iiinova — where your digital self keeps evolving

Yaron Minsky @yminsky.bsky.social · 11/06/2026

I've been telling people for 25 years that Jane Street is not interested in formal methods. No more! And we're actively hiring to form a new formal methods team! blog.janestreet.com/formal-metho...

blog.janestreet.com

Formal methods and the future of programming

I’ve been telling people for the last 25 years that Jane Street as an organization was just not interested in formal methods.

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Yaron Minsky @yminsky.bsky.social · 29/03/2026

This is a fairly wild post about OxCaml Labs from @avsm . It's hard to summarize the stuff they're doing, but, some examples: - Some wild vibecoding - A formal semantics for package managers - A decade of docker containers (including OxCaml!?!) anil.recoil.org/projects/oxc...

anil.recoil.org

OxCaml Labs

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Yaron Minsky @yminsky.bsky.social · 20/03/2026

Another fun hiring spot at Jane Street: we're looking to hire some great hybrid writers-and-engineers. As we grow and do more, communication becomes ever more important, for both internal and external audiences. www.janestreet.com/join-jane-st...

janestreet.com

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Yaron Minsky @yminsky.bsky.social · 17/03/2026

It's been a minute, but, time for another Signals and Threads, this one with Will Wilson about the testing tools he's building at @antithesis.com. And, in a bow to modernity, we have a video version of this one too! youtu.be/F_LvzcdNH3Q?...

youtu.be

Why Testing Is Hard and How to Fix It

YouTube video by Jane Street

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Ty Overby @tyoverby.com · 08/03/2026

A poor craftsman blames his tools. Wealthy craftsmen also blame their tools. Lots of tool-blaming going around.

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Yaron Minsky @yminsky.bsky.social · 03/03/2026

I wonder if we're starting to hit a deflationary era in software engineering. For the first time, we're starting to talk about this in a planning context; it can make sense to put off some projects because we expect they'll be easier to achieve in the future than today.

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Joe Cutler @alphaconvert.bsky.social · 09/02/2026

Seems like a good time as any to say I'm: (1) moving to New York next week, where I'll: (2) be writing OxCaml at Jane Street! Excited to start the next thing :)

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New Ideas in Networked Systems @nines-conference.org · 31/01/2026

February 10th, and thus the inaugural edition of NINeS is just around the corner. You can participate from anywhere in the world, at times that are convenient to you. See nines-conference.org/attend for information on how you can participate. We hope to see you on Feb 10th!

nines-conference.org

Attending NINeS 2026

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Yaron Minsky @yminsky.bsky.social · 18/12/2025

My regular PSA that if you enjoy working on developer tools, then Jane Street is kind of an amazing place. Apply here! There's no special posting, so just apply for the Software Engineering role, and express your interests in dev-tools in a note. janestreet.com/apply

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Yaron Minsky @yminsky.bsky.social · 23/10/2025

We've had an exciting couple of weeks full of opportunities to teach people about the exciting (and mildly bewildering) features of OxCaml. And...we're looking to hire an experienced educator to help us in this work. Please share this with anyone you think might be a good fit!

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Yaron Minsky @yminsky.bsky.social · 20/10/2025

I did anothr version of my "Saga of Mulicore OCaml" talk, but this time, nerve-wrackingly, the authors of the original paper were all there! Here's the link to the talk, which is found towards the end of the recording for the whole session. t.co/FQTmsFWji0

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Yaron Minsky @yminsky.bsky.social · 11/10/2025

Me too! (But Max knows more about it than I do.)

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Kit Eason @kitlovesfsharp.bsky.social · 03/10/2025

Most companies be like “We daren’t go functional, we might not be able to hire”. Jane Street be like “Hold. Our. Beer.”

