Xanthan gum in bread baking I was under the impression that Xanthan Gum could be used in bread in order to increase the hydration and make it fluffier. I have tried it three times (0.5% - 1% of flour weight) in two different recipes (croissants and regular buns), but the dough was not noticeably easier to work with, nor did it rise quite as much as normally. (I did not do a controlled test, so it's hard to pinpoint the cause.)

I know that Xanthan Gum is normally used in gluten free bread, but that's not what I'm after here. I have read (but can't remember the source) that it can be used in regular bread to make the crumb airier, but in my limited experiments, that does not appear to be the case.

What should I expect from adding Xanthan Gum to bread dough? 

I have also seen some cookie recipes that call for it, but I couldn't understand what role it was supposed to have.
You seem to have misunderstood something, or been misinformed. 

The only reason that xanthan gum does something in gluten-free bread is that gluten-free bread cannot trap any air for rising and is a very moist and dense thing on its own. The xanthan gum is a kinda OK gluten replacement, imitating its role somewhat. 

It has no such effect in normal dough with gluten. Indeed, it might make it less airy and generally worse, like dough which has too much gluten added. Or it might have so little effect as to be unnoticeable. But it certainly has no mechanism by which it would improve your normal bread dough. 

I cannot say much about the cookies, but it might be that they needed additional binder. This depends on what kind of cookie it was, but some kinds are full of filler and very prone to crumbling, xanthan may help with that. Or somebody backconverted a gluten free recipe to a wheat one and didn't understand that this makes the xanthan obsolete. There are many possible explanations.