AI assistance disclosure: I designed and directed the experiments described here. I used AI coding agents to help implement the experiment scaffolds under tests and review. OpenAI Codex helped inspect the saved reports, verify the numbers, and draft and edit this article. The match logs and API receipts came from the experiment runtime, not the writing assistant. I remain responsible for the claims and errors.
I recently added a private planner to two LLM players in a repeated Prisoner’s Dilemma game.
The first result looked perfect.
Both mirrored matches followed the same arc:
Rounds 1–6: mutual cooperation
