The tests still waited on real time: the 20 ms and 50 ms pauses behind the "nothing more is sent" checks, Testing Library's waits (a real setInterval and a real end-of-wait setTimeout), and React Query's notices on a real setTimeout of 0. Under load, whether the ordered-replay check saw a PATCH sent too soon depended on when a real timer fired. The tests now wait with until, which lets the page take turns of the event loop (setImmediate inside act) until a check passes, and settle, which lets it take a fixed number of turns before a "nothing more happens" check. No time passes in either, real or fake. React Query's notices go out a turn later on setImmediate, and advance moves the fake clock synchronously. The Testing Library wait wrapper override is gone. The replay assertions are unchanged. Task 880e924e-c248-472f-8e92-1baec5b4cc9f. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>