The 5men and 6men Syzygys challenge for the top 3 Engines.

[Chessqueen]

This is what most engine chose f7 Rg8 Bb2+ Kh7 fxg8Q+ Kxg8 Ne7+ Kh7 Nxc8 having a Bishop + Knight versus Black lonely King
[d]2b3k1/4N3/8/8/8/8/1B6/K7 b - - 0 1

[Chessqueen]

Sorry, but I am too impatient and I got Stash v30.0 which is about Cheng 4.41 strength, but with more endgame Chess knowledge. But I left my other old Computer an intel i5 running with Cheng 4.41 to see if in 7 days it will solve +M53

actually I should thank you for bringing this up. just fixed a bug I introduced recently where Cheng failed to resolve the mate. it takes very long but still.

You are welcome, the composer said it is mate in 12 if Black chose Rook a6+, but most engines chose Rg8 giving up the Rook and it does take much longer to solve f7 Rg8 Bb2+ Kh7 fxg8Q+ Kxg8 Ne7+ Kh7 Nxc8 having a Bishop + Knight versus Black lonely King