docs: session handoff — #137 corridor arc closed, #176/#177 render pair pickup

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/research/2026-07-06-137-closeout-render-pair-pickup.md

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+# Pickup prompt — post-#137-corridor session: the #176/#177 render pair (paste into a fresh session)
+
+**Read `claude-memory/project_render_pipeline_digest.md` FIRST** (Option A —
+one DrawInside(viewer_cell); binding DO-NOT-RETRY table), then **ISSUES #176
+and #177**, then this file. The physics digest
+(`claude-memory/project_physics_collision_digest.md`) carries the full
+2026-07-06 collision saga if background is needed — do NOT reopen it.
+
+## Where we are (2026-07-06 end of session)
+
+**The #137 Facility Hub corridor collision arc is DONE, user-gated** ("not
+collision anymore. Good." / "Looks good"). Branch
+`claude/vigorous-joliot-f0c3ad` (worktree), 10 commits ahead of `e73e45da`,
+NOT merged to main. All suites green (Core 2562 / App 713 / UI 425 / Net 385).
+
+| Commit | Fix |
+|---|---|
+| `a11df5b8` | BSPQuery Contact-branch stub slide responses leaked sliding normals (the absorbing wedge). Retail's BSP layer never writes `collision_info.sliding_normal` — only `validate_transition` 0x0050ac21; body persistence success-only (`SetPositionInternal` 0x005154c2). |
+| `e8651b38` | `slide_sphere` opposing-normals branch returned OK; retail returns COLLIDED_TS (0x0053762c). The "phantom wall" normal was SYNTHETIC (negated movement). PortalSide-poly theory refuted. |
+| `d4869154` | `CheckOtherCells` queried remaining cells at a stale pre-climb center (P2 lesson one loop deeper) — the seam shake. Per-iteration `footCenter = sp.GlobalSphere[0].Origin` refresh. |
+| `aa96d7ad` | The collision capsule topped out at 1.2 m (callers passed `sphereHeight: 1.2f`; head sphere center 0.72). Dat Setup 0x02000001: spheres (0,0,0.475)+(0,0,1.350) r=0.48, top 1.83 = Height 1.835. Callers now pass 1.835. Register TS-46. The window climb. |
+
+**#137 stays OPEN for the DOORS half only** (block/pass per open state).
+The #175 door-pose fix (2026-07-05) still needs its user gate — ask for it
+whenever the user is next at the hub double door (closed blocks AT the
+visual panels from both sides, no embed, no phantom wall).
+
+## NEXT ARC: #176 + #177 (render, both filed 2026-07-06 from the gate session)
+
+- **#176 — purple flashing on dungeon floors at cell seams, camera-angle
+  dependent.** Survives all physics fixes → render-side. Magenta/purple =
+  the placeholder-texture class ([[feedback_ui_resolve_zero_magenta]]).
+- **#177 — stairs between levels pop in/out.** Invisible from the corridor
+  looking into the stair room, appear on entering, vanish on the last step
+  running down. The #119 visibility class, dungeon edition. Anchor cells:
+  the transit `0x8A020182 → 0x8A020183` drops z −6 → −9 on stairs
+  (launch-137-gate2.log).
+
+**The load-bearing topology fact both issues share (discovered this
+session):** Facility Hub corridor FLOORS are portal polygons — PortalSide
+floor-portals to under-rooms (e.g. 0x8A02016E visual polys 1/3/5 → 0x011E,
+horizontal at z=−6, spanning the whole floor; 0x011E is a hall at z=−12).
+Level connections run through these floor-portals. "Purple at the seams" is
+purple exactly where portal surfaces meet, and the stairs' rooms hang off
+the same portal graph — suspect the render portal-flood/portal-surface
+handling of HORIZONTAL portals.
+
+**⚠️ The id-space trap (cost this saga a wrong mechanism):**
+`CellPortal.PolygonId` indexes the VISUAL polygon table (`CellStruct.Polygons`),
+NOT `PhysicsPolygons`. Same ids in both tables are UNRELATED polygons.
+
+## Tooling built this session (reuse, don't rebuild)
+
+- `Issue137CorridorSeamInspectionTests` — dat-inspection theories (add
+  `InlineData` cells as needed): portal spans (`CorridorCell_PortalPolygonWorldSpans`),
+  full-vertex poly dumps (`WindowShaft_FullPolyDump`), physics-BSP leaf
+  membership, hit-normal candidate sweep (use |align| — winding flips),
+  `HumanSetup_CollisionSpheres_DatTruth`.
+- `Issue137CorridorSeamReplayTests` — dat-backed `PhysicsEngine` corridor
+  harness (`BuildCorridorEngine`: hydrate THREE portal rings or ring-3
+  cells are invisible to the flood — why clean-room replays kept passing).
+  In-test probe capture pattern: `Console.SetOut(StringWriter)` +
+  `PhysicsDiagnostics.Probe*Enabled = true` → line-diff offline vs live.
+- Live probe logs (worktree root, PowerShell Tee = UTF-16, `tr -d '\000'`
+  before grep): `launch-137-seam-probes.log` (790 MB, step-level),
+  `launch-137-gate2.log`, `launch-137-gate3.log`,
+  `resolve-137-seam-capture.jsonl` (body snapshots, untracked).
+
+## Physics DO-NOT-RETRY highlights from today (full table in the digest)
+
+- No `SetSlidingNormal` in the BSP/sphere layer; opposing branch returns
+  Collided; failed transitions never write body sliding state.
+- The absorbed exactly-anti-parallel frame against a persisted sliding
+  normal is RETAIL behavior — fix normal PROVENANCE, not the abort.
+- No height-budget check in the step-down accept — retail's climb cap is
+  `adjust_sphere_to_plane`'s walk_interp −0.5 overshoot bound (0x00538210)
+  + the placement insert rejecting the HEAD in solids.
+- Probe-field misreads: `[neg-poly]`/`[neg-poly-dispatch]` print `stepUp=`
+  = NegStepUp (dispatch class), NOT sp.StepUp. `[walkable-nearest]` is a
+  logger, not the decision-maker.
+- Remaining registered leaks (rows exist, fix later): TS-45
+  (`SphereCollision`'s SetSlidingNormal tail), TS-4 (Path-6 steep-tangent),
+  TS-46 (scalar sphere approximation; remotes use human dims).
+
+## Launch protocol (unchanged)
+
+Build green first; PowerShell launch with the env block from CLAUDE.md
+(+ `ACDREAM_PROBE_RESOLVE=1 ACDREAM_PROBE_CELL=1` for gates), background +
+Tee to `launch-*.log`. The user manages client lifecycle. Graceful close →
+ACE session clears in ~5 s; hard kill → ~3 min. The test character may be
+saved in odd places after collision testing (last session it was inside the
+window alcove and ACE bounced it to Holtburg — the user portals back).