FRC castlings questions

[WinPooh]

Going to implement FRC960 in GreKo. Two questions:
1. Wikipedia says there are two conventions for castlings in FEN, KQkq and AHah. Which one is used in Arena, Chessbase and other GUIs?
2. When King is f1 and Rook is h1, and UCI move is f1g1 - how to distinguish between castling and normal move? Does UCI have special notation for FRC castlings?

[Edmund]

Going to implement FRC960 in GreKo. Two questions:
1. Wikipedia says there are two conventions for castlings in FEN, KQkq and AHah. Which one is used in Arena, Chessbase and other GUIs?
2. When King is f1 and Rook is h1, and UCI move is f1g1 - how to distinguish between castling and normal move? Does UCI have special notation for FRC castlings?

The convention is to write the move as "King captures Rook" to castle.

Just saying "castle kingside" is ambiguous, because there could be two rooks on the kingside (one moved there during the game). Thats why KQkq information is not enough.

[hgm]

Shredder uses HAha, (so-called Shredder FEN) and so does WinBoard.

I heard that in Arena FRC support is broken, and UCI engines can only play there when you install them as WB, using Polyglot. (Not sure if that still applies to all versions.) Then it is still broken if you would set up a position with two Rooks on one side of the King, but at least you can play from an opening position (which never has that).

[Modern Times]

If GreKo is a UC engine, then it makes sense (in my opinion) to follow the Shredder standard.

I look forward to adding it to this list when you are done !
http://computerchess.org.uk/ccrl/404FRC/

FYI, I have used ChessGUI exclusively for this list for a while now. It supports both of the FRC standards as well as both UCI and winboard.

Castling seems to be very difficult to get right, good luck !