diff --git a/static/messages.js b/static/messages.js
index cc3f0202..c69efea4 100644
--- a/static/messages.js
+++ b/static/messages.js
@@ -4202,6 +4202,9 @@ function stopApprovalPolling() {
 let _sessionEventSource = null;
 let _sessionStreamSessionId = null;
 let _sessionStreamReconnectTimer = null;
+// Holds the session id across a hidden-tab close so the visibility handler can
+// reopen the per-session SSE on re-show (stopSessionStream nulls _sessionStreamSessionId).
+let _sessionStreamHiddenSid = null;
 
 function startSessionStream(sid) {
   if (!sid) return;
@@ -4210,13 +4213,19 @@ function startSessionStream(sid) {
   if (_sessionStreamSessionId === sid && _sessionEventSource) return;
   stopSessionStream();
   _sessionStreamSessionId = sid;
-  // Visibility hook (install once) — mirror ensureSessionEventsSSE() pattern
+  // Visibility hook (install once) — mirror ensureSessionEventsSSE() pattern.
+  // Capture the active session id into a dedicated var BEFORE closing, because
+  // stopSessionStream() nulls _sessionStreamSessionId — so the reopen path can't
+  // rely on it (that was the bug: the stream never reopened on tab re-show).
   if (typeof document !== 'undefined' && !document._hermesSessionStreamVisibilityHook) {
     document.addEventListener('visibilitychange', () => {
       if (document.hidden) {
+        _sessionStreamHiddenSid = _sessionStreamSessionId;
         stopSessionStream();
-      } else if (_sessionStreamSessionId) {
-        void startSessionStream(_sessionStreamSessionId);
+      } else if (_sessionStreamHiddenSid) {
+        const resumeSid = _sessionStreamHiddenSid;
+        _sessionStreamHiddenSid = null;
+        void startSessionStream(resumeSid);
       }
     });
     document._hermesSessionStreamVisibilityHook = true;