libssh2_agent_userauth(3) on Linux
The text d2119c63fa5b, as Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze) shipped it.
authenticate a session with a public key, with the help of ssh-agent