diff --git a/lib/updater.js b/lib/updater.js
index f935a4e..ac38810 100644
--- a/lib/updater.js
+++ b/lib/updater.js
@@ -179,10 +179,27 @@ async function installUpdate(onProgress) {
     let downloadedBytes = 0;
     const chunks = [];
 
+    const DOWNLOAD_STALL_MS = 45000;
+    let stallTimer = null;
     const reader = res.body.getReader();
     while (true) {
       if (signal.aborted) throw new Error('Abgebrochen');
-      const { done, value } = await reader.read();
+      let chunk;
+      try {
+        chunk = await Promise.race([
+          reader.read(),
+          new Promise((_, reject) => { stallTimer = setTimeout(() => reject(new Error('__STALL__')), DOWNLOAD_STALL_MS); })
+        ]);
+      } catch (e) {
+        if (e && e.message === '__STALL__') {
+          try { activeAbort.abort(); } catch {}
+          throw new Error('Download hängt — seit 45 s keine Daten (Netzwerk/Server überlastet). Bitte laufende Uploads stoppen und erneut versuchen.');
+        }
+        throw e;
+      } finally {
+        if (stallTimer) { clearTimeout(stallTimer); stallTimer = null; }
+      }
+      const { done, value } = chunk;
       if (done) break;
       chunks.push(value);
       downloadedBytes += value.length;
diff --git a/main.js b/main.js
index ea5308e..1add692 100644
--- a/main.js
+++ b/main.js
@@ -2294,6 +2294,7 @@ ipcMain.handle('app:check-updates', async () => {
 });
 
 ipcMain.handle('app:install-update', () => {
+  try { if (uploadManager) uploadManager.cancel(); } catch {}
   installUpdate((progress) => {
     safeSend('app:update-progress', progress);
   }).catch((err) => {