Not so distant future. A colony of autonomous space drones arrives at an asteroid belt. The colony ship contains construction facilities, a basic refinery and a few mining drones. Everything is of most basic, rugged design: hydrogen based propulsion, solar for energy, steel frames, silicone and copper based electronics, standardized, easy to manufacture in space components. All controlled by an AI.
The purpose of this colony is to mine resources out of the belt to eventually build a megastructure in the system: a dyson sphere, a hyperspace gate, a mass relay, whatever. The construction requires truly massive amounts of resources and so you need to build an equivalently big infrastructure to collect them. Worst of all, you're not alone in the belt. Other colonies are arriving and have similar initiatives. Each AI is independent and has its own opinion on where the path of least resistance lies. AIs may decide to work together on the same project, keep neutrality and self-regulate, aggressivel