iiinova — where your digital self keeps evolving

Lean Focused Research Organization @lean-lang.org · 15/09/2026

Lean 4.34.0 is out: 159 changes. Three kernel soundness vulnerabilities fixed, all requiring deliberately constructed inputs rather than ordinary code. 𝚋𝚟_𝚍𝚎𝚌𝚒𝚍𝚎 is up to 6x faster. lean-lang.org/doc/referenc...

092

Lean Focused Research Organization @lean-lang.org · 21/08/2026

The Lean FRO Year 4 Part 1 roadmap, covering September 2026 through February 2027, is now published. It sets out our priorities for Lean and ecosystem support for the first half of our fourth year of operations. 🔗 Read the full roadmap here: lean-lang.org/fro/roadmap/... #LeanLang #LeanProver

074

Lean Focused Research Organization @lean-lang.org · 10/08/2026

Lean 4.33.0 is live! 208 changes: a smoother editor, automatic try? suggestions, and Float finally has a logical model instead of staying opaque. Full notes: lean-lang.org/doc/referenc... #LeanLang #LeanProver

081

Lean Focused Research Organization @lean-lang.org · 13/07/2026

Lean 4.32.0 is live. 102 changes, including the new do elaborator now on by default, a new module linter framework, and roughly a 10% speedup importing Mathlib. Full release notes: lean-lang.org/doc/referenc... #LeanLang #LeanProver #FormalVerification

062

Lean Focused Research Organization @lean-lang.org · 23/06/2026

We're grateful that @simonsfoundation.org has included Lean in three articles of their 2025 annual report. President David Spergel calls it "a proof assistant that brings rigorous machine-verified structure for testing theorems." 📄 www.simonsfoundation.org/series/2025-...

042

Lean Focused Research Organization @lean-lang.org · 18/06/2026

Lean 4.31.0 is live! 305 changes: verifiable do-block loops with no source changes required, mvcgen' (100x+ faster than mvcgen on some benchmarks), and lake lint with Batteries/Mathlib linters built in. lean-lang.org/doc/referenc... #LeanLang #LeanProver #OpenSource

061

Lean Focused Research Organization @lean-lang.org · 09/06/2026

The Proof in the Code, Kevin Hartnett's new book on the development of Lean and Mathlib, is out today. www.quantabooks.org/books/the-pr... To mark the launch, two online panels with the author on June 11 and 12, both 5pm UTC. Registration in the reply.

192

Lean Focused Research Organization @lean-lang.org · 03/06/2026

Two online panels for the launch of The Proof in the Code, @kevinhartnett.bsky.social's new book on Lean and Mathlib. The Mathematicians, June 11. The Builders, June 12. Both 5pm UTC. Learn more and register: The Mathematicians: forms.gle/w16jkmsMqB2g... The Builders: forms.gle/PsxPkq3x2pES...

053

Lean Focused Research Organization @lean-lang.org · 27/05/2026

Lean 4.30.0 is live! 306 changes: new 𝚜𝚢𝚖 => interactive tactic (𝚐𝚛𝚒𝚗𝚍-based, user-controlled), 𝚌𝚋𝚟 out of experimental, LCNF backend complete (~15% smaller binaries), and a full Lake cache overhaul. Release notes: lean-lang.org/doc/referenc...

053

Lean Focused Research Organization @lean-lang.org · 24/04/2026

SVIL in Lean 2026 recordings are now available. Max Tegmark on Signal Shot: "Everybody should be able to be secure." Watch: www.youtube.com/watch?v=eTCW...

beneficial-ai-foundation.github.io

Software Verification in Lean 2026

Software Verification in Lean 2026, Paris

061

Lean Focused Research Organization @lean-lang.org · 02/04/2026

🚀 Lean 4.29.0 is out! Faster startup, simpler 𝚗𝚘𝚗𝚌𝚘𝚖𝚙𝚞𝚝𝚊𝚋𝚕𝚎 semantics, higher-order Miller pattern support in 𝚐𝚛𝚒𝚗𝚍, and a significant overhaul to reducibility and instance handling. 453 changes! 🔗 lean-lang.org/doc/reference/latest/releases/v4.29.0/ #LeanLang #LeanProver

1152

Lean Focused Research Organization @lean-lang.org · 01/04/2026

1/3 New Lean use case: Veil, a multi-modal verification framework for distributed protocols from George Pîrlea, Vladimir Gladshtein, Elad Kinsbruner, Qiyuan Zhao, and Ilya Sergey at NUS.

