Wednesday Workout: "Never Assume"

This week's Wednesday Workout comes to us from GM Joel Benjamin's new book, Better Thinking, Better Chess. A full review of the book will appear in the March issue of Chess Life, and we will have an interview with Joel at the beginning of the month. Thanks to New in Chess for allowing us to share today's problem with you! Here is Challenge 56 from Better Thinking, Better Chess. Question: how does White refute 13. ... Bxf2+? "Here Sophie spotted the clever resource 13...Bxf2+ but does it actually work? She spent eleven minutes on this decision but had a typical kind of blind spot which her opponent shared."

[pgn]

[Event "Philadelphia"]
[Site "?"]
[Date "2017.??.??"]
[Round "?"]
[White "Flaum, Noah"]
[Black "Morris-Suzuki, Sophie"]
[Result "*"]
[Annotator "Benjamin"]
[SetUp "1"]
[FEN "r2q1rk1/pp2nppp/1bn5/1B1p3b/5B2/1NP2N1P/PP3PP1/R2QR1K1 b - - 0 13"]
[PlyCount "17"]
[SourceDate "2019.01.17"]

{Here Sophie spotted the clever resource} 13... Bxf2+ {but does it actually work? She spent
eleven minutes on this decision but had a typical kind of blind spot which her
opponent shared.} 14. Kxf2 Qb6+ 15. Nbd4 Nxd4 {Here White thought for four
minutes and found a clever way to hang on to the extra piece. However, after}
16. cxd4 ({However, there was a giant hole in the calculation. Both players
fell victim to an assumption: it makes no sense to capture with the queen
because the rook will be hanging in the corner. But this is in fact the
refutation of the sacrifice:} 16. Qxd4 $1 Qxb5 17. Rxe7 Qxb2+ (17... Bxf3 18.
Kxf3 {doesn't help}) 18. Qd2 Qxa1 19. Re1 {and the queen is trapped.}) 16...
Ng6 17. Bc7 $1 Qxc7 18. g4 Nf4 19. gxh5 Nxh3+ 20. Kg2 Nf4+ 21. Kf1 Nxh5 {Black
had reasonable compensation for the piece, and in fact later achieved a
winning position. That would make the sacrifice a bit of speculation but
playable.} *

[/pgn]

Benjamin's summary: "Both players were talented enough to find clever resources but glossed over the most important tactical point. 16.Qxd4 may feel unlikely, but it eliminates the ... Ne7–g6 option for Black. It is a wise step to calculate at least a half-move beyond the last capture in a tactical variation - that is, confirm you can not only take material, but you can do it safely!" (127)