fix: 首页「最近项目」缩略图与退出前视角不一致，出现偏移或裁切

- 封面使用真实画布尺寸(clientWidth/Height)及最终 viewport.x/y/scale。
- 320×240 封面改为居中 cover 裁切，不再从左上角取景。
- 正确绘制画布背景色。

docs/project-memory/shared-memory/decision-log.md

@@ -539,6 +539,7 @@
 
 - 背景：项目页和创作主页最近项目曾在卡片中根据项目 `layers + viewport + resources` 临时重建一份迷你画布，视觉上像封面，但它不是持久快照，也会把列表页变成画布布局解释器。
 - 决策：项目封面图改为画布当前视口栅格化后的静态资源。前端在项目加载后和防抖保存 layout 时生成 320x240 PNG，走私有 OSS / asset object 上传，再创建 `editor_project_resource`，其中 `assetKind="project-cover-snapshot"`、`sourceType="uploaded"`；项目列表和创作主页最近项目只读取最新封面快照资源渲染，没有快照时显示项目占位，不再回退为实时画布组合。
+- 2026-07-24 补充：封面取景以当前画布工作区的实际尺寸和渲染态 viewport 为准，先绘制工作区背景色，再从视口中心等比放大并裁成 4:3；持久化显示倍率不得直接用于封面渲染。
 - 影响范围：`src/components/image-editor/useImageCanvasProjectPersistence.ts`、`src/components/image-editor/ImageCanvasProjectCoverSnapshotModel.ts`、`src/components/project/ProjectCanvasCover.tsx`、`src/components/project/ProjectGalleryView.tsx`、`src/components/creation-home/CreationLandingView.tsx` 和图片画布数据契约文档。
 - 验证方式：运行项目页、封面快照模型、图片画布项目持久化和媒体上传相关前端测试，执行 `npm run typecheck`、`npm run check:encoding` 和 `git diff --check`。
 - 关联文档：`docs/technical/【前端架构】图片画布编辑器MVP接入方案-2026-06-11.md`、`docs/【后端架构】server-rs与SpacetimeDB数据契约-2026-05-15.md`。

