# Handoff — membership Stage 1 + the doorway blue-hole are FIXED; render residuals A/B/C next — 2026-06-03

> **Canonical pickup for the next session.** Read this FIRST. This session **fixed the cottage
> doorway "flap"** — it had **two** independent causes (a membership pick bug AND a render-root
> clobbering bug), both now resolved and visual-verified by the user (inside-looking-out is correct).
> What remains are **three separate, already-known render phases** (A camera-collision, B particles,
> C outside-looking-in) and the **Stage 2** membership faithfulness rearchitecture. Branch:
> `claude/thirsty-goldberg-51bb9b`. PowerShell on Windows; launch logs are UTF-16
> (`Select-String` / ripgrep `--encoding utf-16-le`, NOT GNU grep).

---

## 0. TL;DR

- **FIXED (visual-verified):** the doorway flap. Inside-looking-out now renders correctly — solid
  walls, wood floor, sky/terrain only through the doorway. No more full-screen bluish void.
- **The flap had TWO causes** (this is the key lesson — the prior handoff's "it's the pick" was only
  half of it):
  1. **Membership pick ping-pong** — the unordered `HashSet` + the pre-pick fork. Fixed by the
     verbatim ordered-`CELLARRAY` pick + retail's collide-then-pick order (Stage 1, faithful port).
  2. **Render-root clobbering** — `CellGraph.CurrCell` (the render root, "the player's cell") was
     written by the **per-entity** `ResolveWithTransition`/`ResolveCellId`, so a jumping NPC near the
     doorway overwrote the player's render root every tick → the render rooted at the NPC's tiny
     connector cell → only its ~8-triangle shell drew, rest = GL clear color = the blue void. Fixed
     by making the `CurrCell` write **player-only** (`UpdatePlayerCurrCell` via `UpdateCellId`).
- **REMAINING (next sessions):** render residuals **A → C → B** (a fresh render session), then
  membership **Stage 2** (uniform collision + intrinsic building entry), gated on a payoff (see §6).
- **Test state:** Core 1295 pass / 5 fail = the documented baseline (2 step-up + 3 door-collision),
  **zero new breakage**. App 174 green.

---

## 1. Commit ledger (this session, branch `claude/thirsty-goldberg-51bb9b`)

| SHA | What | Layer |
|---|---|---|
| `b44dd14` | `CellArray` — ordered/deduped cell collection (retail `CELLARRAY::add_cell` @701036) | Core |
| `bc56545` | widen cell-candidate helpers `HashSet<uint>` → `ICollection<uint>` (non-behavioral) | Core |
| `22a184c` | **verbatim ordered-CELLARRAY membership pick** (`find_cell_list` @308742); deletes the `5ca2f44` pre-check | Core |
| `e5457f9` | **collide-then-pick** — remove the pre-pick fork; `RunCheckOtherCellsAndAdvance` post-step (`find_env_collisions`→`check_other_cells`) | Core |
| `79fb6e7` | **doorway blue-hole** — `CurrCell` render-root write made player-only (`UpdatePlayerCurrCell`) | Core + App |

(`5ca2f44`, the prior session's current-first pre-check, was **deleted** by `22a184c` as the handoff directed.)

Working tree clean except untracked launch logs + the prior session's screenshots.

---

## 2. What shipped — Stage 1 membership port (faithful)

Ported verbatim from the decomp (`docs/research/named-retail/acclient_2013_pseudo_c.txt`):
- **`find_cell_list` ordered pick** (`CObjCell::find_cell_list @ 0x52b4e0`, pc:308742): an ordered
  `CellArray` (= retail `CELLARRAY`), current cell at **index 0** (`add_cell` @701036, pc:308766),
  single forward-walk expansion via `find_transit_cells` (pc:308775-308785), then **in-order,
  interior-wins-break** pick (pc:308788-308825). Replaced the unordered `HashSet`.
- **Collide-then-pick** (`CEnvCell::find_env_collisions @ 0x52c130` pc:309573 +
  `CTransition::check_other_cells @ 0x50ae50` pc:272717): the primary collision runs against the
  **carried** cell (the seed); the new cell is picked + all other cells collided **after**, in the
  new shared `Transition.RunCheckOtherCellsAndAdvance`. Removed acdream's pre-pick (line ~1958) which
  retail does NOT have — that pre-pick was the engine of the position oscillation (it swapped the
  collision geometry with the cell mid-tick → a bistable feedback loop).
- **Persistence** carried via the seed; committed by `ValidateTransition` (= `validate_transition`
  `curr_cell=check_cell`, pc:272612); applied to the player's object-state cell via `UpdateCellId`
  (= `SetPositionInternal`/`change_cell`, pc:283403/281192).
- Pseudocode: [`docs/research/2026-06-03-cell-membership-ordered-cellarray-pseudocode.md`](2026-06-03-cell-membership-ordered-cellarray-pseudocode.md).
- Plan: [`docs/superpowers/plans/2026-06-03-membership-ordered-cellarray-port.md`](../superpowers/plans/2026-06-03-membership-ordered-cellarray-port.md).

