SSH keys added using "ssh-add -c" not prompting for confirmation
James,

Are you attempting to run before you can walk?

I'm assuming you are using the Mac app Terminal

Have you successfully run ssh-agent and then successfully run ssh-add without the -c argument and then successfully used those credentials to log in to somewhere?

If so then you might be ready to think about using the -c argument.

First thing to note is that if you are relying on an X11 program to pop up the dialog required then you will have to be running in Xterm, rather than Terminal, as an X11 program will have a hard time passing back the information to OS X.

I'd be interested to know your use case. What are you actually trying to do?