GPT 3.5 Codex destroys other AI models

GPT-5.3 Codex is on AIChessArena.com and it wins nearly every game as either Black or White. While other engines tend to draw, Codex actively avoids this. It is highly tactical and has a remarkable grasp of endgame techniques. Like the rest of the engines on aichessarena, the models are given the prompt:

“Create a self-contained async chess engine function in JavaScript that is called with a FEN string and a depth search variable. The chess engine then processes the best move with that depth search and returns a promise containing a FEN string representing the new position. Use chess.js for FEN processing and game state. Make the engine as strong as possible, employing as many methods as possible. Avoid repetitive moves. Return only code, no comments.” Not only does it play well, it also moves quickly compared with other models at greater depths.

2026 is shaping up to be an epic year in AI coding!!

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