I have gotten code reviews from OoenAI's Codex integration that do point out meaningful issues, including across files and using significant context from the rest of the app.

Sometimes they are things I already know but was choosing to ignore for whatever reason. Sometimes it's like "I can see why you think this would be an issue, but actually it's not". But sometimes it's correct and I fix the issue.

I just looked through a couple of PRs to find a concrete example. I found a PR review comment from Codex pointing out a genuine big where I was not handling a particular code path. I happened to know that no production data would trigger that code path as we had migrated away from it. It acted as a prompt to remove some dead code.