Single Comment

OK, I see the problem now. I forgot that the Embassy array is a mirrored
one, with the King starting on e1, rather than f1. And that to avoid any
problems with it in Battle of the Goths, I did not really play Embassy,
but the fully equivalent mirrored Embassy. And with that one, none of the
engines had problems, of course.

Actually it seems that it is not TJchess that is in error here: e1b1 does
seem a legal castling in Embassy. It is WinBoard_F which unjustly rejects
the move. Most likely because of the FEN reader ignoring specified
castling rights for which it does not find a King on f1 and a Rook in the
indicated corner.

The fact that you don't have this problem with Joker80 is because Joker80
is buggy. (Well, not really; it is merely outside its specs. Joker80
considers all castlings with a non-corner Rook and King not in the f-file
as CRC castlings, which are only allowed in variant caparandom, but not in
variants capablanca or *UNSPEAKABLE*. And Joker80 does not support
caparandom yet.) So the fact that you don't see any problems with Joker80
is because it will never castle when you feed it the Embassy setup, so that
WinBoard doesn't get the chance to reject the castling as illegal. And if
the opponent castles, WinBoard would reject it as illegal, and not pass it
on to Joker80.

I guess the fundamental fix will have to wait until I implement variant
caparandom in WinBoard; I think that both WinBoard and Joker80 are correct
in identifying the Embassy opening position as not belonging to Capablanca
Chess, but needing the CRC extension of castling. (Even if it is only a
limited extension, as the Rooks are still in thre corner.) And after I fix
it in WinBoard, I still would have to equip Joker80 with CRC capability
before you could use it to play the Embassy setup.

It is not very high on my list of priorities, though, as I see little
reason to play Embassy rather than mirrored Embassy.