2114

Lean Focused Research Organization @lean-lang.org · 27/02/2026

The Lean Y3 roadmap is building infrastructure to keep performance "visible and actionable." Radar automatically benchmarks every commit and compares it to previous ones to catch regressions and improvements. See more: radar.lean-lang.org/about #LeanLang #LeanProver

081

Lean Focused Research Organization @lean-lang.org · 26/02/2026

The first-ever Lean in Munich meetup happened this week! 🎥 Watch Sebastian Ullrich's full talk on Lean's foundations, software verification, and AI: youtube.com/watch?v=2Dr2149l_9Y #leanlang #leanprover #formalverification #mathematics

084

Lean Focused Research Organization @lean-lang.org · 23/02/2026

Mathematician @davidbessis.bsky.social once waited 7 years for a paper to get accepted. Not because it was wrong, but because it was too complex to verify. In a recent conversation Bessis explained to @curtjaimungal.skystack.xyz how Lean could change that: Watch: www.youtube.com/watch?v=GHGi...

1121

Lean Focused Research Organization @lean-lang.org · 22/02/2026

CSLib just launched — an open-source effort to formalize computer science in Lean, inspired by Mathlib. CS researchers, practitioners & enthusiasts are invited to get involved! Learn more at: 🌐 cslib.io 🤝 Contribute: github.com/leanprover/c... #LeanLang #LeanProver #CSLib #FormalVerification

1207

Lean Focused Research Organization @lean-lang.org · 19/02/2026

Lean 4.28.0 is out! New symbolic simulation framework for 𝚐𝚛𝚒𝚗𝚍, user-defined 𝚐𝚛𝚒𝚗𝚍 attributes for custom tactics, a new 𝚜𝚘𝚕𝚟𝚎𝚛𝙼𝚘𝚍𝚎 in 𝚋𝚟_𝚍𝚎𝚌𝚒𝚍𝚎 for proof vs. counterexample search, and lean4checker available out of the box. lean-lang.org/doc/referenc... #LeanLang #LeanProver #ProofAssistant

0103

Lean Focused Research Organization @lean-lang.org · 12/02/2026

The next bi-monthly #Mathlib community meeting is tomorrow Friday, 13th at 3pm UTC. Join to hear about ongoing #LeanLang formalization projects and connect with other contributors! ➡️ See all upcoming community events on our website: lean-lang.org/community/#e...

021

Lean Focused Research Organization @lean-lang.org · 11/02/2026

Terence Tao on how math is changing, #formalverification as the enabler of scaled human-AI collaboration: "The reason why scaling and AI and broad participation actually is a net win is because we have formal verification." 📺 www.youtube.com/watch?v=SuTx... #leanlang #leanprover

0134

Lean Focused Research Organization @lean-lang.org · 10/02/2026

The next Lean FRO office hours are Feb. 11 at 4pm UTC. Bring your questions, share your projects, or just come to learn from others in the community! See our full calendar here: lean-lang.org/community/#e... #LeanLang #LeanProver

062

Lean Focused Research Organization @lean-lang.org · 25/10/2025

From The Geometry of Machine Learning at Harvard CMSA in Sept: Jared Duker Lichtman's talk explores Math, Inc. Gauss's contributions to number theory and how these results are being formalized in #LeanLang. Watch here: www.youtube.com/watch?v=Ko-P...

youtube.com

Jared Duker Lichtman | Gauss – towards autoformalization for the working mathematician

YouTube video by Harvard CMSA

031

Lean Focused Research Organization @lean-lang.org · 23/10/2025

Looking for a lemma in #LeanLang / #Mathlib but don't know its name? Use Loogle! to search: By pattern: _ * (_ ^ _) finds expressions matching the pattern By conclusion: |- tsum _ = _ * tsum _ finds specific conclusion shapes Combine searches with commas for precision! loogle.lean-lang.org

loogle.lean-lang.org

Loogle - Search Lean and Mathlib

Loogle is a search tool for finding definitions, theorems, and lemmas in Lean 4 and Mathlib.

042

Lean Focused Research Organization @lean-lang.org · 23/10/2025

𝐋𝐞𝐚𝐧 𝟒.𝟐𝟒.𝟎 𝐢𝐬 𝐥𝐢𝐯𝐞! This release improves the module system, strengthens the 𝚐𝚛𝚒𝚗𝚍 tactic, and advances the standard library. Key improvements: 3.5x faster auto-completion, streamlined "try this" suggestions, new 𝚐𝚛𝚒𝚗𝚍 AC solver, enhanced 𝚖𝚟𝚌𝚐𝚎𝚗 syntax. Read more: lean-lang.org/doc/referenc...

