v4.21.0

Name: fastmcp
Author: punkpeye

punkpeye/fastmcpv4.21.0Sep 25, 2026by github-actions[bot]

Upgrading?

What changed from v4.20.18 → v4.21.0?What's new in v4.21.1 after v4.21.0?

AI Summary

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.

Key Highlights

Adds RFC 9207 `iss` to authorization responses
Fixes record value schemas in advertised tool inputs

New Features

RFC 9207 issuer support in authorization responses

Full Release Notes

# [4.21.0](https://github.com/punkpeye/fastmcp/compare/v4.20.18...v4.21.0) (2026-09-25)


### Bug Fixes

* keep record value schemas in advertised tool inputs ([#392](https://github.com/punkpeye/fastmcp/issues/392)) ([38fe313](https://github.com/punkpeye/fastmcp/commit/38fe313d7a67f0aee67d84dbb301b3e2ff26a0b2))


### Features

* **auth:** add RFC 9207 `iss` to authorization responses ([#393](https://github.com/punkpeye/fastmcp/issues/393)) ([45a5791](https://github.com/punkpeye/fastmcp/commit/45a5791165d09f452644fe4fd4d9aaff2f47b7bb))

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