Could you point me towards one that isn't? Or is this something still in the theoretical?

I'm really trying not to be rude, but there's a massive amount of BS being spread around based off what is potentially theoretically possible with these things. AI is in a massive bubble right now, with life changing amounts of money on the line. A lot of people have very vested interest in everyone believing that the theoretical possibilities are just a few months/years away from reality.

I've read enough Popular Science magazine, and heard enough "This is the year of the Linux desktop" to take claims of where technological advances are absolutely going to go with a grain of salt.

But they are. There's no feedback loop and continuous training happening. Once an instance or conversation is done all that context is gone. The context is never integrated directly into the model as it happens. That's more or less the way our brains work. Every stimulus, every thought, every sensation, every idea is added to our brain's model as it happens.