T6 (BR-7) C4: straddle-only outside-add (A6.P5 widening DELETED) + #90 stickiness removed

The two remaining flagged workarounds retired, per the BR-7 plan +
the WF1 [MEDIUM] correction (re-gate, do NOT delete the outside-add):

1. A6.P5 hasExitPortal topology widening DELETED. Outdoor cells enter the
   collision cell array ONLY on the retail straddle gate - |dist| <
   radius + F_EPSILON against an exterior portal plane
   (CEnvCell::find_transit_cells Ghidra 0x0052c820, gate 0052c9d6,
   live-binary verified) - the same flag that already gated the
   membership pick (#112 rider). The widening existed so outdoor-
   registered doors stayed findable from indoor cells under the old flat
   registry query; with per-cell shadow lists the door is found in the
   straddle-admitted outdoor cell's own list (tick-13558 pin holds).
   The hasExitPortal out-param + plumbing deleted from
   FindTransitCellsSphere; the AddAllOutsideCells call in
   BuildCellSetAndPickContaining re-gated on exitOutsideStraddle
   (once-per-walk = retail CELLARRAY.added_outside).

2. #90 ResolveCellId sphere-overlap stickiness REMOVED (the 4ca3596
   workaround, deferred-to-A6.P4 in the physics digest). It was dead
   code: the method's only caller is FindEnvCollisions' cache-null TEST
   fallback, and the indoor branch (where the stickiness lived) required
   a non-null DataCache. Production membership flows exclusively through
   the collide-then-pick advance whose ordered-array hysteresis (current
   cell at index 0, interior-wins-break) is the retail mechanism the
   workaround approximated. ResolveCellId reduced to the bare
   prefix-preserving outdoor re-derive, documented test-only.

Test updates (pins of the deleted behaviors inverted to retail):
- A6P5_BuildCellSetFromIndoorStart_ReachesDoorOutdoorCell (asserted the
  topology widening verbatim) -> DeepInteriorSphere_NoStraddle_
  AddsNoOutdoorCells: a deep-interior sphere admits NO outdoor cells.
- A6P5_BuildCellSetFromAlcove... -> AlcoveSphere_StraddlesExitPortal_
  ReachesDoorOutdoorCell (the captured alcove position genuinely
  straddles - the retail-positive half).
- Issue112MembershipTests straddle pin + the second-sphere straddle test
  updated to the single-flag signature.

Suites: Core 1416/0/2, App 225, UI 420, Net 294 - green.

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

src/AcDream.Core/Physics/CellTransit.cs

@@ -58,20 +58,6 @@ public static class CellTransit
         float sphereRadius,
         ICollection<uint> candidates,
         out bool exitOutside)
-        => FindTransitCellsSphere(
-            cache, currentCell, currentCellId, worldSphereCenter, sphereRadius,
-            candidates, out exitOutside, out _);
-
-    /// <inheritdoc cref="FindTransitCellsSphere(PhysicsDataCache, CellPhysics, uint, IReadOnlyList{Sphere}, int, ICollection{uint}, out bool, out bool)"/>
-    public static void FindTransitCellsSphere(
-        PhysicsDataCache cache,
-        CellPhysics currentCell,
-        uint currentCellId,
-        Vector3 worldSphereCenter,
-        float sphereRadius,
-        ICollection<uint> candidates,
-        out bool exitOutside,
-        out bool hasExitPortal)
     {
         var spheres = new[]
         {
@@ -84,7 +70,7 @@ public static class CellTransit
 
         FindTransitCellsSphere(
             cache, currentCell, currentCellId,
-            spheres, spheres.Length, candidates, out exitOutside, out hasExitPortal);
+            spheres, spheres.Length, candidates, out exitOutside);
     }
 
