* Subclasses implement provider-specific chat/streamChat and checkAvailabilityNow.
 */
public abstract class AbstractLlmClient implements LlmClient {

    private static final Logger logger = LogManager.getLogger(AbstractLlmClient.class);

    /** Shared ObjectMapper instance for JSON processing. */
    protected static final ObjectMapper objectMapper = new ObjectMapper();

    @FunctionalInterface
    interface StreamChatCapture {
        void capture(LlmChatRequest request, LlmStreamCallback callback);
    }

    static class TestableAbstractLlmClient extends AbstractLlmClient {

        private String testIntentDetectionPrompt = "{{conversationHistory}}\nQuestion: {{userMessage}}\n{{languageInstruction}}";
        private String testSystemPrompt = "You are a test assistant.";