Hmm, I'm not sure I've noticed this, except in the case of Cap ships auto-targeting planets for bombardment breaking off to attack a newly arrived enemy fleet. But I believe that if I give them an explicit command, ie right click the planet, they don't cease the bombardment to kill enemies who enter the gravity well.

If this happens the way you say though, I agree that's pretty annoying.

You can shift right-click to queue explicit attack commands to specific targets though, have you tried that? I don't think those attack orders would be interrupted by arriving ships, but I've certainly been wrong before.

-HD

I've seen ships do that when they kill the ship I told them to kill already; they'll assign priorities to their pre-coded mind set. I wish they would continue attacking ships in the same fleet I selected initially ... so maybe if the AI could create "fleets" for its units and when I select a specific target in the fleet my units would continue attacking that fleet .... although it does look cool to see a couple of my ships break away from the main attack and chase down other ships ....