fix(mcp): close transport on failed/timed-out connections#19200
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kitlangton merged 6 commits intodevfrom Mar 26, 2026
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fix(mcp): close transport on failed/timed-out connections#19200kitlangton merged 6 commits intodevfrom
kitlangton merged 6 commits intodevfrom
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When withTimeout rejects during MCP connect, the transport (and its child process for stdio servers) was never closed. Extract a tryConnect helper that ensures transport.close() is always called on failure, eliminating process/connection leaks in all connect paths. Fixes #19168
Replace the async tryConnect helper with connectTransport using Effect.acquireUseRelease for guaranteed transport cleanup on failure. Convert create() from async function to Effect.gen and defs() to return an Effect. Callers now yield* directly instead of wrapping in Effect.promise.
…fect - fetchFromClient: async function -> Effect.tryPromise + Effect.map - collectFromConnected: compose directly with Effect fetchFromClient - closeClient: Effect.promise(.catch) -> Effect.tryPromise + Effect.ignore - Bus.publish calls: .catch() -> busPublish helper with Effect.tryPromise + Effect.ignore - startAuth: Effect.promise(async try/catch) -> Effect.tryPromise + Effect.catch - finishAuth: simplify inner async/await - create(): eliminate mutable let vars, extract connectRemote/connectLocal - Extract sanitize helper, CreateResult interface, busPublish helper - watch callback: use busPublish via Effect.runPromise - getConfig helper function for repeated Config.get() pattern
Move connectTransport, connectRemote, connectLocal, and create inside the layer's Effect.gen closure where they have direct access to the Bus service instance. Replace busPublish helper with bus.publish calls. Add Bus.layer to defaultLayer.
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Summary
tryConnect()helper that ensurestransport.close()is always called on failure, preventing orphaned child processes (stdio) and leaked HTTP connections (remote)Details
When
withTimeout(client.connect(transport), timeout)rejected increate(), the catch blocks never calledtransport.close(). This left:The fix extracts a
tryConnect(transport, timeout)function that wraps the connect call in try/catch and closes the transport on any error. Both the local and remote connect paths now use this helper, eliminating duplicated cleanup logic.Test plan
transport.close()is called when stdio connect hangs past timeouttransport.close()is called when remote connect hangs past timeoutFixes #19168