Fix LCD Communicaiton infinite looping upon failed commands

vesper/src/Communication/CommunicationRouter/CommunicationRouter.cpp

@@ -343,9 +343,29 @@ void CommunicationRouter::onWebSocketMessage(uint32_t clientId, const JsonDocume
 }
 
 void CommunicationRouter::onUartMessage(JsonDocument& message) {
-    // Extract command for logging
-    String cmd = message["cmd"] | "unknown";
-    LOG_INFO("🔌 UART message received: cmd=%s", cmd.c_str());
+    // Extract command and action for filtering
+    String cmd = message["cmd"] | "";
+    String action = message["contents"]["action"] | "";
+
+    // UART COMMAND WHITELIST: Only allow specific commands
+    // This prevents feedback loops between devices when bad messages occur.
+    // To re-enable full UART command support, remove this filter.
+    bool allowed = false;
+
+    if (cmd == "system_info" && action == "sync_time_to_lcd") {
+        allowed = true;
+    } else if (cmd == "playback" && (action == "play" || action == "stop")) {
+        allowed = true;
+    }
+
+    if (!allowed) {
+        // Silently ignore - do NOT send error response to avoid feedback loop
+        LOG_DEBUG("UART: Ignoring non-whitelisted command (cmd=%s, action=%s)",
+                  cmd.c_str(), action.c_str());
+        return;
+    }
+
+    LOG_INFO("🔌 UART command received: cmd=%s, action=%s", cmd.c_str(), action.c_str());
 
     // Create message context for UART
     CommandHandler::MessageContext context(CommandHandler::MessageSource::UART);