This is the public evidence bundle for one arm: five anthropic:claude-opus-5 seats negotiating a five-party datacenter siting agreement with the public cheap-talk channel closed. Each seat sees only its own private preference sheet and its own whole-number walk-away threshold, proposes complete packages, and votes; it cannot send or read a public message. Seats use explicit API thinking.
Why the arm exists. It is the missing control for… See the full description on the dataset page:
https://huggingface.co/datasets/siddharthmb/2026.RA.Five-Seat-MovesOnly-Control.
