[Tiering] Add conformance tests for Version Negotiation #102
Description
Summary
The MCP lifecycle spec requires specific version negotiation behavior during initialization, but the conformance test suite only tests basic initialization without verifying version negotiation. Additionally, HTTP clients must include the MCP-Protocol-Version header on subsequent requests.
Missing Coverage
Check: version-echo
Spec: "If the server supports the requested protocol version, it MUST respond with the same version."
Server receives initialize with a supported version → server responds with the same version.
Check: version-negotiate
Spec: "Otherwise, the server MUST respond with another protocol version it supports."
Server receives initialize with an unsupported version → server responds with a different supported version (not an error).
Check: http-protocol-version-header
Spec: "If using HTTP, the client MUST include the MCP-Protocol-Version: HTTP header on all subsequent requests to the MCP server."
After initialization, client includes MCP-Protocol-Version header on all HTTP requests.
Spec Requirements
| Keyword | Statement |
|---|---|
| MUST | The client MUST send a protocol version it supports |
| SHOULD | This SHOULD be the latest version supported by the client |
| MUST | If the server supports the requested protocol version, it MUST respond with the same version |
| MUST | Otherwise, the server MUST respond with another protocol version it supports |
| SHOULD | This SHOULD be the latest version supported by the server |
| SHOULD | If the client does not support the version in the server's response, it SHOULD disconnect |
| MUST | If using HTTP, the client MUST include the MCP-Protocol-Version header on all subsequent requests |
Current State
lifecycle.ts only tests that initialization succeeds - no version mismatch scenarios.