Most of my time over the past six months has been devoted to ppxlib maintenance. A large proportion of this time has been solo development work. Ppxlib is a cornerstone library of the OCaml ecosystem (whether people like it or not).

$ opam list --depends-on=ppxlib --recursive | wc -l
2030

Moreover, it is completely invaluable to Jane Street too. Like other AST-based tools (e.g. ocamlformat, merlin), ppxlib must follow a regular release schedule to support newer compilers. During the years of multicore OCaml development, ppxlib maintenance was a little easier as the Parsetree rarely changed. However, since then, the same cannot be said. Since OCaml 5.2, here are just some of the Parsetree changes:

• Functions are represented according to their arity.

• Local module opens on types.

• Effect syntax.

• Modular explicits.

• External types.

• Locations for all parts of long identifiers.

• Labeled tuples.

In a perfect world, each of these require a codec for serialising the feature into ASTs that do not support the feature, plenty of tests and new Ast_builder/Ast_pattern functions for using the feature. Nathan and I have been managing pretty well I would say, though we are not getting any technical debt work done.

As the OCaml coordinator for Outreachy I have been running the latest December 2025 round. We are lucky to have four projects on the go!

• Thibaut Mattio is mentoring two projects: an ML dashboard for Raven and an OxCaml backend for Raven.

• Xvw is mentoring a Yocaml project.

• I am mentoring a Geocaml project.

During my work on tools like Shelter I have made a few improvements to Eio including:

• A draft PR for incremental reading of directories.

• New fork actions for processes: setgid, setuid and process groups.

• Utility functions for overriding standard environments.

• Fixing documentation.

I have enjoyed my work on OxCaml went it has happend. I think a few tools have been useful including the try-oxcaml work. David and I also had fun at ICFP discussing some quick experiments related to io_uring and OxCaml.

One road-blocker here is the comparative amount of time spent trying to keep the OxCaml ecosystem working. Given my limited time working on fellowship projects, the rate of change of OxCaml (including the opam ecosystem) meant most of the time was spent making it just work, not exploring or experimenting with the features themselves. I think this has got better in recent months and perhaps jumping back in I would be surprised at the progress that has been made there.

Tarides are funding some work on forester. This site uses forester by way of graft and I have spent some time working on these tools during the fellowship.

This includes a bytesrw-based bibtex library in OCaml that could be released soon.

I had the great fortune of attending ICFP where I presented two talks and was co-author on a few others too.

See also the online hazel of ocaml compiler

I had some great conversations with KC too with respect to my current research.

There are multiple projects that overlap with my work. For example, Irmin, which I wrote a retrospective for. This is at the core of Shelter and suggests an extremely valid use case for a brancheable, mergeable database.

In addition to this, continuing to work on Eio makes sense to me too. Eio currently has no maintainer and no active development, but the issues are piling up. In particular, I am making heavy use of Eio in Merry, a POSIX(ish) shell written in OCaml. Aside from research angles on brancheable and mergeable shells, I am also quite interested in how this might look in terms of OxCaml. I met with Anil and Thomas recently to discuss the future of Eio and there was some agreement that we are all heavy users of it and hope to keep up its maintenance and set of features.

One large piece of work that is sorely needed here is moving Eio to bytes and not bigarray-backed Cstructs. Any libraries using bytesrw (e.g. jsont) incur an extra copy of data into and out of the bytes. Anil has been working on some of the pieces recently to make this better!

I have published quite a few OCaml libraries in my time, below is just a few libraries (filtered to not include OCurrent projects).

$ opam list --all --no-switch --columns=name,authors: | grep -E "sirref|Ferris" | cut -d " " -f1
carbon
geojson
geojsone
graft
hilite
ISO3166
jekyll-format
ppx_deriving_ezjsonm
ppx_deriving_yaml
rtree
search
topojson
topojsone
cid
multibase
multicodec
multihash
multihash-digestif

Some of these are used in the community including hilite, ppx_deriving_yaml and the multi-codecs. I would like to do some general maintenance of some of these tools and release a few iterations of graft which now makes use of bib.

By far, maintenance of ppxlib takes up a majority of my time. I think, given the other work I need to focus on, it would be great to try to minimise the amount of time working on ppxlib. In particular, perhaps only maintaining ppxlib as far as OCaml release-readiness is a possibility and important bug fixes (like the OOM bug reported by Jane Street).

With all of this work, I am eager to communicate what I am up to and my thoughts on open source, OCaml, OxCaml etc. I am glad to be using Forester to do this, particularly as it is written in OCaml (and could make great use of my own work on Eio).

I hope to continue working on Graft and related tools like bib. But I would also like to start writing some long-form content similar to the Irmin retrospective.