Quick DDD terminology question: Say Context B depends on A (e.g. because B uses one of A’s services). Is A always “upstream”, or does this change depending on whether one applies “Conformist” or “Customer/Supplier”?

"Upstream" only defines the direction of the relation ship, not necessarily who drives it, right?

That’s my take as well, but we have a lot of internal discussion about this at the moment

theoretic discussion or driven by a real world problem? From my point of view @olivergierke and you are right.