* @throws LlmException if LLM is not available
     */
    public void generateDocumentNotFoundResponse(final String userMessage, final String documentUrl, final List<LlmMessage> history,
            final LlmStreamCallback callback) {
        if (logger.isDebugEnabled()) {
            logger.debug("[LLM] Delegating generateDocumentNotFoundResponse. llmType={}", getLlmType());
        }

                    phaseStartTime = System.currentTimeMillis();
                    callback.onPhaseStart(ChatPhaseCallback.PHASE_ANSWER, "Generating response...");
                    llmClientManager.generateDocumentNotFoundResponse(userMessage, documentUrl, history, (chunk, done) -> {
                        fullResponse.append(chunk);
                        callback.onChunk(chunk, done);
                    });