fix(socketio): register /chat namespace handler to fix real-time message delivery

The /chat namespace had no server-side connect handler registered. With
python-socketio 5.x (always_connect=False), client connections to
unregistered namespaces are silently rejected. This caused all SocketIO
events (new_message, ack, echo) to never reach the frontend — messages
only appeared via the 60s polling fallback.

Fixes:
- Add @socketio.on('connect', namespace='/chat') handler in main.py
- Add optimistic message append: sent messages appear instantly before
  API round-trip (eliminates 3-4s serial command delay)
- Skip own-message SocketIO events to prevent duplicates
- Add connect_error handler for frontend debugging
- Bump SW cache to v6

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/device_manager.py

@@ -388,6 +388,7 @@ class DeviceManager:
                     'timestamp': ts,
                     'id': msg_id,
                 }, namespace='/chat')
+                logger.debug(f"SocketIO emitted new_message for ch{channel_idx} msg #{msg_id}")
 
         except Exception as e:
             logger.error(f"Error handling channel message: {e}")

app/main.py

@@ -121,6 +121,21 @@ def create_app():
     return app
 
 
+# ============================================================
+# WebSocket handlers for Chat (real-time message push)
+# ============================================================
+
+@socketio.on('connect', namespace='/chat')
+def handle_chat_connect():
+    """Handle chat WebSocket connection — required for /chat namespace to accept clients."""
+    logger.info("Chat WebSocket client connected")
+
+
+@socketio.on('disconnect', namespace='/chat')
+def handle_chat_disconnect():
+    logger.debug("Chat WebSocket client disconnected")
+
+
 # ============================================================
 # WebSocket handlers for Console
 # ============================================================

app/static/js/app.js

@@ -397,6 +397,10 @@ function connectChatSocket() {
         console.log('SocketIO connected to /chat');
     });
 
+    chatSocket.on('connect_error', (err) => {
+        console.error('SocketIO /chat connect error:', err.message);
+    });
+
     // Real-time new channel message
     chatSocket.on('new_message', (data) => {
         // Filter blocked contacts in real-time
@@ -410,6 +414,8 @@ function connectChatSocket() {
                 updateUnreadBadges();
                 checkAndNotify();
             } else if (!currentArchiveDate) {
+                // Skip own messages — already appended optimistically on send
+                if (data.is_own) return;
                 // Current channel and live view — append message directly (no full reload)
                 appendMessageFromSocket(data);
             }
@@ -1063,6 +1069,19 @@ async function sendMessage() {
     const sendBtn = document.getElementById('sendBtn');
     sendBtn.disabled = true;
 
+    // Optimistic append: show sent message immediately before API round-trip
+    input.value = '';
+    updateCharCounter();
+    const optimisticId = '_pending_' + Date.now();
+    appendMessageFromSocket({
+        id: optimisticId,
+        sender: window.MC_CONFIG?.deviceName || 'Me',
+        content: text,
+        timestamp: Math.floor(Date.now() / 1000),
+        is_own: true,
+        channel_idx: currentChannelIdx,
+    });
+
     try {
         const response = await fetch('/api/messages', {
             method: 'POST',
@@ -1078,12 +1097,9 @@ async function sendMessage() {
         const data = await response.json();
 
         if (data.success) {
-            input.value = '';
-            updateCharCounter();
             showNotification('Message sent', 'success');
 
-            // Message will appear via SocketIO 'new_message' event (no reload needed).
-            // Schedule one deferred reload to pick up echo data (echoes arrive within 5-30s).
+            // Schedule deferred reload to pick up echo data + replace optimistic msg with real one
             setTimeout(() => loadMessages(), 15000);
         } else {
             showNotification('Failed to send: ' + data.error, 'danger');

app/static/js/sw.js

@@ -1,4 +1,4 @@
-const CACHE_NAME = 'mc-webui-v5';
+const CACHE_NAME = 'mc-webui-v6';
 const ASSETS_TO_CACHE = [
     '/',
     '/static/css/style.css',