Well, the idea is that you’d be writing low level CUDA kernels that implement operations not already implemented by JAX/CUDA and integrate them into existing projects. Numba[1] is probably the closest thing I can think of that currently exists. (In fact, looking at it right now, it seems this effort from Nvidia is actually based on Numba)

[1]: https://numba.readthedocs.io/en/stable/cuda/overview.html