diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 5dc96e61..d5a64c18 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -68,4 +68,5 @@ export {
 } from './systems/wall/wall-mitering'
 export { WallSystem } from './systems/wall/wall-system'
 export { WindowSystem } from './systems/window/window-system'
+export { cloneSceneGraph } from './utils/clone-scene-graph'
 export { isObject } from './utils/types'
diff --git a/packages/core/src/store/use-scene.ts b/packages/core/src/store/use-scene.ts
index e3773a59..2810db32 100644
--- a/packages/core/src/store/use-scene.ts
+++ b/packages/core/src/store/use-scene.ts
@@ -136,6 +136,7 @@ const useScene: UseSceneStore = create<SceneState>()(
           nodes: patchedNodes,
           rootNodeIds,
           dirtyNodes: new Set<AnyNodeId>(),
+          collections: {},
         })
         // Mark all nodes as dirty to trigger re-validation
         Object.values(patchedNodes).forEach((node) => {
diff --git a/packages/core/src/utils/clone-scene-graph.ts b/packages/core/src/utils/clone-scene-graph.ts
new file mode 100644
index 00000000..eac38192
--- /dev/null
+++ b/packages/core/src/utils/clone-scene-graph.ts
@@ -0,0 +1,141 @@
+import type { AnyNode, AnyNodeId } from '../schema'
+import { generateId } from '../schema/base'
+import type { Collection, CollectionId } from '../schema/collections'
+
+export type SceneGraph = {
+  nodes: Record<AnyNodeId, AnyNode>
+  rootNodeIds: AnyNodeId[]
+  collections?: Record<CollectionId, Collection>
+}
+
+/**
+ * Extracts the type prefix from a node ID (e.g., "wall_abc123" -> "wall")
+ */
+function extractIdPrefix(id: string): string {
+  const underscoreIndex = id.indexOf('_')
+  return underscoreIndex === -1 ? 'node' : id.slice(0, underscoreIndex)
+}
+
+/**
+ * Resolves a child reference to a node ID.
+ * Supports both string IDs and embedded child node objects with an `id` field.
+ */
+function resolveChildRefId(child: unknown): string | undefined {
+  if (typeof child === 'string') {
+    return child
+  }
+
+  if (child && typeof child === 'object' && 'id' in child) {
+    const id = (child as { id?: unknown }).id
+    if (typeof id === 'string') {
+      return id
+    }
+  }
+
+  return undefined
+}
+
+/**
+ * Deep clones a scene graph with all node IDs regenerated while preserving
+ * parent-child relationships and other internal references.
+ *
+ * This is useful for:
+ * - Copying nodes between different projects
+ * - Duplicating a subset of a scene within the same project
+ * - Multi-scene in-memory scenarios
+ */
+export function cloneSceneGraph(sceneGraph: SceneGraph): SceneGraph {
+  const { nodes, rootNodeIds, collections } = sceneGraph
+
+  // Build ID mapping: old ID -> new ID
+  const idMap = new Map<string, string>()
+
+  // Pass 1: Generate new IDs for all nodes
+  for (const nodeId of Object.keys(nodes)) {
+    const prefix = extractIdPrefix(nodeId)
+    idMap.set(nodeId, generateId(prefix))
+  }
+
+  // Pass 2: Clone nodes with remapped references
+  const clonedNodes = {} as Record<AnyNodeId, AnyNode>
+
+  for (const [oldId, node] of Object.entries(nodes)) {
+    const newId = idMap.get(oldId)! as AnyNodeId
+    const clonedNode = { ...node, id: newId } as AnyNode
+
+    // Remap parentId
+    if (clonedNode.parentId && typeof clonedNode.parentId === 'string') {
+      clonedNode.parentId = (idMap.get(clonedNode.parentId) ?? null) as AnyNodeId | null
+    }
+
+    // Remap children array (walls, levels, buildings, sites, items can have children)
+    if ('children' in clonedNode && Array.isArray(clonedNode.children)) {
+      ;(clonedNode as Record<string, unknown>).children = clonedNode.children
+        .map((childRef) => {
+          const childId = resolveChildRefId(childRef)
+          return childId ? idMap.get(childId) : undefined
+        })
+        .filter((id): id is string => id !== undefined) as string[]
+    }
+
+    // Remap wallId (items/doors/windows attached to walls)
+    if ('wallId' in clonedNode && typeof clonedNode.wallId === 'string') {
+      ;(clonedNode as Record<string, unknown>).wallId = idMap.get(clonedNode.wallId) as
+        | string
+        | undefined
+    }
+
+    clonedNodes[newId] = clonedNode
+  }
+
+  // Remap root node IDs
+  const clonedRootNodeIds = rootNodeIds
+    .map((id) => idMap.get(id))
+    .filter((id): id is string => id !== undefined) as AnyNodeId[]
+
+  // Clone and remap collections if present
+  let clonedCollections: Record<CollectionId, Collection> | undefined
+  if (collections) {
+    clonedCollections = {} as Record<CollectionId, Collection>
+    const collectionIdMap = new Map<string, CollectionId>()
+
+    // Generate new collection IDs
+    for (const collectionId of Object.keys(collections)) {
+      collectionIdMap.set(collectionId, generateId('collection'))
+    }
+
+    for (const [oldCollectionId, collection] of Object.entries(collections)) {
+      const newCollectionId = collectionIdMap.get(oldCollectionId)!
+      clonedCollections[newCollectionId] = {
+        ...collection,
+        id: newCollectionId,
+        nodeIds: collection.nodeIds
+          .map((nodeId) => idMap.get(nodeId))
+          .filter((id): id is string => id !== undefined) as AnyNodeId[],
+        controlNodeId: collection.controlNodeId
+          ? (idMap.get(collection.controlNodeId) as AnyNodeId | undefined)
+          : undefined,
+      }
+
+      // Update collectionIds on nodes that reference this collection
+      for (const oldNodeId of collection.nodeIds) {
+        const newNodeId = idMap.get(oldNodeId)
+        if (newNodeId && clonedNodes[newNodeId as AnyNodeId]) {
+          const node = clonedNodes[newNodeId as AnyNodeId] as Record<string, unknown>
+          if ('collectionIds' in node && Array.isArray(node.collectionIds)) {
+            const oldColIds = node.collectionIds as string[]
+            node.collectionIds = oldColIds
+              .map((cid) => collectionIdMap.get(cid))
+              .filter((id): id is CollectionId => id !== undefined)
+          }
+        }
+      }
+    }
+  }
+
+  return {
+    nodes: clonedNodes,
+    rootNodeIds: clonedRootNodeIds,
+    ...(clonedCollections && { collections: clonedCollections }),
+  }
+}