diff --git a/client/src/features/reader/audiobook/__tests__/AudiobookReaderView.spec.ts b/client/src/features/reader/audiobook/__tests__/AudiobookReaderView.spec.ts
index 5a6fc8010..57dc9211b 100644
--- a/client/src/features/reader/audiobook/__tests__/AudiobookReaderView.spec.ts
+++ b/client/src/features/reader/audiobook/__tests__/AudiobookReaderView.spec.ts
@@ -196,7 +196,7 @@ function audiobookManifest(): AudiobookManifest {
     schemaVersion: 2,
     revision: 'manifest-rev-1',
     book: { id: BOOK_ID, title: 'The Long Orbit', authors: ['Ada Vance'], narrators: ['Sam Reed'], hasCover: true },
-    assets: [{ assetId: 'asset-1', sequence: 0, format: 'm4b', durationMs: 3_600_000, sizeBytes: 4096, etag: 'etag-1' }],
+    assets: [{ assetId: 'asset-1', fileId: FILE_ID, sequence: 0, format: 'm4b', durationMs: 3_600_000, sizeBytes: 4096, etag: 'etag-1' }],
     chapters: [{ id: 'chapter-1', title: 'Launch', assetId: 'asset-1', sequence: 0, startMs: 0, endMs: 3_600_000, assetOffsetMs: 0 }],
     totalDurationMs: 3_600_000,
   }
diff --git a/packages/types/src/audiobook.ts b/packages/types/src/audiobook.ts
index bfce4714f..6e3a562ea 100644
--- a/packages/types/src/audiobook.ts
+++ b/packages/types/src/audiobook.ts
@@ -8,6 +8,8 @@ export const AUDIOBOOK_MANIFEST_VERSION = 2 as const;
 
 export interface AudiobookManifestAsset {
   assetId: string;
+  /** The book file id, matching `BookDetail.files[].id`, so clients can pair an asset with its file. */
+  fileId: number;
   sequence: number;
   format: string;
   durationMs: number | null;
diff --git a/server/src/modules/audiobook/audiobook.service.test.ts b/server/src/modules/audiobook/audiobook.service.test.ts
index a8ec7fec1..70272b8ca 100644
--- a/server/src/modules/audiobook/audiobook.service.test.ts
+++ b/server/src/modules/audiobook/audiobook.service.test.ts
@@ -102,8 +102,8 @@ describe('AudiobookService', () => {
     expect(manifest.schemaVersion).toBe(AUDIOBOOK_MANIFEST_VERSION);
     expect(manifest.revision).toMatch(/^[0-9a-f]{64}$/);
     expect(manifest.assets).toEqual([
-      expect.objectContaining({ assetId: `aud_${FIRST_PUBLIC_ID}`, sequence: 0, durationMs: 10_125 }),
-      expect.objectContaining({ assetId: `aud_${SECOND_PUBLIC_ID}`, sequence: 1, durationMs: 20_000 }),
+      expect.objectContaining({ assetId: `aud_${FIRST_PUBLIC_ID}`, fileId: 11, sequence: 0, durationMs: 10_125 }),
+      expect.objectContaining({ assetId: `aud_${SECOND_PUBLIC_ID}`, fileId: 12, sequence: 1, durationMs: 20_000 }),
     ]);
     expect(manifest.chapters).toEqual([
       expect.objectContaining({ sequence: 0, startMs: 0, endMs: 10_125, assetId: `aud_${FIRST_PUBLIC_ID}`, assetOffsetMs: 0 }),
@@ -111,6 +111,18 @@ describe('AudiobookService', () => {
     ]);
   });
 
+  it('keeps the manifest revision independent of the file ids it exposes', async () => {
+    const { service, repo } = makeFixture();
+    const before = await service.getManifest(30, makeUser());
+    const files = await repo.findAudioFiles();
+    repo.findAudioFiles.mockResolvedValue(files.map((file) => ({ ...file, id: file.id + 900 })));
+
+    const after = await service.getManifest(30, makeUser());
+
+    expect(after.assets.map((asset) => asset.fileId)).toEqual([911, 912]);
+    expect(after.revision).toBe(before.revision);
+  });
+
   it('derives percentage and creates revision one from a matching manifest write', async () => {
     const { service, repo, bookService } = makeFixture();
     const manifest = await service.getManifest(30, makeUser());
diff --git a/server/src/modules/audiobook/audiobook.service.ts b/server/src/modules/audiobook/audiobook.service.ts
index 5eb3b67e8..5547f7693 100644
--- a/server/src/modules/audiobook/audiobook.service.ts
+++ b/server/src/modules/audiobook/audiobook.service.ts
@@ -212,6 +212,7 @@ export class AudiobookService {
       .digest('hex');
     const assets = files.map<AudiobookManifestAsset>((file, sequence) => ({
       assetId: this.assetId(file.publicId),
+      fileId: file.id,
       sequence,
       format: file.format!,
       durationMs: file.durationSeconds === null ? null : Math.round(file.durationSeconds * 1000),