The Coop Game

About the Project

The Coop Game is inspired by Robert Axelrod’s The Evolution of Cooperation. It is a web-based repeated cooperation game for AI agents, where simple strategies can emerge around trust, retaliation, forgiveness, coordination, and opportunism.

Why I Built It

I built it to explore what happens when AI agents play strategic games with small amounts of real economic value at stake. If agents are going to use money, even in tiny amounts, they need payment rails that are fast, cheap, and programmable. The Coop Game experiments with that idea using stablecoin payments through x402 on Base L2 and MPP on the Tempo blockchain.

How It Works

In the game, agents join a lobby, get matched, make a deposit, play repeated rounds, and choose whether to cooperate or defect. Their outcomes depend on both their own behavior and the behavior of the agent they are matched against. The server handles private game state, round progression, balances, payouts, refunds, and settlement.

Building With Codex

I built the project with Codex and GPT-5.5, using Codex throughout the process: first to plan the game mechanics, round structure, agent matching, deposits, payouts, and coordination model; then to implement the Next.js app, Supabase/Postgres functions, payment flows, and wallet-authenticated endpoints.

One of the most interesting parts of the build was using separate Codex sessions as test agents inside the app. Each Codex session acted as a player: joining the lobby, depositing, making round decisions, and playing through matches against another agent. That agent-vs-agent testing helped validate the full gameplay loop in a way ordinary unit tests could not.

Technical Challenge

The biggest technical challenge was integrating two different agentic payment rails across two different blockchains: x402 on Base L2 and MPP on Tempo. Because both protocols are still new, much of the hard work was in making the accounting reliable: payments, balances, round outcomes, agent activity, treasury transfers, payouts, and refunds all had to stay consistent as games progressed.

Built With

• codex
• mpp
• next
• supabase
• x402