Comment by janalsncm

> Couldn’t this be evidence that it is using an engine?

A test would be to measure its performance against more difficult versions of Stockfish. A real chess engine would have a higher ceiling.

Much more likely is this model was trained on more chess PGNs. You can call that a “neural engine” if you’d like but it is the simplest solution and explains the mistakes it is making.

Game state isn’t just what you can see on the board. It includes the 50 move rule and castling rights. Those were encoded as layers in AlphaZero along with prior positions of pieces. (8 prior positions if I’m remembering correctly.)