Core Shell to use ~.ssh/config

Core Shell version 1.2 was released, you can switch to system default ssh_config by following this guide:

ProxyCommand is also supported. And for auth agent forwarding, you must enable Forward Agent option:

The ssh command line shipped with macOS actually also integrates Keychain with private keys, so if you didn't invoke ssh-add command, but ssh connects without prompt private key passphrase, then instead of fetch keys from ssh-agent daemon, ssh might actually decrypts key from Keychain silently.