diff --git a/src/hooks/three/useOctreeGraphNode.ts b/src/hooks/three/useOctreeGraphNode.ts
index 5a1fe31..1cdc44b 100644
--- a/src/hooks/three/useOctreeGraphNode.ts
+++ b/src/hooks/three/useOctreeGraphNode.ts
@@ -1,9 +1,29 @@
 import { useEffect, useRef } from "react";
 import type { RefObject } from "react";
-import type { Object3D } from "three";
+import { Mesh, type Object3D } from "three";
 import { Octree } from "three-stdlib";
 import type { OctreeReadyHandler } from "@/types/three/three";
 
+// [diag] temporary — count meshes/triangles captured in the octree graph node
+function snapshotGraphNode(node: Object3D): {
+  meshCount: number;
+  triCount: number;
+} {
+  let meshCount = 0;
+  let triCount = 0;
+  node.traverse((obj) => {
+    if (obj instanceof Mesh) {
+      meshCount += 1;
+      const geom = obj.geometry;
+      const idx = geom.index;
+      triCount += idx
+        ? idx.count / 3
+        : (geom.attributes.position?.count ?? 0) / 3;
+    }
+  });
+  return { meshCount, triCount };
+}
+
 export function useOctreeGraphNode(
   graphNodeRef: RefObject<Object3D | null>,
   onOctreeReady: OctreeReadyHandler,
@@ -28,6 +48,15 @@ export function useOctreeGraphNode(
     const octree = new Octree();
     octree.fromGraphNode(graphNode);
 
+    // [diag] temporary — log octree contents to detect partial builds
+    const snapshot = snapshotGraphNode(graphNode);
+    console.log("[octree:build]", {
+      rebuildKey,
+      meshCount: snapshot.meshCount,
+      triCount: Math.round(snapshot.triCount),
+      timestamp: performance.now().toFixed(0),
+    });
+
     onOctreeReady(octree);
   }, [enabled, graphNodeRef, onOctreeReady, rebuildKey]);
 }
diff --git a/src/world/GameMapCollision.tsx b/src/world/GameMapCollision.tsx
index b9344f8..dd83c76 100644
--- a/src/world/GameMapCollision.tsx
+++ b/src/world/GameMapCollision.tsx
@@ -277,12 +277,22 @@ function CollisionModelInstance({
     // by MergedStaticMapModel and is unaffected.
     if (node.name !== "lafabrik") return;
 
+    // [diag] temporary — collect all door-like candidate names to debug stripping
+    const candidates: string[] = [];
     const removed: THREE.Object3D[] = [];
     sceneInstance.traverse((child) => {
+      if (/porte/i.test(child.name)) {
+        candidates.push(child.name);
+      }
       if (child.name === "porte") {
         removed.push(child);
       }
     });
+    console.log("[lafabrik:porte-strip]", {
+      candidates,
+      strippedCount: removed.length,
+      strippedNames: removed.map((c) => c.name),
+    });
     for (const child of removed) {
       child.removeFromParent();
     }
diff --git a/src/world/Lighting.tsx b/src/world/Lighting.tsx
index d3625ea..547d6df 100644
--- a/src/world/Lighting.tsx
+++ b/src/world/Lighting.tsx
@@ -98,6 +98,27 @@ export function Lighting(): React.JSX.Element {
       hasShadowMap: !!sun.current.shadow.map,
       ...counts,
     });
+
+    // [diag] temporary — track WebGL context loss/restore to correlate with shadow drops
+    const canvas = gl.domElement;
+    const handleContextLost = (event: Event) => {
+      event.preventDefault();
+      console.log("[ctx:lost]", { timestamp: performance.now().toFixed(0) });
+    };
+    const handleContextRestored = () => {
+      console.log("[ctx:restored]", {
+        timestamp: performance.now().toFixed(0),
+      });
+      if (sun.current) {
+        sun.current.shadow.needsUpdate = true;
+      }
+    };
+    canvas.addEventListener("webglcontextlost", handleContextLost);
+    canvas.addEventListener("webglcontextrestored", handleContextRestored);
+    return () => {
+      canvas.removeEventListener("webglcontextlost", handleContextLost);
+      canvas.removeEventListener("webglcontextrestored", handleContextRestored);
+    };
   }, [gl, scene]);
 
   useDebugFolder("Lighting", (folder) => {