LangChain revamps MCP support: moves into main package on FastMCP v4, adds stateless spec
LangChain · x · 2026-09-05
- LangChain released support for the new stateless MCP spec, with a detailed breakdown by Sydney Runkle.
- MCP support now lives in the main package: uv pip install 'langchain[mcp]'.
- It's built on FastMCP v4, which handles protocol negotiation, tool name conflicts, connection lifecycle, transports, auth, and caching.
- New support for elicitation (MCP's human-in-the-loop) via interrupts.
- listtools caching so agents don't re-fetch tool lists on every run — fixing a common TTFT pain point.
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