Google Antigravity now has a /swarm feature, and Google shows Gemini 4 Carbon using it

Builder and critic subagents run iterative loops, checking their own renders across Blender and Three.js to build a playable 3D game

It's a long-horizon coding test, so the interesting part is the self-checking loop, not the game

Would you let subagents review each other's output on your own projects?