     /// <summary>
@@ -98,12 +84,9 @@ public static class CellTransit
     /// This is the only condition under which retail's
     /// <c>CEnvCell::find_transit_cells</c> calls <c>add_all_outside_cells</c>
     /// (acclient.exe 0052c8e5-0052c92d straddle test, 0052c9d2-0052c9f0 gate;
-    /// pseudo-C :310070-310120). Drives the membership pick's outdoor branch.</param>
+    /// pseudo-C :310070-310120). Drives the membership pick's outdoor branch
-    /// <param name="hasExitPortal">Topology-only: this cell has at least one
+    /// AND (BR-7 C4, retail-faithfully) the collision cell-set outside-add —
-    /// exterior (0xFFFF) portal, regardless of sphere position. NOT retail —
+    /// the former <c>hasExitPortal</c> topology widening is deleted.</param>
-    /// kept for the A6.P5 collision cell-set widening (outdoor-registered door
-    /// entities must stay findable from indoor cells until the A6.P4 per-cell
-    /// shadow architecture ships; see the exterior-portal branch comment).</param>
     public static void FindTransitCellsSphere(
         PhysicsDataCache cache,
         CellPhysics currentCell,
@@ -111,11 +94,9 @@ public static class CellTransit
         IReadOnlyList<Sphere> worldSpheres,
         int numSpheres,
         ICollection<uint> candidates,
-        out bool exitOutside,
+        out bool exitOutside)
-        out bool hasExitPortal)
     {
         exitOutside = false;
-        hasExitPortal = false;
 
         uint lbPrefix = currentCellId & 0xFFFF0000u;
         int sphereCount = EffectiveSphereCount(worldSpheres, numSpheres);
@@ -129,8 +110,6 @@ public static class CellTransit
 
             if (portal.OtherCellId == 0xFFFF)
             {
-                hasExitPortal = true;
-
                 // #112 rider (2026-06-10): retail straddle gate, RESTORED and
                 // verified against the LIVE 2013 binary (cdb attach, function
                 // 0052c820; x87 decode at 0052c8e5-0052c92d):
@@ -144,19 +123,17 @@ public static class CellTransit
                 // portal_side / exact_match in this branch — BN's pseudo-C
                 // invented those (feedback_bn_decomp_field_names).
                 //
-                // History: this gate existed pre-A6.P5 and was removed
+                // History: this gate existed pre-A6.P5, was removed 2026-05-25
-                // 2026-05-25 citing the CALLER (find_cell_list :308775-:308785
+                // citing the CALLER (find_cell_list :308775-:308785 walks every
-                // walks every array cell unconditionally — true, but each
+                // array cell unconditionally — true, but each callee still
-                // callee still applies its own straddle gate). The A6.P5
+                // applies its own straddle gate), and was restored for the
-                // symptom it fixed (outdoor-registered cottage DOORS invisible
+                // membership PICK by the #112 rider. BR-7 / A6.P4 C4
-                // to collision from indoor cells) is really the missing
+                // (2026-06-11) finished the story: the per-cell shadow
-                // per-cell shadow_object_list (#99/A6.P4): retail finds those
+                // architecture made the A6.P5 hasExitPortal topology widening
-                // doors via shadow lists, not via outdoor transit cells. Until
+                // unnecessary (doors are found in the straddle-admitted outdoor
-                // A6.P4 ships, BuildCellSetAndPickContaining keeps widening the
+                // cell's own list), so this flag now gates BOTH the pick's
-                // COLLISION cell set on hasExitPortal — but the membership PICK
+                // outdoor branch AND the collision cell-set outside-add —
-                // gates its outdoor branch on this retail flag, which is what
+                // pure retail.
-                // keeps deep-interior containment gaps on curr_cell (retail
-                // keep-curr) instead of demoting to outdoor (#112).
                 if (!exitOutside)
                 {
                     for (int i = 0; i < sphereCount; i++)
@@ -540,7 +517,7 @@ public static class CellTransit
 
                     FindTransitCellsSphere(
                         cache, cell, cellId, worldSpheres, sphereCount,
-                        candidates, out bool exitStraddle, out _);
+                        candidates, out bool exitStraddle);
 
                     if (exitStraddle && !outdoorAdded)
                     {
@@ -787,7 +764,7 @@ public static class CellTransit
 
