Yes
It found the root cause and then asked whether the failure was either a regression or an insufficiently specified test, performed its own investigation, and found that the test harness was missing mocks that were exposed by the bug fix
Daishiman on Hacker News
In the thread “Vibe coding and agentic engineering are getting closer than I'd like”, replying to this comment
Helped: Investigating failing tests in large messy codebases to find root causes.
… I asked it to look at a failing test in a large and messy Python codebase. It found the root cause and then asked whether the failure was either a regression or an insufficiently specified test, performed its own investigation, and found that the test harness was missing mocks that were exposed by the bug fix. It has become amazingly good at investigating.