React Native

Your native app calls your own backend, not a same-origin browser route. Use useChat from @tanstack/ai-react with an XHR adapter and an absolute URL.

1. Set the backend URL

const baseUrl =
  process.env.EXPO_PUBLIC_TANSTACK_AI_BASE_URL ??
  'http://127.0.0.1:8787'
const httpUrl = `${baseUrl}/chat/http`
const sseUrl = `${baseUrl}/chat/sse`

Use a URL that your runtime can reach:

iOS simulator: usually localhost or 127.0.0.1.
Android emulator: usually 10.0.2.2, to reach the host machine.
A physical device: a LAN URL or a tunnel URL.

2. Connect with xhrHttpStream

Use xhrHttpStream() for Expo and React Native. It reads newline-delimited JSON from incremental XHR progress events. Your server returns the stream with toHttpResponse() (see HTTP Stream):

import { useChat, xhrHttpStream } from "@tanstack/ai-react";

const baseUrl = process.env.EXPO_PUBLIC_TANSTACK_AI_BASE_URL ?? 'http://127.0.0.1:8787';
const httpUrl = `${baseUrl}/chat/http`;

const chat = useChat({
  connection: xhrHttpStream(httpUrl),
});

Mobile connections drop often. If the server adds a durability adapter, both XHR adapters reconnect and support joinRun. See Resumable Streams.

Use SSE on mobile

If your server returns text/event-stream with toServerSentEventsResponse() (see Server-Sent Events), use xhrServerSentEvents():

import { useChat, xhrServerSentEvents } from "@tanstack/ai-react";

const baseUrl = process.env.EXPO_PUBLIC_TANSTACK_AI_BASE_URL ?? 'http://127.0.0.1:8787';
const sseUrl = `${baseUrl}/chat/sse`;

const chat = useChat({
  connection: xhrServerSentEvents(sseUrl),
});

Use fetchHttpStream on mobile

fetchHttpStream() works only if your React Native runtime has all of these:

Streaming fetch responses.
Response.body.getReader().
TextDecoder.

The server still returns newline-delimited JSON with toHttpResponse():

import { useChat, fetchHttpStream } from "@tanstack/ai-react";

const baseUrl = process.env.EXPO_PUBLIC_TANSTACK_AI_BASE_URL ?? 'http://127.0.0.1:8787';
const httpUrl = `${baseUrl}/chat/http`;

const chat = useChat({
  connection: fetchHttpStream(httpUrl),
});

If one of these APIs is missing, fetchHttpStream() throws UnsupportedResponseStreamError. A polyfill that buffers the response does not help, because the adapter needs incremental bytes. Use xhrHttpStream() or xhrServerSentEvents().