                 FindTransitCellsSphere(
                     cache, cell, cellId, worldSpheres, sphereCount,
-                    candidates, out bool exitOutsideStraddle, out bool hasExitPortal);
+                    candidates, out bool exitOutsideStraddle);
 
                 // #112 rider (2026-06-10): the retail straddle flag (live-binary
                 // verified — see FindTransitCellsSphere) gates the PICK's outdoor
@@ -795,16 +772,21 @@ public static class CellTransit
                 // when a path sphere straddles an exterior portal plane.
                 outdoorPickAllowed |= exitOutsideStraddle;
 
-                // A6.P5 (kept, NARROWED to the collision cell SET): the first
+                // BR-7 / A6.P4 C4 (2026-06-11): outdoor cells enter the array
-                // exit-portal cell triggers the outdoor neighbourhood add once, by
+                // on the retail STRADDLE gate — |dist| < radius + F_EPSILON
-                // TOPOLOGY — wider than retail. This keeps outdoor-registered door
+                // against an exterior portal plane (CEnvCell::find_transit_cells
-                // entities findable from indoor cells (the 2026-05-25 door capture)
+                // 0x0052c820; gate at 0052c9d6) — replacing the A6.P5
-                // until #99/A6.P4 ships per-cell shadow lists; the pick no longer
+                // hasExitPortal TOPOLOGY widening. The widening existed to keep
-                // consumes these cells unless the retail flag fired, so membership
+                // outdoor-registered doors findable from indoor cells under the
-                // matches retail in both regimes. Appended AFTER the interior cells,
+                // old flat query; with per-cell shadow lists the door is found
-                // matching retail order (add_all_outside_cells at the end,
+                // in the straddle-admitted outdoor cell's OWN list (and the
-                // pseudo_c:310120) — interior-wins is preserved.
+                // straddle fires whenever a sphere is genuinely at the
-                if (hasExitPortal && !outdoorAdded)
+                // threshold — the tick-13558 door pin proves the admission).
+                // Appended AFTER the interior cells, matching retail order
+                // (add_all_outside_cells at the end, pseudo_c:310120) —
+                // interior-wins is preserved. Once-per-walk via outdoorAdded =
+                // retail CELLARRAY.added_outside (0x00533630).
+                if (exitOutsideStraddle && !outdoorAdded)
                 {
                     AddAllOutsideCells(worldSpheres, sphereCount, currentCellId, blockOrigin, candidates);
                     outdoorAdded = true;

src/AcDream.Core/Physics/PhysicsEngine.cs

@@ -290,84 +290,38 @@ public sealed class PhysicsEngine
             cg.CurrCell = cell;
     }
 
+    /// <summary>
+    /// TEST-ONLY outdoor cell re-derive. The single caller is
+    /// <c>Transition.FindEnvCollisions</c>'s cache-null fallback
+    /// (PhysicsEngineTests run engines without a <see cref="DataCache"/>,
+    /// so <see cref="CellTransit.FindCellSet"/> is unavailable). Production
+    /// membership flows exclusively through the collide-then-pick advance
+    /// (<c>RunCheckOtherCellsAndAdvance</c> → <c>FindCellSet</c>).
+    ///
+    /// <para>
+    /// BR-7 / A6.P4 C4 (2026-06-11): the former indoor branch — including
+    /// the #90 sphere-overlap stickiness workaround (4ca3596) and the
+    /// building-transit promotion — was DEAD CODE on this path (it required
+    /// a non-null DataCache; the only caller guarantees null) and is
+    /// removed. #90's doorway ping-pong concern is owned by the retail
+    /// ordered-pick hysteresis (current cell at array index 0,
+    /// interior-wins-break; CellTransit.BuildCellSetAndPickContaining) —
+    /// the workaround is retired, closing the digest's deferred-removal
+    /// item.
+    /// </para>
+    ///
+    /// <para>Preserves the L.2e prefix-preservation fix (always apply the
+    /// matched landblock's high-16 prefix even when
+    /// <paramref name="fallbackCellId"/> arrived bare-low-byte).</para>
+    /// </summary>
     internal uint ResolveCellId(Vector3 worldPos, float sphereRadius, uint fallbackCellId)
     {
         if (fallbackCellId == 0) return 0;
 
