OpenAI response_format in chat completion body breaks observeOpenAI()

[devonkcopeland]

Adding response_format to a child OpenAI observation within a trace will cause the observability to fail. Uncomment the specified line to test.

Example adapted from the Get Started docs page

  const langfuse = new Langfuse();
  const openai = new OpenAI();

  const trace = langfuse.trace({ name: "country-poem-generator" });
  const span = trace.span({ name: "poem-span" });

  const poem = (
    await observeOpenAI(openai, {
      parent: span,
      generationName: "generate-poem",
    }).chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: [
        {
          role: "system",
          content: "You are a poet. Create a haiku about this city.",
        },
        { role: "user", content: "France" },
      ],
      // Uncommenting the line below will break the Langfuse observability
      // OpenAI API will respond as desired
      // response_format: { type: "text" },
    })
  ).choices[0].message.content;

  console.log(poem)
  span.end();