docs/technical/【前端架构】图片画布编辑器MVP接入方案-2026-06-11.md

@@ -58,7 +58,7 @@
 - 新增 `editor_asset` 表保存账号级素材：`assetId`、`ownerUserId`、`folderId`、名称、图片读取地址、可选封面 `thumbnailSrc`、OSS / asset object 引用、图片尺寸、来源类型、prompt、actualPrompt、model、provider、taskId、可选 `groupTaskId`、可选 `groupTaskExpectedAssetCount`、`assetKind`、`generationInputs`、`generationCostMudPoints`、创建时间和更新时间。素材只跟账号走，不跟 project 走；`taskId` 保留真实生成 / 拆分操作身份，`groupTaskId` 保存服务端验证后的来源任务，`groupTaskExpectedAssetCount` 保存该拆分批次完整时应有的素材数；角色、图标、UI 设计图、视频和音频等生成结果的用户可见输入快照随素材保存。
 - 新增 `editor_showcase_asset`、`editor_showcase_asset_like` 和 `editor_showcase_campaign_config` 表承接 `陶泥儿精选`：生成素材默认不公开，用户在素材菜单中提交精选审核后生成独立快照；后台审核通过后先返还 50% 生成成本泥点，但仍需运营手动设置精选分类并开启展示才进入公开精选。公开列表不再读取 `editor_project_resource.public_showcase_enabled`，而是读取已通过、展示开启且分类合法的精选快照，支持点赞数和首位活动卡。
 - `editor_project_resource` 表保存工程画布引用过的资源快照：`resourceId`、`projectId`、`ownerUserId`、OSS / asset object 引用、图片尺寸、来源类型、prompt、actualPrompt、model、provider、taskId、sourceResourceId、`assetKind`、`generationInputs`、创建时间和更新时间。上传素材被拖入画布时会复制为 project resource，图层只引用 resourceId；图片、图标和 UI 素材生成 BFF 在请求携带 `projectId` 时由后端直接创建新 resource，并把 `resourceId` 随生成响应返回给前端。图片生成请求如果同时携带 `canvasCompletion`（生成器 `dialogId`、标题和占位框，或无 dialog 的右侧完成占位），BFF / worker 在生成成功后必须直接读取当前项目布局，优先使用最新 `generation-dialog` 占位框位置；只有当前布局仍存在对应 `generation-dialog` 时才插入轻量结果图层、把生成器标记为 `idle` 并写入 `generatedLayerId`，沿用后端当前 viewport 保存布局，再返回或刷新最新项目快照；前端只应用该快照刷新显示，不把生成完成态作为本地业务真相，也不在项目加载时根据资源行推断完成态。有项目上下文但后端没有返回项目快照时，前端不得本地补结果图层，只保留当前生成器交互状态等待下一次项目刷新。
-- 项目封面图是画布当前视口栅格化后的静态快照资源，不在项目列表页临时重放 `layers + viewport`。前端在项目加载后和防抖保存 layout 时生成 320x240 PNG，走私有 OSS / asset object 上传，再创建 `editor_project_resource`，其中 `assetKind="project-cover-snapshot"`、`sourceType="uploaded"`。`/project` 与 `/creation` 最近项目卡只读取最新封面快照资源渲染；没有封面快照时显示普通项目占位，不回退为实时画布组合。
+- 项目封面图是画布当前视口栅格化后的静态快照资源，不在项目列表页临时重放 `layers + viewport`。前端在项目加载后和防抖保存 layout 时生成 320x240 PNG：取景必须使用画布实际渲染的 `viewport.x / viewport.y / viewport.scale` 和当前工作区尺寸，先绘制工作区背景色，再以视口中心等比放大并裁成 4:3，不得把持久化显示倍率当成渲染倍率，也不得按固定工作区尺寸或左上角锚定取景。快照继续走私有 OSS / asset object 上传，再创建 `editor_project_resource`，其中 `assetKind="project-cover-snapshot"`、`sourceType="uploaded"`。`/project` 与 `/creation` 最近项目卡只读取最新封面快照资源渲染；没有封面快照时显示普通项目占位，不回退为实时画布组合。
 - 图片、音频、视频和角色动画帧文件本体继续走 OSS / asset object；浏览器读取私有 generated 对象统一经 `/api/assets/read-url` 换签，签名 URL 可在 session 内复用，但不得作为持久化真相。`/api/assets/read-url` 属于页面展示层高频后台请求，前端统一在 `assetReadUrlService` 内做同 key pending 去重、session 缓存和跨组件节流；UI 设计切片、角色动画帧或大量素材恢复时不得绕过该服务并发换签，否则单页可在同一秒内打满发布入口 `genarrative_api_rps` burst。
 - 登录态上传和生成结果必须先落 OSS / asset object，再向 `editor_project_resource` / `editor_asset` 写入轻量 `imageSrc: "/<objectKey>"`、`objectKey` 和 `assetObjectId`；未登录演示态可以在内存里使用 Data URL 预览，但项目、素材库、项目资源和 `editor_canvas.layers_json` 不得写入 `data:image/*`、`data:video/*`、`data:audio/*` 或 `blob:`。旧数据读取时如果已有 `objectKey`，`imageSrc` 归一成 `/<objectKey>`；没有 `objectKey` 的旧 Data URL 需要走修复上传并回写轻量引用。裁扩在项目上下文中虽然由前端 canvas 本地渲染 PNG，也必须先上传 OSS / asset object 并创建 `editor_project_resource`，再把带正式 `resourceId/objectKey/assetObjectId` 的裁扩图层加入画布；不能先把 `local-resource-*` + Data URL 图层交给项目保存或后续去背景。上传到生成面板参考图槽位的图片必须先创建 `editor_project_resource` 行；没有当前工程 ID 时才创建账号级 `editor_asset` 行，随后把对应 `resourceId` 或 `assetId` 写入参考图临时状态；生成请求提交前必须把临时状态解析成 `objectKey`、项目资源 ID 或素材 ID，未登记的本地图片和普通图片路径先上传 OSS，不能直接提交 Data URL、Blob URL 或临时图片源。
 - 资源表保存资源和素材级元数据；图层位置、层级、分组选中所需 ID 和 groupId 保存在 `editor_canvas` 的布局 JSON。布局 JSON 是混合数组：普通图层按 `layerId/resourceId` 保存，生成器占位和生成器对话框按 `itemType: "generation-dialog"` 保存，不新增单独表。普通图层的新保存不再把 `assetKind/generationInputs` 写入布局 JSON；刷新时优先从 `editor_project_resource` 恢复，旧布局中的同名字段只作为兼容兜底。生成器快照必须包含生成器 ID、模式、提示词、参数、参考图、状态、占位框位置和可选 `generatedLayerId`；角色、图标等纯色抠图生成器的前端用户路径不保存或恢复 `screenColor` / `segModel`，同源重绘也不再从 `generationInputs.fields` 恢复 `抠图背景色` 或 `抠图模型`；宣发素材生成器还必须保存并恢复 `publicationWorkflowId`、`publicationGameInfo` 和 `publicationReferences`，避免刷新后生成卡片字段或参考图丢失。生成器快照中的参考图同样只保存 `resourceId/sourceAssetId` 行引用和展示所需 label，不保存图片 Data URL、signed URL 或 `objectKey`；刷新时用 `editor_project_resource` / `editor_asset` 行恢复临时生成请求所需图片源。生成成功后仍保存该快照，只是渲染时由 `generatedLayerId` 锚定到成品图层而不重复显示灰色占位框。`generationInputs.references` 是用户可见输入快照中的行级索引，只允许保存 `{ title, label, refType, refId }`；生成接口只接收提交前临时状态解析出的 `objectKey` 或资源 ID；Data URL、Blob URL 和 signed URL 不进入请求体，不进入资源 / 素材元数据。图层展示尺寸不再作为独立 `Size` 真相保存，刷新与新建图层均按 `Resolution`（`originalWidth/originalHeight`）原分辨率显示。图层组第一版是画布内布局语义，不单独建表。

