fix(http): create a fresh MCP server per request in stateless HTTP mode - #118
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fix(http): create a fresh MCP server per request in stateless HTTP mode#118Defilan wants to merge 1 commit into
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createHttpApp built a single McpServer at construction and called mcpServer.connect(transport) on every /mcp request. With the stateless StreamableHTTP transport (sessionIdGenerator: undefined) there is no session to reuse, so once one request's transport was connected, any request arriving before it closed called connect() on the already-connected server and threw "Already connected to a transport ... use a separate Protocol instance per connection", returning HTTP 500. This breaks multi-request MCP clients: a client sends initialize then tools/list (and typically keeps a stream open), so its second call 500s and no tools register. A strictly-sequential caller dodges it because res.on(close) closes the transport and frees the shared server between requests. Move server creation into the /mcp handler so each request gets its own McpServer + transport (the SDK's stateless pattern) and close it on response close. Add a regression test asserting a fresh server is created per request.
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Summary
In HTTP mode,
createHttpAppbuilds a singleMcpServerat construction and callsmcpServer.connect(transport)on every/mcprequest. With the stateless streamable-HTTP transport (sessionIdGenerator: undefined) there is no session to reuse, so once one request's transport is connected, any request arriving before it closes callsconnect()on the already-connected server and throwsAlready connected to a transport … use a separate Protocol instance per connection→ HTTP 500.This breaks multi-request MCP clients:
initializesucceeds,tools/list500s, and no tools register. (A strictly-sequentialcurldodges it becauseres.on("close")frees the shared server between requests, which is why it isn't obvious in one-shot testing.)Fixes #117.
Change
createPerplexityServer()into the/mcphandler so each request gets its own server + transport (the SDK's stateless pattern), and close the per-request server on response close.expected "createPerplexityServer" to be called 2 times, but got 0 times) and passes with the fix.Verification
npm test— 91 passing (new test included).npm run build— clean.initializesucceeded buttools/list500'd and no tools registered; after, the fullinitialize → tools/list → tools/callflow works.