**Verified:** `[cell-transit]` dropped 47 → 13 → DELTA=0 while standing still (no oscillation); the
deterministic membership net is green (`CellTransit|FindEnvCollisions|CellGraph|Doorway|ResolveCellId`).

## 2b. What shipped — the doorway blue-hole fix (the real flap)

The ordered-pick fix alone did NOT clear the visual flap ("exactly the same"). Diagnosed via the
render probes (`ACDREAM_PROBE_FLAP`/`_VIS`/`_SHELL` + `ACDREAM_PROBE_CELL`):

```
[cell-transit] teleport -> 0xA9B40171   (player spawned in the ROOM, then stood still — no more transitions)
[flap-cam] root=0xA9B40170  ×77,951 frames   (render rooted at the VESTIBULE — the wrong cell)
[shell] filter=1 [0xA9B40170:gfx=1 idx=24]   (only 0170's ~8-tri shell drew → rest = blue clear color)
```

The player's cell was stable at `0171` (the room), but the render rooted at `0170` (a tiny connector)
because a Holtburg NPC (`0x000F4240`) jump-looping near the doorway clobbered `CellGraph.CurrCell`
every tick. `CurrCell` is documented as *"the player's cell"* (CellGraph.cs:19) and roots the indoor
render (GameWindow.cs:7172), but it was written by the **per-entity** `SetCurrAndReturn` inside
`ResolveWithTransition` (+ 4 sites in `ResolveCellId`).

**Fix (`79fb6e7`):** `CurrCell` is now written **only by the player** — new
`PhysicsEngine.UpdatePlayerCurrCell(cellId)` called from `PlayerMovementController.UpdateCellId`
(the single player chokepoint for CellId: teleport / server snap @ `SetPosition` + per-frame
resolver). Removed the write from `SetCurrAndReturn` (inlined the 2 resolve call sites) and the 4
`ResolveCellId` sites. NPCs no longer touch the render root. `CellGraphMembershipTests` rewritten to
the new contract (3 tests: `UpdatePlayerCurrCell` writes the root; `ResolveCellId` does NOT — the
blue-hole guard; stale-beats-null preserved).

**Verified:** `[flap-cam]` now shows `root=` the player's cell every frame (0171 in the room, 0170 in
the vestibule), `terrain=Planes/Skip` consistent, never stuck at an NPC's cell. User confirmed
inside-looking-out is correct.

> **Durable lesson (memory written):** a *single-owner* field (the player's render root) written from
> a *per-entity* loop is a clobbering bug. Membership/physics state that "belongs to the player" must
> be written at the player-only chokepoint, never in the shared per-entity resolve.

---

## 3. REMAINING ISSUES (the full list)

### Render residuals — visual, observed this session (do these next, a fresh render session)
- **A — interior walls go grey/transparent *while inside*; particles/NPCs visible through them.**
  Cause: the 3rd-person chase eye sits OUTSIDE the player's cell (`[flap-cam] eyeInRoot=n`), so near
  walls back-face/clip away. Fix: **camera collision** — port retail `SmartBox::update_viewer`
  spring-arm to keep the eye in the cell. Partially present (`[flap-sweep]` runs: `desiredBack`/
  `eyeBack`/`pulledIn`) but not fully containing the eye. Handoff-flagged "highest-leverage."
  **Shares its root mechanism (eye-outside-cell) with C — do A first to shrink C.**
- **B — particles bleed through the ground/floor** (looking out from inside). → **R1b / issue #104**
  (scene particles aren't cell-clipped; needs a cell link on the `ParticleEmitter`). Deferred in the
  R1 plan. Smallest of the three.
- **C — outside-looking-in: interior walls transparent + ground texture over the floor** (the
  cottage renders as a see-through box from the street; includes a detached floating wall piece). →
  **R2 / `PView::DrawPortal @ 0x5a5ab0`** — the outdoor→interior portal render, not yet built. The
  biggest (a whole render phase).