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Yaron Minsky @yminsky.bsky.social · 03/10/2025

Excited to say that we're looking to hire someone to focus on OxCaml education! We're doing enough to change the language that we have a pretty big internal education task ahead of us, and we want to hire someone to focus on it! Please share this with others! www.janestreet.com/join-jane-st...

janestreet.com

OxCaml Educator :: Jane Street

Jane Street is a quantitative trading firm and liquidity provider with a unique focus on technology and collaborative problem solving.

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Yaron Minsky @yminsky.bsky.social · 30/09/2025

A fun talk about...hacking OCaml. Basically, what you get when you supercollide a systems-y OCaml developer and a CTF. www.youtube.com/watch?v=SV9V...

youtube.com

Hacking OCaml

YouTube video by Jane Street

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Richard Primus @richardprimus.bsky.social · 18/09/2025

On Advisory Opinions, Sarah Isgur and David French speak with me about enumerated powers. The segment begins 43-44 minutes in, depending on format. This was a good conversation among people with different approaches to constitutional interpretation. thedispatch.com/podcast/advi...

thedispatch.com

The Oldest Constitutional Question | Interview: Richard Primus

Originalism through the lens of sola scriptura.

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Simmo Saan @sim642.eu · 16/09/2025

They should know the difference between TeX and LaTeX, so they could hate Lamport less and Knuth more.

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Yaron Minsky @yminsky.bsky.social · 16/09/2025

Clearly, the reason for the AI work is to build an AI capable of porting from Latex to Typst.

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a ton of crates @tonofcrates.bsky.social · 16/09/2025

"we need a manhattan project for AI" no what we really need is a manhattan project for porting every math TeX package to Typst (and please start with mathpartir)

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Yaron Minsky @yminsky.bsky.social · 16/09/2025

I've raised my kids well, I think.

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Yaron Minsky @yminsky.bsky.social · 04/09/2025

A new episode of Signals and Threads just dropped! This one is an interview with Chris Lattner talking about Mojo, a new-ish language for GPU programming that's aiming to be an alternative to the CUDA stack. signalsandthreads.com/why-ml-needs...

signalsandthreads.com

Signals and Threads Podcast

Listen in on Jane Street’s Ron Minsky as he has conversations with engineers working on everything from clock synchronization to reliable multicast, build systems to reconfigurable hardware. Get a pee...

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Yaron Minsky @yminsky.bsky.social · 30/08/2025

This was a great talk from Will Crichton. I think Will's approach to approaching questions around language tooling and teaching is compelling, though I wonder how far the approach can scale! youtu.be/R0dP-QR5wQo?...

youtu.be

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Yaron Minsky @yminsky.bsky.social · 28/08/2025

I just finished our yearly roundup of this year's intern projects, and it was a real bumper crop! Lots of fun projects, and some cameos from OxCaml... blog.janestreet.com/wrought-2025/

blog.janestreet.com

What the interns have wrought, 2025 edition

Yet again, we’re at the end of our internship season, and so it’s time to summarize whatthe interns were up to!

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Yaron Minsky @yminsky.bsky.social · 13/08/2025

Just ran across this old post from a former intern about Jane Street's approach to programming and code review. I thought it was a pretty accurate, and I think captures something important about how OCaml's design makes code review easier and more effective. digitalfreepen.com/2017/01/07/j...

digitalfreepen.com

Learned at Jane Street - Practical functional programming and software engineering - Digital Freepen

This is the second of two blog posts on my Summer 2016 internship experience at Jane Street, focusing on the technica...

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Anil Madhavapeddy @anil.recoil.org · 07/08/2025

This will remove so many unnecessary OCaml functors from our codebases. My rough rule of thumb is that if a functor is not applied more than once in a codebase, it doesn’t need to be a functor. Parameterised libraries lets us easily do one-shot reuse of existing modules in a different context.

