langchain==1.4.0a3

Summary

Third alpha of the 1.4.0 line. This release focuses on the new langchain.mcp namespace for adapting MCP servers into LangChain tools. langchain.mcp highlights MCPAdapter adapts any target fastmcp.Client accepts — a URL, a local script, an in-process server, an MCPConfig naming several servers, or a pre-built client — as well as a FastMCP ClientGroup for a fleet of servers behind one client. MCPAdapter.list_tools(*, cache_mode="use") discovers and adapts tools, with optional client-side response caching (SEP-2549): use serves a cached list within the server's TTL hint, refresh repopulates it, bypass skips it. as_langchain_tool(tool, client, *, elicitation=None) converts a single MCP tool for callers managing their own client. Tool metadata is grouped under an mcp namespace on each tool: the tool's annotations (snake_case) and _meta under metadata["mcp"]["tool"] , and the serving server's identity under metadata["mcp"]["server"] . elicitation="interrupt" surfaces a server's mid-call questions as LangGraph interrupts, so a human answers and the run resumes. from langchain . agents import create_agent from langchain . mcp import MCPAdapter async with MCPAdapter ( "https://example.com/mcp" ) as adapter : agent = create_agent ( "anthropic:claude-sonnet-5" , await adapter . list_tools ()) Requires the mcp extra: pip install "langchain[mcp]" (and fastmcp>=4.0.0 ). Install pip install --pre " langchain==1.4.0a3 " This is a pre-release; install with --pre . Release notes curated with the assistance of an AI agent.

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