**Recommended order: A → C → B** (A first = highest-leverage + shrinks C; C second = the big one,
fresh; B last = small, self-contained).

### Membership Stage 2 — faithfulness debt, NOT a visible bug (do after A/B/C; gate on payoff — §6)
- **#4 Forked collision (§4.4 #3):** still branches `cellLow >= 0x0100` (indoor cell-BSP vs outdoor
  terrain-triangles) + `TryFindIndoorWalkablePlane`. Retail does one uniform sphere-sweep over all
  cells. "A real rearchitecture" (handoff's words) — risky; the membership WORKS without it.
- **#5 Building entry is a bridge (§4.4 #4):** `CellTransit.CheckBuildingTransit` + the `#90` `0x90`
  stickiness, instead of retail's intrinsic `find_building_transit_cells` (pc:318309).
- **#6 Outdoor `point_in_cell`:** the pick's outdoor fallback uses a `gx/gy` XY-column adaptation
  (acdream landcells lack retail's `CLandCell::point_in_cell` BSP). Documented adaptation.

### Separate physics — UNVERIFIED this session
- **#7 Stairs Z-oscillation** (~0.2 m/tick on the cellar stairs, #98 family). The prior handoff §8
  said it MAY be mooted by the membership fix. **Not re-tested** — needs a cellar-stairs walk.
  **This is the gate for Stage 2:** if the stairs are still broken, uniform collision (#4) plausibly
  fixes it and Stage 2 earns its risk; if the stairs are fine, Stage 2 stays optional.

### Test baseline — NOT introduced this session (do not "fix" blindly)
- **5 Core failures:** `BSPStepUpTests.B1`, `BSPStepUpTests.D4` (2 step-up gaps) +
  `DoorCollisionApparatusTests.Apparatus_Grounded_50cmOffCenter_FrontApproach_DocumentsBug` +
  `DoorBugTrajectoryReplayTests.LiveCompare_DoorOffCenterWalkthrough_Tick13558` +
  `…LiveCompare_DoorBlocksFromOutside_Tick22760` (3 door-collision). Verified pre-existing; the
  with-change failure set is a strict match to the prior baseline.

---

## 4. KEEP / DON'T-REDO

**KEEP (correct, verified — do not reopen):**
- The Stage-1 membership port: `CellArray`, the ordered `find_cell_list` pick in
  `BuildCellSetAndPickContaining`, the collide-then-pick `RunCheckOtherCellsAndAdvance`. Membership
  is stable (DELTA=0 while still; flap gone).
- The blue-hole fix: `UpdatePlayerCurrCell` (player-only render-root write). Do NOT re-add a `CurrCell`
  write inside `ResolveWithTransition`/`ResolveCellId` (that was the clobbering bug).
- The R1 render (per-cell `DrawInside`, binary decision) — inside-looking-out is correct.

**DON'T:**
- Don't re-add the `5ca2f44` pre-check (the ordered array subsumes it; the prior handoff's "ordered
  pick is too shallow" framing was itself superseded — the pick WAS necessary, it just wasn't the
  whole flap).
- Don't treat Stage 2 as mandatory — it's faithfulness debt; the membership works. Gate it on #7.
- Don't conflate A and C as one fix — A is camera-collision (eye containment while inside), C is the
  separate `DrawPortal` outdoor→interior phase. They share a *mechanism* (eye/viewpoint vs cell), not
  a code path.

