docs(phase): Cluster A — partial ship + handoff

Cluster A's investigation pinned #86 (picker) as structural and closed
it (Phase B). #84 and #85 both pinned on missing indoor cell tracking;
Phase D promoted CellId via AABB containment which un-stuck the
spawn-in-building case (closes #84 partially) but proved too tight for
threshold/doorway cells to keep CellId indoor during normal walking.
The proper fix is retail's portal-based cell traversal; filed as a
new ISSUES.md issue (see body) for the follow-up phase. Phase E
diagnostic infrastructure ([cell-cache] + extended [indoor-bsp]) stays
in place as scaffolding for that work.

ISSUES.md: #86 → Recently closed. #84 status updated to PARTIAL with
resolution paragraph. #85 status update note added. New issue #87 filed
for portal-based indoor cell tracking.

Roadmap: Cluster A added to Recently shipped with partial-ship note.
Forward entry added for the portal-traversal follow-up under Phase G.

CLAUDE.md: current-phase paragraph updated to reflect Cluster A partial
ship. Next phase deferred to Claude's choice in a future session.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/ISSUES.md

@@ -239,7 +239,7 @@ to the second floor without getting stuck.
 
 ## #84 — Blocked by air indoors
 
-**Status:** OPEN
+**Status:** OPEN (partial fix 2026-05-19)
 **Severity:** HIGH (blocks indoor navigation)
 **Filed:** 2026-05-19
 **Component:** physics, collision
@@ -266,6 +266,20 @@ visible cell mesh. Possibilities:
 **Acceptance:** Walking through interior cell space hits collisions
 only where visible walls/furniture exist.
 
+**Resolution (2026-05-19 partial · `c19d6fb`):** Phase D of Cluster A
+extended `ResolveOutdoorCellId` in `PhysicsEngine.cs` with an indoor
+cell-containment scan: when the player's world position falls inside any
+cached EnvCell's AABB, `CellId` is promoted to that indoor cell, which
+enables the `FindEnvCollisions` indoor-BSP branch. This resolved the
+"spawn in building and be stuck above the floor" variant of #84 —
+player's CellId now promotes to the interior cell on spawn-in, the floor
+is walkable, and the player can move freely. The "invisible air obstacle"
+symptom for rooms the player walks INTO from outside is now superseded by
+the root cause in #87 (AABB containment is too tight for threshold/
+doorway cells to keep CellId promoted during normal walking). That
+remaining symptom will be resolved by the portal-based cell tracking
+fix.
+
 ---
 
 ## #85 — Pass through walls from outside→in
@@ -293,30 +307,65 @@ collision polys or per-poly back-face handling.
 **Acceptance:** Walking into an inn wall from outside collides; player
 must enter via the door portal.
 
+**Status update (2026-05-19):** The root cause is now pinned as the
+same failure as #84's remaining symptom — `CellId` isn't promoted to
+the indoor cell during normal outdoor→indoor walking because AABB
+containment is too tight for threshold/doorway cells. Without CellId
+in the indoor cell, the indoor-BSP collision branch in
+`FindEnvCollisions` never fires regardless of approach direction.
+See new issue #87 (portal-based indoor cell tracking) for the
+retail-faithful fix.
+
 ---
 
-## #86 — Click selection penetrates walls
+## #87 — Indoor cell tracking uses AABB containment instead of portal traversal
 
 **Status:** OPEN
-**Severity:** MEDIUM
+**Severity:** HIGH
 **Filed:** 2026-05-19
-**Component:** input, interaction
+**Component:** physics
 
-**Description:** Clicking through a wall from the outside selects NPCs
-and objects inside the building. The `WorldPicker` raycast doesn't
-intersect cell BSP geometry.
+**Description:** `PhysicsDataCache.TryFindContainingCell` promotes the
+player's `CellId` to an indoor EnvCell when their world position falls
+inside any cached cell's local AABB. This is too tight to keep `CellId`
+promoted to an indoor cell during normal walking. Threshold/doorway cells
+(the polys that sit at a room boundary) have AABB Z ranges of only ~0.2 m;
+a standing player at local Z=0.46 m is OUTSIDE the AABB and containment
+fails. Because `CellId` drifts back to the outdoor cell, the indoor-BSP
+collision branch in `TransitionTypes.FindEnvCollisions` is gated out for
+most movement, so walls don't block from inside the house and the floor
+physics is unreliable. The retail fix is portal-based cell traversal —
+when the player crosses a cell portal boundary, the cell ownership
+propagates through portal connectivity data in `CEnvCell`.
 
