Tapir: I am the unfortunate White here. I really didn't know what to do here. What are your ideas, what follow up? I played a, and it went dead wrong. I would now prefer either b or c.
Herman: IMO, b is the obvious move here. Black will probably then try to complicate things (Taisha?) because of his surrounding fighting strength, but white can choose avoiding plays. Once the upper left is settled, white can consider his options in the lower left.
Tapir: I kind of thought is sente because it threatens a, but nothing came from all the cutting there. (Well a dead invasion against some outside strength.)
Herman: Yes, white cannot cut and fight in such a strong moyo. For , I would look at moves like c, d or e. White must be willing to sacrifice something here to settle. This is just cramped, and is the perfect solid attacking move.