SPIKE: Passkey UX in browser extensions

[aristidesstaffieri]

Passkey implementations in browser extensions are still fairly new and may be limited in scope.
We need to understand how passkeys work in the context of a browser extension.

Can you achieve a similar UX as a website given the "extension domain" is not a real domain(some browsers set the relying party ID as this domain behind the scenes)?
Which browsers support passkeys in extensions and are the implementations capable of the same UX?
Are there any other constraints?

Related links:
Relying Parties
https://github.com/w3c/webauthn/issues/1158
https://issues.chromium.org/issues/41378082
https://stackoverflow.com/questions/77485521/can-a-chrome-extension-directly-initiate-the-chrome-webauthn-passkey-dialogu