The differential-repro ladder (2026-08-02, five prod runs + local counter
measurements) narrowed the crash trigger empirically: warm loads of
sibling-heavy projects die at settle (V1/V4 fail 2/2 warm; V2/V3 without
siblings never fail, warm or cold), while the flight-recorder counters show
the settle-time collision windows themselves are universal (fcsTotal=72,
rootHotTotal=3 on V1 AND V3, every load, cold and warm — so the windows are
the shared fan-out, not sibling-made). The sibling restage's room connects +
restage fetches are the only sibling-specific traffic contending with those
windows, and warm IDB compresses it into exactly that moment.
Nothing in the restage is needed for first paint — the boot snapshot staged
every sibling seconds earlier — so it now starts on requestIdleCallback
(5s timeout; setTimeout(3s) fallback), well clear of the settle storm.
Unmount-safe via disposedRef (armed per mount, checked in the deferred
starter and on handle resolution).
Validation is empirical by design: the counters won't move (windows are not
sibling-made); the test is warm V1/V4 prod loads no longer dying. If they
still die, the sibling lever is exonerated too and the remaining suspects
narrow to the ydoc-materialization path差 (second-load file source) — the
next probe either way.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019SE4o46Lnq3hF574FFq8x4
5c7f8a2e85