CS PhD student @DrexelCCI working on formalization in Lean. Maintainer of https://teapaw.org/t.co/waYLdE0QGI. Student Researcher @GoogleDeepMind
Philadelphia, PA
Joined December 2014
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Chris Henson retweeted
Deciding how to help non-expert humans engage with formal verification specifications seems like one of the more important non-verifiable UX problems facing the rise of formal verification. 🧵
Chris Henson retweeted
This is pretty good, and I want to celebrate it, but it is not perfect!
My thoughts (as a Lean developer, Mathlib maintainer, and builder of Tau Ceti) about how we can keep raising the bar: kim-em.github.io/blog/2026-1….
Chris Henson retweeted
Hard times create strong types
Strong types create good times
Good times create weak types
Weak types create hard times
Meanwhile the rest of us schmucks had to make do with this
ALT Screenshot of a window from "Mavis Beacon Teaches Typing" for Windows XP, featuring Mavis Beacon (a tall Black woman with long hair and a suit, arms folded and smiling) next to a whiteboard. The image has been edited so that the whiteboard instead displays the inference rules for the simply-typed lambda calculus
Chris Henson retweeted
I was quite intrigued by oss-verify and convinced a few collaborators to dig deeper.
I thought I’d share what we found: tinyurl.com/oss-verify-audit
As AI makes proofs easier, it’s important to check what we’re proving. And even more important to view claims with caution.
New on our Frontier Red Team blog: using Claude to formally verify software at large scale.
Formal verification can prove that code is free of certain bugs, but historically it has only been feasible for small codebases (or required a lot of expert time).
With AI models, however, this is beginning to change. In collaboration with @theoremlabs, we used Claude to prove security properties in over one hundred real-world open-source libraries over the span of a few weeks.
Read our research in full here: anthropic.com/research/forma…
Chris Henson retweeted
No: a more accurate way of putting whay the say is that there are many misalignments between the natural language (NL) slop and the Lean slop, meaning the the Lean slop is a formal code for a different NL proof (different path). So long as …
A new paper shows that when AI translates a math proof into Lean, passing the Lean check says nothing about whether the original proof is right.
They show a chatbot turning a wrong proof into a valid Lean proof by silently fixing the error.
Knowing when a statement can be translated faithfully is provably harder than the Halting problem, so no AI translator can always do it.
Chris Henson retweeted
Super misleading to post about this without being upfront about all of the caveats and limitations, in a way that is wildly worrying because it will mislead potential funders into thinking this is a solved problem when it is very much not
Lean has a new checker: con-leche, a CONsistent LEan CHEcker. This is an external checker for Lean that is proven (in Lean) to be consistent, meaning it does not accept a proof of False.
Joachim Breitner (@nomeata) is the mastermind behind the project. github.com/leanprover/con-le…
Chris Henson retweeted
Prismriver, a Lean 4 music formalization library - talk at Lean NYC this sun (see lean.nyc), at FARM workshop at ICFP, and a free performance 8/24 evening at IU Indianapolis. we will be playing lean compositions!
arxiv.org/abs/2606.19936
Chris Henson retweeted
i bet even if claude proved 100% of the zeroes of the zeta function were on the critical line, mathematicians wouldnt call it a full proof of the riemann hypothesis
come on that's not "almost" it's 100%!!!!
ai-hating mathematicians constantly moving the goalposts smh
Chris Henson retweeted
You can read my thoughts and those of some others here. In particular I strongly recommend reading what Thomas Bloom and Melanie Matchett Wood have to say about it: cdn.openai.com/pdf/74c24085-…
Chris Henson retweeted
Slightly unfortunate that this article fails to acknowledge (a) the 2 years of hard work that preceded the Gauss formalisation (b) the fact that the project is not finished. It’s also unclear what “verified” means when they say “the proofs had already been verified without AI.”
The Economist on AI, math, formalization.
Includes a choice quote from me and thoughts from @TerrenceTao, @pushmeet, @tachim @HarmonicMath, @wtgowers, Don Knuth & Filip Stappers, and mention of @mathematics_inc and Maryna Viazovska
economist.com/science-and-te…
Chris Henson retweeted
We had a few cryptography in Lean related talks in the last few weeks ahead of ArkLib being presented at RWC later this month:
Chris Henson retweeted
🚨 Putting this back on your radar:
The deadline for the ICERM Graduate Training Workshop on ∞-categories with proof-assistants (organized with @emilyriehl and Jonathan Weinberger) is getting close!
📬Application deadline: March 31, 2026.
Full details in the post below 👇
🌞Summer School Announcement🌞
🎓∞-Category Theory at @ICERM !🎓
I am happy to announce that together with @emilyriehl & Jonathan Weinberger we are organizing a Graduate Training Workshop teaching ∞-category theory via proof assistants!🧠💻
More infos in the next post👉
Chris Henson retweeted
The nLab has exercises, it just labels them as “proposition”, “lemma”, “theorem”, etc. /s
Chris Henson retweeted
"Validating a Lean Proof" in the Lean Language Reference addresses an important question: what if you encounter a proof you suspect may be dishonest or malicious?
The "Validating a Lean Proof" chapter in the Language Reference describes four approaches, from trusting the kernel directly to using independent type checkers to verify exported proofs.
Explore the chapter: lean-lang.org/doc/reference/…
#leanlang #leanprover
Chris Henson retweeted
A reminder for those interested in PLISS 2026: there are 10 days left to register your interest. pliss.org/2026/registration.…
Chris Henson retweeted
Applications are now open for the 2026 Rutgers Math Corps summer camp! Please find all the information and links here: mathcorps.org/rutgers
Applications received before Feb 28th will receive priority.
Please help spread the word! (Flyers attached)
Chris Henson retweeted
❗️Job alert: multiple academic positions (postdoc, tenure-track assistant prof., tenured associate prof., DIAS Fellow) at the Centre for Formal Methods and Future Computing (FORM) in DK.
Links for applications below. 👇
Deadlines in January and February (check the details!).