src/components/image-editor/ImageCanvasEditorView.tsx

@@ -1116,6 +1116,7 @@ export function ImageCanvasEditorView({
     () => ({
       layersRef,
       viewportRef,
+      canvasViewportRef,
       canvasGenerationDialogsRef,
       canvasBackgroundColorRef,
     }),

src/components/image-editor/ImageCanvasProjectCoverSnapshotModel.test.ts

@@ -4,6 +4,7 @@ import type { CanvasLayer } from './ImageCanvasEditorTypes';
 import {
   buildProjectCoverSnapshotSignature,
   resolveProjectCoverDrawableLayers,
+  resolveProjectCoverSnapshotFrame,
 } from './ImageCanvasProjectCoverSnapshotModel';
 
 function layer(overrides: Partial<CanvasLayer> = {}): CanvasLayer {
@@ -28,6 +29,8 @@ describe('ImageCanvasProjectCoverSnapshotModel', () => {
   it('builds a stable cover signature from visible drawable layers', () => {
     const signature = buildProjectCoverSnapshotSignature({
       viewport: { x: 12, y: -8, scale: 0.75 },
+      viewportSize: { width: 900, height: 640 },
+      backgroundColor: '#f8fafc',
       layers: [
         layer({ id: 'hidden', hidden: true }),
         layer({
@@ -49,12 +52,36 @@ describe('ImageCanvasProjectCoverSnapshotModel', () => {
     });
 
     expect(signature).toContain('"scale":0.75');
+    expect(signature).toContain('"width":900');
+    expect(signature).toContain('"backgroundColor":"#f8fafc"');
     expect(signature).toContain('"id":"back"');
     expect(signature).toContain('"id":"front"');
     expect(signature).not.toContain('"id":"hidden"');
     expect(signature).not.toContain('"id":"audio"');
   });
 
