livekit-client fails to import when RTCPeerConnection.prototype.addEventListener is read-only

[ankithedau]

Describe the bug

What I'm expecting

The library should import successfully and handle environments where RTCPeerConnection.prototype.addEventListener is read-only or non-configurable. The library should check if properties are writable before attempting to modify them, or use an alternative approach.

What happens instead

The library fails to import/load with the following error:

TypeError: Cannot assign to read only property 'addEventListener' of object '#<RTCPeerConnection>'

The error occurs during module initialization when importing the library:

import { Room } from 'livekit-client'; // Fails here

Reproduction

Reproduction

1. Embed the livekit-client library in an environment where RTCPeerConnection APIs are frozen/read-only (e.g., Wix website)
2. Attempt to import the library:

   import { Room } from 'livekit-client';

3. The import fails immediately with the TypeError

Note: This occurs in environments like Wix where WebRTC APIs are frozen for security reasons. The error happens during module initialization, before any API calls are made.

Logs

TypeError: Cannot assign to read only property 'addEventListener' of object '#<RTCPeerConnection>'
    at [livekit-client module initialization code]
    at async import('livekit-client')


The error occurs synchronously during the module import, preventing the library from loading at all.

System Info

- **OS**: Any (issue is environment-specific, not OS-specific)
- **Browser**: Any modern browser (Chrome, Firefox, Safari, Edge)
- **Environment**: Wix embedded widget environment (RTCPeerConnection APIs are frozen)
- **livekit-client version**: 2.17.0

**Note**: This issue is not browser-specific but environment-specific. It occurs in any environment where `RTCPeerConnection.prototype.addEventListener` is read-only or non-configurable.

Severity

blocking all usage of LiveKit

Additional Information

This issue prevents the library from being used in:

• Wix websites (embedded widgets)
• Security-restricted environments where WebRTC APIs are frozen
• Some enterprise browser configurations

The library attempts to modify RTCPeerConnection.prototype.addEventListener during module initialization, which fails when the property is read-only or non-configurable. The library should handle this gracefully by checking property descriptors before modification or using an alternative approach that doesn't require modifying the prototype.

[kalvin807]

We hit this same issue with our ElevenAgent widget on Wix sites. Adding some findings from our investigation:

• The bug originates from webrtc-adapter's wrapPeerConnectionEvent function, which is bundled inside livekit-client.
• Wix doesn't Object.freeze(RTCPeerConnection.prototype). Instead, they make EventTarget.prototype.addEventListener non-writable:

  Object.getOwnPropertyDescriptor(EventTarget.prototype, 'addEventListener')
  // → {writable: false, configurable: false, enumerable: true, value: ƒ}

Since RTCPeerConnection.prototype inherits addEventListener from EventTarget.prototype, the assignment proto.addEventListener = ... throws TypeError in strict mode (ESM).

Since our use case doesn't actually need WebRTC, we're patching livekit-client's bundled output with a try-catch guard:

  const proto = window.RTCPeerConnection.prototype;
  try { proto.addEventListener = proto.addEventListener; }
  catch (e) {
    console.warn('skipping RTCPeerConnection event patching — addEventListener is non-writable', e);
    return;
  }

Also not all wix site seems affected, at least I am cannot reproduce with personal free site. maybe it is some enterprise feature.

[fippo]

@lukasIO this should be fixed by bumping webrtc-adapter to 9.0.5

[lukasIO]

thanks @fippo and thanks @ankithedau for the report, closed via #1858