-        uint fallbackLow = fallbackCellId & 0xFFFFu;
+        // Indoor fallback ids pass through unchanged — identical to the old
+        // dead path's `DataCache is null → return fallbackCellId` outcome.
+        if ((fallbackCellId & 0xFFFFu) >= 0x0100u) return fallbackCellId;
 
-        if (fallbackLow >= 0x0100u)
-        {
-            // Indoor branch needs DataCache to look up cells; outdoor uses
-            // _landblocks (no DataCache dependency).
-            if (DataCache is null) return fallbackCellId;
-
-            // ── Cell-stickiness REVERTED (A6.P3 slice 3 v3, 2026-05-22) ──
-            // Slice 3 v1 (sphere-overlap, 8898166) over-corrected — held
-            // player in cellar even when transitioning out at the ramp top.
-            // Slice 3 v2 (point-in, 3e140cf) closed the ping-pong at the
-            // inn doorway (data confirmed) BUT prevented the player from
-            // reaching the top of the cellar ramp (the stuck spot
-            // transitioned from "ping-pong at top" to "never reach top").
-            //
-            // Reverting to no-stickiness for now. The ping-pong at the inn
-            // doorway returns but is a lesser evil than blocking cellar-up
-            // entirely. Issue #98 cellar-up has a deeper bug that needs
-            // separate investigation (BSP step-physics or AdjustOffset
-            // slope-projection at the cottage main floor boundary).
-            //
-            // Slice 3 work remains valuable as research evidence; the fix
-            // shape was wrong. Issue #90 stays as workaround until a
-            // better stickiness mechanism is designed (probably needs to
-            // be GATED by some "near cell boundary" check rather than
-            // applied unconditionally).
-
-            // Fallback cell no longer valid → re-resolve via portal-graph BFS.
-            uint indoorResult = CellTransit.FindCellList(DataCache, worldPos, sphereRadius, fallbackCellId);
-
-            // ISSUES #83 / Phase A1.7 (2026-05-21): verify the indoor result
-            // actually contains the player. CellTransit.FindCellList falls back
-            // to currentCellId when no candidate cell's CellBSP contains the
-            // sphere center — but this happens even when the player has walked
-            // OUTSIDE the entire portal-connected indoor cell graph (e.g.,
-            // exited through an unblocked wall or doorway gap). In that state
-            // the player's CellId is stuck on an indoor cell whose BSP is
-            // far away, every indoor-bsp query returns OK (NodeIntersects
-            // fails at root), and no walls block.
-            //
-            // If the resolved indoor cell's BSP does NOT contain the sphere
-            // center, fall through to the outdoor cell resolution below — it
-            // will compute the correct landcell from the terrain grid and
-            // optionally re-enter an indoor cell via CheckBuildingTransit.
-            var indoorCell = DataCache.GetCellStruct(indoorResult);
-            if (indoorCell?.CellBSP?.Root is null)
-                return indoorResult;   // render root (CurrCell) set by the player's UpdateCellId  // Can't verify (no CellBSP); trust FindCellList.
-
-            // Issue #90 fix (2026-05-20): use SPHERE-overlap instead of POINT-in
-            // for the indoor verification. The previous point-only check caused
-            // a per-frame ping-pong at the inn doorway: indoor BSP push-back
-            // moved the sphere CENTER a few cm outside the indoor CellBSP
-            // volume → point-only check returned false → fell through to outdoor
-            // → next tick re-promoted to indoor → wall hit → push-back →
-            // outdoor → repeat. Net visual behavior: "walls walk through"
-            // because outdoor ticks bypass indoor BSP entirely. With sphere-
-            // overlap, the player stays classified indoor as long as ANY part
-            // of the foot sphere still overlaps the indoor cell volume.
-            //
-            // Retail oracle: CCellStruct::sphere_intersects_cell at
-            // acclient_2013_pseudo_c.txt:317666 →
-            // BSPTREE::sphere_intersects_cell_bsp at :323267.
-            var localCenter = Vector3.Transform(worldPos, indoorCell.InverseWorldTransform);
-            if (BSPQuery.SphereIntersectsCellBsp(indoorCell.CellBSP.Root, localCenter, sphereRadius))
-                return indoorResult;   // render root (CurrCell) set by the player's UpdateCellId
-
-            // Fall through to outdoor resolution: player has FULLY left the
-            // indoor portal-connected graph (sphere no longer overlaps).
-        }
-
-        // Outdoor seed: use terrain grid to compute the prefixed cell id.
-        // Preserves the L.2e prefix-preservation fix (always apply the matched
-        // landblock's high-16 prefix even when fallbackCellId arrived bare-low-byte).
         foreach (var kvp in _landblocks)
         {
             var lb = kvp.Value;
@@ -376,29 +330,7 @@ public sealed class PhysicsEngine
             if (localX >= 0f && localX < 192f && localY >= 0f && localY < 192f)
             {
                 uint lowCellId = lb.Terrain.ComputeOutdoorCellId(localX, localY);
-                uint outdoorCellId = (kvp.Key & 0xFFFF0000u) | lowCellId;
+                return (kvp.Key & 0xFFFF0000u) | lowCellId;
-
-                // Outdoor→indoor entry: if this landcell has a cached building,
-                // check whether the sphere has crossed into one of its interior
-                // EnvCells via the building's portals.
-                if (DataCache is not null)
-                {
-                    var building = DataCache.GetBuilding(outdoorCellId);
-                    if (building is not null)
-                    {
-                        var candidates = new System.Collections.Generic.HashSet<uint>();
-                        CellTransit.CheckBuildingTransit(
-                            DataCache, building, worldPos, sphereRadius, candidates);
-                        if (candidates.Count > 0)
-                        {
-                            // First candidate wins — building portal containment is
-                            // mutually exclusive in retail (one interior cell per portal).
-                            foreach (var c in candidates) return c;
-                        }
-                    }
-                }
-
-                return outdoorCellId;   // render root (CurrCell) set by the player's UpdateCellId
             }
         }
 