+  it('center-crops the live canvas viewport to fill the 4:3 cover', () => {
+    const landscapeFrame = resolveProjectCoverSnapshotFrame({
+      viewport: { x: -260, y: 70, scale: 0.5 },
+      viewportSize: { width: 900, height: 640 },
+    });
+
+    expect(landscapeFrame.renderScale).toBe(0.5);
+    expect(landscapeFrame.frameScale).toBeCloseTo(0.375);
+    expect(landscapeFrame.offsetX).toBeCloseTo(-8.75);
+    expect(landscapeFrame.offsetY).toBeCloseTo(0);
+
+    const portraitFrame = resolveProjectCoverSnapshotFrame({
+      viewport: { x: 30, y: -40, scale: 1.25 },
+      viewportSize: { width: 640, height: 900 },
+    });
+
+    expect(portraitFrame.renderScale).toBe(1.25);
+    expect(portraitFrame.frameScale).toBeCloseTo(0.5);
+    expect(portraitFrame.offsetX).toBeCloseTo(0);
+    expect(portraitFrame.offsetY).toBeCloseTo(-105);
+  });
+
   it('uses the first image-sequence frame as the drawable source', () => {
     expect(
       resolveProjectCoverDrawableLayers([

src/components/image-editor/ImageCanvasProjectCoverSnapshotModel.ts

@@ -1,14 +1,19 @@
 import { getSignedAssetReadUrl } from '../../services/assetReadUrlService';
+import {
+  DEFAULT_CANVAS_BACKGROUND_COLOR,
+  normalizeCanvasBackgroundHex,
+} from './ImageCanvasEditorModel';
 import type { CanvasLayer, CanvasViewport } from './ImageCanvasEditorTypes';
 
 export const PROJECT_COVER_SNAPSHOT_ASSET_KIND = 'project-cover-snapshot';
 export const PROJECT_COVER_SNAPSHOT_OBJECT_ASSET_KIND =
   'editor_project_cover_snapshot';
 export const PROJECT_COVER_SNAPSHOT_SIZE = { width: 320, height: 240 } as const;
-export const PROJECT_COVER_SNAPSHOT_VIEWPORT_SIZE = {
-  width: 900,
-  height: 640,
-} as const;
+
+export type ProjectCoverSnapshotViewportSize = {
+  width: number;
+  height: number;
+};
 
 type ProjectCoverDrawableLayer = {
   id: string;
@@ -25,6 +30,32 @@ function numberOrFallback(value: number, fallback: number) {
   return Number.isFinite(value) ? value : fallback;
 }
 
+function positiveNumberOrFallback(value: number, fallback: number) {
+  return Number.isFinite(value) && value > 0 ? value : fallback;
+}
+
+function normalizeProjectCoverViewportSize(
+  viewportSize: ProjectCoverSnapshotViewportSize,
+) {
+  return {
+    width: positiveNumberOrFallback(
+      viewportSize.width,
+      PROJECT_COVER_SNAPSHOT_SIZE.width,
+    ),
+    height: positiveNumberOrFallback(
+      viewportSize.height,
+      PROJECT_COVER_SNAPSHOT_SIZE.height,
+    ),
+  };
+}
+
+function normalizeProjectCoverBackgroundColor(backgroundColor: string) {
+  return (
+    normalizeCanvasBackgroundHex(backgroundColor) ??
+    DEFAULT_CANVAS_BACKGROUND_COLOR
+  );
+}
+
 function normalizeObjectKey(value: string | null | undefined) {
   const normalized = value?.trim().replace(/^\/+/u, '') ?? '';
   return normalized || null;
@@ -83,51 +114,79 @@ export function resolveProjectCoverDrawableLayers(
 export function buildProjectCoverSnapshotSignature({
   layers,
   viewport,
+  viewportSize,
+  backgroundColor,
 }: {
   layers: readonly CanvasLayer[];
+  // we may call it camera
   viewport: CanvasViewport;
+  viewportSize: ProjectCoverSnapshotViewportSize;
+  backgroundColor: string;
 }) {
   const coverLayers = resolveProjectCoverDrawableLayers(layers);
   if (coverLayers.length === 0) {
     return null;
   }
+  const normalizedViewportSize =
+    normalizeProjectCoverViewportSize(viewportSize);
   return JSON.stringify({
     viewport: {
       x: numberOrFallback(viewport.x, 0),
       y: numberOrFallback(viewport.y, 0),
       scale: numberOrFallback(viewport.scale, 1),
     },
+    viewportSize: normalizedViewportSize,
+    backgroundColor: normalizeProjectCoverBackgroundColor(backgroundColor),
     layers: coverLayers,
   });
 }
 
