diff --git a/packages/core/src/lib/opening-casing.test.ts b/packages/core/src/lib/opening-casing.test.ts
index 1a38dc8d77..2d45f260d4 100644
--- a/packages/core/src/lib/opening-casing.test.ts
+++ b/packages/core/src/lib/opening-casing.test.ts
@@ -6,6 +6,7 @@ import {
   type OpeningCasingBoard,
   openingCasingBoards,
   openingCasingFaces,
+  openingCasingWidth,
   resolveOpeningCasingHost,
 } from './opening-casing'
 
@@ -55,10 +56,12 @@ describe('opening casing schema', () => {
       WindowNode.parse({ id: 'window_old', width: 1.2, height: 1 }),
       DoorNode.parse({ id: 'door_old', width: 0.9, height: 2.1 }),
     ]) {
-      expect(legacy.casingFaceA).toBe(false)
-      expect(legacy.casingFaceB).toBe(false)
+      // Loading adds no casing fields: absent faces are uncased.
+      expect('casingFaceA' in legacy || 'casingFaceB' in legacy || 'casingWidth' in legacy).toBe(
+        false,
+      )
       expect(openingCasingBoards(legacy, host)).toEqual([])
-      expect(legacy.casingWidth).toBeCloseTo(2 * INCH, 12)
+      expect(openingCasingWidth(legacy)).toBeCloseTo(2 * INCH, 12)
     }
     expect(DEFAULT_OPENING_CASING_WIDTH).toBeCloseTo(2 * INCH, 12)
     expect(OPENING_CASING_PROUD).toBeCloseTo(0.75 * INCH, 12)
@@ -67,7 +70,7 @@ describe('opening casing schema', () => {
   test('a casing face turned off stays off', () => {
     const parsed = WindowNode.parse({ id: 'window_off', casingFaceA: false, casingWidth: 0.09 })
     expect(parsed.casingFaceA).toBe(false)
-    expect(parsed.casingFaceB).toBe(false)
+    expect(parsed.casingFaceB).toBeUndefined()
     expect(parsed.casingWidth).toBe(0.09)
   })
 })
diff --git a/packages/core/src/schema/host-children.test.ts b/packages/core/src/schema/host-children.test.ts
index 8326ee75cc..304b226cba 100644
--- a/packages/core/src/schema/host-children.test.ts
+++ b/packages/core/src/schema/host-children.test.ts
@@ -57,10 +57,6 @@ test.each(baseline)(
           ? {
               ...expected,
               floorThresholdVersion: 1,
-              // Saved before casing: no casing.
-              casingFaceA: false,
-              casingFaceB: false,
-              casingWidth: 0.0508,
             }
           : saved.type === 'fence'
             ? {
diff --git a/packages/core/src/schema/nodes/door.ts b/packages/core/src/schema/nodes/door.ts
index 915e34f57c..62fa97a950 100644
--- a/packages/core/src/schema/nodes/door.ts
+++ b/packages/core/src/schema/nodes/door.ts
@@ -3,12 +3,7 @@ import { z } from 'zod'
 import { BaseNode, nodeType, objectId } from '../base'
 import { GeometryScriptSource } from '../geometry-source'
 import { MaterialSchema } from '../material'
-import {
-  DEFAULT_DOOR_CONTENT_PADDING,
-  DEFAULT_OPENING_CASING_WIDTH,
-  DoorType,
-  defaultDoorSegments,
-} from './opening-types'
+import { DEFAULT_DOOR_CONTENT_PADDING, DoorType, defaultDoorSegments } from './opening-types'
 
 export { DoorType } from './opening-types'
 
@@ -144,10 +139,11 @@ export const DoorNode = BaseNode.extend({
   // opening (head and both legs, none at the floor), never inside it, so the
   // wall cutout stays width × height. The faces are the host's `a` / `b`
   // (WallFace), not the door's front and back, so flipping the swing leaves
-  // the casing where it is. Absent casing fields keep saved openings uncased.
-  casingFaceA: z.boolean().default(false),
-  casingFaceB: z.boolean().default(false),
-  casingWidth: z.number().positive().default(DEFAULT_OPENING_CASING_WIDTH),
+  // the casing where it is. Optional, never defaulted, so loading a saved
+  // opening adds no fields: absent faces are uncased, an absent width is 2 in.
+  casingFaceA: z.boolean().optional(),
+  casingFaceB: z.boolean().optional(),
+  casingWidth: z.number().positive().optional(),
 
   // Swing
   hingesSide: z.enum(['left', 'right']).default('left'),
diff --git a/packages/core/src/schema/nodes/window.ts b/packages/core/src/schema/nodes/window.ts
index 8d56f0e6b9..c6160fed8c 100644
--- a/packages/core/src/schema/nodes/window.ts
+++ b/packages/core/src/schema/nodes/window.ts
@@ -3,7 +3,7 @@ import { z } from 'zod'
 import { BaseNode, nodeType, objectId } from '../base'
 import { GeometryScriptSource } from '../geometry-source'
 import { MaterialSchema } from '../material'
-import { DEFAULT_OPENING_CASING_WIDTH, WindowType } from './opening-types'
+import { WindowType } from './opening-types'
 
 export { WindowType } from './opening-types'
 
