Stateful Streamable-HTTP: send 404 Not Found on unknown Mcp-Session-Id#1417
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Zalewa wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Stateful Streamable-HTTP: send 404 Not Found on unknown Mcp-Session-Id#1417Zalewa wants to merge 1 commit intomodelcontextprotocol:mainfrom
Zalewa wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Zalewa
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felixweinberger
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Motivation and Context
Fixes #1004
MCP protocol spec states that when Mcp-Session-Id arrives for a session that has been removed, the server MUST reply with a "404 Not Found" HTTP status code. It was replying with a "400 Bad Request" instead. The relevant part of the spec is here in point 2.5.3: https://modelcontextprotocol.io/specification/2025-06-18/basic/transports#session-management
How Has This Been Tested?
I wrote a unit test.
Breaking Changes
User apps may be relying on the incorrect behavior of sending "400 Bad Request".
https://xkcd.com/927/
Types of changes
Checklist
Additional context
https://github.com/modelcontextprotocol/python-sdk/pull/641/files#r2394152091