How to keep the user signed in between Android native code and a browser (WebView or Chrome tab)?

[niqo01]

Is your feature request related to a problem? Please describe.
I have an Android app where some screens are in native and others will be in HTML/CSS.
Ideally the transition to through those screens should not be noticeable by the user. I am looking through the following options: WebView, Chrome Custom Tab, Trusted Web Activity, however, for all of them, I can't figure out how to keep the user signed in when navigating from a native screen to an HTML one (or the opposite) using Firebase Auth.
Is there a way to achieve this today?

Describe the solution you'd like
I am not sure what the security implication are but if we could get the user auth token (or one time token) from Firebase Auth for Android and give it as a parameter to Firebase auth UI for web which would auto sign in, I think that would be great.

Describe alternatives you've considered
N/A

Additional context
I posted a similar question to SO just in case:
https://stackoverflow.com/questions/57320188/is-there-a-way-to-keep-the-user-signed-in-between-native-code-and-a-webview-usin

[icuham]

I'd like this to be straightforward as well. I've tried different combinations of Firebase Auth UI, onStateChanged, sending the Auth Token in headers, etc. The webView should easily recognize the existing native authentication state, or in the reverse onAuthStateChanged should fire following the webView login seamlessly.

[Shygar]

This would be very helpful if possible.

[johnstrutton]

were you able to solve this @niqo01 ?