There are many tools for unprivileged sandboxing on Linux. You should probably go use one of them. But I wrote shandbox to scratch my itch muxup.com/shandbox /home/$user/sandbox shows up as /home/sandbox within the shared sandbox, which otherwise can only access explicitly mapped files/dirs.

The program for Leaning In! 2026 is settled. We've got 11 (!) wonderful talks lined up. This is going to be a wonderufl time for digging into Lean, Registration is open, but space is limited so if you're thinking of coming, please do register soon. See you in Berlin! leaning.in/2026/

Amazing work on an Erdős problem (whose original statement needed to be tweaked), demonstrating the power of AI-assisted proving in math. mathstodon.xyz/@tao/1158558...

Lean Together 2026 starts today! It'll be four days of juicy Lean stuff. It's a remote-only conference, so feel free to join. See you there! leanprover-community.github.io/lt2026/

Really alarming to see this story of "LLM psychosis".I first saw it in a video by Nate Jones. It looks like there's an attempt to solve the wildly difficult Navier-Stokes problem, backed up by a Lean formalization. youtu.be/AzOJ9QLgfIk

Claude Code helps me so much with the household chores. The dishes get washed more frequently, the apartment is appreciably tidier, the vacuum cleaner spends an above-average amount of time turned on, the trash gets taken out more quickly.

💥 Breaking news from my Inbox 💥 I saved 251 hours on email with @SaneBox in 2025 #UnwrapYourInbox See for yourself 👉 www.sanebox.com/unwrap/2pktu...

TIL there's a JSON Schema validator for #lean at github.com/CAIMEOX/json... It seems to be abandoned, though (no activity for a year).

Enjoying the video from the December 2025 Mathlib community call.

We''ve landed a few more talks since the last update! * Sorrachai Yingchareonthawornchai: The CSLib initiative * Simon Sorg: Machine learning for Lean * Jannis Limperg on Lean metaprogramming for AI * Will Turner on the new ProofBench effort Come join us for a day of #lean! leaning.in

Incredible results with #lean and Gemini Deep Think by Tao in the Erdős Problem. It feels like a lot of doors in the formalization space, whether that's math or hardware/software verification, are opening quickly. mathstodon.xyz/@tao/1155914...

The 2026 edition of the ITP (Interactive Theorem Proving) conference back in October featured a #lean event. It was great to be there and connect with so many Lean folks. The videos are finally available: www.youtube.com/playlist?lis...

Leaning In! 2026 is ON! If you like #lean and are in Berlin, Germany, Europe, or anywhere on Earth, you are invited. We've got a room at Spielfeld in Berlin. See you on March 12th! More information, including tickets and the CfP, here: leaning.in/2026/

Fascinating talk by Kevin Buzzard about where he sees math going, why it has a big problem (for some time now, even predating the internet), and why #lean might be part of the solution. hackaday.com/2025/10/08/w...

Really excited to see the #lean Mathlib Initiative take off. Here’s their new web page. Mathlib is such a huge, and growing, project; this help from Renaissance Philanthropy is very welcome.

TIL In Lean you can output the axioms that a proof depends on using a simple `#print axioms` command.

Even if you didn't have the chance to listen to any of the amazing Igalia Chats - it's time for you to start with a really good chat about #Webassembly, with the one and only @wingolog.org . open.spotify.com/episode/0DmQ...

I was reminded of the Blueprint tool for sketching mathematical profs in Lean. I haven’t used it yet but I’m going to see if this can help me structure my work. Also curious to see how Blueprint applies in other scenarios such as software verification.

Some reflections by Terence Tao on different levels, of formalization and rigor in math. This was offered as a discussion topic in the afternoon session of the Lean workshop at ITP 2026 but we didn’t really get around to it.

This is a real eye-opening article where @ghuntley.com builds a compiler for a new language using LLVM and the amazing technique he calls Ralph Wiggum.

I haven’t yet dived in to git worktrees but as I continue to learn and reflect more on AI-assisted working, I realize this is pretty much the feature i need. This article made things click.

No more juggling CommonJS and faux-ESM. @joyeecheung.bsky.social revealed how Node.js is moving to full ESM and why the future looks brighter for developers. #NordicJS #NordicJS2025

OOPSLA 2026 deadline is just a week away! Can you please help us get the word out by sharing? Thanks! 2026.splashcon.org/track/oopsla...

Just arrived in Reykjavik for the #lean workshop as part of ITP 2025 leanprover-community.github.io/itp-2025-lea... I'll be presenting some of my recent work. Looking forwrard to (re)connecting with some fellow Leaners!

TIL pre-commit.com I was just browsing the #lean Mathlib repo toplevel directory and noticed a file with an unusual, but suggestive name. Took a look inside and...love it!

