Thanks! This looks nice.
I have used Fix in the past, but I was not aware that it is doing more than efficient fixpoint computation thanks to dynamic dependency checking. (It looks like the project has gone from “descriptive name” to “nice-sounding name that’s not entirely related to what’s in the package”.)
Some idle feedback from just looking at the documentation: I find the main documentation page unstructured and difficult to read. The README is much nicer, but also not what people will get by looking for “the documentation” of the package, manually or through automated tools.
Have you considered moving the README content and structure to the documentation proper, and having a shorter README that points to the documentation for usage examples etc.?
Note: you may be interested in this Discuss thread on how to write a good documentation landing page for packages using Dune. (This is documented in the Dune documentation, but only if you select the “latest” as opposed to “stable” version of the documentation website.)