There seems to be more nuance to this, because even if we include the missing \usepackage, myst will still complain of Undefined control sequence:

👍 Any Progress on this?

I must say, it is not easy to find out of to get some \usepackage in mystmd working. I need \reflectbox from \graphicx, and struggling quite a bit finding the correct way to get that done.

@LecrisUT I've rebased your fix/978 branch and rebuilt the mystmd codebase on my machine. Could you please give me some guidance / advice as to how to use this imports field ?

Iirc, you just need to add an imports field to the front-matter e.g.:

exports:
  - format: pdf+tex
    imports:
      - physics

@LecrisUT Then, I'm doing something else wrong that I do not understand. Thank you, and sorry for disturbing you needlessly.

@LecrisUT Erratum: it in fact does work. I just checked it by importing the "cancel" package as follows:

exports:
  - format: pdf+tex
    template: curvenote
    imports:
      - cancel

I am now able to write \cancel{\exists} with it, and could not before. So it indeed does work.

The main branch of my fork of mystmd contains the merge of current main branch and of your fix/978 branch.

https://github.com/gl-yziquel/mystmd

Please feel free to update your PR.

Feel free to take over that PR. It would need some documentation and tests. I'm not that proficient in node stuff so I don't know if the approach there is appropriate.