v4.21.0 v4.21.1

Name: fastmcp
Author: punkpeye

punkpeye/fastmcpSep 25, 2026 → Sep 25, 20260 days between releases

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Analyzing what changed between v4.21.0 and v4.21.1. This page updates automatically — usually within a minute.

The Two Releases

v4.21.0

Sep 25, 2026· 27 days ago

This release introduces support for the `iss` (issuer) claim in authorization responses according to RFC 9207. It also includes a bug fix to ensure record value schemas are correctly advertised in tool inputs.

Full release notes

v4.21.1

Sep 25, 2026· 27 days ago

A maintenance release addressing various bugs, including incorrect error codes for unknown prompts, hanging validation commands, and type-checking issues. It ensures proper access control for authenticated stdio sessions.

Full release notes