Why isn't the OpenAI runs API streaming response working in React Native with react-native-sse?

Below is a summary of what’s likely happening and some recommendations:

What's Happening

1. Fetch API Limitations in React Native
   Unlike in browsers, React Native’s implementation of the fetch API does not support streaming responses in the same way. When you call response.text(), React Native waits for the response to finish before returning all of its data as a single string. This results in your observation that the entire response is available only at the end instead of being streamed.

2. EventSource and react-native-sse
   The polyfill you’re using through react-native-sse is intended to help with Server-Sent Events (SSE). However, if you’re not getting any events, it could be due to one or more of the following:

   • The underlying networking stack (or ATS on iOS / cleartext traffic issues on Android) may not be correctly configured for streaming SSE connections.
   • The server might not actually be sending events in the proper text/event-stream format that the library expects.
   • There may be a bug or configuration issue with react-native-sse itself.

3. OpenAI Completions API Works
   OpenAI’s API might use a slightly different mechanism or be tested specifically to work with how React Native currently handles streams – for example via a WebSocket or a custom polling mechanism – which is why you see streaming only for that endpoint.

Recommendations

• Double-Check Server Response Headers
  Ensure that the API endpoint you’re trying to stream from uses the correct HTTP headers (e.g.,
  Content-Type: text/event-stream) and is formatted per the SSE specification. A misconfiguration at the server can cause the connection not to be handled as a stream.

• Review react-native-sse Usage
  Make sure that you’re initializing and using the library according to its documentation. For example:

  JAVASCRIPTCopied
  import EventSource from 'react-native-sse';
  
  const url = 'https://your-endpoint.com/stream';
  const eventSource = new EventSource(url, {
    headers: {
      Authorization: 'Bearer YOUR API TOKEN',
      Accept: 'text/event-stream',
    },
  });
  
  eventSource.onopen = () => {
    console.log('Connection opened');
  };
  
  eventSource.onmessage = (event) => {
    console.log('New event:', event.data);
  };
  
  eventSource.onerror = (error) => {
    console.error('EventSource error:', error);
  };

  In this setup, you should see events logged one-by-one as they arrive.

• Platform Configuration
  Verify that your platform (iOS/Android) networking settings allow such connections. For iOS, if you are not using HTTPS, look into configuring App Transport Security (ATS) exceptions. On Android (API Level 28+), ensure clear text traffic is allowed if necessary.

• Alternative Libraries/Approaches
  If you continue having issues with react-native-sse:

  • Consider using WebSockets if your backend supports it, as they are well-supported in React Native.
  • Alternatively, use the XMLHttpRequest API directly for streaming if you need finer control, though note that you’ll have to handle the streaming protocol manually.

Summary

The behavior you see when using fetch (getting the complete response at the end) is a known limitation due to how React Native currently implements fetch and its streaming support. When using SSE libraries like react-native-sse, confirm that your server is sending proper SSE responses, your network configuration is correct, and that you’re initializing the library as per its guidelines. If issues persist, consider using WebSockets or the XMLHttpRequest API to handle a streaming connection.

This should help you narrow down the root cause and identify the best approach for streaming data in your React Native app.