diff --git a/agents-docs/LESSONS.md b/agents-docs/LESSONS.md
index ca2f51e..506e8c5 100644
--- a/agents-docs/LESSONS.md
+++ b/agents-docs/LESSONS.md
@@ -102,6 +102,13 @@ Durable rules for AI agents working on this project. Read this file at session s
 - **Why:** `npm run test` only runs the toju-app Vitest suite — it doesn't cover the server, Electron, or website packages. ESLint (flat config in `eslint.config.js`) is the universal check across every package; type-style violations slip through tests and break Gitea Workflows for the next agent.
 - **Example:** `npm run lint && echo OK` — only claim done after seeing `OK`. For Electron type errors specifically, also confirm `npm run build:electron` succeeds (it invokes `tsc -p tsconfig.electron.json`).
 
+### Use blob URLs for inline attachment previews [attachments] [electron]
+
+- **Trigger:** receiving users see broken image icons or video players that never start, but "Download" saves a valid file.
+- **Rule:** never bind `attachment.objectUrl` to `file://` URLs for chat `<img>`, `<video>`, or `<audio>` — always create a `blob:` URL from the bytes on disk or in memory; keep `savedPath`/`filePath` for IPC download/open only.
+- **Why:** Electron runs with `webSecurity: true`, so renderer pages cannot load arbitrary `file://` app-data paths even when CSP allows `file:`; IPC download still works because it reads the path in the main process.
+- **Example:** `ensureInlineDisplayObjectUrl()` in `AttachmentPersistenceService`, and `URL.createObjectURL(blob)` in `finalizeTransferIfComplete` / `handleDiskFileChunk` instead of `getFileUrl(savedPath)`.
+
 ### Resolve Electron drag-and-drop file paths with webUtils [attachments] [electron]
 
 - **Trigger:** large videos play after drag-and-drop upload, but after restart the uploader sees a peer-download error even though they sent the file from disk.
diff --git a/toju-app/src/app/domains/attachment/application/services/attachment-persistence.service.ts b/toju-app/src/app/domains/attachment/application/services/attachment-persistence.service.ts
index 825a75e..51a560c 100644
--- a/toju-app/src/app/domains/attachment/application/services/attachment-persistence.service.ts
+++ b/toju-app/src/app/domains/attachment/application/services/attachment-persistence.service.ts
@@ -5,8 +5,8 @@ import { selectCurrentRoomName } from '../../../../store/rooms/rooms.selectors';
 import { DatabaseService } from '../../../../infrastructure/persistence';
 import { AttachmentStorageService } from '../../infrastructure/services/attachment-storage.service';
 import type { Attachment, AttachmentMeta } from '../../domain/models/attachment.model';
-import { MAX_AUTO_SAVE_SIZE_BYTES } from '../../domain/constants/attachment.constants';
 import { LEGACY_ATTACHMENTS_STORAGE_KEY } from '../../domain/constants/attachment-transfer.constants';
+import { isBlobObjectUrl, needsBlobObjectUrlForInlineDisplay } from '../../domain/logic/attachment-display-url.rules';
 import { mergeAttachmentLocalPaths } from '../../domain/logic/attachment-persistence.rules';
 import { AttachmentRuntimeStore } from './attachment-runtime.store';
 
@@ -113,7 +113,17 @@ export class AttachmentPersistenceService {
   }
 
   async tryRestoreAttachmentFromLocal(attachment: Attachment): Promise<boolean> {
-    if (attachment.available) {
+    const restored = await this.ensureInlineDisplayObjectUrl(attachment);
+
+    if (restored) {
+      attachment.requestError = undefined;
+    }
+
+    return restored;
+  }
+
+  async ensureInlineDisplayObjectUrl(attachment: Attachment): Promise<boolean> {
+    if (!needsBlobObjectUrlForInlineDisplay(attachment.objectUrl)) {
       return true;
     }
 
@@ -134,19 +144,14 @@ export class AttachmentPersistenceService {
       return false;
     }
 
-    if (await this.restoreMediaAttachmentFromFileUrl(attachment, diskPath)) {
-      attachment.requestError = undefined;
-      return true;
-    }
-
     const base64 = await this.attachmentStorage.readFile(diskPath);
 
     if (!base64) {
       return false;
     }
 
+    this.revokeAttachmentObjectUrl(attachment);
     this.restoreAttachmentFromDisk(attachment, base64);
-    attachment.requestError = undefined;
     return true;
   }
 
@@ -291,24 +296,14 @@ export class AttachmentPersistenceService {
     );
   }
 
-  private async restoreMediaAttachmentFromFileUrl(attachment: Attachment, filePath: string): Promise<boolean> {
-    if (!this.isPlayableMedia(attachment)) {
-      return false;
+  private revokeAttachmentObjectUrl(attachment: Attachment): void {
+    if (!attachment.objectUrl || !isBlobObjectUrl(attachment.objectUrl)) {
+      return;
     }
 
