OCaml Weekly News

Hi all,

LexiFi is looking for a Software Engineer to join our development team in Paris. The work is primarily in OCaml, contributing to our codebase across core components, tooling, and product features.

If you're interested in working on a large, long-lived OCaml system used in production by financial institutions, you can find the full job description here: https://www.lexifi.com/careers/software_engineer/

Happy to answer any questions!

Dear everyone,

we did another run of the archival based on the x-maintenance-intent of opam packages. The run was using opam-repository at commit d684c896eb6f7e6030d6ee65338d9db22a612f01 (Dec 9th, 20:00:00 CET).

The tool used is maintenance-intent-filter with opam 2.5 and OCaml 5.4. It took around 1GB of memory and around 100h of CPU time (donations welcome).

In total, 4510 packages were candidates, out of which 3361 are scheduled for archival.

I am pleased to announce the development of blame, a unikernel that provides a search engine in the form of a web interface based on an email archive.

This work is sponsored by NLnet as part of our PTT project. For more details on the unikernel, our archive system, and our search engine, we recommend reading our article available here. This project is the synthesis of several projects on the subject:

• mrmime to parse/encode emails
• carton to archive emails
• stem to search emails
• blaze like a Swiss Army knife for manipulating emails and archives
• and of course some of our projects like miou, utcp or vif

If you like our work, you can sponsor us via GitHub or by following the instructions available here. Thank you to everyone who has participated in the development of these projects, whether directly or indirectly.

So, happy hacking "discriminating hackers" :) !

Hello,

I have been following @sabine's post, https://discuss.ocaml.org/t/looking-for-maintainers-moderators-for-the-ocaml-cookbook/16497.

I really want to contribute but like any engineer, I am pressured on deadlines, which incentivizes me to ask here or in Discord. There are even wonderful books like Type Theory and Formal Proof, but I cannot allocate good time to read them.

That motivated me to think of a new mechanism, where documentations and question-answers are bridged, through Snippet project.

Someone asks a question like this. Instead of answering the question, you must contribute a self-contained paragraph, called "snippet", then cite it in the question. For example the question cites:

• snippet Parametric Abstraction with Functors and Modules design pattern in OCaml, citing
• snippet Functor, OCaml linking to OCaml's doc, citing
• snippet Functor, PL linking to Category theory blog, citing
• snippet Abstract Data Types linking to Software Foundations book.

If some snippet gets a high number of citations, then that would be a signal to contribute it to OCaml's documentations or OCamlverse. In other words, OCaml's cookbooks will be naturally contributed as more people's questions get answered, and will be naturally certified as more people cite it!

The project is built on Dream, open-source, and CC 4.0 licensed. I'd be happy to see OCaml's maintainers self-host an instance of it in OCaml's official website. We could even design a voting mechanism to elect snippets for the official documentation.

For now, I am happy to listen to your feedback.

Hi there!

I'm happy to announce the first release of the serialport library. The library is planned to be a cross-platform library for serial port communication in OCaml, which supports both POSIX and Windows systems. It provides synchronous and asynchronous interfaces using various I/O libraries (like Lwt and other).

The library currently only supports POSIX systems.

The main motivation behind creating this project is to address the lack of a comprehensive library for managing serial port communication in different environments, as well as the lack of an intuitive API for this task. The existing OSerial library has significant limitations in terms of functionality and future development, making it unsuitable for use in modern environments.

The serial port library is most inspired by similar implementations in other languages, such as Rust's serialport and Golang's bugst/go-serial.

lwt.6.0.0-beta01 has been released!

With this release comes a change in the title of this thread:

- [ANN] Lwt.6.0.0~beta (direct-style, multi-domain parallelism)
+ [ANN] Lwt.6.0.0~beta (direct-style, runtime-event tracing)

This is likely the last beta before the release of Lwt.6.0.0, please test and share your feedback. The highlights are

• (compared to previous beta) no more multidomain-multischeduler parallelism
  • it was too buggy,
  • you can still use Lwt_domain
• (compared to previous beta) runtime-events produce a trace of execution of your lwt program for better debugging
  • only if lwt_runtime_events is installed,
  • tracing instructions added by ppx,
  • example producing a trace of recent events in case of crash in https://github.com/ocsigen/lwt/tree/6.0.0-beta01/examples/tracing
  • example live monitoring the events to send signal in case of stall in https://github.com/ocsigen/lwt/tree/6.0.0-beta01/examples/stall_detection
• (compared to Lwt.5.9) direct-style with Lwt_direct
  • you can write direct-style lwt (within a given scope)

  • e.g., you can interact with libraries that only provide iter : ('a -> unit) -> 'a -> unit such as

    let iter_s f h =
      Lwt_direct.spawn @@ fun () ->
        Hashtbl.iter (fun k v -> Lwt_direct.await (f k v)) h
    

Once again, thanks to @c-cube for the direct-style feature which makes it possible to use Lwt in conjunction with libraries even if they don't include special amenities for it.

Thanks again for @edwin for the bug report on multi-scheduler-related failures.

Finally, lots of OCaml content at BOB!

Here are links from many OCaml blogs aggregated at the ocaml.org blog.

• AoAH Day 14: Debugging a Karakeep CLI against the live service
• AoAH Day 13: Heckling an OCaml HTTP client from 50 implementations in 10 languages
• Advent of Code 2025
• AoAH Day 12: Eio Connection pooling and event tracing
• One Mollymawk, Multiple Albatross servers
• AoAH Day 10: Building a TUI for Sortal using Mosaic
• AoAH Day 11: HTTP Cookies and vibing RFCs for breakfast
• Creating ocaml.nvim to Bring Neovim Support to OCaml's LSP Server
• AoAH Day 9: Adding a Bonsai terminal UI to Sortal
• OCaml Roundup: November 2025
• An SVG is all you need
• AoAH Day 8: Building a contacts CLI manager with Sortal
• AoAH Day 7: Converting between JSON and Yaml with yamlt
• AoAH Day 6: Getting a Yaml 1.2 implementation in pure OCaml
• Private repos in OCurrent
• AoAH Day 5: Bytesrw Eio adapters and automating opam metadata
• A webapp to search emails as an unikernel
• AoAH Day 4: Going recursive with Claudeio for Claude
• AoAH Day 3: XDG filesystem paths using Eio capabilities
• AoAH Day 2: Building an OCaml JSONFeed library
• AoAH Day 1: Building a Base32 Crockford library in OCaml
• The AI French Connection to the Practice of Science
• 2025 Advent of Agentic Humps: Building a useful O(x)Caml library every day