v4.20.15

Name: fastmcp
Author: punkpeye

punkpeye/fastmcpv4.20.15Sep 21, 2026by github-actions[bot]

Upgrading?

What changed from 4.19.1 → v4.20.15?What's new in v4.20.16 after v4.20.15?

AI Summary

This release improves server stability and robustness by fixing crash scenarios related to logging failures and ensuring proper handling of tools calls with missing arguments.

Key Highlights

Prevents server crashes caused by failed log notifications
Fixes parameter handling for tools/call requests that omit arguments
Preserves JSON dictionary bodies with empty properties in OpenAPI definitions
Addresses issues #381, #382, and #383

Full Release Notes

## [4.20.15](https://github.com/punkpeye/fastmcp/compare/v4.20.14...v4.20.15) (2026-09-21)


### Bug Fixes

* accept a tools/call that omits params.arguments ([#383](https://github.com/punkpeye/fastmcp/issues/383)) ([e7e4520](https://github.com/punkpeye/fastmcp/commit/e7e45208d339101d8cf0eb39323fb3de56dbd960))
* catch failed log notifications instead of crashing the server ([#382](https://github.com/punkpeye/fastmcp/issues/382)) ([c15e194](https://github.com/punkpeye/fastmcp/commit/c15e194eab508e798cc43ca4e8c8cb66d3c29445))
* **openapi:** preserve JSON dictionary bodies with empty properties ([#381](https://github.com/punkpeye/fastmcp/issues/381)) ([d9edf6c](https://github.com/punkpeye/fastmcp/commit/d9edf6cb5befd49e65723b860fb5418cfb0c3c06))

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