Update app.py

app.py

@@ -317,21 +317,19 @@ def handle_batch(workbook_path, fmt, w, h):
         tasks.append((code, url, dl_path, suf))
 
     # Download with tracking
-    futures = {}
+    future_to_task = {}
     with ThreadPoolExecutor(max_workers=min(32, CPU_CORES*2)) as ex:
-        futures = []
+        # submit each download job *and* remember its (code, suf)
         for code, url, dl_path, suf in tasks:
-            futures.append(ex.submit(
-            download_image_fast, url, dl_path, fail_log, code, suf
-            ))
-        for fut in as_completed(futures):
-            success = fut.result()
-        # failures logged inside download_image_fast already
+            fut = ex.submit(download_image_fast, url, dl_path, fail_log, code, suf)
+            future_to_task[fut] = (code, suf)
 
-            code, suf = futures[fut]
+        # as each future finishes, look up its metadata
+        for fut in as_completed(future_to_task):
+            success = fut.result()
+            code, suf = future_to_task[fut]
             if not success:
                 log_failure(fail_log, f"{code}{suf}: download failed")
-
     processed = []
     for code, url, dl_path, suf in tasks:
         if not os.path.exists(dl_path): continue