# P2 pickup handoff — door / building-shell collision = BSP Path 5 grounded step-up

> **🔴 CORRECTED 2026-06-04 — the localization below (the step-up CLIMB) was WRONG; B1 is FIXED.**
> An `ITestOutputHelper` capture of B1 (xunit swallows `Console.WriteLine`) proved the climb code
> (`find_walkable`/`AdjustSphereToPlane`/`step_sphere_down`/`DoStepUp`/`DoStepDown`) is **correct** and
> matches ACE exactly. The real B1 bug was the **A6.P4 near-miss dispatch in `BSPQuery.FindCollisions`
> Path 5 (Contact branch)**, which diverged from retail three ways: (1) recorded a near-miss
> `NegPolyHit` **unconditionally** — retail gates both `set_neg_poly_hit` calls behind
> `if (num_sphere > 1)` (`acclient_2013_pseudo_c.txt:323852`); (2) checked the foot near-miss before
> the head's (retail checks the head/sphere1 first); (3) reversed the `neg_step_up` mapping (retail:
> head index0→FALSE/slide, foot index1→TRUE/step-up, per `SPHEREPATH::set_neg_poly_hit` :323279).
> For B1's single foot sphere the spurious near-miss → outer `!NegStepUp → Collided` → revert → the
> mover wedged at x=0.1, never reached the wall to step up. **Verbatim fix committed (`abbd761`):**
> the gate+order+mapping now match retail; B1 climbs (foot→(0.6,0,0.25)); the Holtburg door blocks
> faithfully (slab `(0,-1,0)` normal) when the scenario has a real floor.
>
> **Remaining red (NOT simple flips — all separate from B1):**
> - `Apparatus_Grounded_50cmOffCenter` — its tick-0 `(0,0,1)` "block" is a **synthetic-test artifact**:
>   the apparatus sets `terrain=-1000` so the only BSP is the door slab; the contact-maintenance
>   step-down finds no floor underfoot → false Collided/revert, then the mover walks through. With a
>   real floor (`terrain=0`) the door blocks faithfully at Y≈11.5 with `(0,-1,0)`. Fix = give the
>   grounded test a real floor + assert the block normal is the door's ±Y (NOT the tick-0 `(0,0,1)`
>   contact-maintenance hiccup, which is a separate cold-seed first-frame artifact). Do **NOT** just
>   flip to `Assert.True(blocked)` — that blesses the artifact.
> - `LiveCompare_DoorOffCenterWalkthrough_Tick13558` / `_DoorBlocksFromOutside_Tick22760` — compare
>   against captured **buggy-live** positions; a correct fix makes the harness diverge (blocks earlier).
>   Re-baseline to the corrected behavior or retire as documents-the-bug.
> - `D4_AirborneMover_TallWall_PersistsSlidingNormalAcrossFrames` — **airborne (Path 6)**, a separate
>   sliding-normal-persistence issue, unrelated to the Path 5 grounded near-miss. Pre-existing.
>
> See `memory/project_p2_door_stepup_findings.md`. **Next: USER VISUAL GATE** (walk through a cottage
> door cleanly; step up a stair) — the authoritative P2 acceptance. The original (wrong) analysis is
> retained below for the record.

> **Canonical pickup for the next session.** Branch `claude/thirsty-goldberg-51bb9b`
> (do NOT branch/worktree; do NOT push without asking; NEVER `git stash`/`gc`). PowerShell on
> Windows; launch logs are UTF-16. Read this FIRST.

## State both altitudes

- **Milestone:** M1.5 — Indoor world feels right.
- **Effort:** the VERBATIM spatial-pipeline port (master plan:
  `docs/superpowers/specs/2026-06-03-verbatim-spatial-pipeline-port-master-plan.md`).
- **P1 (membership) = DONE.** Proven to already match retail; the "0/11 lag" was a cdb capture
  artifact. Merged to `main` + pushed to both remotes (HEAD `f0d37d8`). See
  `docs/research/2026-06-03-p1-membership-swept-advance-handoff.md` (RESOLVED banner) +
  `memory/project_retail_membership_criterion.md`.
- **P2 (door / building-shell collision) = IN PROGRESS, root cause LOCALIZED.** The fix is the next step.
- **Next concrete step:** read+compare acdream `find_walkable`/`step_sphere_down` vs retail
  `BSPTREE::step_sphere_down` (pc:323665) + `find_walkable`, pin the step-up CLIMB divergence, and
  drive `B1_GroundedMover_LowStep_StepsUp` + the door apparatus RED→GREEN.

