diff --git a/README.md b/README.md
index 3b75018..7ed87e7 100644
--- a/README.md
+++ b/README.md
@@ -131,6 +131,7 @@ Collection of awesome Python resources for testing and generating test data.
 - [bough](https://github.com/CodeEnPlace/bough) - Bough is a polyglot incremental mutation tester.
 - [Cosmic Ray](https://github.com/sixty-north/cosmic-ray) - makes small changes to your source code, running your test suite for each one.
 - [Crucible](https://github.com/Jott2121/crucible) - Adversarial test-hardening for AI-written code, built on mutmut. A Tester agent writes tests, mutation testing names the survivors, and a Critic agent kills exactly those.
+- [gatecheck](https://github.com/simin-yuan/self-auditing-agent/tree/main/gatecheck) - Mutation testing aimed at the checker instead of the code: it mutates a known-good input and reports which mutations a validator, linter or CI quality gate fails to reject. Stdlib only.
 - [Mutatest](https://github.com/EvanKepner/mutatest) - Python mutation testing.
 - [Mutmut](https://github.com/boxed/mutmut) - is a mutation testing system for Python, with a strong focus on ease of use.
 - [MutPy](https://github.com/mutpy/mutpy) - MutPy is a mutation testing tool for Python 3.x source code