MCP in LangChain: Stateless Protocol, Elicitation, and More!

LangChain has revamped its MCP integration in response to rapid adoption of the Model Context Protocol and its major July 2026 specification update, moving support into the main `langchain.mcp` package and building it on FastMCP. The revised MCP protocol replaces session-based communication with a stateless core, improving server scalability and reliability by eliminating session pinning while enabling server-directed tool-list caching and elicitation, where tools can pause for user input or approval. LangChain represents elicitation through LangGraph interrupts, allowing an agent run to pause and resume after a reviewer supplies an answer, while cached tool catalogs can reduce repeated discovery requests according to server-defined TTLs. FastMCP supplies transport handling, authentication, protocol negotiation, logging, progress notifications, and compatibility with both legacy and current MCP servers, including mixed-server configurations through separate clients and automatically prefixed tool names. The beta Python implementation is available with `langchain[mcp]` version 1.4.0 or later, replaces the former `langchain-mcp-adapters` package and its multi-server client, and is expected to gain TypeScript support later.

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