Do you have an Intel or M series mac? I've found the Xcode codex plugin in ~Library/Developer/Xcode/CodingAssistant/Agents/Versions/26.3 But when I try to run the codex file it says "zsh: bad CPU type in executable: ./codex" so I assume it is built for M series only. Shame the Xcode UI couldn't flag that up.

I just got it working by rebooting my Mac!

Since speaking with Apple through my bug report, I’ve found a pattern. It happens after my Bot Integration finishes. Im hoping that as I’ve had dialogue through my bug report that they’ll be able to fix it. I suggest you add a bug report yourself and reference mine: FB12001344

Thank you very much for the update. I'll certainly report that back to them.

12.3.1 on both an i7 and an M1