Currently, when sshd runs with HostKeyAgent, it still requires to list the server keys with HostKey options pointing to the public keys that agent provides. It would be nice to have an option to load this list from the agent when a client connects, not on startup.

This is very useful when sshd runs, for example, in a restricted container that do not have access to a file system holding the private keys. Thus to change the server keys I not only need to signal sshd to reload its config, but also to ensure that the public keys are transferred into the sshd container complicating the key management.