Ideally, x-braces are modelled as two independent members with no intersection (no node connecting all 4 'parts'). Having a node at the intersection can create instability due to load sharing among all 4 members.
[EDIT]:
I just realised I didn't answer the question. We typically consider them pinned and avoid having them resist moment to simplify calcs and detailing. Basically, have the behaviour as a truss consider purely axial forces and no bending (EA - stiffness)