0111

Lean Focused Research Organization @lean-lang.org · 23/10/2025

Tactic tip: Lean's 𝚜𝚒𝚖𝚙? is an optimization tool that shows the minimal 𝚜𝚒𝚖𝚙 𝚘𝚗𝚕𝚢 call needed to close a goal. Use the 𝚜𝚒𝚖𝚙? "Try this" suggestion to insert the precise 𝚜𝚒𝚖𝚙 𝚘𝚗𝚕𝚢 call into your proof. Learn more: lean-lang.org/theorem_prov... #LeanLang #LeanProver #ProofAssistant

042

Lean Focused Research Organization @lean-lang.org · 21/10/2025

"Theorem Proving in Lean 4" is the essential guide for anyone using Lean for mathematical proofs. Kept up-to-date with each new Lean release, it covers everything from basic tactics to advanced proof strategies. Read the book here: lean-lang.org/theorem_prov... #LeanLang #LeanProver #Mathematics

0193

Lean Focused Research Organization @lean-lang.org · 17/10/2025

Reservoir is #LeanLang's package registry, inspired by crates.io (thanks @rustfoundation.org!) Browse community-created packages and discover new tools: reservoir.lean-lang.org Sharing is easy! GitHub repos meeting the inclusion criteria are auto-indexed: reservoir.lean-lang.org/inclusion-cr...

0103

Lean Focused Research Organization @lean-lang.org · 15/10/2025

Speed up your #LeanLang workflow in #VSCode with shortcuts: ℹ️Ctrl/Cmd+Shift+Enter: Open the InfoView 🔡Ctrl/Cmd+Shift+O: List current file declarations, namespaces and sections 🔄Ctrl/Cmd+Shift+X: Restart the current file See more in the Lean VS Code extension manual: github.com/leanprover/v...

github.com

040

Lean Focused Research Organization @lean-lang.org · 15/10/2025

#LeanLang office hours are tomorrow (Wednesday the 15th) at 23:00 UTC. Bring your questions, share your projects, or just come to learn from others in the community. ➡ Find calendar and meeting links on our website: lean-lang.org/community/#e...

lean-lang.org

Lean Programming Language

Lean is an open-source programming language and proof assistant that enables correct, maintainable, and formally verified code.

060

Lean Focused Research Organization @lean-lang.org · 15/10/2025

New use case on our website: AWS's Cedar authorization policy language verified with Lean, using "verification-guided development", and integrated into Cedar's development workflow. ➡️Read more: lean-lang.org/use-cases/ce... #LeanLang #LeanProver #CedarPolicy #FormalVerification #AWS

lean-lang.org

Lean Programming Language

Lean is an open-source programming language and proof assistant that enables correct, maintainable, and formally verified code.

051

Reposted by Lean Focused Research Organization

Pietro Monticone @pietromonticone.bsky.social · 14/10/2025

We’re pleased to announce #ItaLean2025: Bridging Formal Mathematics and AI, an international conference dedicated to @lean-lang.org, Formal Mathematics, and AI4Math. 📍 University of Bologna 🗓 9–12 December 2025 Proudly supported by #Harmonic. #LeanLang #FormalMath #AI4Math

143

Lean Focused Research Organization @lean-lang.org · 10/10/2025

💡Did you know you can run #LeanLang in your browser without installing anything? The Lean Playground provides a full environment for experimentation, learning, and for sharing code snippets with others. Try it out! live.lean-lang.org

192

Lean Focused Research Organization @lean-lang.org · 09/10/2025

The next bi-monthly #Mathlib community meeting is tomorrow (Friday Oct 10) at 2pm UTC. Join to hear about ongoing #LeanLang formalization projects and connect with contributors. See all community events on our website: lean-lang.org/community/?u...

lean-lang.org

Lean Programming Language

Lean is an open-source programming language and proof assistant that enables correct, maintainable, and formally verified code.

010

Lean Focused Research Organization @lean-lang.org · 06/10/2025

Did you know the Info View in #LeanLang's #VSCode extension updates in real-time as you write proofs? Click on any part of your code to see the current proof state, goals, and hypotheses at that exact point. Learn more about the Lean VS Code extension: github.com/leanprover/v...

071

Lean Focused Research Organization @lean-lang.org · 24/09/2025

We really loved this series of tutorials on #metaprogramming in #LeanLang by Heather Macbeth. It's a great intro to a complex topic for novice users of #LeanProver! Pt 1: youtube.com/watch?v=cKvg... Pt 2: youtube.com/watch?v=5er4... Pt 3: youtube.com/watch?v=TJ8T...

1143

Lean Focused Research Organization @lean-lang.org · 23/09/2025

Two great talks at #HLF25 last week: Sanjeev Arora on superhuman AI mathematicians using #LeanLang, and David Silver on AI learning through experience with #LeanProver verification. www.youtube.com/watch?v=q9MJ... #AI #FormalMath #ReinforcementLearning

youtube.com

Spark Session | September 15

YouTube video by Heidelberg Laureate Forum

041

Lean Focused Research Organization @lean-lang.org · 18/09/2025

ICYMI: A great summary on the #LeanLang Community Blog of the @simonsfoundation.org 2025 MPS (Math and Phys Sciences) Workshop on #LeanProver. The post includes links to lecture slides, videos, and a list of proposed projects and participants! leanprover-community.github.io/blog/posts/s...

