Apparatus + handoff for the indoor flap. Confirmed (primary evidence): the flap is the
portal-flood clip being µm-sensitive at the threshold, driven by a ~1-8µm jitter in the
player RenderPosition (physics resting position not bit-stable; Lerp surfaces it). REFUTES
the 2026-06-07 see-through/EnvCell/outdoor-node diagnosis (ModelId GfxObj 0x01000A2B IS the
solid exterior) AND an enqueue-once attempt (retail propagates late slices via AddToCell;
the existing PropagatesNewSlicesToExit test caught it; reverted). Adds: Build determinism
test, A8CellAudit gfxobj dump, [pv-input] 6dp probe + [render-sig] outRoot/bshell fields.
No functional fix shipped. Next: higher-precision physics rest trace -> port retail
kill_velocity/contact rest-stability. Canonical: docs/research/2026-06-08-flap-rootcause-physics-rest-handoff.md
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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