--- a/frontend/opfs.js
+++ b/frontend/opfs.js
@@ -108,6 +108,19 @@
       }
     },
 
+    // Bytes [offset, offset+length) of a saved video — answers the server's
+    // P2P range challenges (p2p-client.js). null when the file is missing.
+    async readRange(videoId, offset, length) {
+      try {
+        const found = await findHandle(videoId);
+        if (!found) return null;
+        const file = await found[0].getFile();
+        return new Uint8Array(await file.slice(offset, offset + length).arrayBuffer());
+      } catch {
+        return null;
+      }
+    },
+
     revokeUrl(url) {
       if (url && _blobUrls.has(url)) {
         URL.revokeObjectURL(url);