Y Combinator · 2026-10-29 · notable
YC Labs — AI agent swarms play Minecraft and Mindustry
YC Labs ran groups of AI agents in Minecraft and Mindustry, and open-sourced the Minecraft harness. In Mindustry, GPT-6.1 Sol agents beat Claude Opus 5.5 agents 6-1 over 7 games.
Y Combinator's lab put dozens of coding agents into games and watched how they organize.
What is it?
The YC Labs 'Agents in Games' write-up reports experiments with teams of AI agents in Minecraft and Mindustry, made with Olam Labs. In the Civ50 run, 50 GPT-6.1 Sol agents spent 3 hours in a survival world with the goal 'Build a thriving civilization'. They sent about 5,900 messages and formed a food-rationing system and a pseudo-government.
How does it work?
The team open-sourced its Minecraft harness. It runs the agent loop on Pi, gives agents Mineflayer-based tools and keeps persistent sessions with shell sandboxes. In Mindustry, each agent ran in its own Linux sandbox with the same game API and no strategy instructions: GPT-6.1 Sol in Codex against Claude Opus 5.5 in Claude Code.
Why does it matter?
The runs give a rare look at how large agent groups behave. GPT agents acted like a hive with far more messages and won the Mindustry series 6-1. Claude agents kept one fixed leader and decided by '+1' votes. The authors say the Minecraft colony became more cautious over time, a pattern they also see in coding agents.
Who is it for?
Multi-agent and agent-harness builders
Try it
https://github.com/yc-software/minecraft-agent-harness