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Yaron Minsky @yminsky.bsky.social · 01/08/2025

We've finally landed a full version internally (coming to an OxCaml near you soon!) of a new feature called parameterized libraries. It's basically an answer to a problem I first ran into 23 years ago. Here's a thread about it on the caml-list. inbox.vuxu.org/caml-list/10...

inbox.vuxu.org

[Caml-list] Functorizing large collections of modules - Yaron M. Minsky

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Yaron Minsky @yminsky.bsky.social · 25/07/2025

A new epsiode of Signals and Threads has just dropped: "The Thermodynamics of Trading". I got to talk to Dan Pontecorvo from our physical engineering team about the complex work that goes into our physical spaces to make the work we do at Jane Street possible. signalsandthreads.com/the-thermody...

signalsandthreads.com

Signals and Threads Podcast

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Yaron Minsky @yminsky.bsky.social · 24/07/2025

I had a lot of fun giving this talk in Singapore about the many-years-long saga of multicore OCaml, and in particular, the work over the least 2.5 years of getting it ready for production work within Jane Street's walls. www.youtube.com/watch?v=XGGS...

youtube.com

The Saga of Multicore OCaml

YouTube video by Jane Street

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Thomas Gazagnaire @gazagnaire.org · 23/07/2025

My approach so far is to treat AI code assistants as an extension of “a large team with communication challenges working on the same codebase.” You need better tools to clean up the local optima that individual agents get stuck in. See prune and merlint: discuss.ocaml.org/t/ann-new-to...

discuss.ocaml.org

[ANN] new tools to keep your projects clean (after AI, or just after yourself)

Hi all, I’ve been experimenting with AI code assistants lately. They’re surprisingly good at generating new code but it’s not very good at remembering things: it’s like having a steady stream of good...

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Yaron Minsky @yminsky.bsky.social · 21/07/2025

Yet another small OCaml/OxCaml diff has been squished! Polymorphic parameters has just gotten merged upstream: github.com/ocaml/ocaml/... There's more to go (include functor, for example: github.com/ocaml/RFCs/p...), but it's nice to see more progress in this space.

github.com

Polymorphic Parameters by voodoos · Pull Request #13806 · ocaml/ocaml

This upstreaming PR adds the possibility to have function parameters with polymorphic types in the language. This work was originally done by @lpw25 in Jane Street's fork of the compiler with e...

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Yaron Minsky @yminsky.bsky.social · 18/07/2025

We're starting to think about how to evolve OCaml to be a more effective language for agentic programming. One intuition here is that agents change what's important in 2 ways: - the toil of writing matters less - the ease of understanding and verifying matters more 🧵1/3

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Yaron Minsky @yminsky.bsky.social · 18/07/2025

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Anil Madhavapeddy @anil.recoil.org · 15/07/2025

Some fun OCaml GC projects here with @sadiq.toao.com and @kcsrk.info if any students are looking for projects involving programming languages toao.com/blog/ocaml-0...

toao.com

Last three months in OCaml (July 2025) - Sadiq Jaffer

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Kiran @kirancodes.me · 06/07/2025

PSA! Please share around! Due to a limited number of submissions, we're extending the OCaml Workshop deadline by a week to July 10th AoE! Functional programmers! Heed my call! We need your submissions!!

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Yaron Minsky @yminsky.bsky.social · 24/06/2025

A gem from Stephen Dolan, which proposes replacing the "generational hypothesis" that drives the design of generational GCs with a notion of lifetime dispersion as measured by the gini coefficient. Nice to see economics playing a role here! dl.acm.org/doi/pdf/10.1...

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Ty Overby @tyoverby.com · 22/06/2025

Something I predict will happen soon is using LLMs to port large test suites from one language / framework to another. Imagine starting a graphics or networking project and having hundreds of thousands of test cases already implemented!

