fix

node-api/src/sse.js

@@ -6,7 +6,10 @@ const requests = [];
 export function registerSse(req, res, initialStatus = {}) {
   res.setHeader('Content-Type', 'text/event-stream');
   res.setHeader('Cache-Control', 'no-cache');
+  res.setHeader('Cache-Control', 'no-transform');
   res.setHeader('Connection', 'keep-alive');
+  // Disable proxy buffering in Nginx
+  res.setHeader('X-Accel-Buffering', 'no');
   res.flushHeaders?.();
   res.write(`event: hello\n`);
   res.write(`data: {"ok":true}\n\n`);
@@ -15,7 +18,15 @@ export function registerSse(req, res, initialStatus = {}) {
     res.write(`data: ${JSON.stringify(initialStatus)}\n\n`);
   }
   sseClients.add(res);
-  req.on('close', () => sseClients.delete(res));
+  // Heartbeat to keep proxies/load balancers from timing out idle SSE
+  // Send a comment line every 20s
+  const hb = setInterval(() => {
+    try { res.write(`: ping\n\n`); } catch { /* ignore */ }
+  }, 20000);
+  req.on('close', () => {
+    clearInterval(hb);
+    sseClients.delete(res);
+  });
 }
 
 export function pushRequest(rec) {
@@ -45,4 +56,3 @@ export function clearRequests() {
 export function getRecentRequests() {
   return requests.slice(-MAX_REQUESTS);
 }
-