## TL;DR (the P2 finding)

All **5 failing Core tests** localize to **BSP Path 5 (the grounded `Contact + StepSphereUp` branch)**:
| Test | Symptom |
|---|---|
| `BSPStepUpTests.B1_GroundedMover_LowStep_StepsUp` | grounded mover wall-slides a **walkable 0.25 m step** instead of stepping up (`CurPos.Z` stays 0). The cleanest isolation of the bug. |
| `BSPStepUpTests.D4_AirborneMover_TallWall_PersistsSlidingNormalAcrossFrames` | airborne tall-wall sliding-normal count (`Expected: 2`) — Path 4/5 sliding-normal family. |
| `DoorCollisionApparatusTests.Apparatus_Grounded_50cmOffCenter_FrontApproach_DocumentsBug` | synthetic door + grounded off-center: now blocks at tick 0 with an `(0,0,1)` up-normal + goes airborne (Path 5 step-up artifact, not a faithful door block). |
| `DoorBugTrajectoryReplayTests.LiveCompare_DoorOffCenterWalkthrough_Tick13558` | replay of captured live tick diverges from the engine (documents-the-bug). |
| `DoorBugTrajectoryReplayTests.LiveCompare_DoorBlocksFromOutside_Tick22760` | same, outdoor-block tick. |

These have been the documented baseline RED set for a while (they are P2's target). They did NOT
regress this session — P1's work only touched conformance tests + docs.

## Root cause — PRECISELY localized (the whole upstream chain is verified faithful)

For B1 (the cleanest case), the path is reached + dispatched correctly; the divergence is deep in the
climb. Verified faithful and ruled out this session (DO NOT re-investigate these — see DO-NOT-RETRY):

1. **Path 5 dispatch is reached.** `BSPStepUpFixtures.MakeGroundedTransition` sets `State = Contact |
   OnWalkable` + `StepDown=true` — but that `StepDown` is `ObjectInfo`'s flag; the Path 3 dispatch
   gates on the `SpherePath.StepDown` flag (only set during a step-down probe), so the **main sweep
   correctly lands in Path 5's `Contact` branch** (`BSPQuery.cs:1814`).
2. **Recursion guard passes.** `if (engine is not null && !path.StepUp && !path.StepDown) return
   StepSphereUp(...)` (`BSPQuery.cs:1848`) — on the main sweep both `SpherePath` flags are false →
   `StepSphereUp` → `DoStepUp` IS called on the wall hit.
3. **`DoStepUp` (`TransitionTypes.cs:3254`) = faithful port of retail `CTransition::step_up`
   (pc:273099).** Same structure: clear contact-plane, `stepDownHeight = OnWalkable ? StepUpHeight :
   0.04`, `walkableAllowance = OnWalkable ? GetWalkableZ() : LandingZ`, call `DoStepDown(...)`, return
   its result. (acdream adds a restore-contact-plane-on-failure block — benign.)
4. **`DoStepDown` (`TransitionTypes.cs:3074`) = faithful port of retail `CTransition::step_down`
   (pc:272946).** Skips the down-offset when `StepUp` is set, runs `TransitionalInsert(5)`, accepts
   iff `OK && ContactPlaneValid && ContactPlane.N.z >= walkableZ`, then placement-validates.

**So the divergence is INSIDE the step-up climb:** `DoStepDown` → `TransitionalInsert(5)` → Path 3
`step_sphere_down` → **`find_walkable`'s upper-floor find + sphere-up-adjust when `sp.StepUp=true`**.
It fails to locate/lift onto the 0.25 floor within the 0.30 budget → `DoStepDown` returns false →
`StepUpSlide` → wall-slide → `Z=0`. The retail oracle for the climb is `BSPTREE::step_sphere_down`
(`@ 0x53a210` pc:323665) + `BSPNODE/BSPLEAF::find_walkable` + `adjust_sphere_to_plane`.

acdream code map: `BSPQuery.StepSphereUp` (`:1372`), `BSPQuery.step_sphere_down` (`:1206`),
`BSPQuery.find_walkable` (`:693`), `BSPQuery.AdjustSphereToPlane` (search it), `Transition.DoStepUp`
(`:3254`), `Transition.DoStepDown` (`:3074`).

