So right now I've got a threat fleet of 750 or so ships. Nearly all these ships are the result of the ai's periodic waves not actually attacking me, but instead deciding to stare at me menacingly from a neighboring system. I've tried to travel to said system, hoping to thin out the threatfleet a bit before it gets any more out of hand, but the moment my fleet pops into the system, all the threatfleet ships disappear, presumably one system deeper, out of fear of my main fleet.
The threatfleet will inevitably only get larger, since it feeds off waves, and it's only a matter of time before the AI wises up and punches straight through my defenses while my fleet is off conquering the other side of the galaxy.
How do you deal with this situation?