Python MCP SDK 2.0 Breaking Change Forces Emergency Patch for AI Memory Server
The official MCP Python SDK jumped to version 2.0.0 and removed the mcp.server.fastmcp module without a deprecation window, breaking downstream packages including yantrikdb-mcp, an MCP server for AI agent memory. The maintainer issued a temporary version pin within hours and then released v0.12.0 the same morning, introducing a compatibility layer that probes for available imports rather than branching on version strings. The fix covered key API renames — FastMCP to MCPServer, relocated Context and ToolError paths — while identifying that most of the SDK's surface area remained unchanged. A follow-up patch, v0.12.1, was released five hours later after SSE and streamable-HTTP transports were found broken in v0.12.0, a gap missed because the test suite only exercised the stdio transport. The package had been growing rapidly, reaching over 2,100 monthly downloads by late August 2026, making the brief breakage window more consequential than it might otherwise have been.
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