vercel ai - How to confirm onFinish is functioning correctly?

Question

I was following rather a complex tutorial https://github.com/tierrun/tier-vercel-openai/blob/main/src/components/app/GenerateSection.tsx but couldn't confirm if the onFinish is working as expected. So now I'm doing a simple logging check using onFinish.

const {
    completion,
    setCompletion,
    input,
    setInput,
    isLoading,
    handleInputChange,
    handleSubmit,
  } = useCompletion({
    api: "/api/generate2",
    body: {
      model: "gpt-4",
    },
    onFinish: (input: string, completion: string) => {
        console.log(`input: ${input}, completion: ${completion}`);
  }});

The code above successfully generates the completion and I can render it through html, however, even after the completion, this simple console.log using onFinish isn't working.

Can someone point out how to verify onFinish is actually working?