While looking at the code for some of the DH on Github, I’ve noticed that some of the handlers are able to run locally on the hub. I’m wondering who or what determines which handler is actually able to be executed locally though?
Samsung engineering staff makes this determination. The only device type handlers that are eligible to run locally are those that are written by SmartThings and distributed to all customers with the hub firmware. They keep adding to this list.
That said, my understanding is that some stock DTHs, and in particular those that create child devices, are not eligible for this. But others will know more about that aspect.
No custom code is eligible to run locally at this time.