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Sam Westrick @shwestrick.bsky.social · 19/06/2025

taking a go at oxcaml today first attempt: let's try a parallel reduction. Idea is to compute the "sum" of [f(lo), ..., f(hi-1)] in parallel, combining via some associative function g (and corresponding zero element, z).

a picture of the following OxCaml code:

let rec reduce _par grain g z (lo, hi) f =
let n = hi - lo in
if n <= grain then
let rec loop acc i =
if i >= hi then acc else loop (g acc (f i)) (i+1)
in
loop z lo
else
let mid = lo + n / 2 in
let l, r = Parallel.fork_join2 _par
(fun _par -> reduce _par grain g z (lo, mid) f)
(fun _par -> reduce _par grain g z (mid, hi) f)
in
g l r

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Sam Tobin-Hochstadt @samth.bsky.social · 17/06/2025

Over the 10 days, I wrote a new Racket library for "expect testing", a style that @yminsky.bsky.social has advocated for in OCaml. github.com/samth/recspe... As an experiment, I built it entirely with Codex (the OpenAI async AI programming tool). I have some thoughts.

A screencast of using recspecs in emacs.

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Yaron Minsky @yminsky.bsky.social · 15/06/2025

A thing that people may not realize is how new some of the OxCaml extensions are. We are on the verge of rolling our very first data race free parallel program into production. Almost no one at Jane Street knows how to use this stuff yet!

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Brendan Zab @brendanzab.bsky.social · 15/06/2025

The memory management aside, I’m really excited about the stuff already in the process of being upstreamed, like labelled tuples, polymorphic parameters and include functor. Those will be really handy to have!

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Sam Westrick @shwestrick.bsky.social · 13/06/2025

OxCaml SIMD primitives are looking really nice 👀 > [unboxed vector values] are passed between functions in XMM registers, stored in structures as flat data, … > Within a function, all SIMD vectors live in floating-point registers or 16-byte aligned stack slots. oxcaml.org/documentatio...

oxcaml.org

OxCaml | SIMD | Intro

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Yaron Minsky @yminsky.bsky.social · 13/06/2025

I'm pleased to announce OxCaml! OxCaml is Jane Street's branch of OCaml. We've given it a new name and a snazzy logo, and done a bunch of work to make it easy for people to try.

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Yaron Minsky @yminsky.bsky.social · 12/06/2025

Fun talk preparation trick: use Claude Code to create HTML animations for complex diagrams I want. Talk it through, explain in English, maybe even share a snapshot of a hand-draw diagram to get it going. It takes some babysitting, but the results are better than what I would have gotten on my own.

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Yaron Minsky @yminsky.bsky.social · 11/06/2025

I was recently reminded of this old post, highlighting how broken IEEE NaNs are. Really, ML and its descendents had the right idea here, and everything else is kinda broken. blog.janestreet.com/making-somet...

blog.janestreet.com

Making something out of nothing (or, why None is better than NaN and NULL)

Null is a pervasive concept in computing. Virtually all programming languageshave a way of expressing nothing, nullity, no answer. But handling nullscorrectl...

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KC Sivaramakrishnan @kcsrk.info · 30/05/2025

Using uniqueness mode for improving behavioural types: kcsrk.info/ocaml/modes/...

kcsrk.info

Uniqueness for Behavioural Types · KC Sivaramakrishnan

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Yaron Minsky @yminsky.bsky.social · 28/05/2025

A new Signals and Threads just dropped, with @ianthehenry.bsky.social! This one is about building tools for traders, but it also has some fun dives into Ian's personal projects, including bauble.studio and janet.guide. Anyway, more here: signalsandthreads.com/building-too...

bauble.studio

Bauble

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Yaron Minsky @yminsky.bsky.social · 27/05/2025

I'm curious if anyone could summarize for me the state of evidence on the utility of type systems in reducing software faults. I'm aware of and even the source of some of the anecdotal evidence, but I'm curious if there's anything even vaguely methodologically rigorous.

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Yaron Minsky @yminsky.bsky.social · 25/05/2025

The other great thing about AI-assisted programming in OCaml is expect tests. They give you a great way of making the behavior of your program visible, both to you, and to the AI. It provides a valuable feedback loop that the AI can leverage in all sorts of flexible ways.

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