tests/AcDream.Core.Tests/Conformance/Issue112MembershipTests.cs

@@ -101,21 +101,22 @@ public sealed class Issue112MembershipTests
         var cell102 = cache.GetCellStruct(0xA9B30102u)!;
 
         // (a) Deep inside the room, 3 m from the door plane: the cell HAS an
-        //     exterior portal (topology flag) but no straddle → no outdoor
+        //     exterior portal but no straddle → no outdoor admission flag
-        //     admission flag (retail: var_44 stays 0, add_all_outside skipped).
+        //     (retail: var_44 stays 0, add_all_outside skipped). (BR-7 C4
+        //     deleted the non-retail hasExitPortal topology output — the
+        //     straddle flag is the only outdoor-admission signal, like
+        //     retail.)
         var farCandidates = new List<uint>();
         CellTransit.FindTransitCellsSphere(
             cache, cell102, 0xA9B30102u, new Vector3(183.0f, 86.5f, 117.0f),
-            FootRadius, farCandidates, out bool farStraddle, out bool farHasExit);
+            FootRadius, farCandidates, out bool farStraddle);
-        Assert.True(farHasExit);
         Assert.False(farStraddle);
 
         // (b) At the door plane (0.30 m away < 0.48 radius): straddle fires.
         var nearCandidates = new List<uint>();
         CellTransit.FindTransitCellsSphere(
             cache, cell102, 0xA9B30102u, new Vector3(185.70f, 85.5f, 117.0f),
-            FootRadius, nearCandidates, out bool nearStraddle, out bool nearHasExit);
+            FootRadius, nearCandidates, out bool nearStraddle);
-        Assert.True(nearHasExit);
         Assert.True(nearStraddle);
     }
 

tests/AcDream.Core.Tests/Physics/CellTransitFindTransitCellsSphereTests.cs

@@ -212,7 +212,7 @@ public class CellTransitFindTransitCellsSphereTests
 
         CellTransit.FindTransitCellsSphere(
             cache, exitCell, currentCellId: 0xA9B40100u,
-            spheres, spheres.Length, candidates, out bool exitOutside, out _);
+            spheres, spheres.Length, candidates, out bool exitOutside);
 
