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Stream OpenAI API Responses

Use the OpenAI v4 SDK to stream responses from OpenAI.

In order to run this code, you must install the OpenAI SDK by running npm i openai.

import OpenAI from "openai";


export default {
  async fetch(request, env, ctx): Promise<Response> {
    const openai = new OpenAI({
      apiKey: env.OPENAI_API_KEY,
    });


    // Create a TransformStream to handle streaming data
    let { readable, writable } = new TransformStream();
    let writer = writable.getWriter();
    const textEncoder = new TextEncoder();


    ctx.waitUntil(
      (async () => {
        const stream = await openai.chat.completions.create({
          model: "gpt-4o-mini",
          messages: [{ role: "user", content: "Tell me a story" }],
          stream: true,
        });


        // loop over the data as it is streamed and write to the writeable
        for await (const part of stream) {
          writer.write(
            textEncoder.encode(part.choices[0]?.delta?.content || ""),
          );
        }
        writer.close();
      })(),
    );


    // Send the readable back to the browser
    return new Response(readable);
  },
} satisfies ExportedHandler<Env>;