def respond(user_message, history, state_history):
    if not user_message:
        return "", history

    # ✅ Retrieve stored method choice
    last_method = state_history.get("selected_method", None)

    # ✅ If the user selects a method, store it
    if user_message.lower() in ["bar model", "double number line", "equation"]:
        state_history["selected_method"] = user_message.lower()  # Store method
        response = get_prompt_for_method(user_message)
        history.append((user_message, response))
        return "", history, state_history

    # ✅ If no method was selected, ask for one
    if not last_method:
        return "I didn’t understand that. Please select a method first (Bar Model, Double Number Line, or Equation).", history, state_history

    # ✅ Process teacher’s reasoning and give feedback
    response = get_feedback_for_method(last_method, user_message)
    history.append((user_message, response))
    return "", history, state_history