Fix: Handle mobile UI disconnects during LLM query via SSE keep-alives and UI alerts

app.py

@@ -870,7 +870,12 @@ def query():
         _llm_query_queue.put((_run, ()))
 
         while True:
-            event = q_events.get()
+            try:
+                event = q_events.get(timeout=10)
+            except queue.Empty:
+                yield ": keep-alive\n\n"
+                continue
+
             if "error" in event:
                 yield f"data: {json.dumps({'error': event['error']})}\n\n"
                 break

static/app.js

@@ -1005,15 +1005,22 @@ async function submitQuery() {
   } catch(err) {
     diag.error('Query error:', err);
     stopTimer();
+    
+    // Check if the browser recently suspended the tab (common on mobile)
+    let errorMsg = err.message;
+    if (document.hidden || document.visibilityState === 'hidden') {
+      errorMsg = "Connection lost because the app was moved to the background. Please keep the app open during analysis to prevent the network from dropping.";
+    }
+
     if (currentMsId) {
       const el = $(currentMsId);
       if (el) el.querySelector('.milestone-dot').className = 'milestone-dot failed';
     }
-    addChatMsg(`❌ ${escHtml(err.message)}`, 'assistant');
+    addChatMsg(`❌ ${escHtml(errorMsg)}`, 'assistant');
     outputContainer.innerHTML = `<div class="output-placeholder" style="color:var(--red)">
-      <div class="ph-icon">⚠️</div><div>${escHtml(err.message)}</div>
+      <div class="ph-icon">⚠️</div><div>${escHtml(errorMsg)}</div>
     </div>`;
-    notify(err.message, 'error', 8000);
+    notify(errorMsg, 'error', 8000);
   } finally {
     state.isQuerying = false;
     sendBtn.disabled = false;