I’m not sure how you mean that, but I don’t see every site having a dedicated passkey-login-button (yet?).
And if I have a passkey for a given site 1. in Bitwarden AND 2. also on my YubiKeys - and sometimes want (or have) to use the former or the latter… how would I be able doing that - especially using my YubiKey-passkey - if automatically (without any dialogue / pop up) only the Bitwarden-passkey would be offered or rather directly used?
How would I then be able to login with my YubiKey-passkey ever again? (while being logged in and unlocked in Bitwarden - of course I could lock/log out… but that is not a comfortable solution either… and may not even be a solution, since I can initiate the passkey-login-process also with a locked vault, which then leads to the unlock dialogue, so that I can use the Bitwarden-passkey…)
Sure, but you asked specifically about how Yubikeys would work, so that’s what my answer was about. UV is a different matter. Personally, I think that better UX is enough UV (ie having an “OK” button already focused so I can just press enter, along with the BitWarden window opening much more quickly than it does now), but that’s a matter of what the FIDO alliance will consider compliant.
This is simply not the case. I have at least one site in which the passkey prompt appears without clicking a dedicated “login with passkey” button. And login is not unintended, since the authenticator prompts you to interact with the passkey.
Regardless, it is not the job of the website (Relying Party) to verify user presence.