This is one of the leaf-cutting or resin bees in the genus Megachile. There are over 1,500 species world-wide and about 130 in our area. While I could eliminate a few species from consideration, I really have no idea which of them this is. It’s a little but not tiny bee, measuring about 12 to 15mm in length (I didn’t actually measure it with a ruler or anything).
This is one of a growing number of bees and wasps that is now enjoying the mountain mint (Pycnanthemum muticum).