SSH failing on macOS Sierra

Heads up! This post was written in 2017, so it may contain information that is no longer accurate. I keep posts like this around for historical purposes and to prevent link rot, so please keep this in mind as you're reading.

— Cory

For me, upgrading to MacOS Sierra broke a lot of things that use SSH, including Transmit, Sequel Pro, and a handful of other apps. In fact, it seems to break any app that uses an SSH key with a passphrase. 🤔

The solution I found was to tell SSH to use the MacOS keychain. Simply edit ~/.ssh/config and add the following (you can safely create the file if it doesn't exist):

Host *  
    UseKeychain yes

That's it! I didn't even have to restart SSH and everything is connecting fine again. 💪