fix(mcp): don't report stateless StreamableHTTP servers as stdio - #7224
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ericapisani merged 3 commits intoAug 24, 2026
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`mcp.transport` was only set to "http" when the request carried an `mcp-session-id` header. A StreamableHTTP server running stateless issues no session id, so no client ever sends that header back and the span kept the "stdio" default, reporting a plainly HTTP server as a local pipe. Drop the header requirement from the transport check. The header still supplies `mcp.session.id` when the server is stateful, and is simply absent otherwise: per the spec a server MAY assign a session id, so its absence says nothing about the transport.
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Thanks for opening a PR with us @Snaylaker ! I've read the conversation so far with @alexander-alderman-webb in the issue that you originally opened and the changes you have here LGTM. I've looked into the failing tests and it looks due to an assumption on our test fixture/helper, not your changes specifically (they just uncovered the assumption). I'm opening a PR shortly to address this and once that's merged, we'll look to get your changes in. |
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`select_transactions_with_mcp_spans` assumes that all events provided to the helper are transactions and contain a `type` key. However, not all events contain 'type's and so passing events that may contain a log would raise a KeyError. Relates to #7224
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`select_transactions_with_mcp_spans` assumes that all events provided to the helper are transactions and contain a `type` key. However, not all events contain 'type's and so passing events that may contain a log would raise a KeyError. Relates to #7224
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`MCPIntegration` reports `mcp.transport: "stdio"` and `network.transport: "pipe"` for a StreamableHTTP server running stateless. `_get_request_context_data` only sets `"http"` when the request carries an `mcp-session-id` header, and a stateless server issues no session id, so no client sends that header back and the `"stdio"` default stands. The header is a session signal, not a transport signal: per the spec a server *"MAY assign a session ID at initialization time"*, so its presence is a deployment choice. This drops it from the transport check and leaves it supplying `mcp.session.id` when the server is stateful. stdio is unaffected: it attaches no request object, so the outer guard stops it before this branch. | server | before | after | | --- | --- | --- | | stdio | `stdio` | unchanged | | SSE | `sse` + session id from `?session_id=` | unchanged | | StreamableHTTP, stateful | `http` + session id from header | unchanged | | StreamableHTTP, stateless | `stdio` | `http`, no session id | `test_tool_handler_stateless_streamable_http` drives a real stateless `StreamableHTTPSessionManager` app and fails on `master` with `assert 'stdio' == 'http'`. Green on mcp 1.x and 2.x. #### Issues * resolves: #7225
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Description
MCPIntegrationreportsmcp.transport: "stdio"andnetwork.transport: "pipe"for a StreamableHTTP server running stateless._get_request_context_dataonly sets"http"when the request carries anmcp-session-idheader, and a stateless server issues no session id, so no client sends that header back and the"stdio"default stands.The header is a session signal, not a transport signal: per the spec a server "MAY assign a session ID at initialization time", so its presence is a deployment choice. This drops it from the transport check and leaves it supplying
mcp.session.idwhen the server is stateful. stdio is unaffected: it attaches no request object, so the outer guard stops it before this branch.stdiosse+ session id from?session_id=http+ session id from headerstdiohttp, no session idtest_tool_handler_stateless_streamable_httpdrives a real statelessStreamableHTTPSessionManagerapp and fails onmasterwithassert 'stdio' == 'http'. Green on mcp 1.x and 2.x.Issues