@@ -122,11 +122,12 @@ export const WindowNode = BaseNode.extend({
   // Casing: flat boards on the finished faces of the host wall around the
   // opening, never inside it, so the wall cutout stays width × height. The
   // faces are the host's `a` / `b` (WallFace), not the unit's own front and
-  // back, so flipping the window leaves its casing where it is. Absent casing fields keep
-  // saved openings uncased.
-  casingFaceA: z.boolean().default(false),
-  casingFaceB: z.boolean().default(false),
-  casingWidth: z.number().positive().default(DEFAULT_OPENING_CASING_WIDTH),
+  // back, so flipping the window leaves its casing where it is. Optional, never
+  // defaulted, so loading a saved opening adds no fields: absent faces are
+  // uncased, an absent width is 2 in.
+  casingFaceA: z.boolean().optional(),
+  casingFaceB: z.boolean().optional(),
+  casingWidth: z.number().positive().optional(),
 }).describe(dedent`Window node - a parametric window placed on a wall
   - position: center of the window in wall-local coordinate system
   - width/height: overall outer dimensions, which are also the wall cutout
diff --git a/packages/core/src/store/use-scene-window-migration.test.ts b/packages/core/src/store/use-scene-window-migration.test.ts
index 7d957c7250..169305717f 100644
--- a/packages/core/src/store/use-scene-window-migration.test.ts
+++ b/packages/core/src/store/use-scene-window-migration.test.ts
@@ -83,8 +83,8 @@ describe('scene window migrations', () => {
     expect(window.columnRatios).toEqual([1])
     expect(window.rowRatios).toEqual([1])
     expect(window.frameThickness).toBe(0.05)
-    expect(window.casingFaceA).toBe(false)
-    expect(window.casingFaceB).toBe(false)
+    // Casing has no default: a window saved before it stays uncased, fieldless.
+    expect('casingFaceA' in window).toBe(false)
     expect(window.sill).toBe(true)
     // …and authored fields survive.
     expect(window.width).toBe(1.2)
diff --git a/packages/core/src/systems/wall/wall-merge.test.ts b/packages/core/src/systems/wall/wall-merge.test.ts
index 9edb65d1da..58e4c3810c 100644
--- a/packages/core/src/systems/wall/wall-merge.test.ts
+++ b/packages/core/src/systems/wall/wall-merge.test.ts
@@ -228,7 +228,7 @@ describe('explicit wall merge through the store', () => {
       const moved = nodes[absorbedWindow.id] as WindowNode
       expect(moved.position[0]).toBeCloseTo(expectedX)
       expect(moved.side).toBe('back')
-      expect([moved.casingFaceA, moved.casingFaceB]).toEqual([false, false])
+      expect([moved.casingFaceA, moved.casingFaceB]).toEqual([undefined, undefined])
       // A door on the reversed wall turns with its frame — depth and yaw — while
       // its hinges and handle, hung off that yaw, keep their stored side.
       const door = nodes[absorbedDoor.id] as DoorNode
diff --git a/packages/nodes/src/door/floorplan-move.ts b/packages/nodes/src/door/floorplan-move.ts
index 5ffb4b48aa..26a93c793a 100644
--- a/packages/nodes/src/door/floorplan-move.ts
+++ b/packages/nodes/src/door/floorplan-move.ts
@@ -84,8 +84,8 @@ export const doorFloorplanMoveTarget: FloorplanMoveTarget<DoorNode> = ({ node })
     roofSegmentId: undefined
     roofFace: undefined
     visible: true
-    casingFaceA: boolean
-    casingFaceB: boolean
+    casingFaceA?: boolean
+    casingFaceB?: boolean
   } | null = null
 
   // R flips the door's facing (front ↔ back) mid-placement. `apply` re-derives
diff --git a/packages/nodes/src/shared/opening-casing.test.ts b/packages/nodes/src/shared/opening-casing.test.ts
index ea3a6db467..497f33e06d 100644
--- a/packages/nodes/src/shared/opening-casing.test.ts
+++ b/packages/nodes/src/shared/opening-casing.test.ts
@@ -6,6 +6,7 @@ import {
   type GeometryContext,
   LevelNode,
   OPENING_CASING_PROUD,
+  openingCasingWidth,
   sceneRegistry,
   slotPaintMaterial,
   useScene,
@@ -224,7 +225,7 @@ test('casing paint targets each host side, inherits the frame, and previews and
               part.geometry.computeBoundingBox()
               const local = part.geometry.boundingBox!.getCenter(new Vector3())
               if (part.geometry.type === 'ExtrudeGeometry') {
-                local.x = node.width / 2 + node.casingWidth / 2
+                local.x = node.width / 2 + openingCasingWidth(node) / 2
                 local.y = 0
               }
               const center = local.applyMatrix4(mesh.matrixWorld)
diff --git a/packages/nodes/src/window/floorplan-move.ts b/packages/nodes/src/window/floorplan-move.ts
index ecc604157e..fdffd24508 100644
--- a/packages/nodes/src/window/floorplan-move.ts
+++ b/packages/nodes/src/window/floorplan-move.ts
@@ -87,8 +87,8 @@ export const windowFloorplanMoveTarget: FloorplanMoveTarget<WindowNode> = ({ nod
     roofSegmentId: undefined
     roofFace: undefined
     visible: true
-    casingFaceA: boolean
-    casingFaceB: boolean
+    casingFaceA?: boolean
+    casingFaceB?: boolean
   } | null = null
 
   // R flips the window's facing (front ↔ back) mid-placement — see