fix!: require negotiated version when using HTTP #548
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@bhosmer-ant Updated to address feedback, PTAL |
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Would this be better placed in https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/docs/specification/draft/basic/transports.mdx#streamable-http? I think it fits better alongside the requirements for the |
@halter73 agree that it's uncomfortably far from the transport spec here. Ideally you'd find some evidence of it in both places - #658 moves it per your suggestion and added a note/link in the original spot, lmk what you think. |
| The protocol version sent by the client **SHOULD** be the one negotiated during [initialization](https://modelcontextprotocol.io/specification/draft/basic/lifecycle#initialization). | ||
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| If the server receives a request with a missing, invalid, or unsupported | ||
| MCP-Protocol-VERSION, it **MUST** respond with `400 Bad Request`. |
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Isn't this going to mean that existing clients will no longer be able to communicate with any compliant server? (Previously this header wasn't required, and now it is.)
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@stephentoub good point. I think one option here is to say: IF there is no MCP-Protocol-Version the version is assumed to be 2025-03-26. What do you think? Does that work or is there a better appraoch?
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sidenote: There is a type in the line, should be
| MCP-Protocol-VERSION, it **MUST** respond with `400 Bad Request`. | |
| MCP-Protocol-Version, it **MUST** respond with `400 Bad Request`. |
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#668 adds this language, cc @dsp-ant @stephentoub if that seems like the right approach
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That's better, thank you.
Add integration tests to verify the new spec requirement that HTTP clients must include the negotiated MCP-Protocol-Version header in all requests after initialization. Tests verify: 1. Client includes MCP-Protocol-Version header after initialization 2. Server validates header presence and returns 400 for missing/invalid 3. Server accepts requests with valid negotiated version These tests currently fail as the feature is not yet implemented. Related to spec change: modelcontextprotocol/modelcontextprotocol#548
Add integration tests to verify the new spec requirement that HTTP clients must include the negotiated MCP-Protocol-Version header in all requests after initialization. Tests verify: 1. Client includes MCP-Protocol-Version header after initialization 2. Server validates header presence and returns 400 for missing/invalid 3. Server accepts requests with valid negotiated version These tests currently fail as the feature is not yet implemented. Related to spec change: modelcontextprotocol/modelcontextprotocol#548
Add integration tests to verify the new spec requirement that HTTP clients must include the negotiated MCP-Protocol-Version header in all requests after initialization. Tests verify: 1. Client includes MCP-Protocol-Version header after initialization 2. Server validates header presence and returns 400 for missing/invalid 3. Server accepts requests with valid negotiated version These tests currently fail as the feature is not yet implemented. Related to spec change: modelcontextprotocol/modelcontextprotocol#548
Add integration tests to verify the new spec requirement that HTTP clients must include the negotiated MCP-Protocol-Version header in all requests after initialization. Tests verify: 1. Client includes MCP-Protocol-Version header after initialization 2. Server validates header presence and returns 400 for missing/invalid 3. Server accepts requests with valid negotiated version These tests currently fail as the feature is not yet implemented. Related to spec change: modelcontextprotocol/modelcontextprotocol#548
Add integration tests to verify the new spec requirement that HTTP clients must include the negotiated MCP-Protocol-Version header in all requests after initialization. Tests verify: 1. Client includes MCP-Protocol-Version header after initialization 2. Server validates header presence and returns 400 for missing/invalid 3. Server accepts requests with valid negotiated version These tests currently fail as the feature is not yet implemented. Related to spec change: modelcontextprotocol/modelcontextprotocol#548
Add integration tests to verify the new spec requirement that HTTP clients must include the negotiated MCP-Protocol-Version header in all requests after initialization. Tests verify: 1. Client includes MCP-Protocol-Version header after initialization 2. Server validates header presence and returns 400 for missing/invalid 3. Server accepts requests with valid negotiated version These tests currently fail as the feature is not yet implemented. Related to spec change: modelcontextprotocol/modelcontextprotocol#548
Motivation and Context
This PR requires clients/server to specify previously negotiated versions, fixing the issue described in #478.
Breaking Changes
This change is a breaking change and is not backwards compatible with the previous version. It requires both server and clients to enforce new behaviors.
Types of changes
Checklist
Additional context