diff --git a/packages/mcp/src/templates/empty-studio.ts b/packages/mcp/src/templates/empty-studio.ts
index 84ae6547f..10a4b7c0b 100644
--- a/packages/mcp/src/templates/empty-studio.ts
+++ b/packages/mcp/src/templates/empty-studio.ts
@@ -238,16 +238,6 @@ function buildTemplate(): SceneGraph {
     nodes[node.id as AnyNodeId] = node
   }
 
-  // SiteNode.children is a discriminatedUnion of BuildingNode/ItemNode objects
-  // (not string ids) — so the site must embed the full building node. The
-  // rest of the tree uses string ids per the BaseNode/LevelNode/WallNode
-  // schemas. We mutate the flat-dict copy of the site here so the nested
-  // representation round-trips through AnyNode.safeParse.
-  const siteInDict = nodes['site_empty' as AnyNodeId] as unknown as {
-    children: unknown[]
-  }
-  siteInDict.children = [nodes['building_empty' as AnyNodeId]]
-
   return {
     nodes,
     rootNodeIds: ['site_empty'] as AnyNodeId[],
diff --git a/packages/mcp/src/templates/garden-house.ts b/packages/mcp/src/templates/garden-house.ts
index b7205b452..5dd8dcd73 100644
--- a/packages/mcp/src/templates/garden-house.ts
+++ b/packages/mcp/src/templates/garden-house.ts
@@ -263,10 +263,6 @@ function buildTemplate(): SceneGraph {
     ],
   } as unknown as AnyNode
 
-  // SiteNode.children is a discriminatedUnion of BuildingNode/ItemNode objects
-  // (not string ids) per the schema — embed the full building node here.
-  ;(nodes.site_garden as unknown as { children: unknown[] }).children = [nodes.building_garden!]
-
   return {
     nodes: nodes as Record<AnyNodeId, AnyNode>,
     rootNodeIds: ['site_garden'] as AnyNodeId[],
diff --git a/packages/mcp/src/templates/two-bedroom.ts b/packages/mcp/src/templates/two-bedroom.ts
index 80fcc18fb..d41a14b1d 100644
--- a/packages/mcp/src/templates/two-bedroom.ts
+++ b/packages/mcp/src/templates/two-bedroom.ts
@@ -291,10 +291,6 @@ function buildTemplate(): SceneGraph {
     ],
   } as unknown as AnyNode
 
-  // SiteNode.children is a discriminatedUnion of BuildingNode/ItemNode objects
-  // (not string ids) per the schema — embed the full building node here.
-  ;(nodes.site_2br as unknown as { children: unknown[] }).children = [nodes.building_2br!]
-
   return {
     nodes: nodes as Record<AnyNodeId, AnyNode>,
     rootNodeIds: ['site_2br'] as AnyNodeId[],