diff --git a/src/components/game-distribution/GamePublishPage.tsx b/src/components/game-distribution/GamePublishPage.tsx
index af46eced9..139ea958d 100644
--- a/src/components/game-distribution/GamePublishPage.tsx
+++ b/src/components/game-distribution/GamePublishPage.tsx
@@ -29,6 +29,7 @@ import {
   resolveGameInputModes,
 } from './gameMetadataOptions';
 import {
+  buildGamePublishMediaSubmission,
   type GamePublishImage,
   revokeGamePublishImagePreview,
 } from './gamePublishAssets';
@@ -312,19 +313,19 @@ export function GamePublishPage({
    * 组装提交给服务端的资料 DTO。
    *
    * 媒体槽位只描述来源：本地新图写 `null`（由对应的二进制 part 补位），沿用线上图写 objectKey；
-   * 原始字节另由 `buildPublishMediaParts` 作为 multipart part 提交。
+   * 原始字节另由 `buildPublishMediaParts` 作为 multipart part 提交。两者共用
+   * `buildGamePublishMediaSubmission`，槽位映射与 part 组装不会各改各的。
    */
   function buildPublishGameMetadata() {
+    const media = buildGamePublishMediaSubmission(coverImage, screenshotImages);
     return {
       title: title.trim(),
       summary: summary.trim(),
       description: description.trim() || summary.trim(),
       category,
       tags: parseGameTagsInput(tagsInput),
-      coverObjectKey: coverImage?.file ? null : (coverImage?.objectKey ?? null),
-      screenshots: screenshotImages.map((image) =>
-        image.file ? null : (image.objectKey ?? null),
-      ),
+      coverObjectKey: media.coverObjectKey,
+      screenshots: media.screenshots,
       deviceSupport,
       inputModes: resolveGameInputModes(deviceSupport),
       orientation,
@@ -332,10 +333,7 @@ export function GamePublishPage({
   }
 
   function buildPublishMediaParts() {
-    return {
-      cover: coverImage?.file ?? null,
-      screenshots: screenshotImages.map((image) => image.file ?? null),
-    };
+    return buildGamePublishMediaSubmission(coverImage, screenshotImages).parts;
   }
 
   /** 是否已有封面：本地新图或沿用线上图都算。 */
diff --git a/src/components/game-distribution/GameWorkMetadataEditor.tsx b/src/components/game-distribution/GameWorkMetadataEditor.tsx
index d0b426266..9bfdad4e6 100644
--- a/src/components/game-distribution/GameWorkMetadataEditor.tsx
+++ b/src/components/game-distribution/GameWorkMetadataEditor.tsx
@@ -24,6 +24,7 @@ import {
   resolveGameInputModes,
 } from './gameMetadataOptions';
 import {
+  buildGamePublishMediaSubmission,
   type GamePublishImage,
   revokeGamePublishImagePreview,
 } from './gamePublishAssets';
@@ -176,10 +177,12 @@ export function GameWorkMetadataEditor({
     }
     const saveKey = saveKeyRef.current ?? createMetadataKey(game.id);
     saveKeyRef.current = saveKey;
-    const media = {
-      cover: coverImage?.file ?? null,
-      screenshots: screenshotImages.map((image) => image.file ?? null),
-    };
+    // 槽位映射与二进制 part 同源，和发布页共用同一份合成规则。
+    const submission = buildGamePublishMediaSubmission(
+      coverImage,
+      screenshotImages,
+    );
+    const media = submission.parts;
     const payload: GameDistributionUpdateGameMetadataRequest = {
       expectedPublicationRevision: game.publicationRevision,
       title: title.trim(),
@@ -187,12 +190,8 @@ export function GameWorkMetadataEditor({
       description: description.trim() || summary.trim(),
       category,
       tags: parseGameTagsInput(tagsInput),
-      coverObjectKey: coverImage?.file
-        ? null
-        : (coverImage?.objectKey?.trim() ?? null),
-      screenshots: screenshotImages.map((image) =>
-        image.file ? null : (image.objectKey?.trim() ?? null),
-      ),
+      coverObjectKey: submission.coverObjectKey,
+      screenshots: submission.screenshots,
       deviceSupport,
       inputModes: resolveGameInputModes(deviceSupport),
       orientation,
diff --git a/src/components/game-distribution/gamePublishAssets.test.ts b/src/components/game-distribution/gamePublishAssets.test.ts
index 77b636ce4..c4c867ff7 100644
--- a/src/components/game-distribution/gamePublishAssets.test.ts
+++ b/src/components/game-distribution/gamePublishAssets.test.ts
@@ -2,7 +2,10 @@
 
 import { describe, expect, it } from 'vitest';
 
