diff --git a/packages/editor/src/components/ui/panels/ceiling-panel.tsx b/packages/editor/src/components/ui/panels/ceiling-panel.tsx
index 314f2380..31acea62 100644
--- a/packages/editor/src/components/ui/panels/ceiling-panel.tsx
+++ b/packages/editor/src/components/ui/panels/ceiling-panel.tsx
@@ -3,7 +3,7 @@
 import { type AnyNode, type CeilingNode, useScene } from '@pascal-app/core'
 import { useViewer } from '@pascal-app/viewer'
 import { Edit, Move, Plus, Trash2 } from 'lucide-react'
-import { useCallback, useEffect } from 'react'
+import { useCallback, useEffect, useRef } from 'react'
 import { sfxEmitter } from '../../../lib/sfx-bus'
 import useEditor from '../../../store/use-editor'
 import { ActionButton, ActionGroup } from '../controls/action-button'
@@ -14,7 +14,6 @@ import { PanelWrapper } from './panel-wrapper'
 export function CeilingPanel() {
   const selectedId = useViewer((s) => s.selection.selectedIds[0])
   const setSelection = useViewer((s) => s.setSelection)
-  const updateNode = useScene((s) => s.updateNode)
   const editingHole = useEditor((s) => s.editingHole)
   const setEditingHole = useEditor((s) => s.setEditingHole)
   const setMovingNode = useEditor((s) => s.setMovingNode)
@@ -23,12 +22,17 @@ export function CeilingPanel() {
     selectedId ? (s.nodes[selectedId as AnyNode['id']] as CeilingNode | undefined) : undefined,
   )
 
+  // Panel slider-drag fix recipe (plans/editor-node-registry.md): stable
+  // handler refs so slider drags don't trigger Maximum update depth.
+  const nodeRef = useRef(node)
+  nodeRef.current = node
+
   const handleUpdate = useCallback(
     (updates: Partial<CeilingNode>) => {
       if (!selectedId) return
-      updateNode(selectedId as AnyNode['id'], updates)
+      useScene.getState().updateNode(selectedId as AnyNode['id'], updates)
     },
-    [selectedId, updateNode],
+    [selectedId],
   )
 
