age-github command is a wrapper to filippo.io/age tool which expands recipients in -r @username format to first ssh key of github user "username", fetching keys from https://github.com/username.keys endpoint. It caches keys for 1 hour in "age-github" subdirectory under os.UserCacheDir directory. Github user handles should have @ prefix, i.e. to encrypt file for https://github.com/artyom user, you call it as All other flags/arguments are passed unmodified.