## ⚠ TOOLING NOTE (cost me a probe cycle — don't repeat)

**xunit swallows `Console.WriteLine`.** The built-in `ACDREAM_DUMP_STEPUP=1` trace (in `DoStepUp`)
and the `[step-walk]` probe (`PhysicsDiagnostics.ProbeStepWalkEnabled`) both print via `Console` →
they do NOT surface in `dotnet test ... -l "console;verbosity=detailed"`. The tests that DID show
output used `ITestOutputHelper` (`_out.WriteLine`). So to trace which climb condition fails
(`TransitionalInsert(5)` result / contact-plane / `N.z` / placement), **add an `ITestOutputHelper`-based
trace to B1 (or a focused harness) — don't rely on the `Console` probes inside the engine.**

## DO-NOT-RETRY (verified faithful this session)

1. Path 5 dispatch / the Contact-branch reachability — confirmed B1 reaches Path 5.
2. The recursion guard / `StepSphereUp` call — confirmed `DoStepUp` is called.
3. `DoStepUp` vs retail `step_up` — faithful, ruled out.
4. `DoStepDown` vs retail `step_down` — faithful, ruled out.
The bug is downstream in `find_walkable`/`step_sphere_down`'s **step-up adjust**. Start there.

## Next steps (evidence-first — the door saga burned many SPECULATIVE fixes; do NOT repeat)

1. **Read+compare** acdream `BSPQuery.find_walkable` (`:693`) + `step_sphere_down` (`:1206`) +
   `AdjustSphereToPlane` against retail `BSPTREE::step_sphere_down` (pc:323665) + `BSPNODE/BSPLEAF::
   find_walkable` + `adjust_sphere_to_plane`. Focus on the `step_up==1` path: how retail lifts the
   sphere onto a step within `step_down_amt`, and where acdream fails to.
2. **Instrument B1 with `ITestOutputHelper`** (Console is swallowed — see tooling note) to pin which
   condition fails: does `TransitionalInsert(5)` return OK? is `ContactPlaneValid` set? is the landing
   `N.z >= walkableZ`? does placement (`TransitionalInsert(1)`) reject? `B1` is sub-second, headless.
3. **Fix the climb verbatim** (cite the decomp anchor), drive `B1` GREEN, then `B2` (must still
   block the 5 m wall), then the door apparatus (`Apparatus_Grounded_50cmOffCenter…` flips to
   block-not-walkthrough → rewrite its assertion to `Assert.True(blocked) && pos.Y < 12.0`), then the
   2 `LiveCompare` ticks, then `D4`.
4. **Definitive cross-check if the decomp is ambiguous:** cdb-attach to retail at a Holtburg cottage
   doorway, break on `CTransition::step_up`/`step_down`/`BSPTREE::step_sphere_down`, walk a low step +
   the door, capture what retail does. PDB MATCHES; tooling in `tools/cdb/` (CLAUDE.md "Retail debugger
   toolchain"). Needs the user's retail client up + walking.
5. **User visual gate:** at a doorway, walk through cleanly (foot Y stable, no oscillation), walls
   block; step up a low step (cottage stair) climbs.

## Test baseline (going into the P2 fix)

Core **1309 pass / 5 fail / 1 skip** — the 5 are exactly this P2 target (`Apparatus_Grounded…`,
`LiveCompare_DoorOffCenterWalkthrough_Tick13558`, `LiveCompare_DoorBlocksFromOutside_Tick22760`,
`BSPStepUpTests.D4…`, `BSPStepUpTests.B1…`). Conformance 60 pass / 1 skip / 0 fail. App 177 green.

## Parked (do NOT touch without explicit user approval)

- **(a)–(d) membership cleanups** — approval-gated refactors of WORKING code (CLAUDE.md "don't replace
  working retail-faithful logic without approval"): (a) remove redundant `ResolveCellId` (already out
  of the prod per-frame path; survives only in the `DataCache==null` test fallback); (b) unify the
  forked `find_env_collisions`; (c) replace the `CheckBuildingTransit` bridge with intrinsic building
  stabs in `find_transit_cells`; (d) make the per-cell ObjCell graph the collision authority (collision
  still uses the landblock-wide `ShadowObjectRegistry`). The one soft spot: outdoor→indoor `0031↔0170`
  building-entry is live-clean but NOT conformance-locked (rides on `CheckBuildingTransit`).
- **Render residuals (P3/P4)** — the VISIBLE doorway seam is now in the render path: the flap =
  camera-collision residual (chase eye drifts out of the cell → viewer-cell flips; master-plan P3,
  `SmartBox::update_viewer`); the void = unported PView seal (P4). Membership (physics) is correct.
  See `docs/research/2026-06-03-p1-visual-gate-render-residuals.md`. Master-plan order: P2 → P3 → P4.

