Weird bug in CuteChess GUI?

[Jouni]

I played FRC match between Stockfish and Reckless. When I looked at PGN there was mysterious book moves in most games . Example:

[Event "FRC"]
[Site "?"]
[Date "2026.05.20"]
[Round "47"]
[White "Reckless010"]
[Black "SFdev"]
[Result "1/2-1/2"]
[FEN "rbbknrnq/pppppppp/8/8/8/8/PPPPPPPP/RBBKNRNQ w KQkq - 0 1"]
[Variant "fischerandom"]

1. d4 {book} Ngf6 {book} 2. c4 {book} e6 {book} 3. Ngf3 {book} b6 {book}
4. g3 {book} Bb7 {book} 5. Nd3 {+0.69/16 0.77s} Nd6 {-0.06/17 0.38s}
6. b3 {+0.88/14 0.15s} a5 {-0.20/19 2.2s} 7. a4 {+0.42/16 0.35s}
Nde4 {-0.22/18 0.70s} 8. Bb2 {+0.41/14 0.15s} h5

I used Chess960.pgn with definitely has no moves. What happened? BTW match result with 10 + 0.1 level:

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1   SFdev        +124/=552/-124 50.00%  400.0/800
2   Reckless010  +124/=552/-124 50.00%  400.0/800

[Modern Times]

I've never seen that is CuteChess. But I have seen in another GUI in the very distant past that when an engine moved instantly the GUI mistook that for a book move. I can't recall the exact details.

[Jouni]

With several tries this didn't happened again. Same match repeated:

Code: Select all

                       
1   Reckless010    +90/=625/-85 50.31%  402.5/800
2   SFdev          +85/=625/-90 49.69%  397.5/800