Hi everyone,
Since today, all my Codex requests have been failing in both Xcode 26.5 and Xcode 27 beta.
The Codex integration appears to be connected and authenticated correctly, but every request fails immediately with the error shown in the attached screenshot.
Error message:
The data couldn’t be read because it isn’t in the correct format.
I fixed this problem by logging out from codex / OpenAI and using an API key instead.
Before I tried to reinstall the codex agent (via Xcode) I also deleted the whole ~/Library/Developer/Xcode/CodingAssistant folder. But nothing helped.
@patrick You can also try deleting the items in your Keychain named "Codex ___" and let us know if that helps. We'll look into improving the error messages here.
@Engineer no this didn't work. I removed every keychain entry named Codex* (had a few of them in my keychain). After that I reopened Xcode and signed in via my OpenAI account. Same problem again. So I switched back to the API key, which works again without problems.
