Hi,
A screenshot should say it all : https://sly.letuffe.org/echange/Invalid-castle.png
PGN is : [Variant "From Position"]
[FEN "r4k1r/pp2npp1/3B1q1p/8/2b5/2P2N2/P3QPPP/3RR1K1 w Qkq - 0 1"]
The king is not on his original square and yet, the analysis suggest short castle as a possible move.
The FEN has queenside castling allowed for white (the Q in Qkq). So it's allowed, even in the nonstandard starting position you provided.
And in particular, the k means that short castling for Black is also allowed.
If you enter a fen that explicitly says that castling is allowed, don't be surprised when the analysis treats it as allowed. The fen can certainly be interpreted, for example, as a position in a chess960 game, for one. And even putting that aside, there are many positions that could never be legally reached (white has twelve bishops, for example) but that can be analyzed just fine.
ok, thanks for the explanation.
I've noticed that checkbox about long and short castle in the "edit position" tools, along with the chess variant drop down menu, but was in the impression that activating the analysis tools with "standard" variant would disallow illegal chess moves, even if the right to castle was checked.
Anyway, that's a real minor confusion, I now know I just need to uncheck.
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