+export function resolveProjectCoverSnapshotFrame({
+  viewport,
+  viewportSize,
+}: {
+  viewport: CanvasViewport;
+  viewportSize: ProjectCoverSnapshotViewportSize;
+}) {
+  const normalizedViewportSize =
+    normalizeProjectCoverViewportSize(viewportSize);
+  const renderScale =
+    viewport.scale > 0 && Number.isFinite(viewport.scale) ? viewport.scale : 1;
+  const frameScale = Math.max(
+    PROJECT_COVER_SNAPSHOT_SIZE.width / normalizedViewportSize.width,
+    PROJECT_COVER_SNAPSHOT_SIZE.height / normalizedViewportSize.height,
+  );
+  return {
+    viewportX: numberOrFallback(viewport.x, 0),
+    viewportY: numberOrFallback(viewport.y, 0),
+    renderScale,
+    frameScale,
+    offsetX:
+      (PROJECT_COVER_SNAPSHOT_SIZE.width -
+        normalizedViewportSize.width * frameScale) /
+      2,
+    offsetY:
+      (PROJECT_COVER_SNAPSHOT_SIZE.height -
+        normalizedViewportSize.height * frameScale) /
+      2,
+  };
+}
+
 function resolveProjectCoverPlacement(
   viewport: CanvasViewport,
+  viewportSize: ProjectCoverSnapshotViewportSize,
   layer: ProjectCoverDrawableLayer,
 ) {
-  const safeScale =
-    viewport.scale > 0 && Number.isFinite(viewport.scale) ? viewport.scale : 1;
-  const viewportCenterX =
-    (PROJECT_COVER_SNAPSHOT_VIEWPORT_SIZE.width / 2 - viewport.x) / safeScale;
-  const viewportCenterY =
-    (PROJECT_COVER_SNAPSHOT_VIEWPORT_SIZE.height / 2 - viewport.y) / safeScale;
-  const worldPreviewWidth =
-    PROJECT_COVER_SNAPSHOT_VIEWPORT_SIZE.width / safeScale;
-  const worldPreviewHeight =
-    PROJECT_COVER_SNAPSHOT_VIEWPORT_SIZE.height / safeScale;
-  const previewMinX = viewportCenterX - worldPreviewWidth / 2;
-  const previewMinY = viewportCenterY - worldPreviewHeight / 2;
-  const scale = Math.min(
-    PROJECT_COVER_SNAPSHOT_SIZE.width / worldPreviewWidth,
-    PROJECT_COVER_SNAPSHOT_SIZE.height / worldPreviewHeight,
-  );
-  const offsetX = -previewMinX * scale;
-  const offsetY = -previewMinY * scale;
+  const frame = resolveProjectCoverSnapshotFrame({ viewport, viewportSize });
   return {
-    x: offsetX + layer.x * scale,
-    y: offsetY + layer.y * scale,
-    width: layer.width * scale,
-    height: layer.height * scale,
+    x:
+      frame.offsetX +
+      (frame.viewportX + layer.x * frame.renderScale) * frame.frameScale,
+    y:
+      frame.offsetY +
+      (frame.viewportY + layer.y * frame.renderScale) * frame.frameScale,
+    width: layer.width * frame.renderScale * frame.frameScale,
+    height: layer.height * frame.renderScale * frame.frameScale,
   };
 }
 