-**Root cause / status:** `WorldPicker.BuildRay + Pick` (introduced in
-Phase B.4) tests against entity AABBs and scenery BSPs but probably
-not cell BSP. Outdoor NPCs are pickable because their entity AABB is
-the test target; indoor NPCs are pickable from outside because the
-wall isn't in the ray's intersection set.
+**Evidence:** `launch-cluster-a-cache-diag3.log` (Cluster A Phase E
+capture). Cell `0xA9B40143` (real room) has
+`physicsPolyCount=14 bspTotalLeafPolys=14 bspUnmatchedIds=0
+aabbMin=(-11.60,-1.60,0.00) aabbMax=(-6.20,7.60,2.80)` — geometry is
+complete and the AABB spans 2.8 m height, which works. Cell `0xA9B40146`
+(threshold/doorway) has `physicsPolyCount=4
+aabbMin=(-11.60,2.80,-0.20) aabbMax=(-10.00,7.60,0.00)` — Z range is
+only 0.2 m; a standing player is always outside it. Only 6 `[indoor-bsp]`
+lines fired across an entire indoor walking session (all during mid-jump
+frames when the player was briefly inside the room AABB at jump height).
 
 **Files:**
-- `src/AcDream.App/Rendering/WorldPicker.cs` (or equivalent — check
-  Phase B.4b reference).
+- `src/AcDream.Core/Physics/PhysicsDataCache.cs` (`TryFindContainingCell`,
+  approximately line 261)
+- `src/AcDream.Core/Physics/PhysicsEngine.cs` (`ResolveOutdoorCellId`,
+  approximately line 238)
+- `src/AcDream.Core/Physics/TransitionTypes.cs` (`FindEnvCollisions` cell
+  branch, approximately line 1188)
 
-**Acceptance:** Clicking on a wall doesn't select NPCs behind it.
+**Retail reference:** PDB symbols `CObjMaint::HandleObjectEnterCell` and
+`CEnvCell` portal data. See `docs/research/named-retail/acclient.h` lines
+31715-31726 for `CCellStructure` shape; `acclient_2013_pseudo_c.txt` for
+the implementations.
+
+**Acceptance:** Player walking from outside the Holtburg cottage into the
+interior crosses portals and `CellId` updates accordingly; walls block
+from both inside and outside; the `[indoor-bsp]` probe fires consistently
+during indoor walking (not just during mid-jump frames).
 
 ---
 
@@ -2847,6 +2896,23 @@ Unverified. The likely culprits, ranked by suspected probability:
 
 # Recently closed
 
+## #86 — [DONE 2026-05-19 · 3764867 + 4e308d5] Click selection penetrates walls
+
+**Closed:** 2026-05-19
+**Commits:** `3764867` — fix(picker): Cluster A #86 — cell-BSP ray occlusion in WorldPicker; `4e308d5` — test(picker): Cluster A #86 — screen-rect cell-occlusion tests
+**Component:** input, interaction
+
+**Resolution:** `WorldPicker.Pick` now accepts a `cellOccluder` callback
+(`CellBspRayOccluder`). Before returning a hit, both `Pick` overloads
+consult the occluder's `NearestWallT` value; any candidate entity whose
+ray parameter exceeds the nearest-wall intersection is filtered out.
+The occluder is wired from `GameWindow` using the loaded `PhysicsDataCache`
+cell structs. Entities behind walls from the camera's perspective are no
+longer selectable. Screen-rect occlusion tests verify the filter across
+several hit/miss scenarios.
+
+---
+
 ## #77 — [DONE 2026-05-18 · 3be7000] Auto-walk doesn't engage at walking range; pickup at walking range overshoots and snaps back
 
 **Closed:** 2026-05-18