Closes the apparatus loop. Side-by-sides acdream's deterministic replay
(commit 856aa78) against retail's cdb capture taken via Step 4's
runner. The divergence target is named; the fix plan is the next plan.
Retail data (cellar_up_capture_1):
- 35,219 BP hits over ~5 seconds of motion
- BPE (set_contact_plane): 161 writes, ALL to one of two flat planes
(n=(0,0,1) d=-93.9998 = cottage floor @ Z=94, OR d=-90.95 = cellar
floor @ Z=90.95). Retail NEVER sets ContactPlane to the cellar ramp.
- BPC (find_crossed_edge): 1 hit in 35K. Retail barely uses this
predicate during cellar-up.
- BPA (find_walkable) sphere position at each cottage-floor
acceptance: sphere LOCAL Z = +0.48 to +0.63 (resting on top of the
floor plane). Sphere world Z ≈ 94.48.
acdream replay (Issue98CellarUpReplayTests):
- At the failing-frame sphere (world (141.7, 8.4, 92.0)), the cottage
cell 0xA9B40143's poly 0x0004 reports insideEdges=false AND
overlapsSphere=false. Sphere local Z = -0.69 (below the cottage
floor plane). 0xA9B40146 has no walkable candidate at all. Step-up
has nothing to step onto → stuck.
Sphere world Z delta: 2.47m. Retail's sphere is 2.5m higher than ours
at the decision point. The fix targets, in priority order:
1. (HIGHEST CONFIDENCE) Step-up + ramp climb doesn't gain enough Z per
tick. Retail climbs the ramp GRADUALLY across thousands of ticks;
ours oscillates at world Z ≈ 92 without altitude gain. Look at
Transition.AdjustOffset (slope projection) and Transition.DoStepUp
(does it reset WalkInterp like retail's step_sphere_up?).
2. Cottage-cell candidacy uses wrong sphere reference. Check what
sphere CheckOtherCells passes to BSPQuery.FindCollisions — is it
the step-lifted sphere or the pre-step sphere?
3. (SECONDARY) find_crossed_edge over-use. Our walkable test calls
FindCrossedEdge heavily; retail barely uses it. Possibly a
code-shape mismatch in step-up vs walkable-acceptance flow.
4. (LOW CONFIDENCE) Ramp polygon normal divergence. Verify via test
after any fix.
The apparatus that gets us here:
- tests/AcDream.Core.Tests/Fixtures/issue98/*.json (real cell geometry)
- Issue98CellarUpReplayTests (7 tests, <1ms each, deterministic bug
reproduction)
- tools/cdb/issue98-runner.ps1 (reusable for any future capture)
- docs/research/2026-05-23-a6-captures/cellar_up_capture_1/ (this
capture, checked in for future analyses)
Next plan: pick Target 1 or 2 from the comparison doc and write the
fix plan against it. The replay harness is the test loop; a fix that
doesn't change the failing assertions in Issue98CellarUpReplayTests is
not the fix.
