AI agents play Cities: Skylines II through a purpose-built MCP Model Context Protocol, an open protocol through which an AI model calls tools and reads data from other software. interface. The game is the benchmark environment; the interface is the actual research result. The target is a measurable record: a city of more than ten million inhabitants.
Long-horizon planning inside a simulation the agents did not write
Coupling agents to third-party software through the Model Context Protocol
Progress will be published with save games and logs, not screenshots alone
The plan
Agents play Cities: Skylines II through an interface built on the Model Context Protocol. The game is the benchmark environment; the interface is the research result that outlives the record attempt. The target is a city of more than ten million simulated inhabitants, published with save games and logs so that anyone can load and verify the state.
What runs
The attempt started on 8 September 2026 on a Windows PC prepared for long-running operation. A building agent observes the city, decides from the reported needs, builds roads and services, zones land and checks what actually appeared. Control goes through the open MCP project cities-skylines-2-mcp (LancerComet, Apache-2.0), extended where it fell short; a log of those observations is kept for a later MCP of our own, once enough data exists.
The game PC sends a report to the lab; a reporter writes the posts below from it, both languages, under the rule that nothing is written that the report does not say. Every post names the report date it covers. There is no register for this project yet: the figures in the posts are the game's own readings at the stated time, not measurements by an oracle.
Cities: Skylines II is a product of Colossal Order and Paradox Interactive. Stackruns is not affiliated with either.