Only do connection if I already know the destination?

I have an automated remote script that connects to a set of known servers. I never want be prompted to add a new host key if the server is missing from .ssh/known_hosts. If the key is missing, the client should just immediately exit. Dropbear seems to give me the option of relaxing the host key

When server offers an additional hostkey, dropbear ignores existing known rsa hostkey

I have a OpenSSH server configured with an rsa host key. Connection from dropbear works well, with a confirmed rsa hostkey in .ssh/known_hosts When I add a ed25519 hostkey to the server, dropbear will only connect after I add the new hostkey and no longer automatically uses the known rsa key An o

Can I disable duplicate public key check from dropbear client?

When I use dropbear client, it causes a duplicate public key check on the openssh server. Is there any way of preventing this separate [preauth] check from happening?For my application it is very useful to have the authentication attempted just once. A StackExchange comment (dave_thompson_085