diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index 018892a..f788b83 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -5939,7 +5939,7 @@ public sealed class GameWindow : IDisposable
             // the physics-resolved location each frame.
             if (_entitiesByServerGuid.TryGetValue(_playerServerGuid, out var pe))
             {
-                pe.Position = result.RenderPosition;
+                pe.SetPosition(result.RenderPosition); // A.5 T18: SetPosition propagates AabbDirty
                 pe.Rotation = System.Numerics.Quaternion.CreateFromAxisAngle(
                     System.Numerics.Vector3.UnitZ, _playerController.Yaw - MathF.PI / 2f);
 
@@ -6948,7 +6948,7 @@ public sealed class GameWindow : IDisposable
                             rm.MaxSeqSpeedSinceLastUP = seqSpeedNow;
                     }
 
-                    ae.Entity.Position = rm.Body.Position;
+                    ae.Entity.SetPosition(rm.Body.Position); // A.5 T18: SetPosition propagates AabbDirty
                     ae.Entity.Rotation = rm.Body.Orientation;
                 }
                 else
@@ -7276,7 +7276,7 @@ public sealed class GameWindow : IDisposable
                         }
                     }
 
-                    ae.Entity.Position = rm.Body.Position;
+                    ae.Entity.SetPosition(rm.Body.Position); // A.5 T18: SetPosition propagates AabbDirty
                     ae.Entity.Rotation = rm.Body.Orientation;
                 }
             }
diff --git a/src/AcDream.App/Rendering/Wb/EntitySpawnAdapter.cs b/src/AcDream.App/Rendering/Wb/EntitySpawnAdapter.cs
index eb05d92..6303220 100644
--- a/src/AcDream.App/Rendering/Wb/EntitySpawnAdapter.cs
+++ b/src/AcDream.App/Rendering/Wb/EntitySpawnAdapter.cs
@@ -128,6 +128,12 @@ public sealed class EntitySpawnAdapter
             }
         }
 
+        // A.5 T18: populate cached AABB so WalkEntities reads from the cache
+        // rather than recomputing Position±5 per frame. Called here because
+        // all entity-state initialization (position, rotation) is complete
+        // by this point via the WorldEntity passed in.
+        entity.RefreshAabb();
+
         // Build the per-entity AnimatedEntityState. The sequencer factory
         // may return a stub (in tests) or a fully-constructed sequencer from
         // the MotionTable (in production). Factory must not return null —
diff --git a/src/AcDream.Core/World/LandblockLoader.cs b/src/AcDream.Core/World/LandblockLoader.cs
index 4234c11..fc3d30e 100644
--- a/src/AcDream.Core/World/LandblockLoader.cs
+++ b/src/AcDream.Core/World/LandblockLoader.cs
@@ -42,28 +42,32 @@ public static class LandblockLoader
         {
             if (!IsSupported(stab.Id))
                 continue;
-            result.Add(new WorldEntity
+            var stabEntity = new WorldEntity
             {
                 Id = nextId++,
                 SourceGfxObjOrSetupId = stab.Id,
                 Position = stab.Frame.Origin,
                 Rotation = stab.Frame.Orientation,
                 MeshRefs = Array.Empty<MeshRef>(),
-            });
+            };
+            stabEntity.RefreshAabb(); // A.5 T18: populate cached AABB at construction
+            result.Add(stabEntity);
         }
 
         foreach (var building in info.Buildings)
         {
             if (!IsSupported(building.ModelId))
                 continue;
-            result.Add(new WorldEntity
+            var buildingEntity = new WorldEntity
             {
                 Id = nextId++,
                 SourceGfxObjOrSetupId = building.ModelId,
                 Position = building.Frame.Origin,
                 Rotation = building.Frame.Orientation,
                 MeshRefs = Array.Empty<MeshRef>(),
-            });
+            };
+            buildingEntity.RefreshAabb(); // A.5 T18: populate cached AABB at construction
+            result.Add(buildingEntity);
         }
 
         return result;