if isinstance(message_input, str):
        user_message = message_input
        print(f"\n=== New Request (Text) ===")
        print(f"User message: {user_message}")
        if not user_message.strip(): # Check if text message is empty or whitespace
            messages.append(ChatMessage(role="assistant", content="Please input a text message or upload a file. Empty input is not allowed."))
            yield messages
            return