I guess passenger timed out here but I don't see a win for black now anyway. But I thought |40.h10 looked like a win for black. If attacked from below you get something like:

|40.h10 41.l12 42.g8 43.f13 44.e9

or from above something like:

|40.h10 41.g9 42.i12 43.h12 44.f11

Does white have a winning response to |40.h10?

Keep in mind that White has an unspoken resource at R15. If White gets the first-mover advantage in that corner, that black line (to o15) becomes worthless. For example, Black may have been thinking:

|42.g11 43.f11 44.c9 45.d8 46.e10 47.h10 48.s15

But move 43 wouldn't have necessarily gone that way, so it still appears to be a winning position for White, if he's paying attention:

|42.g11 43.h10 44.c9 45.d8 46.e10 47.r15

Now, recognizing that R15 threat and turning back to your proposed move:

|40.h10 41.g9, and then what? Black's top line is dead, and White's double threat is R15 and L12.

Ah, the right side carries the response, of course. Thanks, I was obsessing on the left side of this game waiting for the tournament to end, and didn't understand the value of 40.i12 at all.