diff --git a/src/background/index.ts b/src/background/index.ts
index 2f5cb92..b033080 100644
--- a/src/background/index.ts
+++ b/src/background/index.ts
@@ -1,5 +1,5 @@
 import { Logger } from '../shared/logger';
-import { base64ToBlob } from '../shared/binary';
+import { base64ToBlob, blobToBase64 } from '../shared/binary';
 import type {
   Message,
   TransferredVideoSegment,
@@ -391,14 +391,12 @@ async function downloadArchive(archiveBlob: Blob) {
 
   logger.log(`Downloading archive: ${filename} (${archiveBlob.size} bytes)`);
 
-  // Конвертируем Blob в Data URL (работает в Service Worker)
-  const arrayBuffer = await archiveBlob.arrayBuffer();
-  const uint8Array = new Uint8Array(arrayBuffer);
-  let binary = '';
-  for (let i = 0; i < uint8Array.length; i++) {
-    binary += String.fromCharCode(uint8Array[i]);
-  }
-  const base64 = btoa(binary);
+  // WR-08 fix: delegate to the shared `blobToBase64` helper instead of
+  // re-implementing the same per-byte concat + btoa inline. Keeps the
+  // wire-format encoding single-source-of-truth (also used by the
+  // offscreen↔SW port; see src/shared/binary.ts) and ensures any future
+  // performance work (chunked apply, etc.) propagates to both call sites.
+  const base64 = await blobToBase64(archiveBlob);
   const url = `data:application/zip;base64,${base64}`;
 
   await chrome.downloads.download({