diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index 37e5087..4d5f26c 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -5887,7 +5887,8 @@ public sealed class GameWindow : IDisposable
                     partPos, partRot, worldRadius,
                     origin.X, origin.Y, lb.LandblockId,
                     AcDream.Core.Physics.ShadowCollisionType.BSP, 0f,
-                    partScale);
+                    partScale,
+                    cellScope: entity.ParentCellId ?? 0u);
                 // L.2d slice 1 (2026-05-13): [entity-source] greppable from [resolve-bldg].
                 // partCached?.BSP?.Root non-null was checked above (else `continue`),
                 // so hasPhys=true on this path.
@@ -5946,7 +5947,8 @@ public sealed class GameWindow : IDisposable
                             entity.Position + worldOffset,
                             entity.Rotation, cylRadius,
                             origin.X, origin.Y, lb.LandblockId,
-                            AcDream.Core.Physics.ShadowCollisionType.Cylinder, cylHeight);
+                            AcDream.Core.Physics.ShadowCollisionType.Cylinder, cylHeight,
+                            cellScope: entity.ParentCellId ?? 0u);
                         // L.2d slice 1 (2026-05-13): [entity-source] greppable from [resolve-bldg].
                         // state/flags literals: landblock-baked scenery; no server PhysicsState.
                         if (AcDream.Core.Physics.PhysicsDiagnostics.ProbeBuildingEnabled)
@@ -5981,7 +5983,8 @@ public sealed class GameWindow : IDisposable
                                 entity.Position + worldOffset,
                                 entity.Rotation, sphRadius,
                                 origin.X, origin.Y, lb.LandblockId,
-                                AcDream.Core.Physics.ShadowCollisionType.Cylinder, sphHeight);
+                                AcDream.Core.Physics.ShadowCollisionType.Cylinder, sphHeight,
+                                cellScope: entity.ParentCellId ?? 0u);
                             // L.2d slice 1 (2026-05-13): [entity-source] greppable from [resolve-bldg].
                             // state/flags literals: landblock-baked scenery; no server PhysicsState.
                             if (AcDream.Core.Physics.PhysicsDiagnostics.ProbeBuildingEnabled)
@@ -6004,7 +6007,8 @@ public sealed class GameWindow : IDisposable
                             shapeId, entity.SourceGfxObjOrSetupId,
                             entity.Position, entity.Rotation, fr,
                             origin.X, origin.Y, lb.LandblockId,
-                            AcDream.Core.Physics.ShadowCollisionType.Cylinder, fh);
+                            AcDream.Core.Physics.ShadowCollisionType.Cylinder, fh,
+                            cellScope: entity.ParentCellId ?? 0u);
                         // L.2d slice 1 (2026-05-13): [entity-source] greppable from [resolve-bldg].
                         // state/flags literals: landblock-baked scenery; no server PhysicsState.
                         if (AcDream.Core.Physics.PhysicsDiagnostics.ProbeBuildingEnabled)
@@ -6191,7 +6195,8 @@ public sealed class GameWindow : IDisposable
                         entity.SourceGfxObjOrSetupId,
                         baseCenter, entity.Rotation, cylRadius,
                         origin.X, origin.Y, lb.LandblockId,
-                        AcDream.Core.Physics.ShadowCollisionType.Cylinder, cylHeight);
+                        AcDream.Core.Physics.ShadowCollisionType.Cylinder, cylHeight,
+                        cellScope: entity.ParentCellId ?? 0u);
                     // L.2d slice 1 (2026-05-13): [entity-source] greppable from [resolve-bldg].
                     // state/flags literals: landblock-baked scenery; no server PhysicsState.
                     if (AcDream.Core.Physics.PhysicsDiagnostics.ProbeBuildingEnabled)
diff --git a/src/AcDream.Core/Physics/ShadowObjectRegistry.cs b/src/AcDream.Core/Physics/ShadowObjectRegistry.cs
index fd3673e..9c52435 100644
--- a/src/AcDream.Core/Physics/ShadowObjectRegistry.cs
+++ b/src/AcDream.Core/Physics/ShadowObjectRegistry.cs
@@ -36,10 +36,34 @@ public sealed class ShadowObjectRegistry
                          ShadowCollisionType collisionType = ShadowCollisionType.BSP,
                          float cylHeight = 0f, float scale = 1.0f,
                          uint state = 0u,
-                         EntityCollisionFlags flags = EntityCollisionFlags.None)
+                         EntityCollisionFlags flags = EntityCollisionFlags.None,
+                         uint cellScope = 0u)
     {
         Deregister(entityId);
 
+        var entry = new ShadowEntry(entityId, gfxObjId, worldPos, rotation, radius,
+                                    collisionType, cylHeight, scale, state, flags);
+
+        // ISSUES #83 / Phase A1.5 (2026-05-21): if the caller passed a
+        // cellScope (typically the entity's ParentCellId for an interior
+        // EnvCell static), scope the shadow to ONLY that cell instead of
+        // computing outdoor-landcell occupancy from XY. Without this,
+        // interior statics (a fireplace inside cell 0xA9B40121) get
+        // registered into the outdoor landcell whose XY they overlap
+        // (e.g. 0xA9B40029) and fire collisions when the player is OUTSIDE
+        // the building — the user-reported "thin air" collision outdoors.
+        if (cellScope != 0u)
+        {
+            if (!_cells.TryGetValue(cellScope, out var scopedList))
+            {
+                scopedList = new List<ShadowEntry>();
+                _cells[cellScope] = scopedList;
+            }
+            scopedList.Add(entry);
+            _entityToCells[entityId] = new List<uint> { cellScope };
+            return;
+        }
+
         // The radius parameter should already be the WORLD-SPACE bounding
         // radius (i.e., already multiplied by scale) so the broad-phase cell
         // occupancy is correct. Callers are responsible for that.
@@ -51,8 +75,6 @@ public sealed class ShadowObjectRegistry
         int minCy = Math.Max(0, (int)((localY - radius) / 24f));
         int maxCy = Math.Min(7, (int)((localY + radius) / 24f));
 
-        var entry = new ShadowEntry(entityId, gfxObjId, worldPos, rotation, radius,
-                                    collisionType, cylHeight, scale, state, flags);
         var cellIds = new List<uint>();
 
         uint lbPrefix = landblockId & 0xFFFF0000u;