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FastMCP 4 beta 5 adds ClientGroup, letting each MCP server negotiate its own protocol version with no proxy in between
Released 2026-08-28, v4.0.0b5 introduces ClientGroup: one managed client per server, each negotiating its protocol era independently, with collision-checked tool namespacing and call routing. That replaces the usual pattern of fronting several servers with a proxy that forces a single negotiated version across all of them. The release also aligns middleware response limits with output schemas.
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