codeflux:

It does give me a grad, but in respect to what?


End node (dloss/dv). In other words, it is a vector-Jacobian product 1 @ J_loss_y @ J_y_v.
These Jacobians may be diagonal, but they’re not materialized / exported anyway. So, dy/dv=dPow(v,2)/dv=2v is not normally accessible (outside of PowBackward)
Last version has “experimental forward mode AD” that may facilitate this, but I haven’t looked into it yet.