Reject POST requests without session ID in stateful mode#274
Merged
koic merged 1 commit intomodelcontextprotocol:mainfrom Mar 29, 2026
Merged
Reject POST requests without session ID in stateful mode#274koic merged 1 commit intomodelcontextprotocol:mainfrom
koic merged 1 commit intomodelcontextprotocol:mainfrom
Conversation
Per the MCP specification (Streamable HTTP > Session Management): > Servers that require a session ID SHOULD respond to requests without an `Mcp-Session-Id` header > (other than initialization) with HTTP 400 Bad Request. https://modelcontextprotocol.io/specification/2025-11-25/basic/transports#session-management Previously, non-initialize POST requests without `Mcp-Session-Id` in stateful mode were processed with HTTP 200 (for regular requests) or HTTP 202 (for notifications/responses). This change adds an explicit check in `handle_post` to return HTTP 400 Bad Request when the session ID is missing in stateful mode for all non-initialize requests, aligning with the specification.
atesgoral
approved these changes
Mar 29, 2026
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Motivation and Context
Per the MCP specification (Streamable HTTP > Session Management):
https://modelcontextprotocol.io/specification/2025-11-25/basic/transports#session-management
Previously, non-initialize POST requests without
Mcp-Session-Idin stateful mode were processed with HTTP 200 (for regular requests) or HTTP 202 (for notifications/responses).This change adds an explicit check in
handle_postto return HTTP 400 Bad Request when the session ID is missing in stateful mode for all non-initialize requests, aligning with the specification.How Has This Been Tested?
Added a regression test and passed.
Breaking Changes
This is not a breaking change, as it is a bug fix to align with the MCP specification.
Types of changes
Checklist