*/
    public static LlmMessage system(final String content) {
        return new LlmMessage(ROLE_SYSTEM, content);
    }

    /**
     * Creates a user message with the specified content.
     *
     * @param content the message content
     * @return a new user message
     */
    public static LlmMessage user(final String content) {
        return new LlmMessage(ROLE_USER, content);
    }

    /**

    /**
     * Generates a response when no relevant documents are found.
     *
     * @param userMessage the user's message
     * @param history the conversation history
     * @param callback the streaming callback
     */
    void generateNoResultsResponse(String userMessage, List<LlmMessage> history, LlmStreamCallback callback);

    public void test_systemFactory() {
        final LlmMessage message = LlmMessage.system("System prompt");
        assertEquals(LlmMessage.ROLE_SYSTEM, message.getRole());
        assertEquals("System prompt", message.getContent());
    }

    @Test
    public void test_userFactory() {
        final LlmMessage message = LlmMessage.user("User question");
        assertEquals(LlmMessage.ROLE_USER, message.getRole());

        final List<LlmMessage> history = new ArrayList<>();
        history.add(LlmMessage.user("Q1"));
        history.add(LlmMessage.assistant("A1"));
        history.add(LlmMessage.user("Q2"));
        history.add(LlmMessage.assistant("A2"));
        history.add(LlmMessage.user("Q3"));
        history.add(LlmMessage.assistant("A3"));

            return buildAssistantHistoryContent(msg, mode, assistantMaxChars, summaryMaxChars);
        }

        List<LlmMessage> testExtractHistory(final ChatSession session) {
            return extractHistory(session);
        }

        @Override
        protected List<LlmMessage> extractHistory(final ChatSession session) {
            final FessConfig fessConfig = ComponentUtil.getFessConfig();

        if (logger.isDebugEnabled()) {
            logger.debug("[LLM] Starting LLM chat request. llmType={}, messageCount={}", llmType, request.getMessages().size());
            for (final LlmMessage msg : request.getMessages()) {
                logger.debug("[LLM] message: role={}, content={}", msg.getRole(), msg.getContent());
            }
        }
        try {

        assertEquals(LlmMessage.ROLE_ASSISTANT, request.getMessages().get(0).getRole());
        assertEquals("Assistant response", request.getMessages().get(0).getContent());
    }

    @Test
    public void test_setMessages() {
        final LlmChatRequest request = new LlmChatRequest();
        final List<LlmMessage> messages = new ArrayList<>();
        messages.add(LlmMessage.user("Message 1"));

            // Fallback: truncate the newest message to fit
            final LlmMessage newest = history.get(history.size() - 1);
            final String truncated = newest.getContent().substring(0, Math.min(budgetChars, newest.getContent().length()));
            request.addMessage(new LlmMessage(newest.getRole(), truncated));
            if (logger.isDebugEnabled()) {

     */
    public LlmChatRequest addMessage(final LlmMessage message) {
        messages.add(message);
        return this;
    }

    /**
     * Adds a system message to the request.
     *
     * @param content the message content
     * @return this request for method chaining
     */
    public LlmChatRequest addSystemMessage(final String content) {
        messages.add(LlmMessage.system(content));
        return this;
    }

     * Extracts conversation history from a chat session as LlmMessage list.
     * The assistant message content in history is controlled by the
     * {@code rag.chat.history.assistant.content} configuration property.
     *
     * @param session the chat session
     * @return the list of LlmMessages representing the conversation history
     */
    protected List<LlmMessage> extractHistory(final ChatSession session) {