Reduction.
The moves are getting very hard to make. I think that's well shown by the fact that, as far as I can see, he just randomly attached to my strong stones like a 20kyu. I still have that ladder, so my stones are connected. Does he think I don't have the crucial liberty at 11-7?
I was considering what the best way to respond would be, but I didn't see anything that looked clearly punishing. If I'm really treating my stones as strong, then the consistent thing to do would be to tenuki.
So where to tenuki? 8-19 is huge, but when I was counting I realized he genuinely has significant potential on the right provided I don't play there first. I want to get in a move over there, while the upper right still has some aji of being captured. I was considering direct invasions on the 3rd or 4th lines, but then I realized that it was way too much hassle to attach myself to a group when he's so strong on both sides. So I'm playing the softer move on the fifth line, which is much harder to fight against, and he can back off at 17-10 and be totally fine. I've learned that LZ usually only barely favors the best reduction over the second or third best, so playing safely while reducing is just the better way to control the game. My move is still a very good exchange compared to white getting initiative in this area.
If my move isn't sente then it's close enough for me, because of the followup at 17-11 busting his side and making his shape very awkward. I don't think he has any beautiful sente sequences in the center. I expect that he just wants to simplify the game, and so will respond at 17-10. I'll then have another tough choice, between taking 8-19 at last or doing something more controlling in the center - the semi-net, perhaps?