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The spring-cleaning continues! When I originally prototyped Relocatable OCaml, it was during the OCaml 4.13 development cycle. The focus for the work originally was always about multiple versions of the compiler co-existing without interfering with each other, so even the early prototypes were done on both OCaml 4.12 and OCaml 4.13. In fact, I see that in this talk, I even demo’d it on both versions. My intention from the start had always been to be able to provide either backports or re-releases of older compilers, on the basis that it would be tedious to have only the latest releases of OCaml supporting the various fixes, given that the failing CI systems which had motivated the project would continue to test older versions for several/many years after completion. In 2021, OCaml 4.08 (from June 2019) was still a recent memory. From a technical perspective, OCaml 4.08 was a very important release. It’s the first version of OCaml with a reliably namespaced Standard Library (the Stdlib module, though introduced in 4.07, had various issues with shadowing modules which weren’t completely addressed until 4.08). For my work, it was the version where we switched the configuration system to autoconf, and thus introduced a configuration system for the Windows ports. It provided a natural baseline in 2022 for the backports, and thus the workshop demonstration I gave in Ljubljana featured Windows and Linux for OCaml 4.08-4.14 as well as preview of OCaml 5.0.

opam 2.5.0 was released on 27th November, and this update needs to be propagated through the CI infrastructure. This post mirrors the steps taken for the release of opam 2.4.1.

In Numberphile’s latest video, Tony Padilla does a ‘magic trick’ with Fibonacci numbers and talks about Zeckendorf decompositions, and I had my laptop out even before the video ended.

Hosting the Conservation Evidence conference at Pembroke, recovering from the India trip, and keeping up with LLM developments.

As we settle into 2026, I have been doing a little early spring-cleaning. A few years ago, we had a slightly chaotic time in opam-repository over what should have been a migration from gforge.inria.fr to a new GitLab instance. Unfortunately, some release archives effectively disappeared from official locations, and although the content was available elsewhere, the precise archives weren’t generally available, which is a problem for the checksums in opam files. We’ve had similar problems with GitHub in the past. As a ‘temporary solution’, @avsm created ocaml/opam-source-archives to house copies of these archives (I think it’s a somewhat prescient sha for that first commit!). As is so often the case with temporary solutions, it’s grown somewhat. Rather against my personal better judgement, the repo got used to house files which used to be shipped as part of ocaml/opam-repository. Removing the files from the repository was a good change, because they were always being shipped as part of opam update, but unfortunately moving them to an “archive” repository has made it rather too tempting to add new files, making an archive repository a primary source.

Extending the Pico 2 implementation to add effects-based WiFi networking and improve the build system.

Curious about the origins of opam? Check out this short history on its evolution as the de facto package manager and environment manager for OCaml. Welcome back to the opam deep-dives series! In this article, we cover two essential topics for any OCaml developer: Setting up a development environment...