diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index 8b867e0..1831713 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -1801,10 +1801,10 @@ public sealed class GameWindow : IDisposable
                 partIndex++;
             }
 
-            // If no BSP parts were registered, check for CylSphere collision
-            // from the Setup (trees, rocks, NPCs use cylinder collision).
-            if (partIndex == 0 || !entity.MeshRefs.Any(mr =>
-                _physicsDataCache.GetGfxObj(mr.GfxObjId)?.BSP?.Root is not null))
+            // ALWAYS register CylSphere when the Setup has one, even if BSP parts
+            // were also registered. Retail tests both: CylSphere as the broad
+            // collision volume (trunk) plus BSP parts for precise polygon collision.
+            // The CylSphere catches the base/trunk that BSP parts might miss.
             {
                 var setup = _physicsDataCache.GetSetup(entity.SourceGfxObjOrSetupId);
                 if (setup is not null && setup.CylSpheres.Count > 0)
@@ -1813,6 +1813,7 @@ public sealed class GameWindow : IDisposable
                     float cylRadius = cyl.Radius > 0 ? cyl.Radius : setup.Radius;
                     if (cylRadius > 0)
                     {
+                        // Use entity.Id directly (not partId) for the CylSphere entry.
                         _physicsEngine.ShadowObjects.Register(
                             entity.Id, entity.SourceGfxObjOrSetupId,
                             entity.Position + new System.Numerics.Vector3(cyl.Origin.X, cyl.Origin.Y, cyl.Origin.Z),
@@ -1821,8 +1822,9 @@ public sealed class GameWindow : IDisposable
                             AcDream.Core.Physics.ShadowCollisionType.Cylinder, cyl.Height);
                     }
                 }
-                else if (setup is not null && setup.Spheres.Count > 0)
+                else if (setup is not null && setup.Spheres.Count > 0 && partIndex == 0)
                 {
+                    // Fallback: use bounding sphere only if no BSP and no CylSphere.
                     var sph = setup.Spheres[0];
                     if (sph.Radius > 0)
                     {