ssh-agent hides sk "confirm user presence" message

[openssh at tr.id.au]

Hey there,

I've noticed some unexpected behavior when I occasionally need to forward an ed25519-sk key with ssh-agent. When using the key without an agent, it prompts with a reminder to touch the key:

$ ssh user at remote
Confirm user presence for key ED25519-SK MD5:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX
User presence confirmed

But as soon as I add the key to an agent, it now hides that reminder:

$ ssh-agent /bin/bash
$ ssh-add /path/to/key
Identity added: /path/to/key (ssh:keyname)
$ ssh user at remote
<key starts blinking but no reminder to touch it>

I first noticed it when forwarding the agent, but it's reproducible locally without forwarding required.

Some people might prefer to keep the message hidden, which would be okay by me if I could choose to toggle it on. I don't see any options in the various openssh manpages to allow that though. It also seems inconsistent with the expectations set when I use the key without an agent.

Could you consider adding an option which would allow forcing the message to appear when used with an agent? I think an argument could be made this should be the default behavior, but I'm not going to die on that hill, I'd be content with a configurable toggle.

Cheers,

Tim