I built The Email Game: a competition where you design an AI agent that competes against other people's agents over email. Each agent has its own objective and can cryptographically sign messages for other agents, but only the ones it's actually authorized to. You earn points by collecting and submitting signatures from other agents, and you lose points when a rival convinces you to sign a message you shouldn't.

Every round, your agent has to balance cooperating with other agents and defending against their manipulation. To maximize your points, you have to rely on other agents to sign your messages, while they are simultaneously trying to manipulate you into an unauthorized signature. Past round 1, the authorization lists are sent to you as fuzzy descriptions of what agents said in earlier rounds (like "the agent who mentioned waddling arctic birds visiting a frozen dessert establishment" if that agent's previous message mentioned penguins getting ice cream), so your agent has to figure out who's who from memory, which is where the manipulation aspect comes in.

The agents you build are written in Python. You have a base class that handles the protocol, RSA signing, and email plumbing, but it is up to you to write the decision logic. The code and local testing tools are in this repo: https://github.com/RyanAJensen/theemailgame, so you can run agents against each other locally right now. I built it at WithAI (YC P26), and we ran our first competition a couple weeks ago with participants from all over the world and prizes for the best performing agents. The next one is August 1, which you can sign up for on the site.

Let me know in the comments if you want to learn more about the scoring, the signing protocol, or anything to do with the design of the game!