050

Lean Focused Research Organization @lean-lang.org · 18/09/2025

Fun to see snippets of #LeanLang interspersed into this fantastic @3blue1brown.com guest video by @bensyversen.bsky.social about Euclid's Elements!

050

Lean Focused Research Organization @lean-lang.org · 16/09/2025

🎉 Lean 4.23.0 is here! Includes many usability improvements, including: 🎯 Enhanced 'Go to Definition' supporting type class instances 🔧 Interactive error hints for faster debugging Release notes: lean-lang.org/doc/referenc... #LeanLang #LeanProver #OpenSource #Mathematics #FormalVerification

0205

Lean Focused Research Organization @lean-lang.org · 10/09/2025

Recently came across @filiplajszczak.bsky.social's series formalizing a 1967 math textbook in #LeanLang. Designed for those "with no prior experience with formalization" - nice bridge for newcomers to #LeanProver! Read the intro post here: filip.lajszczak.dev/lean-4-with-...

filip.lajszczak.dev

Lean 4 with a Math Textbook - Part 0 - Introduction — Some opinions, held with varying degrees of certainty.

0106

Reposted by Lean Focused Research Organization

dan @danabra.mov · 02/09/2025

⚛️📝 New on Overreacted: Lean for JavaScript Developers

overreacted.io

Lean for JavaScript Developers — overreacted

Programming with proofs.

510015

Lean Focused Research Organization @lean-lang.org · 05/09/2025

If you're you curious about #LeanLang and want to understand the connection between #programming and #proofs, check out this great new video by Ank Yog. The analogy between Chess and true propositions is particularly compelling! www.youtube.com/watch?v=QXQN...

0177

Lean Focused Research Organization @lean-lang.org · 15/08/2025

🎉 Lean 4.22.0 is here! It represents the culmination of our Year 2 roadmap! Including: 🧠 New grind tactic (SMT-style automated reasoning) 🏗️ New compiler (major performance foundation) Read the release notes: lean-lang.org/doc/reference/latest/releases/v4.22.0/ #LeanLang #LeanProver

1247

Lean Focused Research Organization @lean-lang.org · 06/08/2025

Just saw this post on LinkedIn about a new #DiscreteMath game on the #LeanLang Game Server. The author, Shrey Vivek, won a "Best Poster" award at the SPMS Odyssey Research Symposium. 🎉 The Discrete Math game: adam.math.hhu.de#/g/shreyvive... The LinkedIn post: www.linkedin.com/posts/shrey-...

adam.math.hhu.de

Lean Game Server

You need to enable JavaScript to use the Lean Game Server, as it is built using React.

042

Lean Focused Research Organization @lean-lang.org · 06/08/2025

Thorsten Altenkirch explains Gödel's Incompleteness Theorem on @computerphile.bsky.social, and shows some definitions in #LeanLang! 🎯 Watch here: www.youtube.com/watch?v=IuX8...

youtube.com

Gödel's Incompleteness Theorem - Computerphile

YouTube video by Computerphile

095

Lean Focused Research Organization @lean-lang.org · 05/08/2025

We're excited to share the Lean FRO Year 3 Roadmap today! It builds on work completed in the first two years of Lean FRO operations and will guide all #LeanLang development through July 2026. ➡️ Read the roadmap at lean-lang.org/fro/ #LeanProver #FormalMathematics #FormalVerification

lean-lang.org

Lean Programming Language

Lean is a theorem prover and programming language that enables correct, maintainable, and formally verified code.

0115

Lean Focused Research Organization @lean-lang.org · 15/07/2025

The first volume of the new Open Access journal "Annals of Formalized Mathematics" was released today! ➡️ afm.episciences.org/volume/view/... #FormalMath #Mathematics #OpenAccess

1103

Reposted by Lean Focused Research Organization

José A. Alonso @jalonso.eurosky.social · 15/07/2025

IMO 1996 P3: Lean 4 formalization. ~ David Renshaw. youtu.be/5NbYtDfXfR4 #ITP #LeanProver #Math

youtu.be

IMO 1996 P3: Lean 4 Formalization

YouTube video by David Renshaw

063

Reposted by Lean Focused Research Organization

xenaproject.bsky.social @xenaproject.bsky.social · 06/07/2025

Markus Himmel has written a blog post about how to write a simple imperative program in Lean and then how to verify that the program is bug-free. markushimmel.de/blog/my-firs...

markushimmel.de

My first verified (imperative) program

One of the many exciting new features in the upcoming Lean 4.22 release is a preview of the new verification infrastructure for proving properties of imperative programs. In this post, I’ll take a fir...

1197