args: { name: 'me' }
Tool result:
Hello, me!
> greet me
Calling tool 'greet' with args: { name: 'me' }
...hangs there until timeout.
Expected behavior
Some sort of "resumption of completed tool request" error.
Logs
Server output:
Logging on server is
MCP Streamable HTTP Server listening on port 3000
Received MCP request: {
method: 'initialize',
params: {
protocolVersion: '2025-03-26',
capabilities: {},
clientInfo: { name: 'example-client', version: '1.0.0' }
},
jsonrpc: '2.0',
id: 0
}
Session initialized with ID: 506946fa-89ba-4f33-ac81-713f3c95d0e6
Received MCP request: { method: 'notifications/initialized', jsonrpc: '2.0' }
Establishing new SSE stream for session 506946fa-89ba-4f33-ac81-713f3c95d0e6
Received MCP request: {
method: 'tools/call',
params: { name: 'greet', arguments: { name: 'me' } },
jsonrpc: '2.0',
id: 1
}
Client reconnecting with Last-Event-ID: cbd79d0f-f8fd-4a83-b42f-3e019ebe2714_1747864424092_k15f32kn
Additional context
Add any other context about the problem here.