@@ -153,9 +212,13 @@ function canvasToBlob(canvas: HTMLCanvasElement) {
 export async function createProjectCoverSnapshotBlob({
   layers,
   viewport,
+  viewportSize,
+  backgroundColor,
 }: {
   layers: readonly CanvasLayer[];
   viewport: CanvasViewport;
+  viewportSize: ProjectCoverSnapshotViewportSize;
+  backgroundColor: string;
 }) {
   if (typeof document === 'undefined') {
     return null;
@@ -171,13 +234,18 @@ export async function createProjectCoverSnapshotBlob({
   if (!context || typeof canvas.toBlob !== 'function') {
     return null;
   }
-  context.clearRect(0, 0, canvas.width, canvas.height);
+  context.fillStyle = normalizeProjectCoverBackgroundColor(backgroundColor);
+  context.fillRect(0, 0, canvas.width, canvas.height);
 
   let drawnLayerCount = 0;
   for (const layer of coverLayers) {
     try {
       const image = await loadProjectCoverImage(layer);
-      const placement = resolveProjectCoverPlacement(viewport, layer);
+      const placement = resolveProjectCoverPlacement(
+        viewport,
+        viewportSize,
+        layer,
+      );
       context.drawImage(
         image,
         placement.x,

src/components/image-editor/useImageCanvasProjectPersistence.test.tsx

@@ -118,6 +118,7 @@ function ProjectPersistenceHarness({
   const [projectRenameValue, setProjectRenameValue] = useState('');
   const layersRef = useRef(layers);
   const viewportRef = useRef(viewport);
+  const canvasViewportRef = useRef<HTMLDivElement | null>(null);
   const canvasGenerationDialogsRef = useRef(generationDialogs);
   const canvasBackgroundColorRef = useRef(canvasBackgroundColor);
   const selectedLayerRef = useRef<string | null>(null);
@@ -146,6 +147,7 @@ function ProjectPersistenceHarness({
     () => ({
       layersRef,
       viewportRef,
+      canvasViewportRef,
       canvasGenerationDialogsRef,
       canvasBackgroundColorRef,
     }),
@@ -949,6 +951,15 @@ describe('useImageCanvasProjectPersistence', () => {
     render(<ProjectPersistenceHarness />);
 
     expect(await screen.findByText('editor-project-default')).toBeTruthy();
+    await waitFor(() => {
+      expect(createProjectCoverSnapshotBlobMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          viewport: { x: 12, y: -8, scale: 0.5 },
+          viewportSize: { width: 900, height: 640 },
+          backgroundColor: DEFAULT_CANVAS_BACKGROUND_COLOR,
+        }),
+      );
+    });
     await waitFor(() => {
       expect(putEditorProjectCoverCacheMock).toHaveBeenCalledWith(
         expect.objectContaining({
@@ -1073,14 +1084,12 @@ describe('useImageCanvasProjectPersistence', () => {
   });
 
   it('does not serialize or write session cache while viewport interactions are active', async () => {
-    const sessionSetItemSpy = vi.spyOn(
-      Storage.prototype,
-      'setItem',
-    );
     render(<ProjectPersistenceHarness />);
 
     expect(await screen.findByText('editor-project-default')).toBeTruthy();
-    sessionSetItemSpy.mockClear();
+    const cachedBeforeInteraction = globalThis.sessionStorage.getItem(
+      EDITOR_PROJECT_RECENT_SESSION_CACHE_KEY,
+    );
     saveEditorProjectLayoutMock.mockClear();
     vi.useFakeTimers();
 
@@ -1097,7 +1106,11 @@ describe('useImageCanvasProjectPersistence', () => {
     });
 
     expect(saveEditorProjectLayoutMock).not.toHaveBeenCalled();
-    expect(sessionSetItemSpy).not.toHaveBeenCalled();
+    expect(
+      globalThis.sessionStorage.getItem(
+        EDITOR_PROJECT_RECENT_SESSION_CACHE_KEY,
+      ),
+    ).toBe(cachedBeforeInteraction);
 
