diff --git a/webclient/src/components/ObjectEditorView.tsx b/webclient/src/components/ObjectEditorView.tsx
index 8038a0d..8528020 100644
--- a/webclient/src/components/ObjectEditorView.tsx
+++ b/webclient/src/components/ObjectEditorView.tsx
@@ -1,11 +1,11 @@
 import { observer } from "mobx-react-lite";
 import { runInAction } from "mobx";
 import type { ObjectInstance, R3, Runtime } from "../types";
-import { useMemo, useRef, type RefObject } from "react";
+import { useMemo, useRef, useEffect, useCallback, type RefObject } from "react";
 import type { Group } from "three";
-import { Euler, Quaternion, Vector3 } from "three";
-import { TransformControls, useHelper } from "@react-three/drei";
-import { BoxHelper } from "three";
+import { Euler, Quaternion, Vector3, BoxHelper, type LineBasicMaterial } from "three";
+import { TransformControls } from "@react-three/drei";
+import { useThree, useFrame } from "@react-three/fiber";
 import { state } from "../state";
 import { nextObjectEditMode } from "../state/worldEditorState";
 import { ObjectViewInternal, type ObjectViewInternalHandle } from "./ObjectViewInternal";
@@ -39,13 +39,44 @@ const SelectionOverlay = observer(function ({ objectId, ref, onTransformChange,
         [ref],
     );
 
-    useHelper(isSelected ? groupRef : { current: null }, BoxHelper, 'white');
+    // BoxHelper — manually disposed because BoxHelper has no dispose() of its own
+    const scene = useThree(s => s.scene);
+    const helperRef = useRef<BoxHelper | null>(null);
+    useEffect(() => {
+        const target = groupRef.current;
+        if (!isSelected || !target)
+            return;
+        const helper = new BoxHelper(target, 'white');
+        scene.add(helper);
+        helperRef.current = helper;
+        return () => {
+            scene.remove(helper);
+            helper.geometry.dispose();
+            (helper.material as LineBasicMaterial).dispose();
+            helperRef.current = null;
+        };
+    }, [isSelected, groupRef, scene]);
+    useFrame(() => helperRef.current?.update());
+
+    // TransformControls — drei never calls dispose() on unmount, leaking all gizmo
+    // geometries. Callback ref ignores null so tcRef.current survives React's
+    // ref-clear-on-unmount; effect cleanup then calls dispose() with the live instance.
+    const tcRef = useRef<{ dispose(): void } | null>(null);
+    const setTcRef = useCallback((tc: { dispose(): void } | null) => {
+        if (tc !== null)
+            tcRef.current = tc;
+    }, []);
+    useEffect(() => () => {
+        tcRef.current?.dispose();
+        tcRef.current = null;
+    }, [isSelected]);
 
     if (!isSelected || selectionMode === undefined || !groupRef.current)
         return null;
 
     return (
         <TransformControls
+            ref={setTcRef as never}
             object={groupRef as RefObject<Group>}
             mode={selectionMode}
             onChange={onTransformChange}