[boibombeiro]

Looks neat.

I've though about using tree-sitter DSL to generate zsh completion.

Your project seems to be a better candidate for this. Tree-sitter DSL, with some extra annotations, could be used to generate the specification. With the added bonus of being a format that can provide syntax highlight on text editors (in commands in sh files).

If I not mistaken, tree-sitter also uses TS.

I only gave a quick look at fig (only use HN on mobile). Will have a better look when at the desktop.