AskCapability is like Ask, generalized to work for arbitrary Handles. localCapability locally overrides the value of a capability in a well-scoped way. The original capability will be restored when you exit the localCapability block regardless of whether the exit was normal or via an exception.

AskCapability supports functionality similiar to effectful's interpose and polysemy's intercept, that is, locally augmenting an effect with new behaviors. If you want to do the same in Bluefin you may want to start with Bluefin.GadtEffect.interpose.