fix: negotiate MCP protocol version instead of hardcoding#324
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bensig merged 3 commits intoMemPalace:mainfrom Apr 9, 2026
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The initialize handler hardcoded protocolVersion "2024-11-05", which causes newer MCP clients (e.g. Claude Code) to reject the connection when they negotiate "2025-11-25" or later. Echo the client's requested version if it is in the supported set, otherwise fall back to the latest supported version. This keeps backwards compatibility with older clients while allowing newer ones to connect. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>
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The initialize handler replied with a fixed protocolVersion "2024-11-05", which causes newer MCP clients (Claude Code negotiating 2025-11-25) to refuse the connection. Echo the client's requested version when it is in the supported set, otherwise fall back to the newest we know. Ported from upstream 950d52b (PR MemPalace#324), by @virgil-at-biocompute. Amusing note: the upstream commit is co-authored by Claude Opus 4.6. Co-Authored-By: virgil-at-biocompute <[email protected]> Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>
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Summary
initializehandler hardcodesprotocolVersion: "2024-11-05", which causes newer MCP clients (Claude Code, Cursor, etc.) to reject the connection when they negotiate2025-11-25or laterSUPPORTED_PROTOCOL_VERSIONSlist for easy maintenance as new versions are releasedWhat broke
Claude Code's MCP client sends
protocolVersion: "2025-11-25"in theinitializerequest. The server responded with"2024-11-05", causing the client to reject the handshake. All 18 mempalace tools failed to load as a result.Changes
mempalace/mcp_server.pySUPPORTED_PROTOCOL_VERSIONSlist (2025-11-25through2024-11-05)tests/test_mcp_server.pytest_initialize_negotiates_client_version— client sends2025-11-25, server echoes ittest_initialize_negotiates_older_supported_version— client sends2025-03-26, server echoes ittest_initialize_unknown_version_falls_back_to_latest— unknown version gets latest supportedtest_initialize_missing_version_uses_oldest— no version in params gets2024-11-05(backwards compat)Test plan
TestHandleRequesttests passruff checkandruff format --checkclean