fix(canvas): report retained backing failures

- Warn once with the rejected surface dimensions and original CanvasKit error
- Disable repeated cache allocation attempts until the renderer surface is replaced
- Keep direct scene rendering as the visible fallback

packages/core/src/canvas/renderer.ts

@@ -122,6 +122,7 @@ export class SkiaRenderer {
   } | null = null
   sceneBackingPreviewUntil = 0
   sceneBackingNeedsCrispRender = false
+  sceneBackingAllocationFailed = false
   sceneBackingBuild: {
     surface: Surface
     graph: SceneGraph
@@ -451,6 +452,7 @@ export class SkiaRenderer {
   replaceSurface(surface: Surface): void {
     this.surface.delete()
     this.surface = surface
+    this.sceneBackingAllocationFailed = false
     this.invalidateScenePicture()
   }
 

packages/core/src/canvas/renderer/retained-backing.ts

@@ -187,15 +187,22 @@ function sceneBackingGeometry(r: SkiaRenderer) {
 }
 
 function createSceneBackingSurface(r: SkiaRenderer, width: number, height: number): Surface | null {
+  if (r.sceneBackingAllocationFailed) return null
+  const info = {
+    width: Math.ceil(width * r.dpr),
+    height: Math.ceil(height * r.dpr),
+    colorType: r.ck.ColorType.RGBA_8888,
+    alphaType: r.ck.AlphaType.Premul,
+    colorSpace: r.ck.ColorSpace.SRGB
+  }
   try {
-    return r.surface.makeSurface({
-      width: Math.ceil(width * r.dpr),
-      height: Math.ceil(height * r.dpr),
-      colorType: r.ck.ColorType.RGBA_8888,
-      alphaType: r.ck.AlphaType.Premul,
-      colorSpace: r.ck.ColorSpace.SRGB
-    })
-  } catch {
+    return r.surface.makeSurface(info)
+  } catch (error) {
+    r.sceneBackingAllocationFailed = true
+    console.warn(
+      `Disabling retained scene backing after CanvasKit failed to allocate ${info.width}×${info.height}`,
+      error
+    )
     return null
   }
 }
@@ -452,6 +459,7 @@ export function renderSceneBacking(
   graph: SceneGraph,
   sceneVersion: number
 ): boolean {
+  if (r.sceneBackingAllocationFailed) return false
   const positionPreviewVersion = graph.positionPreviewVersion
   const allowStaleZoom = now() < r.sceneBackingPreviewUntil
   const hasCoverage = backingCoverageContainsLiveViewport(

tests/engine/render/canvas/retained-backing.test.ts

@@ -1,4 +1,4 @@
-import { expect, mock, test } from 'bun:test'
+import { expect, mock, spyOn, test } from 'bun:test'
 
 import type { Canvas, Image as CKImage, ImageInfo, Surface } from 'canvaskit-wasm'
 
@@ -39,6 +39,7 @@ function createRenderer(surfaceFactory: (info: ImageInfo) => Surface | null) {
     pageId: 'page',
     sceneBacking: null,
     sceneBackingBuild: null,
+    sceneBackingAllocationFailed: false,
     sceneBackingNeedsCrispRender: false,
     sceneBackingPreviewUntil: 0,
     sceneBackingAverageRecordMs: 40,
@@ -124,15 +125,27 @@ test('retained scene backing preserves the full margin when it fits the allocati
   expect(requests[0]).toMatchObject({ width: 2400, height: 1800 })
 })
 
-test('retained scene backing falls back when CanvasKit throws during allocation', () => {
+test('retained scene backing reports a throwing allocation and disables further attempts', () => {
+  const error = new TypeError("Cannot set properties of null (setting 'be')")
   const r = createRenderer(() => {
-    throw new TypeError("Cannot set properties of null (setting 'be')")
+    throw error
   })
   const canvas = createCanvas()
+  const warn = spyOn(console, 'warn').mockImplementation(() => undefined)
 
   expect(() => renderSceneBacking(r, canvas, createGraph(), 1)).not.toThrow()
+  expect(renderSceneBacking(r, canvas, createGraph(), 1)).toBe(false)
+
+  expect(r.sceneBackingAllocationFailed).toBe(true)
+  expect(r.surface.makeSurface).toHaveBeenCalledTimes(1)
+  expect(warn).toHaveBeenCalledTimes(1)
+  expect(warn).toHaveBeenCalledWith(
+    'Disabling retained scene backing after CanvasKit failed to allocate 300×300',
+    error
+  )
   expect(r.sceneBacking).toBeNull()
   expect(canvas.drawImageRectOptions).not.toHaveBeenCalled()
+  warn.mockRestore()
 })
 
 test('retained scene backing filters cross-zoom previews instead of falling back to live rendering', () => {