diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 5a28397e..2d254f64 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -130,6 +130,7 @@ export {
   resolveElevatorServiceLevels,
 } from './systems/elevator/elevator-service'
 export { syncAutoStairOpenings } from './systems/stair/stair-opening-sync'
+export { StairOpeningSystem } from './systems/stair/stair-opening-system'
 export {
   getClampedWallCurveOffset,
   getMaxWallCurveOffset,
diff --git a/packages/core/src/systems/stair/stair-opening-system.tsx b/packages/core/src/systems/stair/stair-opening-system.tsx
new file mode 100644
index 00000000..2558fcc5
--- /dev/null
+++ b/packages/core/src/systems/stair/stair-opening-system.tsx
@@ -0,0 +1,59 @@
+'use client'
+
+import { useEffect, useRef } from 'react'
+import type { AnyNode } from '../../schema'
+import useScene from '../../store/use-scene'
+import { syncAutoStairOpenings } from './stair-opening-sync'
+
+function isOpeningRelevantNode(node: AnyNode | undefined) {
+  return (
+    node?.type === 'building' ||
+    node?.type === 'ceiling' ||
+    node?.type === 'level' ||
+    node?.type === 'slab' ||
+    node?.type === 'stair' ||
+    node?.type === 'stair-segment'
+  )
+}
+
+function hasOpeningRelevantNodeChange(
+  nextNodes: Record<string, AnyNode>,
+  prevNodes: Record<string, AnyNode>,
+) {
+  if (nextNodes === prevNodes) return false
+
+  const ids = new Set([...Object.keys(nextNodes), ...Object.keys(prevNodes)])
+  for (const id of ids) {
+    const nextNode = nextNodes[id]
+    const prevNode = prevNodes[id]
+    if (nextNode === prevNode) continue
+    if (isOpeningRelevantNode(nextNode) || isOpeningRelevantNode(prevNode)) return true
+  }
+
+  return false
+}
+
+export const StairOpeningSystem = () => {
+  const syncingAutoOpeningsRef = useRef(false)
+
+  useEffect(() => {
+    const applyUpdates = (updates: ReturnType<typeof syncAutoStairOpenings>) => {
+      if (updates.length === 0) return
+      syncingAutoOpeningsRef.current = true
+      useScene.getState().updateNodes(updates)
+      queueMicrotask(() => {
+        syncingAutoOpeningsRef.current = false
+      })
+    }
+
+    applyUpdates(syncAutoStairOpenings(useScene.getState().nodes))
+
+    return useScene.subscribe((state, prevState) => {
+      if (syncingAutoOpeningsRef.current) return
+      if (!hasOpeningRelevantNodeChange(state.nodes, prevState.nodes)) return
+      applyUpdates(syncAutoStairOpenings(state.nodes))
+    })
+  }, [])
+
+  return null
+}
diff --git a/packages/editor/src/components/editor/custom-camera-controls.tsx b/packages/editor/src/components/editor/custom-camera-controls.tsx
index 38214e30..7392da7b 100644
--- a/packages/editor/src/components/editor/custom-camera-controls.tsx
+++ b/packages/editor/src/components/editor/custom-camera-controls.tsx
@@ -7,7 +7,7 @@ import {
   sceneRegistry,
   useScene,
 } from '@pascal-app/core'
-import { useViewer, ZONE_LAYER } from '@pascal-app/viewer'
+import { useViewer, WalkthroughControls, ZONE_LAYER } from '@pascal-app/viewer'
 import { CameraControls, CameraControlsImpl } from '@react-three/drei'
 import { useThree } from '@react-three/fiber'
 import { useCallback, useEffect, useMemo, useRef } from 'react'
@@ -440,9 +440,9 @@ export const CustomCameraControls = () => {
   return (
     <CameraControls
       makeDefault
-      maxDistance={250}
+      maxDistance={100}
       maxPolarAngle={maxPolarAngle}
-      minDistance={2}
+      minDistance={10}
       minPolarAngle={0}
       mouseButtons={mouseButtons}
       onRest={onRest}
diff --git a/packages/viewer/src/components/viewer/index.tsx b/packages/viewer/src/components/viewer/index.tsx
index d3d5dc54..0676e2ff 100644
--- a/packages/viewer/src/components/viewer/index.tsx
+++ b/packages/viewer/src/components/viewer/index.tsx
@@ -1,5 +1,6 @@
 'use client'
 
+import { StairOpeningSystem } from '@pascal-app/core'
 import { Canvas, extend, type ThreeToJSXElements, useFrame, useThree } from '@react-three/fiber'
 import { useEffect, useMemo, useRef } from 'react'
 import * as THREE from 'three/webgpu'
@@ -216,6 +217,9 @@ const Viewer: React.FC<ViewerProps> = ({
             builder, swaps the registered group's children. See
             wiki/architecture/node-definitions.md. */}
         <GeometrySystem />
+        {/* Automated stair opening sync — updates slab/ceiling cutouts
+            whenever stairs, slabs, or levels change. */}
+        <StairOpeningSystem />
         {/* Mounts systems contributed by registry-backed kinds. Each
             kind's `def.system` is loaded via lazy() and rendered here,
             ordered by `system.priority`. */}
diff --git a/packages/viewer/src/systems/stair/stair-system.tsx b/packages/viewer/src/systems/stair/stair-system.tsx
index 99601d6a..fd2a74d6 100644
--- a/packages/viewer/src/systems/stair/stair-system.tsx
+++ b/packages/viewer/src/systems/stair/stair-system.tsx
@@ -6,11 +6,10 @@ import {
   type StairSegmentNode,
   sceneRegistry,
   spatialGridManager,
-  syncAutoStairOpenings,
   useScene,
 } from '@pascal-app/core'
 import { useFrame } from '@react-three/fiber'
-import { useEffect, useRef } from 'react'
+import { useRef } from 'react'
 import * as THREE from 'three'
 import { mergeGeometries } from 'three/examples/jsm/utils/BufferGeometryUtils.js'
 
@@ -30,26 +29,6 @@ export const StairSystem = () => {
   const dirtyNodes = useScene((state) => state.dirtyNodes)
   const clearDirty = useScene((state) => state.clearDirty)
   const rootNodeIds = useScene((state) => state.rootNodeIds)
-  const syncingAutoOpeningsRef = useRef(false)
-
-  useEffect(() => {
-    const applyUpdates = (updates: ReturnType<typeof syncAutoStairOpenings>) => {
-      if (updates.length === 0) return
-      syncingAutoOpeningsRef.current = true
-      useScene.getState().updateNodes(updates)
-      queueMicrotask(() => {
-        syncingAutoOpeningsRef.current = false
-      })
-    }
-
-    applyUpdates(syncAutoStairOpenings(useScene.getState().nodes))
-
-    return useScene.subscribe((state, prevState) => {
-      if (syncingAutoOpeningsRef.current) return
-      if (state.nodes === prevState.nodes) return
-      applyUpdates(syncAutoStairOpenings(state.nodes))
-    })
-  }, [])
 
   useFrame(() => {
     if (rootNodeIds.length === 0) {