Report-only investigation of the local player running off cliff edges. No
production or test code changed.
Retail's rim slide is CTransition::cliff_slide (0x0050a6d0), whose direction is
cross(steep contact normal, last_known_contact_plane.N) — it needs the surface
the mover was standing on as its second vector. Disassembly of the PDB-paired
binary shows COLLISIONINFO::set_contact_plane (0x00509d80, 22 bytes) writes only
contact_plane_valid / contact_plane / contact_plane_is_water; the last-known
group has exactly four semantic writers in retail, all outside the per-substep
collision response (CTransition::init_contact_plane 0x0050e850,
init_last_known_contact_plane 0x0050e8e0, the validate_transition tail
0x0050ad07, and the clears).
acdream's CollisionInfo.SetContactPlane latches the last-known group on every
write, at all 13 call sites. The step-down probe's own steep plane therefore
overwrites the ground reference before EdgeSlideAfterStepDownFailed reads it,
CliffSlide's cross product goes to zero, its degenerate OK return displaces
nothing, and TransitionalInsert's retry accepts the candidate hanging over the
drop. The latch dates to 9ea8ae51 (2026-04-13) and was never retail-verified,
matching the user's "pre-existing, not a regression".
Also established: every edge_slide branch, gate and threshold in acdream is
byte-exact against 0x0050b3d0 / 0x0050b812 / 0x0050b886 (the step-down probe
schedule is confirmed against the disassembly, which corrects a Binary Ninja
stack-slot misread at 0x0050b8ba); 204d0ae0 deleted four remote-only forgeries
and never touched the sweep, the edge family or contact-plane maintenance, so
it could not have covered the local player; #134 is the same family with an
unverified 2026-07-09 triage closure; and six claims in #32's own text are
stale at HEAD.
The causal link to the user's cliff is a hypothesis, not a proof — it needs
edge_slide to take branch 2. ACDREAM_DUMP_EDGE_SLIDE=1 already prints the
branch and both normals at the deciding site; the report carries the run
command and a six-row decision table. No code before that run.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
