createUIMessageStreamResponse

import { createUIMessageStream, createUIMessageStreamResponse } from 'ai';

const response = createUIMessageStreamResponse({
  status: 200,
  statusText: 'OK',
  headers: {
    'Custom-Header': 'value',
  },
  stream: createUIMessageStream({
    execute({ writer }) {
      // Write custom data
      writer.write({
        type: 'data',
        value: { message: 'Hello' },
      });

      // Write text content
      writer.write({
        type: 'text',
        value: 'Hello, world!',
      });

      // Write source information
      writer.write({
        type: 'source-url',
        value: {
          type: 'source',
          id: 'source-1',
          url: 'https://example.com',
          title: 'Example Source',
        },
      });

      // Merge with LLM stream
      const result = streamText({
        model: openai('gpt-4'),
        prompt: 'Say hello',
      });

      writer.merge(result.toUIMessageStream());
    },
  }),
});