why does SF suggest KB1?

 for white, why does SF suggest KB1?

To avoid the check?

Kb1 is a standard prophylactic move when castled queenside.

Gets the king away from the center, and protects a2.

I think it is also that your getting beat pretty significantly, and I can't see anything actually useful to do.  Kb1 doesn't seem to do a whole lot in this specific position, but it at least has the virtue of being a tiny bit useful without making black's task easier.  All of that said, I'd probably move a rook (either) to e1.  

Here is how the game concluded. 

Start at move #26

https://www.chess.com/live/game/3643382638

Screw the engines for now. Kb1 is a completely natural move. So is Kh1 when castling kingside. There is absolutely no need to use stockfish for this. 

Hi all

The move you have played (26.Rd7) loses the exchange after 26...Qe3+ plus ...Ne5.

The computer suggests 26.Kb1 because he assumes your opponent is not dumb enough to dismiss the above line and play 26...Qe6? (which is also winning for Black- it needed a second blunder to offer you a mate in 3 moves).

ok

umm... not usually.

I'd want to keep the f1 rook there to at least pretend I'm pressuring f7...

But I guess after Ne5 white can't even pretend to be doing anything (no infiltration on d7 either).

In fact after 1...Ne5 it's so miserable it's almost time to resign.

Right.  Like I said, its a terrible position and nothing really helps, so stockfish is trying to slightly improve in some way, any way, without doing further damage.  Kb1 may be a great move in many positions, but here I don't see it as being terribly relevant.  Its mostly just harmless, where most moves are not.  Attacking the queen is at least doing something, and maybe creates a higher risk of error without making things worse, which OP's move should do.  However, given how bad the position is, maybe OP had the right idea after all.  

Always play Kb1. Even Stockfish knows this.

not always...