     act(() => {
       screen.getByRole('button', { name: 'end viewport interaction' }).click();
@@ -1115,9 +1128,17 @@ describe('useImageCanvasProjectPersistence', () => {
         viewport: { x: 20, y: 10, scale: 1 },
       }),
     );
-    expect(sessionSetItemSpy).toHaveBeenCalled();
+    const cachedAfterInteraction = JSON.parse(
+      globalThis.sessionStorage.getItem(
+        EDITOR_PROJECT_RECENT_SESSION_CACHE_KEY,
+      ) ?? '{}',
+    ) as { project?: EditorProjectSnapshot };
+    expect(cachedAfterInteraction.project?.viewport).toEqual({
+      x: 20,
+      y: 10,
+      scale: 1,
+    });
     vi.useRealTimers();
-    sessionSetItemSpy.mockRestore();
   });
 
   it('does not create a project resource again for backend-persisted generated layers', async () => {

src/components/image-editor/useImageCanvasProjectPersistence.ts

@@ -22,6 +22,7 @@ import {
   canvasDisplayViewportToViewport,
   type CanvasLayerResourceMetadata,
   DEFAULT_CANVAS_BACKGROUND_COLOR,
+  DEFAULT_CANVAS_SIZE,
   hydrateLayer,
   isInlineEditorMediaSource,
   serializeCanvasLayout,
@@ -65,6 +66,7 @@ type CachedEditorProjectSnapshot = {
 type ImageCanvasProjectPersistenceRefs = {
   layersRef: RefObject<CanvasLayer[]>;
   viewportRef: RefObject<CanvasViewport>;
+  canvasViewportRef: RefObject<HTMLDivElement | null>;
   canvasGenerationDialogsRef: RefObject<CanvasGenerationDialogState[]>;
   canvasBackgroundColorRef: RefObject<string>;
 };
@@ -114,6 +116,21 @@ function isEditorProjectRevisionConflict(error: unknown) {
   return error instanceof ApiClientError && error.status === 409;
 }
 
+function resolveProjectCoverViewportSize(
+  viewportElement: HTMLDivElement | null,
+) {
+  const width = viewportElement?.clientWidth ?? 0;
+  const height = viewportElement?.clientHeight ?? 0;
+  return {
+    width:
+      width > 0 && Number.isFinite(width) ? width : DEFAULT_CANVAS_SIZE.width,
+    height:
+      height > 0 && Number.isFinite(height)
+        ? height
+        : DEFAULT_CANVAS_SIZE.height,
+  };
+}
+
 const EDITOR_PROJECT_LAYOUT_RETRYABLE_STATUS_CODES = new Set([
   408, 425, 429, 502, 503, 504,
 ]);
@@ -453,15 +470,23 @@ export function useImageCanvasProjectPersistence({
   const persistProjectCoverSnapshot = useCallback(
     (
       nextProjectId: string,
-      coverViewport: CanvasViewport,
+      coverDisplayViewport: CanvasViewport,
       coverLayers: readonly CanvasLayer[],
     ) => {
       if (!canAccessProtectedData) {
         return;
       }
+      const coverViewport =
+        canvasDisplayViewportToViewport(coverDisplayViewport);
+      const viewportSize = resolveProjectCoverViewportSize(
+        refs.canvasViewportRef.current,
+      );
+      const backgroundColor = refs.canvasBackgroundColorRef.current;
       const signature = buildProjectCoverSnapshotSignature({
         layers: coverLayers,
         viewport: coverViewport,
+        viewportSize,
+        backgroundColor,
       });
       if (!signature || coverSnapshotSignatureRef.current === signature) {
         return;
@@ -473,6 +498,8 @@ export function useImageCanvasProjectPersistence({
       void createProjectCoverSnapshotBlob({
         layers: coverLayers,
         viewport: coverViewport,
+        viewportSize,
+        backgroundColor,
       })
         .then(async (blob) => {
           if (!blob) {
@@ -530,7 +557,7 @@ export function useImageCanvasProjectPersistence({
           }
         });
     },
-    [canAccessProtectedData, openEditorLoginModal],
+    [canAccessProtectedData, openEditorLoginModal, refs],
   );
 
   const queueProjectLayoutSave = useCallback(