drukenknight: simpler is 25...Rxe6 to stop Sneaky's mate threat.
The reason I think 25...Qh6 is wrong is that black has just fallen behind in material, he can't give the tempo back to white AND be down in material. You cant fall behind in two departments and expect to hold the game.
How do we know black is behind in material? At black's 25th he has 4 connected pawns to 3, but there is a passed pawn for white. I'll count the passed pawn as 1 1/2 but you can just say it's something more than 1 pt.
Okay sometimes you can fall behind in BOTH tempo and material if you are able to sack material in order to gain a mating attack, that can happen. Which essentially means you trade material in order to gain position (ie a mating position).
So maybe there is a mate for black in there. We'll have to check for that.
Okay, if there is no mating net for black, then it seems black must regain material in order to keep the balance.
25...gxh5 does get back material (B v 2P) but we said white was up by 1 1/2, so it would be white up by a fraction of material AND having the move if we do that. Doesnt seem correct.
Okay what about Rxe6, seems simplest and it also stops the Bxg6 threat.
Hmmm, 26 Rxe6 Nxe6 and material remains even for the moment.
27 Bxg6 what then?
INteresting, there must be a save in here.