This is copy of reply by Lee Robinson on this thread here https://github.com/vercel/next.js/issues/9965#issuecomment-1489481795

Server Side Streaming on Next JS

// Copy of reply by Lee Robinson
// https://github.com/vercel/next.js/issues/9965#issuecomment-1489481795

// app/api/route.ts
import { Configuration, OpenAIApi } from 'openai';

export const runtime = 'nodejs';
// This is required to enable streaming
export const dynamic = 'force-dynamic';

export async function GET() {
  const configuration = new Configuration({
    apiKey: process.env.OPENAI_API_KEY,
  });
  const openai = new OpenAIApi(configuration);

  let responseStream = new TransformStream();
  const writer = responseStream.writable.getWriter();
  const encoder = new TextEncoder();

  writer.write(encoder.encode('Vercel is a platform for....'));

  try {
    const openaiRes = await openai.createCompletion(
      {
        model: 'text-davinci-002',
        prompt: 'Vercel is a platform for',
        max_tokens: 100,
        temperature: 0,
        stream: true,
      },
      { responseType: 'stream' }
    );

    // @ts-ignore
    openaiRes.data.on('data', async (data: Buffer) => {
      const lines = data
        .toString()
        .split('\n')
        .filter((line: string) => line.trim() !== '');
      for (const line of lines) {
        const message = line.replace(/^data: /, '');
        if (message === '[DONE]') {
          console.log('Stream completed');
          writer.close();
          return;
        }
        try {
          const parsed = JSON.parse(message);
          await writer.write(encoder.encode(`${parsed.choices[0].text}`));
        } catch (error) {
          console.error('Could not JSON parse stream message', message, error);
        }
      }
    });
  } catch (error) {
    console.error('An error occurred during OpenAI request', error);
    writer.write(encoder.encode('An error occurred during OpenAI request'));
    writer.close();
  }

  return new Response(responseStream.readable, {
    headers: {
      'Content-Type': 'text/event-stream',
      Connection: 'keep-alive',
      'Cache-Control': 'no-cache, no-transform',
    },
  });
}