I'm happy to announce that I've finally wrapped up a proof of Euler's polyhedron formula ("V - E + F = 2") and submitted a PR to Mathlib. I've been working on this in bits and pieces on evenings and weekends. github.com/leanprover-c...

TFW you start to realize you're not going to win the game of type tetris.

The Kimina theorem prover at Project Numina is an amazing piece of technology. This kind of targeted, special-purpose LLMs seems to be just what is needed. They don't even need to be large; "small" LLMs might be just fine. demo.projectnumina.ai

Just had my first success using the new grind tactic in a #lean proof. I didn't know it was even going to work; I was stuck and reached for it only as a hail-mary desparation move. It worked! Mind blown.

Happy to announce a new polyfill for the in-progress Ecma TC39 amount proposal! The proposal all about mathematical values together (optionally) with a unit and a precision (understood either as significant or fractional digitis)

Huge congratulations in order for the #lean Mathlib team for securing a generous donation to help keep things going and improve things further there. Really looking forward to seeing the next steps here. www.renaissancephilanthropy.org/news-and-ins...

Congratulations to the #lean team on the 4.22 release! This is an exciting one for me for two reasons: the new grind tactic and new support for verification of imperative programs using Hoare triples. lean-lang.org/doc/referenc...

Delighted to see the new Institute for Computer-Aided Reasoning in Mathematics. With many overlapping and fellow-travelling communities in academia, industry, even citizen science, a new institute of this kind is probably what we need right now. www.cmu.edu/news/stories...

The August 2025 Mathlib community call was really great to watch. Thanks for putting it on YouTube. youtu.be/dUWiG12ZQ4g

Great overview of the LeanDojo project by Kaiyu Yang from what appears to be a lunchtime CS talk at Stanford. This is all about custom LLM technology for #lean. I haven't kicked the tires on LeanDojo yet but it's on my shortlist of things to explore. youtu.be/qvaR_VXB4fA

I'm learning about zod, a JS package for working with TypeScript data schemes (going well beyond just types). I want to ensure that my compiled TypeScript enforces type checks at runtime in a JS engine. The TS compiler deletes such things, but I want them back! zod.dev

Hacker News discussion of Markus Himmel's post on the upcoming verification framework for imperative code in #lean news.ycombinator.com/item?id=4449...

Just learned about template literal types in TypeScript. This kinda sorta helps me to turn regular expressions (at least, of a certain restricted kind of regexp) as bona fide types. www.typescriptlang.org/docs/handboo...

TIL PutnamBench leaderboard for benchmarking performance of LLMs on problems from the famous Putnam competition. Several models score really high, whereas e.g. GPT 4o can solve only one problem (in #lean). trishullab.github.io/PutnamBench/...

I'm taking a look at the Goedel Prover v2 for doing #lean work. Seems quite impressive; I'm awaiting a system description paper on arXiv. goedel-lm.github.io

Fascinating project by Google DeepMind on formalizing mathematical conjectures in #lean. Not necessarily solving them (many remain open), just formalizing them. They're also graded by their difficulty (research open question, high school problem, etc.). google-deepmind.github.io/formal-conje...

I'm using the base16-shell approach with fish (learned about this from Julia Evans -- thanks!). Just load this into your fish.config and tab complete base16- to see the themes github.com/chriskempson...

Unfortunately I couldn't make it to Big Proof 2025 but the program looks amazing:

Congratulations to the #lean team on receiving the SIGPLAN Programming Languages software award at PLDI 2025! www.sigplan.org/Awards/Softw...

Really excited to see the latest #lean CSLib effort (Lean formalizations of basic and not-so-basic computer science). leanprover.zulipchat.com#narrow/chann...

Landed support for proxies in Node.js http/https builtins github.com/nodejs/node/... To enable proxies configured from *_PROXY env vars: use NODE_USE_ENV_PROXY=1. This was already implemented for fetch and released in 24 github.com/nodejs/node/... - soon the old builtins will also support it.

Kicking the tires of my new coffee machine, a Nivona 8', I really enjoyed this tongue-in-cheek promotional video. It's in German (with a sprinkling of Italian) but I think you'll get it.

The upcoming imperative proving functionality opens the door to even more verification for those thorny bits of #lean programs that are just better done imperatively. Big kudos to the Lean team for adding this functonality. Looking forward to kicking the tires.

Really excited to see support for verifying imperative programs in #lean 4.22 . Markus Himmel has a neat little worked-out example showing what that look like. markushimmel.de/blog/my-firs...

Returning to this talk by Jakob von Raumer of Lindy Labs on verifying smart contracts in #lean. Jakob is doing the hard work bridging Lean and other languages (in this case, Cairo, a language for smart contracts). www.youtube.com/watch?v=1uBh...