diff --git a/frontend/src/lib/offline/DownloadManager.ts b/frontend/src/lib/offline/DownloadManager.ts
index 2b5d697..02da5a8 100644
--- a/frontend/src/lib/offline/DownloadManager.ts
+++ b/frontend/src/lib/offline/DownloadManager.ts
@@ -242,7 +242,8 @@ class DownloadManagerClass {
       const job = this.queue.shift();
       if (!job) break;
 
-      this.activeDownloads.set(job.url, job);
+      // Use storageKey as Map key (stable) instead of url (can change on fallback)
+      this.activeDownloads.set(job.storageKey, job);
       this.downloadAsset(job);
     }
 
@@ -466,7 +467,7 @@ class DownloadManagerClass {
         job.reject?.(error instanceof Error ? error : new Error(errorMessage));
       }
     } finally {
-      this.activeDownloads.delete(job.url);
+      this.activeDownloads.delete(job.storageKey);
       downloadEventBus.emitQueueUpdate();
       this.processQueue();
     }
@@ -507,12 +508,12 @@ class DownloadManagerClass {
    * Cancel a specific download
    */
   cancelJob(jobId: string): void {
-    // Check active downloads
+    // Check active downloads (keyed by storageKey)
     const entries = Array.from(this.activeDownloads.entries());
-    for (const [url, job] of entries) {
+    for (const [storageKey, job] of entries) {
       if (job.id === jobId) {
         job.abortController?.abort();
-        this.activeDownloads.delete(url);
+        this.activeDownloads.delete(storageKey);
         OfflineDbManager.removeFromQueue(jobId);
         downloadEventBus.emitQueueUpdate();
         return;
@@ -532,12 +533,12 @@ class DownloadManagerClass {
    * Cancel all downloads for a project
    */
   cancelProjectDownloads(projectId: string): void {
-    // Cancel active downloads
+    // Cancel active downloads (keyed by storageKey)
     const entries = Array.from(this.activeDownloads.entries());
-    for (const [url, job] of entries) {
+    for (const [storageKey, job] of entries) {
       if (job.projectId === projectId) {
         job.abortController?.abort();
-        this.activeDownloads.delete(url);
+        this.activeDownloads.delete(storageKey);
       }
     }