wrapMcpServerWithSentry: tool-call spans missing with stateless StreamableHTTPServerTransport

[maxproske]

AI disclaimer: used Claude Code to generate as much useful context as possible.

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/node - express

SDK Version

10.48.0

Framework Version

@modelcontextprotocol/sdk 2.x (Node StreamableHTTPServerTransport)

Link to Sentry event

N/A — no spans are emitted

Reproduction Example/SDK Setup

Sentry.init({ dsn: process.env.DSN, tracesSampleRate: 1.0 });

app.all('/mcp', auth, async (req, res) => {
  const transport = new StreamableHTTPServerTransport({
    sessionIdGenerator: undefined,   // stateless
    enableJsonResponse: true,
  });
  const server = Sentry.wrapMcpServerWithSentry(
    new McpServer({ name: 'x', version: '1.0.0' }),
    { recordInputs: true, recordOutputs: true },
  );
  registerTools(server);
  await server.connect(transport);
  await transport.handleRequest(req, res, req.body);
});

Steps to Reproduce

1. Use @sentry/node ≥ 10.39.0 (post-#19172).
2. Construct a per-request McpServer + Node StreamableHTTPServerTransport with sessionIdGenerator: undefined (stateless mode, per the official MCP SDK simpleStatelessStreamableHttp.ts example).
3. Wrap with wrapMcpServerWithSentry, server.connect(transport), transport.handleRequest(...).
4. Call any tool from a client.

Expected Result

An mcp.server span with mcp.tool.name attribute for each tools/call, visible on the MCP insights dashboard.

Actual Result

Zero mcp.server spans emitted. http.server transactions for POST /mcp are recorded fine, but tool-call correlation never resolves, so spans are created on onmessage and never .end()-ed on send.

Additional Context

This is the stateless follow-up to JS-1663 / PR #19172, which the reporter flagged in this comment and a maintainer acknowledged here ("about the stateless issue, we'll get that fixed, it slipped by").

I'm using stateless because I am deploying to a scale-to-zero Fly.io server.

Priority

React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.

[linear-code]

JS-2164

[logaretm]

Thanks for reporting this, I have submitted a PR just moments ago.

[maxproske]

That was incredibly quick. Thank you Abdelrahman :)