The P2 cellar-lip lesson one loop deeper. CheckOtherCells takes footCenter
by value and used it for every cell in the loop — but a mid-loop query can
MOVE the sphere: at the Facility Hub cell boundaries the neighbor's ramp
floor full-hits, step_sphere_up climbs the foot +0.6mm and returns OK, and
the loop continued querying the REMAINING cells (including the under-room,
portal-ring-3) at the pre-climb height — 0.4mm inside the double-faced
floor slab, grazing its underside (the under-room's ceiling) within the
near-miss window. That dispatched a neg-poly step-up with a DOWNWARD
normal, whose failure funneled into slide_sphere's opposing branch ->
synthetic reversed-movement collision -> Collided -> revert, every frame:
the seam shake (and, pre-mechanism-2-fix, the original absorbing wedge's
entry).
Retail check_other_cells reads the LIVE sphere_path.global_sphere for
every cell (each cell's find_collisions receives the transition itself,
pc:272717+). Fix: re-read footCenter = sp.GlobalSphere[0].Origin at the
top of each loop iteration.
All three Issue137CorridorSeamReplayTests repros un-skipped: the
snapshot-exact west-boundary crossing (capture tick 4101), the east
deep-straddle, and the clean-run lifecycle all GREEN. Full suites: Core
2556 / App 713 / UI 425 / Net 385, 0 failures.
Visual gate pending: corridor run + the purple seam flashing re-check
(expected to be the render exposing the same per-frame oscillation).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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