v4.21.1
punkpeye/fastmcpv4.21.1Sep 25, 2026by github-actions[bot]
Upgrading?
AI Summary
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.
Key Highlights
- Fixes error code -32602 for unknown prompt names on prompts/get
- Applies canAccess restrictions to stdio sessions with authentication
- Fixes CLI validate hanging when a server starts on import
- Enables type-checking validate targets with the project's tsconfig
Full Release Notes
## [4.21.1](https://github.com/punkpeye/fastmcp/compare/v4.21.0...v4.21.1) (2026-09-25) ### Bug Fixes * answer -32602 when prompts/get names an unknown prompt ([33caed8](https://github.com/punkpeye/fastmcp/commit/33caed8b8bbf7df2bf8287e81e57b417ecc971de)) * apply canAccess to stdio sessions that have auth ([5095511](https://github.com/punkpeye/fastmcp/commit/50955115b62db47699b1a9ee4958e0be93149218)) * **cli:** stop validate hanging on a server that starts when imported ([2c67be9](https://github.com/punkpeye/fastmcp/commit/2c67be91d0c33daf750d4d0355843a1f7d9cc40b)) * **cli:** type-check validate targets with their project's tsconfig ([8bf56bf](https://github.com/punkpeye/fastmcp/commit/8bf56bf4d34e4887fe7aba67e09ec7471f6b8d54))
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