Goliath guess the rules :-)

This is Goliath. Goliath is a basic bot, it has one rule and one exception to the rule. The only way Goliath can break its rule, is if all legal moves go against it.

Apart from this, Goliath will behave like any other chess engine and simply choose the best move.

If you know the rule, beating Goliath becomes possible even with a big Elo differences. If you don't know the rule, you are still playing a restricted bot (since all moves have to follow the rule), One game should be enough to find the rule here. Goliath is black at 2500 elo, Stockfish is white at 2000 elo.

If you know the rule, beating Goliath becomes possible even with a huge Elo difference. If you don't know the rule, you are still playing a restricted bot (since all moves have to follow the rule), and you can get lucky by steering into a sequence that destroys it.

Stockfish, not understanding the rule, just plays chess. Under these conditions, if Goliath is set to 2500 Elo (the strength of Camille), its win rate over 100 games will be 0.56 vs. Stockfish at 2000, 0.42 vs. Stockfish at 2200, and 0.24 vs. Stockfish at 2400. So Goliath at 2500 Elo is functionally around 2100 Elo ,and against a human who knows the rule, more like 1400 Elo.

Camille can control bots at 5 different levels. Current engines mostly handle level 1, and some can do a second category in a limited fashion.

Once you've found the rule and the exception, do you have any suggestions for making this bot more stable?