         Assert.True(exitOutside);
     }

tests/AcDream.Core.Tests/Physics/CellTransitTests.cs

@@ -16,37 +16,29 @@ namespace AcDream.Core.Tests.Physics;
 /// Tests for <see cref="CellTransit"/> portal-graph expansion.
 ///
 /// <para>
-/// A6.P5 (2026-05-25) — unit-tests the cellSet build for the cottage door
+/// History: A6.P5 (2026-05-25) widened the collision cell set on exit-
-/// scenario, where pre-fix the <c>exitOutside</c> gate produced over-
+/// portal TOPOLOGY (outdoor cells added whenever an overlapped cell had a
-/// penetration ticks (sphere advanced 0.27 m INTO the door slab because
+/// 0xFFFF portal) so outdoor-registered doors stayed findable from indoor
-/// the door's outdoor cell wasn't in the cellSet during a cell-crossing
+/// cells under the flat registry query. BR-7 / A6.P4 C4 (2026-06-11)
-/// substep).
+/// removed the widening: outdoor cells enter the array only on the retail
-/// </para>
+/// STRADDLE gate (|dist| &lt; radius + F_EPSILON vs the exterior portal
-///
+/// plane — CEnvCell::find_transit_cells, Ghidra 0x0052c820, live-binary
-/// <para>
+/// verified), and doors are found per-cell via registration-time
-/// Loads cells <c>0xA9B4013F</c> (player's starting indoor cell at the
+/// membership instead. These tests pin BOTH halves of the retail
-/// over-penetration tick) and <c>0xA9B40150</c> (alcove cell adjacent to
+/// semantics on real Holtburg dat geometry.
-/// the doorway) from the real dat. Asserts that BFS expansion from
-/// <c>0xA9B4013F</c> reaches the door's outdoor cell <c>0xA9B40029</c>
-/// via the portal chain. The fix makes this hold unconditionally;
-/// pre-fix it only held when the sphere physically straddled an exit
-/// portal.
 /// </para>
 /// </summary>
 public class CellTransitTests
 {
     [Fact]
-    public void A6P5_BuildCellSetFromIndoorStart_ReachesDoorOutdoorCell()
+    public void DeepInteriorSphere_NoStraddle_AddsNoOutdoorCells()
     {
         var datDir = ResolveDatDir();
         if (datDir is null) return;
 
         // Hydrate the cells in the portal chain.
-        //   0xA9B4013F — start cell at the over-penetration tick
+        //   0xA9B4013F — deep interior cell (the old over-penetration tick)
-        //   0xA9B40150 — alcove cell adjacent to doorway (has exit portal)
+        //   0xA9B40150 — alcove cell adjacent to the doorway (exit portal)
-        // The door lives in outdoor cell 0xA9B40029 (registered as a
-        // shadow entry on the landblock — not loaded here; this test
-        // only asserts the cellSet membership, not collision).
         var cache = new PhysicsDataCache();
         HydrateCell(cache, datDir, 0xA9B4013Fu);
         HydrateCell(cache, datDir, 0xA9B40150u);
@@ -54,16 +46,15 @@ public class CellTransitTests
         Assert.NotNull(cache.GetCellStruct(0xA9B4013Fu));
         Assert.NotNull(cache.GetCellStruct(0xA9B40150u));
 
