Mavericks SSH keys and Keychain Before Mavericks I could use Keychain to store my SSH keyfile passwords

The connection between private key and Keychain was like this:

ssh-add -K /path/of/private/key

However now in Mavericks, the -K option has been removed.

Of course, I can skip the "-K" option and manually copy paste the password every time I start my computer... but I would rather use the keychain method again.

How can I use Keychain for my ssh private file passwords again? Is it down in a different way now?
Are you sure you aren't using ssh-add from another source?  On my Mavs, ssh-add—which is /usr/bin/ssh-add—does have the -K flag.  It's in the manpage, shows in the usage message, and is accepted.

Check which ssh-add to see if you're pulling in ssh-add from elsewhere due to your PATH.