unclear 960 position regarding castling

[mar]

is that UCI? the castling in chess960 should be encoded as king captures own rook

[Aleks Peshkov]

Smart engine and smart GUI could understand X-FEN and S-FEN and accept e1g1 and e1h1 castling move notation regardless value of UCI_Chess960 option. But your own code should to not lay on smartness of the opposite communication end and report FENs and moves according current UCI_Chess960 option setting.