Word implying this object is required by another

I'm looking for a word that has the opposite implication to "depends on" or "has this prerequisite". Something which describes the relationship of B to A if A is a prerequisite of B.

Something that could mean "dependor" or "requirer", for example?

If B requires A, then B is dependent on A. So B is a dependent of A.

Dependent: (adj) determined or conditioned by another : contingent (e.g., plans that are dependent on the weather) Merriam-Webster

The corresponding noun has the same spelling.

Logically, we might say: If A is necessary for B, then B is sufficient for A. Then B is a sufficient condition for A.

Assume that if A is a prerequisite of B, then A must be completed before B starts; otherwise, A would be a corequisite with respect to B. Then B is subsequent to A. The same webpage says subsequent is also a noun, so B is A's subsequent.

Contingent is similar. But I think it's more general because it is not related to "sequence"; B needs A, but B doesn't always happen when A does.