diff --git a/diagnostic/server.js b/diagnostic/server.js
index 7719b75..b51d2cd 100644
--- a/diagnostic/server.js
+++ b/diagnostic/server.js
@@ -1506,7 +1506,12 @@ const server = http.createServer((req, res) => {
           log("error", "server", `zip exit ${code}: ${stderr.slice(0, 200)}`);
         }
       });
-      req.on("close", () => { if (!zip.killed) zip.kill("SIGTERM"); });
+      // SIGTERM an zip nur wenn der Client wirklich disconnected
+      // (res.close vor res.end). req.on("close") feuert auch wenn
+      // der Request-Body durch ist — das wuerde zip vorzeitig killen.
+      res.on("close", () => {
+        if (!res.writableEnded && !zip.killed) zip.kill("SIGTERM");
+      });
     });
     return;
   } else if (req.url === "/api/files-delete-batch" && req.method === "POST") {