ChatKit usecase without frontend

I want to call ChatKit directly from my Java code. I successfully generated a secret, but I don't understand what I should do next?

public void callOpenAI() {
        OpenAIClient client = OpenAIOkHttpClient.builder()
                .fromEnv()
                .apiKey("key")
                .build();

        var param2 = ChatSessionWorkflowParam.builder().id("id").build();
        var params = SessionCreateParams.builder().user("name").workflow( param2).build();

        ChatSession chatSession = client.beta().chatkit().sessions().create(params);

        String secret = chatSession.clientSecret();
    }

I want to call ChatKit with an initial text to begin the agent workflow

Start with the Java example using client.beta().chatkit().sessions().create(params), ChatSessionWorkflowParam, and SessionCreateParams. Trace how the returned clientSecret is intended to be used without a frontend and determine the supported way to provide initial text; done means a documented or tested Java path that starts the agent workflow with that text.