v2.18.1 breaks React Native: DOMException is not globally available in Hermes

[mfairley]

Description

livekit-client v2.18.1 crashes at module load time in React Native (Hermes engine) with:

ERROR  [ReferenceError: Property 'DOMException' doesn't exist]

Root Cause

PR #1820 ("Data track integration") added class DeferrableMapAbortError extends DOMException in src/utils/deferrable-map.ts. Since DOMException is not exposed as a global in React Native's Hermes engine, this extends clause fails at class evaluation time, preventing the entire SDK from loading.

There are also other DOMException references (e.g. new DOMException(...) in WebSocketStream.ts and abort-signal-polyfill.ts) that would fail at call time on affected code paths.

Environment

• livekit-client: 2.18.1
• @livekit/react-native: 2.10.0
• React Native with Hermes engine (Expo)

Workaround

Adding a DOMException polyfill before any livekit imports:

if (typeof globalThis.DOMException === "undefined") {
  class DOMException extends Error {
    code: number;
    constructor(message?: string, name?: string) {
      super(message);
      this.name = name ?? "Error";
      this.code = 0;
    }
  }
  globalThis.DOMException = DOMException;
}

Suggested Fix

@livekit/react-native already polyfills WritableStream, ReadableStream, and crypto.randomUUID for React Native compatibility. A DOMException polyfill should be added there as well. Alternatively, the SDK could avoid extending DOMException directly to maintain compatibility with environments where it's not available.