---

## 5. KEY FILES + ANCHORS

```
MEMBERSHIP (Stage 1 — shipped)
  src/AcDream.Core/Physics/CellArray.cs                    ← retail CELLARRAY (ordered+dedup)
  src/AcDream.Core/Physics/CellTransit.cs
    BuildCellSetAndPickContaining                          ← the ordered find_cell_list pick
  src/AcDream.Core/Physics/TransitionTypes.cs
    FindEnvCollisions (~1939)                              ← primary-collide-against-seed (no pre-pick)
    RunCheckOtherCellsAndAdvance (~after FindEnvCollisions)← the check_other_cells post-step
  src/AcDream.Core/Physics/PhysicsEngine.cs
    UpdatePlayerCurrCell (~259)                            ← player-only render-root write (blue-hole fix)
    ResolveWithTransition (~608, returns sp.CurCellId)
  src/AcDream.App/Input/PlayerMovementController.cs
    UpdateCellId (~774)                                    ← calls _physics.UpdatePlayerCurrCell
  tests/AcDream.Core.Tests/Physics/CellGraphMembershipTests.cs ← new contract (3 tests)
  tests/AcDream.Core.Tests/Physics/CellTransitFindCellSetTests.cs ← ordered-pick conformance

RENDER (residuals A/B/C — next)
  src/AcDream.App/Rendering/GameWindow.cs (OnRender ~7300-7600) ← binary decision, landscape-thru-door, Z-clear
  src/AcDream.App/Rendering/InteriorRenderer.cs            ← per-cell DrawInside loop
  src/AcDream.App/Rendering/PhysicsCameraCollisionProbe.cs ← [flap-sweep] camera-collision (A lives near here)
  src/AcDream.App/Rendering/CellVisibility.cs              ← ComputeVisibilityFromRoot (root=player cell)
  src/AcDream.App/Rendering/ClipFrameAssembler.cs          ← TerrainMode / HasOutsideView (consistent)
  src/AcDream.App/Rendering/PortalVisibilityBuilder.cs     ← the PView BFS ([flap] probe)
  (R2/DrawPortal does not exist yet — C builds it)

RETAIL DECOMP (docs/research/named-retail/acclient_2013_pseudo_c.txt)
  CObjCell::find_cell_list        0x52b4e0  pc:308742    (pick 308788-308825; add_cell @701036)
  CEnvCell::find_env_collisions   0x52c130  pc:309573    (primary BSP vs the carried cell — no pre-pick)
  CTransition::check_other_cells  0x50ae50  pc:272717    (build array + collide others + advance)
  CTransition::validate_transition 0x50aa70 pc:272547    (curr_cell = check_cell @272612)
  CPhysicsObj::SetPositionInternal 0x515330 pc:283399    (change_cell iff this->cell != curr_cell)
  SmartBox::update_viewer          (camera spring-arm — A)   ; PView::DrawPortal 0x5a5ab0 (C)

PROBES
  ACDREAM_PROBE_CELL=1   [cell-transit] (player CellId changes)
  ACDREAM_PROBE_FLAP=1   [flap-cam] root/eyeInRoot/terrain/eye-vs-player  +  [flap] PView BFS  +  [flap-sweep] camera-collision
  ACDREAM_PROBE_VIS=1    [vis] visible cells + OutsideView
  ACDREAM_PROBE_SHELL=1  [shell] per-cell shell draw (NOSNAP/gfx/idx/zh/tr)
```

---

## 6. SEQUENCING DECISION (agreed with the user, 2026-06-03)

1. **This session: wrap** (this handoff + doc/roadmap updates). DONE.
2. **Next session: render residuals A → C → B** (a fresh render session — load the render design spec
   `docs/superpowers/specs/2026-06-02-render-pipeline-redesign-design.md` first; render is a different
   subsystem than this session's physics).
3. **After A/B/C: membership Stage 2** (#4 uniform collision + #5 intrinsic entry), **gated on #7** —
   first re-test the cellar stairs; if still oscillating, Stage 2 (uniform collision) is the likely
   fix and earns its risk; if fine, Stage 2 stays optional faithfulness debt.

---

## 7. RUNNING THE CLIENT (PowerShell; `+Acdream` spawns at/near the Holtburg cottage)

```powershell
$env:ACDREAM_DAT_DIR="$env:USERPROFILE\Documents\Asheron's Call"; $env:ACDREAM_LIVE="1"
$env:ACDREAM_TEST_HOST="127.0.0.1"; $env:ACDREAM_TEST_PORT="9000"
$env:ACDREAM_TEST_USER="testaccount"; $env:ACDREAM_TEST_PASS="testpassword"
$env:ACDREAM_PROBE_FLAP="1"; $env:ACDREAM_PROBE_CELL="1"   # for A: watch eyeInRoot + the camera sweep
dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug *>&1 | Tee-Object -FilePath launch.log
```
Build green BEFORE launching. Logs are UTF-16. Close gracefully (CloseMainWindow, not Stop-Process) so
ACE clears the session in ~3-5s.