-        // Sphere at the over-penetration tick start position: world
+        // Sphere deep in 0x13F's volume — no path sphere straddles
-        // (132.594, 16.350, 94.48 sphere center). Foot Z = 94, sphere
+        // 0x150's exit portal plane from here (the A6.P5 pin's own
-        // radius 0.48 → center Z = 94 + radius? Actually the live
+        // message documented exactly that). Retail adds NO outdoor cells
-        // capture's sphere center is at Z = 94.48 since foot Z = 94
+        // in this state; the door (outdoor 0xA9B40029) is reached only
-        // and sphere is foot-anchored. For this test the Z value
+        // when the sphere actually straddles the threshold — pinned by
-        // doesn't matter — only XY portal membership.
+        // the alcove test below and the tick-13558 door pin.
         var sphereWorld = new Vector3(132.5935f, 16.350428f, 94.48f);
         const float sphereRadius = 0.48f;
         const uint startCellId = 0xA9B4013Fu;
-        const uint doorOutdoorCell = 0xA9B40029u;
 
         _ = CellTransit.FindCellSet(
             cache,
@@ -72,37 +63,25 @@ public class CellTransitTests
             startCellId,
             out var cellSet);
 
-        Assert.True(
+        Assert.DoesNotContain(cellSet, c => (c & 0xFFFFu) < 0x0100u);
-            cellSet.Contains(doorOutdoorCell),
+        Assert.Contains(startCellId, cellSet);
-            $"A6.P5: BFS portal expansion from indoor start cell " +
-            $"0x{startCellId:X8} (sphere world XY = " +
-            $"({sphereWorld.X:F3}, {sphereWorld.Y:F3})) should include " +
-            $"the door's outdoor cell 0x{doorOutdoorCell:X8} via the " +
-            $"portal chain 0x{startCellId:X8} → 0xA9B40150 → outdoor. " +
-            $"Pre-fix: the exitOutside gate required the sphere to " +
-            $"straddle 0xA9B40150's exit portal — sphere is in " +
-            $"0x{startCellId:X8}'s volume, so the gate didn't fire and " +
-            $"the door's cell wasn't added. Post-fix: gate removed; " +
-            $"exit-portal topology adds outdoor cells unconditionally. " +
-            $"Actual cellSet: {string.Join(",", cellSet.Select(c => $"0x{c:X8}"))}");
     }
 
     [Fact]
-    public void A6P5_BuildCellSetFromAlcove_AlsoReachesDoorOutdoorCell()
+    public void AlcoveSphere_StraddlesExitPortal_ReachesDoorOutdoorCell()
     {
         var datDir = ResolveDatDir();
         if (datDir is null) return;
 
-        // The alcove cell 0xA9B40150 IS the cell with the exit portal.
+        // The alcove cell 0xA9B40150 IS the cell with the exit portal, and
-        // Pre-fix this worked SOMETIMES (when the sphere straddled the
+        // at this captured position the foot sphere straddles its plane
-        // portal). Post-fix it works ALWAYS. This is a regression guard
+        // (|dist| < 0.48 + ε — same geometry the tick-13558 straddle pin
-        // for the previously-sometimes-working case.
+        // proves). Retail admits the outdoor cells exactly here, which is
+        // how the indoor-side sphere reaches the outdoor-registered door's
+        // per-cell shadow list.
         var cache = new PhysicsDataCache();
         HydrateCell(cache, datDir, 0xA9B40150u);
 
-        // Sphere at the stuck position — sphere center is NOT at the
-        // exit portal plane (sphere is in the alcove volume, away from
-        // the doorway threshold geometrically).
         var sphereWorld = new Vector3(132.4014f, 16.761757f, 94.48f);
         const float sphereRadius = 0.48f;
 
@@ -115,8 +94,10 @@ public class CellTransitTests
 
         Assert.True(
             cellSet.Contains(0xA9B40029u),
-            $"A6.P5: BFS from alcove cell 0xA9B40150 should always " +
+            $"Straddle-gated outside-add: the alcove sphere straddles " +
-            $"include the door's outdoor cell 0xA9B40029. " +
+            $"0xA9B40150's exit portal, so the door's outdoor cell " +
+            $"0xA9B40029 must enter the set (retail " +
+            $"CEnvCell::find_transit_cells straddle, Ghidra 0x0052c820). " +
             $"Actual: {string.Join(",", cellSet.Select(c => $"0x{c:X8}"))}");
     }