diff --git a/packages/core/src/hooks/spatial-grid/spatial-grid-sync.ts b/packages/core/src/hooks/spatial-grid/spatial-grid-sync.ts
index 8e4e8c7c..250a0f31 100644
--- a/packages/core/src/hooks/spatial-grid/spatial-grid-sync.ts
+++ b/packages/core/src/hooks/spatial-grid/spatial-grid-sync.ts
@@ -34,8 +34,10 @@ export function resolveLevelId(node: AnyNode, nodes: Record<string, AnyNode>): s
   return 'default' // fallback for orphaned items
 }
 
-// Call this once at app initialization
-export function initSpatialGridSync() {
+// Call this once at app initialization. Returns an unsubscribe function that
+// detaches the scene-store listener (useful when the editor is unmounted so
+// the spatial grid singleton does not hold stale references to old scenes).
+export function initSpatialGridSync(): () => void {
   const store = useScene
   // 1. Initial sync - process all existing nodes
   const state = store.getState()
@@ -48,7 +50,7 @@ export function initSpatialGridSync() {
   const markDirty = (id: AnyNodeId) => store.getState().markDirty(id)
 
   // Subscribe to all changes
-  store.subscribe((state, prevState) => {
+  const unsubscribe = store.subscribe((state, prevState) => {
     // Detect added nodes
     for (const [id, node] of Object.entries(state.nodes)) {
       if (!prevState.nodes[id as AnyNode['id']]) {
@@ -113,6 +115,8 @@ export function initSpatialGridSync() {
       }
     }
   })
+
+  return unsubscribe
 }
 
 function arraysEqual(a: number[], b: number[]): boolean {
diff --git a/packages/editor/src/components/editor/index.tsx b/packages/editor/src/components/editor/index.tsx
index eeb841ad..659c3fb8 100644
--- a/packages/editor/src/components/editor/index.tsx
+++ b/packages/editor/src/components/editor/index.tsx
@@ -1,7 +1,12 @@
 'use client'
 
 import { Icon } from '@iconify/react'
-import { initSpaceDetectionSync, initSpatialGridSync, useScene } from '@pascal-app/core'
+import {
+  initSpaceDetectionSync,
+  initSpatialGridSync,
+  spatialGridManager,
+  useScene,
+} from '@pascal-app/core'
 import { InteractiveSystem, useViewer, Viewer } from '@pascal-app/viewer'
 import { type ReactNode, useCallback, useEffect, useRef, useState } from 'react'
 import { ViewerOverlay } from '../../components/viewer-overlay'
@@ -52,16 +57,39 @@ import { SiteEdgeLabels } from './site-edge-labels'
 import { ThumbnailGenerator } from './thumbnail-generator'
 import { WallMeasurementLabel } from './wall-measurement-label'
 
-let hasInitializedEditorRuntime = false
 const CAMERA_CONTROLS_HINT_DISMISSED_STORAGE_KEY = 'editor-camera-controls-hint-dismissed:v1'
 
-function initializeEditorRuntime() {
-  if (hasInitializedEditorRuntime) return
-  initSpatialGridSync()
-  initSpaceDetectionSync(useScene, useEditor)
+/**
+ * Wire up module-level singletons (spatial grid, space detection, SFX) for
+ * an Editor mount. Returns a teardown function that detaches the scene-store
+ * subscriptions and resets the shared singletons so a subsequent remount —
+ * including hot navigation back to the editor in the same tab — starts from
+ * a clean slate. Without this, the spatial-grid manager and viewer outliner
+ * accumulate stale references from the previous Editor instance and can
+ * freeze the app on re-entry.
+ */
+function initializeEditorRuntime(): () => void {
+  const unsubscribeSpatialGrid = initSpatialGridSync()
+  const unsubscribeSpaceDetection = initSpaceDetectionSync(useScene, useEditor)
   initSFXBus()
 
-  hasInitializedEditorRuntime = true
+  return () => {
+    unsubscribeSpatialGrid()
+    unsubscribeSpaceDetection?.()
+
+    // Drop all entries the spatial-grid singleton accumulated for the
+    // previous scene so the next mount re-syncs from current state instead
+    // of layering on top of stale data.
+    spatialGridManager.clear()
+
+    // The viewer outliner holds direct Object3D references used by the
+    // post-processing selection pass. Clearing the underlying arrays (we
+    // intentionally mutate in place — there is no setter by design) releases
+    // those refs so the disposed Three.js scene graph can be GC'd.
+    const outliner = useViewer.getState().outliner
+    outliner.selectedObjects.length = 0
+    outliner.hoveredObjects.length = 0
+  }
 }
 export interface EditorProps {
   // Layout version — 'v1' (default) or 'v2' (navbar + two-column)
@@ -521,7 +549,8 @@ export default function Editor({
   }, [])
 
   useEffect(() => {
-    initializeEditorRuntime()
+    const teardown = initializeEditorRuntime()
+    return teardown
   }, [])
 
   useEffect(() => {
diff --git a/packages/editor/src/lib/sfx-bus.ts b/packages/editor/src/lib/sfx-bus.ts
index 308718d2..6e838ce6 100644
--- a/packages/editor/src/lib/sfx-bus.ts
+++ b/packages/editor/src/lib/sfx-bus.ts
@@ -20,11 +20,15 @@ type SFXEvents = {
  */
 export const sfxEmitter = mitt<SFXEvents>()
 
+let sfxBusInitialized = false
+
 /**
- * Initialize SFX Bus - connects SFX events to actual sound playback
- * Call once in your app initialization
+ * Initialize SFX Bus - connects SFX events to actual sound playback.
+ * Safe to call multiple times; re-registration is a no-op once initialized.
  */
 export function initSFXBus() {
+  if (sfxBusInitialized) return
+  sfxBusInitialized = true
   // Map SFX events to sound playback
   sfxEmitter.on('sfx:grid-snap', () => playSFX('gridSnap'))
   sfxEmitter.on('sfx:item-delete', () => playSFX('itemDelete'))