fix: return 404 instead of 400 for invalid session IDs in examples#1678
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kai-agent-free wants to merge 1 commit intomodelcontextprotocol:mainfrom
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fix: return 404 instead of 400 for invalid session IDs in examples#1678kai-agent-free wants to merge 1 commit intomodelcontextprotocol:mainfrom
kai-agent-free wants to merge 1 commit intomodelcontextprotocol:mainfrom
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The MCP spec states that servers should return HTTP 404 for invalid session IDs so clients know to start a new session. The SDK transport (streamableHttp.ts) already correctly returns 404, but the example servers and conformance test server were returning 400. Fixes modelcontextprotocol#389
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@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
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Summary
Fixes #389
The MCP spec states that servers SHOULD return HTTP 404 for requests with invalid session IDs, so clients know the session is gone and can start a new one:
The SDK's own transport implementation (
streamableHttp.ts) already correctly returns 404 with error code-32001("Session not found"). However, all the example servers and the conformance test server were returning 400 instead.Changes
res.status(400)→res.status(404)for invalid/missing session ID responsesFiles changed
examples/server/src/simpleStreamableHttp.tsexamples/server/src/simpleTaskInteractive.tsexamples/server/src/elicitationFormExample.tsexamples/server/src/elicitationUrlExample.tsexamples/server/src/standaloneSseWithGetStreamableHttp.tstest/conformance/src/everythingServer.tsAll existing tests pass (28/28 in streamableHttp.test.ts).