---

## 8. PICKUP PROMPT (copy-paste for the next session)

```
RENDER RESIDUALS A → C → B at the Holtburg cottage doorway. The cottage doorway "flap" is FIXED this
session (membership Stage 1 + the blue-hole render-root clobbering) — inside-looking-out renders
correctly, user-verified. Continue on branch claude/thirsty-goldberg-51bb9b (do NOT branch/worktree;
do NOT push without asking; NEVER git stash/gc — a shared stash is under investigation). PowerShell on
Windows; launch logs are UTF-16 (Select-String / ripgrep --encoding utf-16-le, NOT GNU grep).

READ FIRST:
1. docs/research/2026-06-03-membership-and-bluehole-shipped-handoff.md  (THIS handoff — what shipped,
   the full remaining-issues list §3, KEEP/DON'T-REDO §4, key files §5, sequencing §6).
2. docs/superpowers/specs/2026-06-02-render-pipeline-redesign-design.md  (the render redesign — R1
   shipped + correct; R1b/R2 are the remaining phases; §2 the binary model, §4 the seal mechanics).

THE JOB — three known render phases, in order (render is a DIFFERENT subsystem than the physics this
handoff describes — load the render design spec, work in GameWindow.OnRender / CellVisibility /
PhysicsCameraCollisionProbe / PortalVisibilityBuilder / ParticleRenderer):
- A (camera collision — highest-leverage, do FIRST): interior walls go grey/transparent WHILE INSIDE
  because the 3rd-person chase EYE sits outside the player's cell ([flap-cam] eyeInRoot=n) → near
  walls back-face/clip away. Port retail SmartBox::update_viewer spring-arm to keep the eye in the
  cell. A [flap-sweep] camera-collision already runs (desiredBack/eyeBack/pulledIn) but doesn't fully
  contain the eye — refine it. Shares the eye-outside-cell mechanism with C, so A shrinks C.
- C (R2 outside-looking-in, do SECOND — the big one): from the street the cottage renders as a
  see-through box (interior walls transparent + ground texture over the floor). Build the
  outdoor→interior portal render — retail PView::DrawPortal @ 0x5a5ab0 (ConstructView(CBldPortal) →
  recurse → DrawCells the interior through the door's clip). Not built yet.
- B (R1b / #104, do LAST — smallest): particles bleed through the ground/floor when looking out.
  Cell-clip scene particles (give the ParticleEmitter a cell link via ParentCellId; clip per-cell in
  the DrawInside loop).

WORKFLOW: render is verified ON SCREEN (user's eyes) + the probes (ACDREAM_PROBE_FLAP/_VIS/_SHELL/
_CELL), never off the test suite (CLAUDE.md). For AC-specific render algorithms use the WB pipeline +
the retail decomp as the oracle (design spec). superpowers:writing-plans → executing-plans; verify
each phase at a user visual gate. Get a screenshot EARLY for render bugs (memory: render-one-gate).

DO NOT RE-LITIGATE: the flap is FIXED (membership + render-root, both committed + verified — KEEP §4).
Do NOT re-add a CurrCell write inside the per-entity ResolveWithTransition/ResolveCellId (that was the
blue-hole clobbering bug). Do NOT re-add the 5ca2f44 pre-check.

AFTER A/B/C: membership Stage 2 (uniform collision #4 + intrinsic building entry #5), but GATE it on
issue #7 first — re-test the cellar stairs (ACDREAM_PROBE_CELL + ACDREAM_CAPTURE_RESOLVE): if the
~0.2m/tick Z-oscillation persists, uniform collision is the likely fix and Stage 2 earns its risk; if
the stairs are fine, Stage 2 stays optional faithfulness debt (the membership works without it).

TEST BASELINE: Core 1295 pass / 5 fail (2 step-up BSPStepUp B1/D4 + 3 door-collision DoorCollision/
DoorBug) = pre-existing, NOT yours. App 174 green.
```
```