-import { createLocalGamePublishImage } from './gamePublishAssets';
+import {
+  buildGamePublishMediaSubmission,
+  createLocalGamePublishImage,
+} from './gamePublishAssets';
 
 describe('createLocalGamePublishImage', () => {
   it('本地新选图各自带稳定且不同的 id', () => {
@@ -21,3 +24,43 @@ describe('createLocalGamePublishImage', () => {
     expect(first.id).not.toBe(second.id);
   });
 });
+
+describe('buildGamePublishMediaSubmission', () => {
+  it('本地新图只进 parts、槽位留 null，沿用线上图反之', () => {
+    const localCover = createLocalGamePublishImage(
+      new File(['a'], 'cover.png', { type: 'image/png' }),
+      'cover',
+    );
+    const onlineCover = {
+      id: 'online-cover',
+      objectKey: '  agc/cover.png  ',
+      src: 'https://cdn/cover.png',
+      name: '线上封面',
+    };
+    const localShot = createLocalGamePublishImage(
+      new File(['b'], 'shot.png', { type: 'image/png' }),
+      'screenshot',
+    );
+    const onlineShot = {
+      id: 'online-shot',
+      objectKey: '   ',
+      src: '',
+      name: '截图 1',
+    };
+
+    const submission = buildGamePublishMediaSubmission(onlineCover, [
+      localShot,
+      onlineShot,
+    ]);
+
+    // 槽位与 part 必须同源：封面沿用时 objectKey 去空白，本地截图占 null 槽位。
+    expect(submission.coverObjectKey).toBe('agc/cover.png');
+    expect(submission.parts.cover).toBeNull();
+    expect(submission.screenshots).toEqual([null, null]);
+    expect(submission.parts.screenshots).toEqual([localShot.file, null]);
+
+    const localSubmission = buildGamePublishMediaSubmission(localCover, []);
+    expect(localSubmission.coverObjectKey).toBeNull();
+    expect(localSubmission.parts.cover).toBe(localCover.file);
+  });
+});
diff --git a/src/components/game-distribution/gamePublishAssets.ts b/src/components/game-distribution/gamePublishAssets.ts
index 6d08da5ab..831252f81 100644
--- a/src/components/game-distribution/gamePublishAssets.ts
+++ b/src/components/game-distribution/gamePublishAssets.ts
@@ -99,6 +99,40 @@ export function createLocalGamePublishImage(
   };
 }
 
+/** 一次发布/编辑提交里的媒体：metadata 槽位与随请求提交的二进制 part。 */
+export type GamePublishMediaSubmission = {
+  /** 沿用线上封面时的 objectKey；本次带本地新封面时为 `null`。 */
+  coverObjectKey: string | null;
+  /** 与最终截图顺序一一对应：`string` 沿用线上，`null` 表示消费对应的本地 `parts`。 */
+  screenshots: (string | null)[];
+  parts: {
+    cover: File | null;
+    screenshots: (File | null)[];
+  };
+};
+
+/**
+ * 把表单里的封面/截图列表合成一份提交：metadata 槽位与 multipart part 同源。
+ *
+ * 「本地新图 / 沿用线上」是二选一：有 `file` 就归到 `parts` 并把槽位置 `null`，否则槽位取
+ * 去空白后的 `objectKey`。发布与编辑两条链路共用这一份，避免槽位映射或 part 组装各改各的。
+ */
+export function buildGamePublishMediaSubmission(
+  cover: GamePublishImage | null,
+  screenshots: GamePublishImage[],
+): GamePublishMediaSubmission {
+  const objectKeyOf = (image: GamePublishImage | null | undefined) =>
+    image?.file ? null : image?.objectKey?.trim() || null;
+  return {
+    coverObjectKey: objectKeyOf(cover),
+    screenshots: screenshots.map(objectKeyOf),
+    parts: {
+      cover: cover?.file ?? null,
+      screenshots: screenshots.map((image) => image.file ?? null),
+    },
+  };
+}
+
 /** 释放本地预览的 blob URL；远程签名地址与空地址直接忽略。 */
 export function revokeGamePublishImagePreview(
   image: GamePublishImage | null | undefined,