diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index c96ad05f..290b70e9 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -5655,6 +5655,11 @@ public sealed class GameWindow : IDisposable
                     // fall through floor) and the visibility node for any geometry-less
                     // collision cell. CacheCellStruct self-gates on a null PhysicsBSP
                     // (PhysicsDataCache), so this is safe for cells with no physics.
+                    // Note CacheCellStruct DOES register every resolved cell into the UCG
+                    // CellGraph unconditionally (before that BSP gate), so a geometry-less
+                    // cell now enters the graph — but it never enters the _cellStruct BSP
+                    // dictionary that membership/placement resolve through, so the player
+                    // can never be rooted in such a cell. The added graph entry is inert.
                     //
                     // BuildLoadedCell uses the PHYSICS (unlifted) transform. The +0.02 m
                     // render lift above is a DRAW concern (shell z-fighting vs terrain);