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FastMCP 4.0.3 stops sending images twice when a tool returns an unconstrained sequence
Released 2026-09-05 at 00:30 UTC under the PrefectHQ org (the repo moved from jlowin/fastmcp and both paths serve the same release). PR #4999 stops inferring an output schema for unconstrained sequences, which was causing image content to be transmitted twice; #4971 avoids duplicate startup retries for multi-server clients with legacy-only backends; #5003 fixes task timing field serialization that strict clients were rejecting; and #5005 cleans up unfinished Monty callbacks when execution ends. The docs also correct the back-channel removal attribution to SEP-2322/2575 rather than SEP-2577.
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