nbextensions should be installed and enabled on a per-kernel basis, not per-user.

We are running into some problems with the way the jupyter notebook extension system works.

It appears that notebook extensions are installed and enabled either system-wide, or per-user.

This makes life difficult when sharing notebooks with other users on JupyterHub. The other user would need access to the terminal, to install and enable any extensions needed by a given notebook. God forbid if different kernels need different versions of the same extension.

I believe that installing and enabling notebook extensions on a per-kernel basis would make more sense. If you are going to share a notebook to another user, chances are that you want the other user to run it with the same kernel.

Start by examining the Jupyter Notebook extension system and how it currently installs and enables extensions system-wide or per-user. Compare that behavior with kernel selection and shared notebooks on JupyterHub, including cases where different kernels need different extension versions. Done means extensions can be installed and enabled per kernel without requiring each user to use a terminal.

Written by the indexing model from the issue text.