I'm playing a match as Lumeris against my neighbors the Cravers. I have a fleet of 2 Guarding my border planet. Next turn, a fleet of 6 Craver ships immediately jumps into said system, declares war, and destroys my ground forces in one battle without fighting my ships at all. Is this working as intended? Or is it a bug?

Actually, just discovered I can attack their ships on the turn they invade and reduce the number of troops they deploy. Still, this seems like a potential exploit: a 6-command point fleet can blitz (and usually win) any colony that doesn't have bunkers, including your home planet.