This is a documentation generator by Fernando Boretti.
It is built for extensibility and uses CommonDoc as an internal format for document representation and manipulation.
Another interesting feature is a custom markup language Scriba (reviewed in post #0178). Actually, Codex supports any number of markup languages, you just need to write a parser from this markup into CommonDoc.
The sad part is that there is no support for cross-referencing and there are a number of bugs :(
As always, I’ve created a template project for you, demonstrating how to use Codex to document a simple Common Lisp library:
https://github.com/cl-doc-systems/codex
Read about other pros and cons on this page:
https://cl-doc-systems.github.io/codex/pros-&-cons-of-codex.html