Tools
LangChain 1.4.0 gives MCP a first-class namespace in the core package
The langchain==1.4.0 release on 2026-09-03 adds a langchain.mcp namespace with an MCPAdapter (#39939) plus runnable examples (#39976), moving MCP from adapter-package territory into core. The same release includes a perf change omitting middleware trace inputs (#40098) and a fix to include the model destination in agent tool routing (#38355). Separately, langchain-anthropic 1.7.1 shipped Claude Fable 5.1 support (#40106) the same day.
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