> You generate another passkey is your answer. How do you do that? The exact same way you do today.

How can I do that, if Passkeys are the only option to log in?

If I can just use a password to log into a website without Passkeys, then Passkey is useless and doesn't add any security benefit.

> Why would you need to delete invalid passkeys? You wouldn't.

I sell my old (and no longer updated) phone or PC and don't want someone to get access to my account by getting access to the secret keys.

An non-revocable authentication mechanism is just stupid.