Prevent iOS from Switching Between Back Camera Lenses in getUserMedia (Safari/WebView, iOS 18)

I’m developing a hybrid app (WebView / Turbo Native) that uses getUserMedia to access the back camera for a PPG/heart rate measurement feature (the user places their finger on the camera).

Problem: Even when I specify constraints like:

{

  video: {

    deviceId: '...',

    facingMode: { exact: 'environment' },

    advanced: [{ zoom: 1.0 }]

  },

  audio: false

}

On iPhone 15 (iOS 18), iOS unexpectedly switches between the wide, ultra-wide, and telephoto lenses during the measurement.

This breaks the heart rate detection, and it forces the user to move their finger in the middle of the measurement.

Question: Is there any way, via getUserMedia/WebRTC, to force iOS to use only the wide-angle lens and prevent automatic lens switching?

I know that with AVFoundation (Swift) you can pick .builtInWideAngleCamera, but I’m hoping to avoid building a custom native layer and would prefer to stick with WebView/JavaScript if possible to save time and complexity.

Any suggestions, workarounds, or updates from Apple would be greatly appreciated!

Thanks a lot!