v4.22.8 v4.22.9

Name: fastmcp
Author: punkpeye

medium risk

punkpeye/fastmcpOct 14, 2026 → Oct 14, 20260 days between releases

What's New

Improves CLI robustness and session management in this patch release.

Breaking Changes

Rejects unknown CLI commands and options instead of ignoring them.

Improvements

Improves CLI robustness by validating arguments and rejecting unknown commands.
Enhances session ping management by stopping pings when the client disconnects.
Better OpenAPI media type recognition for different casing or parameters.

Bug Fixes

Fixes JSON-RPC error responses for malformed URIs and missing arguments.
Fixes warnings for client capabilities in closed sessions.
Accepts --name=value arguments and ignores transport/stateless values.
Stops pinging sessions once the client hangs up.
Fixes OpenAPI recognition of JSON and form media types.

Upgrade Notes

Unknown CLI commands or options will now cause an error instead of being silently ignored. Session pinging is now stopped immediately upon client disconnection. The CLI now properly supports the --name=value argument format.

The Two Releases

v4.22.8

Oct 14, 2026· 8 days ago

Corrects JSON-RPC error responses for malformed URIs and missing arguments, and enhances OpenAPI media type recognition.

Full release notes

v4.22.9

Oct 14, 2026· 7 days ago

Improves CLI robustness by validating arguments and rejecting unknown commands/options, alongside better session ping management.

Full release notes