Over the past week, he's lost the last of his deciduous canines, made a dramatic leap in his attention span and self-control, and generally started showing signs of "adult brain" peeking up through puppy brain. He's no longer rebellious for the sake of itself, he rebels at very specific times to test very specific rules and rewards. He is much less obnoxious about his needs, but is also much more assertive, specific, and responsive. He understands word-sounds and items associated with his needs; when I'm lucky, he'll do something like bring me his grooming brush or knock the leash off the table or ring the potty bells or bat his empty food bowl around loudly. When I'm less lucky, I can usually run off a verbal list of "noms? water? cuddles? brush? potty? poo? tuggie? play? bone? walk?" and he'll respond with enthusiasm when I hit the right one. I can string two or three words together with gestures and he can often follow and retain a basic compound like "go curb sit cookie" or "up that sit wait". He also seems to have become capable of understanding the concept of waiting for me to finish what I'm right in the middle of before I do whatever he needs, so his interrupts are much less jarring on my brain than they were a month ago, though I still have to box him if I want say a whole hour to focus on something.
We still have bad days sometimes, and I still end each bad day convinced I'm utterly unqualified to be a parental, but on the good days he's a fabulous companion with impressive manners. Six months is coming up, and by then the adult brain should have more influence than the puppy brain on a consistent basis.