   const handleClose = useCallback(() => {
diff --git a/packages/nodes/src/ceiling/definition.ts b/packages/nodes/src/ceiling/definition.ts
new file mode 100644
index 00000000..afd197d8
--- /dev/null
+++ b/packages/nodes/src/ceiling/definition.ts
@@ -0,0 +1,80 @@
+import type { NodeDefinition } from '@pascal-app/core'
+import { ceilingParametrics } from './parametrics'
+import { CeilingNode } from './schema'
+
+/**
+ * Ceiling — Phase 5 batch kind, polygon-based. Structurally identical
+ * to slab but mounted at `height` rather than `elevation`.
+ *
+ * Capabilities:
+ *  - **No `movable`**: ceiling move is bespoke via legacy `MoveCeilingTool`
+ *    + the floor-plan boundary / hole editors. Capability-driven dispatch
+ *    keeps the legacy mover (preserves polygon-aware behavior).
+ *  - **`surfaces.top`**: items host on the ceiling at `height`.
+ *  - `selectable`, `duplicable`, `deletable` standard.
+ *
+ * Relations: `hosts: ['item']` for ceiling-mounted items (lights, fans).
+ * `cascadeDelete: 'descendants'` removes hosted items on ceiling delete.
+ */
+export const ceilingDefinition: NodeDefinition<typeof CeilingNode> = {
+  kind: 'ceiling',
+  schemaVersion: 1,
+  schema: CeilingNode,
+  category: 'structure',
+
+  defaults: () => ({
+    object: 'node',
+    parentId: null,
+    visible: true,
+    metadata: {},
+    children: [],
+    polygon: [],
+    holes: [],
+    holeMetadata: [],
+    height: 2.5,
+    autoFromWalls: false,
+  }),
+
+  capabilities: {
+    selectable: { hitVolume: 'bbox' },
+    surfaces: {
+      top: { height: (n) => (n as CeilingNode).height },
+    },
+    duplicable: true,
+    deletable: true,
+  },
+
+  relations: {
+    hosts: ['item'],
+    cascadeDelete: 'descendants',
+  },
+
+  parametrics: ceilingParametrics,
+
+  renderer: {
+    kind: 'parametric',
+    module: () => import('./renderer'),
+  },
+  system: {
+    module: () => import('./system'),
+    priority: 4,
+  },
+
+  toolHints: [
+    { key: 'Left click', label: 'Trace ceiling outline' },
+    { key: 'Enter', label: 'Finish ceiling' },
+    { key: 'Esc', label: 'Cancel' },
+  ],
+
+  presentation: {
+    label: 'Ceiling',
+    description: 'A polygon-bounded ceiling surface that hosts ceiling-mounted items.',
+    icon: { kind: 'iconify', name: 'lucide:square-dashed' },
+    paletteSection: 'structure',
+    paletteOrder: 40,
+  },
+
+  mcp: {
+    description: 'A polygon-bounded ceiling with optional cutout holes.',
+  },
+}
diff --git a/packages/nodes/src/ceiling/index.ts b/packages/nodes/src/ceiling/index.ts
new file mode 100644
index 00000000..1c0a3575
--- /dev/null
+++ b/packages/nodes/src/ceiling/index.ts
@@ -0,0 +1,2 @@
+export { ceilingDefinition } from './definition'
+export { CeilingNode } from './schema'
diff --git a/packages/nodes/src/ceiling/parametrics.ts b/packages/nodes/src/ceiling/parametrics.ts
new file mode 100644
index 00000000..87793ae3
--- /dev/null
+++ b/packages/nodes/src/ceiling/parametrics.ts
@@ -0,0 +1,16 @@
+import type { ParametricDescriptor } from '@pascal-app/core'
+import type { CeilingNode } from './schema'
+
+/**
+ * Inspector descriptor for ceiling. Polygon + holes are edited via the
+ * floor-plan boundary / hole editors — not number inputs. Inspector
+ * exposes only the per-instance scalar (height).
+ */
+export const ceilingParametrics: ParametricDescriptor<CeilingNode> = {
+  groups: [
+    {
+      label: 'Dimensions',
+      fields: [{ key: 'height', kind: 'number', unit: 'm', min: 1.5, max: 6, step: 0.05 }],
+    },
+  ],
+}
diff --git a/packages/nodes/src/ceiling/renderer.tsx b/packages/nodes/src/ceiling/renderer.tsx
new file mode 100644
index 00000000..13be02ef
--- /dev/null
+++ b/packages/nodes/src/ceiling/renderer.tsx
@@ -0,0 +1,15 @@
+'use client'
+
+import { CeilingRenderer } from '@pascal-app/viewer'
+
+/**
+ * Wrap-export of the legacy `CeilingRenderer`.
+ *
+ * Ceiling's renderer uses TSL shader code for the grid-line pattern
+ * (~100 lines incl. material setup) — too much to duplicate at Stage A.
+ * The legacy file stays in viewer; the registry imports it through the
+ * public export. Phase 5 Stage B/F (per-kind migration stages, see
+ * plans/editor-node-registry.md) moves the renderer body into this
+ * folder and deletes the legacy file.
+ */
+export default CeilingRenderer
diff --git a/packages/nodes/src/ceiling/schema.ts b/packages/nodes/src/ceiling/schema.ts
new file mode 100644
index 00000000..f562ccaa
--- /dev/null
+++ b/packages/nodes/src/ceiling/schema.ts
@@ -0,0 +1 @@
+export { CeilingNode } from '@pascal-app/core'
diff --git a/packages/nodes/src/ceiling/system.tsx b/packages/nodes/src/ceiling/system.tsx
new file mode 100644
index 00000000..49dbf3be
--- /dev/null
+++ b/packages/nodes/src/ceiling/system.tsx
@@ -0,0 +1,19 @@
+'use client'
+
+import { CeilingSystem } from '@pascal-app/viewer'
+
+/**
+ * Registry-driven ceiling system bundle. Re-exports the legacy
+ * `CeilingSystem` so it mounts via `RegisteredSystems` when ceiling is
+ * registry-driven. `<LegacySystem kind="ceiling">` in viewer/components/
+ * viewer/index.tsx short-circuits whenever `nodeRegistry.has('ceiling')`
+ * is true — same shape wall / fence / slab use.
+ *
+ * Future Phase 5+: extract polygon triangulation + hole CSG into a pure
+ * `buildCeilingGeometry(node)` and migrate to `def.geometry`.
+ */
+const CeilingSystems = () => {
+  return <CeilingSystem />
+}
+
+export default CeilingSystems
diff --git a/packages/nodes/src/index.ts b/packages/nodes/src/index.ts
index 436b3f6f..f00a7004 100644
--- a/packages/nodes/src/index.ts
+++ b/packages/nodes/src/index.ts
@@ -1,4 +1,5 @@
 import type { AnyNodeDefinition, Plugin } from '@pascal-app/core'
+import { ceilingDefinition } from './ceiling'
 import { fenceDefinition } from './fence'
 import { shelfDefinition } from './shelf'
 import { slabDefinition } from './slab'
@@ -32,9 +33,11 @@ export const builtinPlugin: Plugin = {
     wallDefinition as unknown as AnyNodeDefinition,
     fenceDefinition as unknown as AnyNodeDefinition,
     slabDefinition as unknown as AnyNodeDefinition,
+    ceilingDefinition as unknown as AnyNodeDefinition,
   ],
 }
 
+export { ceilingDefinition } from './ceiling'
 export { fenceDefinition } from './fence'
 export { shelfDefinition } from './shelf'
 export { slabDefinition } from './slab'
diff --git a/packages/viewer/src/index.ts b/packages/viewer/src/index.ts
index 0a0c2b21..7ea2af6f 100644
--- a/packages/viewer/src/index.ts
+++ b/packages/viewer/src/index.ts
@@ -2,6 +2,12 @@
 // renderers (wall renders doors/windows, slab renders hosted items).
 // Public so registry-driven kinds can compose children without reaching
 // into viewer's internal paths.
+
+// Ceiling internals re-exported for the registry-driven ceiling definition.
+// The ceiling renderer uses TSL shaders for a grid pattern — too much code
+// to duplicate at Stage A. Wrap-exported here, ported into the nodes
+// folder in a later stage.
+export { CeilingRenderer } from './components/renderers/ceiling/ceiling-renderer'
 export { NodeRenderer } from './components/renderers/node-renderer'
 export { default as Viewer } from './components/viewer'
 export type { HoverStyle, HoverStyles } from './components/viewer/post-processing'
@@ -31,6 +37,7 @@ export {
 } from './lib/materials'
 export { mergedOutline } from './lib/merged-outline-node'
 export { default as useViewer } from './store/use-viewer'
+export { CeilingSystem } from './systems/ceiling/ceiling-system'
 // Fence system follows the wall re-export pattern — composed into the
 // registry-driven fence definition's `def.system`. Removed in Phase 6
 // alongside the legacy fence mount point.