-    const fileUrl = await this.attachmentStorage.getFileUrl(filePath);
-
-    if (!fileUrl) {
-      return false;
-    }
-
-    attachment.objectUrl = fileUrl;
-    attachment.available = true;
-    return true;
-  }
-
-  private isPlayableMedia(attachment: Pick<Attachment, 'mime'>): boolean {
-    return attachment.mime.startsWith('video/') || attachment.mime.startsWith('audio/');
+    try {
+      URL.revokeObjectURL(attachment.objectUrl);
+    } catch { /* ignore */ }
   }
 
   private async getRetainedSavedPathsForOtherMessages(messageId: string): Promise<Set<string>> {
diff --git a/toju-app/src/app/domains/attachment/application/services/attachment-transfer.service.ts b/toju-app/src/app/domains/attachment/application/services/attachment-transfer.service.ts
index 7b666e0..4a09b11 100644
--- a/toju-app/src/app/domains/attachment/application/services/attachment-transfer.service.ts
+++ b/toju-app/src/app/domains/attachment/application/services/attachment-transfer.service.ts
@@ -148,6 +148,7 @@ export class AttachmentTransferService {
       attachment.requestError = isUploader
         ? UPLOADER_LOCAL_FILE_MISSING_ERROR
         : NO_CONNECTED_PEERS_REQUEST_ERROR;
+
       this.runtimeStore.touch();
       console.warn('[Attachments] No connected peers to request file from');
       return;
@@ -236,8 +237,8 @@ export class AttachmentTransferService {
         attachment,
         attachment.filePath,
         this.attachmentStorage.canCopyFiles()
-      )) {
-        const savedPath = await this.persistence.persistUploadCopyFromSourcePath(attachment, attachment.filePath!);
+      ) && attachment.filePath) {
+        const savedPath = await this.persistence.persistUploadCopyFromSourcePath(attachment, attachment.filePath);
 
         if (savedPath) {
           const fileUrl = await this.attachmentStorage.getFileUrl(savedPath);
@@ -659,20 +660,11 @@ export class AttachmentTransferService {
     this.runtimeStore.deleteChunkCount(assemblyKey);
 
     if (shouldPersistDownloadedAttachment(attachment)) {
-      const diskPath = await this.persistence.saveFileToDisk(attachment, blob);
-      const fileUrl = diskPath && this.isPlayableMedia(attachment)
-        ? await this.attachmentStorage.getFileUrl(diskPath)
-        : null;
-
-      if (fileUrl) {
-        attachment.objectUrl = fileUrl;
-      } else {
-        attachment.objectUrl = URL.createObjectURL(blob);
-      }
-    } else {
-      attachment.objectUrl = URL.createObjectURL(blob);
+      await this.persistence.saveFileToDisk(attachment, blob);
     }
 
+    attachment.objectUrl = URL.createObjectURL(blob);
+
     attachment.available = true;
     this.runtimeStore.touch();
     void this.persistence.persistAttachmentMeta(attachment);
@@ -745,14 +737,14 @@ export class AttachmentTransferService {
       return;
     }
 
-    const fileUrl = await this.attachmentStorage.getFileUrl(assembly.path);
+    attachment.savedPath = assembly.path;
 
-    if (!fileUrl) {
+    const restoredForDisplay = await this.persistence.ensureInlineDisplayObjectUrl(attachment);
+
+    if (!restoredForDisplay) {
       throw new Error('Could not open completed media download from disk.');
     }
 
-    attachment.savedPath = assembly.path;
-    attachment.objectUrl = fileUrl;
     attachment.available = true;
     this.diskReceiveAssemblies.delete(assemblyKey);
     this.runtimeStore.touch();
diff --git a/toju-app/src/app/domains/attachment/domain/logic/attachment-display-url.rules.spec.ts b/toju-app/src/app/domains/attachment/domain/logic/attachment-display-url.rules.spec.ts
new file mode 100644
index 0000000..ebc4094
--- /dev/null
+++ b/toju-app/src/app/domains/attachment/domain/logic/attachment-display-url.rules.spec.ts
@@ -0,0 +1,20 @@
+import {
+  isBlobObjectUrl,
+  isFileProtocolObjectUrl,
+  needsBlobObjectUrlForInlineDisplay
+} from './attachment-display-url.rules';
+
+describe('attachment display url rules', () => {
+  it('detects blob and file protocol urls', () => {
+    expect(isBlobObjectUrl('blob:http://localhost/abc')).toBe(true);
+    expect(isBlobObjectUrl('file:///tmp/video.mp4')).toBe(false);
+    expect(isFileProtocolObjectUrl('file:///tmp/video.mp4')).toBe(true);
+    expect(isFileProtocolObjectUrl('blob:http://localhost/abc')).toBe(false);
+  });
+
+  it('requires blob urls for inline display when missing or file protocol', () => {
+    expect(needsBlobObjectUrlForInlineDisplay(undefined)).toBe(true);
+    expect(needsBlobObjectUrlForInlineDisplay('file:///appdata/image.png')).toBe(true);
+    expect(needsBlobObjectUrlForInlineDisplay('blob:http://localhost/abc')).toBe(false);
+  });
+});
diff --git a/toju-app/src/app/domains/attachment/domain/logic/attachment-display-url.rules.ts b/toju-app/src/app/domains/attachment/domain/logic/attachment-display-url.rules.ts
new file mode 100644
index 0000000..ce927bc
--- /dev/null
+++ b/toju-app/src/app/domains/attachment/domain/logic/attachment-display-url.rules.ts
@@ -0,0 +1,11 @@
+export function isBlobObjectUrl(url: string): boolean {
+  return url.startsWith('blob:');
+}
+
+export function isFileProtocolObjectUrl(url: string): boolean {
+  return url.startsWith('file:');
+}
+
+export function needsBlobObjectUrlForInlineDisplay(objectUrl?: string): boolean {
+  return !objectUrl || isFileProtocolObjectUrl(objectUrl);
+}