[317070]

How would you enforce the three repetitions rule this way?

[Anotheroneagain]

I guess you can't do that without the full PGN. I guess the 50 move rule might be extraneous as well.

[Someone]

You don’t always need the entire move list.

Whenever any piece is taken (permanently decreasing the number of occupied squares), a pawn is moved, castling rights change, or an en passant opportunity isn’t taken, there won’t be any more repetitions of the board matching past board positions, so you can forget all earlier board positions.