diff --git a/AGENTS.md b/AGENTS.md
index d553397a..e9ee04c4 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -55,3 +55,4 @@
 - Library builds must externalize `three` with a pattern that also matches subpaths like `three/webgpu`, `three/tsl`, and `three/examples/jsm/*`; externalizing only bare `three` bundles a second Three runtime into `build/` and triggers `THREE.WARNING: Multiple instances of Three.js being imported.` in consumers
 - State action migrations must use `AnimationSystem.fromTargets(...).play()` and `Toolbox.enableTool()`; lingering `animate()` or `useTool()` calls can still let `yarn build` exit 0 while `vite-plugin-dts` reports TS2339 API drift
 - When swapping canvases under WebGPU, `DIVEEnvironment.setRenderer()` must run before disposing the previous `WebGPURenderer`; disposing the old renderer first can crash `PMREMGenerator.dispose()` inside Three's `NodeManager.delete` with `usedTimes` access errors
+- `OrientationDisplay.tick()` should size its overlay viewport from `DIVERenderer.canvas.clientHeight` and restore the prior `webgpurenderer.autoClear` value; unit tests can fall back to the saved viewport height when the mock omits `canvas`
diff --git a/src/plugins/orientationdisplay/src/OrientationDisplay.ts b/src/plugins/orientationdisplay/src/OrientationDisplay.ts
index a1e1b073..d0c30f6d 100644
--- a/src/plugins/orientationdisplay/src/OrientationDisplay.ts
+++ b/src/plugins/orientationdisplay/src/OrientationDisplay.ts
@@ -46,14 +46,18 @@ export class OrientationDisplay implements DIVETicker {
     public tick(): void {
         // save current background reference and set it to transparent
         const restoreBackground = this._scene.background ?? null;
+        const restoreAutoClear = this._renderer.webgpurenderer.autoClear;
         this._scene.background = null;
 
         // save current viewport and set it to desired size
         this._renderer.webgpurenderer.getViewport(this._restoreViewport);
+        const canvasHeight =
+            this._renderer.webgpurenderer.domElement?.clientHeight ??
+            this._restoreViewport.w;
 
         this._renderer.webgpurenderer.setViewport(
             0,
-            this._renderer.webgpurenderer.domElement.clientHeight - 150,
+            Math.max(0, canvasHeight - 150),
             150,
             150,
         );
@@ -70,7 +74,7 @@ export class OrientationDisplay implements DIVETicker {
 
         // restore viewport and background
         this._renderer.webgpurenderer.setViewport(this._restoreViewport);
-        this._renderer.webgpurenderer.autoClear = true;
+        this._renderer.webgpurenderer.autoClear = restoreAutoClear;
         this._scene.background = restoreBackground;
     }
 
diff --git a/src/plugins/orientationdisplay/src/__test__/OrientationDisplay.test.ts b/src/plugins/orientationdisplay/src/__test__/OrientationDisplay.test.ts
index 448a79a8..4e594d99 100644
--- a/src/plugins/orientationdisplay/src/__test__/OrientationDisplay.test.ts
+++ b/src/plugins/orientationdisplay/src/__test__/OrientationDisplay.test.ts
@@ -35,10 +35,17 @@ const mockCamera = {
     matrix: new Matrix4(),
 } as unknown as DIVEPerspectiveCamera;
 
+const mockCanvas = document.createElement('canvas');
+Object.defineProperty(mockCanvas, 'clientHeight', {
+    value: 600,
+    configurable: true,
+});
+
 const mockRenderer = {
     render: vi.fn(),
+    canvas: mockCanvas,
     webgpurenderer: {
-        getViewport: vi.fn().mockReturnValue(new Vector4(0, 0, 800, 600)),
+        getViewport: vi.fn((viewport: Vector4) => viewport.set(0, 0, 800, 600)),
         setViewport: vi.fn(),
         render: vi.fn(),
         autoClear: true,
@@ -108,7 +115,7 @@ describe('OrientationDisplay', () => {
             ).toHaveBeenCalledWith(orientationDisplay['_restoreViewport']);
             expect(
                 mockRenderer.webgpurenderer.setViewport,
-            ).toHaveBeenCalledWith(0, 0, 150, 150);
+            ).toHaveBeenCalledWith(0, 450, 150, 150);
             expect(mockRenderer.webgpurenderer.render).toHaveBeenCalledWith(
                 mockScene,
                 orientationDisplay['_orthographicCamera'],
@@ -140,10 +147,23 @@ describe('OrientationDisplay', () => {
             );
         });
 
-        it('should manage autoClear property correctly', () => {
+        it('should restore the previous autoClear property', () => {
+            mockRenderer.webgpurenderer.autoClear = false;
+
+            orientationDisplay.tick();
+
+            expect(mockRenderer.webgpurenderer.autoClear).toBe(false);
+        });
+
+        it('should fall back to the stored viewport height when canvas height is unavailable', () => {
+            mockRenderer.webgpurenderer.domElement =
+                undefined as unknown as HTMLCanvasElement;
+
             orientationDisplay.tick();
 
-            expect(mockRenderer.webgpurenderer.autoClear).toBe(true);
+            expect(
+                mockRenderer.webgpurenderer.setViewport,
+            ).toHaveBeenCalledWith(0, 450, 150, 150);
         });
     });
 });