I'm playing a game with 4 AIs (unlocked teams) And i have a cease fire with 2 of tehm but not with the third.

That third AI then saw fit to send me a siege fleet of death against one of my least defended planets (cool) and to prevent it's destruction.

The problem was that the AI actually accepted. A human player would always finish off the planet first (the AI only needed like 3 or 4 more secs to finish the planet off) and then say : "sorry was busy somewhere else and couldn't withdraw my fleet in time, looking forward to improve our relations"