Alex Weldon: This seems to be best play for both sides, as far as I can tell. I don't see any way for White to do this in sente.
SnotNose: White's only hope for sente is the hane and connect of and . Compared to Alex's solution above, this result is four points better for Black, but White retains sente. Note that isn't necessary for life so even this might not be sente for White. However, if Black omits , White can make a further reduction, as shown in the next diagram.
SnotNose: If Black omits of the previous diagram, White can play as shown. This is equivalent to Alex's solution (in terms of Black's area). A difference is that White has fully protected the right edge (i.e., Black cannot hane and connect to the right anymore.)
Velobici: Play on the point of symmetry is a proverb. does just that, as does . At this point, White must be careful in choosing which way to move in connecting to the outside, the two directions of not symmetrical. The marked black stone decreases White's liberty count if White plays at a in place of .
White must sacrifice a stone with , forcing Black to connect with , and preventing Black from creating the connect and die. Black can not play at a due to his own shortage of liberties. This allows White to connect at the point formerly occupied by and at b. Black will live by playing at c, forcing White to connect at the point formerly occupied by . Black then plays at a, forming his second eye by capturing and forcing White to connect at b.
dnerra: Looking at everything proposed so far, it seems to me that this is the correct sequence for both. After , Black can tenuki, as White cannot play at himself. Black has to add the exchange - at some time when it has become sente and before he has lost his liberties all around. Since Black a-White b can be counted as Black's priviledge, this seems approximately one point better for Black than the sequence suggested above as optimal for both sides.
Dieter: Aside from the tenuki issue, this is indeed the solution we found when watching the game on KGS. Note that White can't play at due to shortage of liberties. In the game, joeker? missed , either or not deliberately since he was winning anyway.
If White wishes to retain sente, he can play as in the Black resists more strongly diagram. That loses only 1/6 of a point.