---

## FRESH-SESSION PROMPT (copy-paste)

```
Continue the VERBATIM retail spatial-pipeline port for acdream. Branch claude/thirsty-goldberg-51bb9b
(do NOT branch/worktree; do NOT push without asking; NEVER git stash/gc). PowerShell on Windows;
launch logs are UTF-16.

STATE: M1.5 (Indoor world feels right). P1 membership = DONE (proven to already match retail; the
"0/11 lag" was a cdb capture artifact; merged + pushed, HEAD f0d37d8). P2 (door/building-shell
collision) = IN PROGRESS, root cause LOCALIZED to BSP Path 5 grounded step-up. The fix is the job.

READ FIRST (canonical, in order):
1. docs/research/2026-06-03-p2-door-stepup-handoff.md  (THIS handoff — the localization, the
   DO-NOT-RETRY list, the tooling note, the next steps).
2. docs/superpowers/specs/2026-06-03-verbatim-spatial-pipeline-port-master-plan.md (§3 P2; §1/§2 B3/B4).
3. docs/research/2026-05-25-door-bug-partial-fix-shipped.md (the door saga state + its do-not list).

THE FINDING: all 5 failing Core tests localize to BSP Path 5 (grounded Contact + StepSphereUp). For
B1 (cleanest: a grounded mover wall-slides a walkable 0.25 m step with a 0.30 m budget, Z stays 0),
the whole upstream chain is VERIFIED FAITHFUL + correctly reached — Path 5 dispatch, the recursion
guard, DoStepUp (= retail CTransition::step_up pc:273099), DoStepDown (= retail step_down pc:272946).
The divergence is INSIDE the step-up CLIMB: DoStepDown → TransitionalInsert(5) → Path 3
step_sphere_down → find_walkable's upper-floor find + sphere-up-adjust when sp.StepUp=true. It fails
to lift onto the 0.25 floor → StepUpSlide → wall-slide.

DO NOT RE-INVESTIGATE (verified faithful): Path 5 dispatch, the recursion guard, DoStepUp, DoStepDown.
DO NOT speculate on the BSP fix without apparatus (the door saga burned many speculative fixes).
TOOLING: xunit swallows Console.WriteLine — the ACDREAM_DUMP_STEPUP / [step-walk] probes don't surface
in the runner; instrument B1 with ITestOutputHelper to trace the climb conditions.

THE JOB (P2 fix, evidence-first):
1. Read+compare acdream BSPQuery.find_walkable (:693) / step_sphere_down (:1206) / AdjustSphereToPlane
   vs retail BSPTREE::step_sphere_down (pc:323665) + BSPNODE/BSPLEAF::find_walkable + adjust_sphere_to_plane,
   focused on the step_up==1 climb. Pin the divergence (instrument B1 with ITestOutputHelper if needed).
2. Port the climb verbatim (cite the anchor). Drive RED→GREEN: B1 (steps up), then B2 (still blocks the
   5 m wall), then DoorCollisionApparatusTests.Apparatus_Grounded_50cmOffCenter (flips to block — then
   rewrite its documents-the-bug assertion to Assert.True(blocked) && pos.Y < 12.0), then the 2
   LiveCompare ticks, then D4.
3. If the decomp is ambiguous: cdb-attach to retail at a cottage doorway (break on step_up/step_down/
   step_sphere_down) — needs the user's retail client. PDB matches; tools/cdb/.
4. USER VISUAL GATE: walk through a doorway cleanly (foot Y stable, walls block); step up a cottage
   stair (climbs).

TEST BASELINE: Core 1309 pass / 5 fail (the P2 target above) / 1 skip; Conformance 60 pass / 1 skip;
App 177 green. PARKED (need explicit approval): the (a)-(d) membership cleanups + the render residuals
(P3/P4 — the visible doorway flap/void). Do NOT speculate a Path-5 fix before the climb divergence is
pinned with evidence.
```