Then the interface doesn’t belong to Linalg from the layering perspective. If LinalgExt and GmlSt, both downstream, may choose to depend on Linalg for the purpose of implementing the interface, Tensor should not. (I know that we can avoid the dependency cycle by having an external implementation of the interface for Tensor, but this still sounds hacky).
I don’t mind it being extracted within Linalg first, you gotta start somewhere.