Dark Beer Decoction ?

Should roasted / black malts be part of a decoction boil or added to the mash after the step up?  Or does it depend on the style?

Why would you do it that way?
When I do decoction I do not exclude ane grain.
I doubt that pro brewers in Germany / Czech would hold some grain back.

Black Patent is the only grain I’ve ever seen left out of a mash and then added before the sparge.  Not sure why?  Maybe to reduce the bitterness?

yes, I think the idea is to reduce bitterness but I like to add all grain in the beginning. Much less chance that I’ll forget the additional grain later.

Kai