[acdha]

I mentioned those because key management is the hard part and most people are going to be using platform authenticators for that reason. In some cases there are APIs (this was one of the features in the last macOS / iOS release) but I was also thinking that moving it closer to a browser is interesting because between platform passkeys and SSO, there are a lot of people who have all of their credentials & MFA ready in a browser and would like to reuse that.

Some searching suggests there’s at least one implementation of the SSH agent protocol using Windows Hello, which is great.