This is a End-Game Crisis. It happens when you or another Empire uses Android technology and researches synths (final upgrade to robot pops).
After a while the Ghost Signal event will occur, the event chain has robot pops acting weird, disappearing and eventually one reaches signal sparking a AI sentience rebellion via The Contingency.
During the war, a event chain will pop up to do some research. When you complete it, boom, achievement done..........now you jst gotta survive the massive robot fleets.