Video of Julia Himmel's #BOBkonf2026 talk "Proofs for programs, programs for proofs" is now up on our website! bobkonf.de/2026/himmel....

New Type Theory Forall episode is out! I had the pleasure to partner with @serokell to bring you a conversation with Vladislav Zavialov, one of the main GHC contributors, former GHC Steering Committee member, and current implementer of Dependent Haskell. 1/3

We have an opening in the Type Theory Forall schedule this month for a sponsored episode. 1/3

The Budapest type theory group is hiring a postdoc to work on higher observational type theory. lists.seas.upenn.edu/pipermail/ty...

The TTFA store is closing May 19. Last chance (for a while) to grab: PL mugs, shirts, hoodies, hats — plus the Tony Hoare tribute drop. https://twp.ai/9OUsKk After a year, we basically broke even — so going forward: • Open once a year • Next reopening: holidays Don’t miss this window.

The TTFA store is closing May 19. Last chance (for a while) to grab: PL mugs, shirts, hoodies, hats — plus the Tony Hoare tribute drop. https://twp.ai/9OUvqF After a year, we basically broke even — so going forward: • Open once a year • Next reopening: holidays Don’t miss this window.

Dropping 2 new items today in tribute to Tony Hoare: • C.A.R T-Shirt • Hoare Triple Hat A small way to celebrate someone who shaped how we think about programming and correctness. https://twp.ai/9OVSQV The store will now only open once a month ⏳ This drop closes May 19 1/2

New TTFA episode I sat down with Farhad Mehta, one of the main organizers of Zurihac, the largest Haskell event in the world. We talk about: • the story behind Zurihac • what it takes to run it • Farhad’s path across academia and industry Zurihac 2026: June 6–8 in Zurich

Dropping 2 new items today in tribute to Tony Hoare: • C.A.R T-Shirt • Hoare Triple Hat A small way to celebrate someone who shaped how we think about programming and correctness. https://twp.ai/9OVKq1 1/2

Ordered Agda and OCaml mugs from the @ttforall.bsky.social merch store and Pedro threw in a little bonus! 💚

men are from Type, women are from Prop

Hey everyone! I’ve just started a short series for Patreons where I study and discuss the story of the logicians that make up the intuitionistic lineage. I'm trying to connect the people, ideas, and historical context in a more linear narrative. 1/4

New TTFA episode 🎙️ What does it mean to build a research career today? With Dan Plyukhin we talk about: • meditation & staying sane • the reality of the job market • reaching out to professors • AI (hype vs reality) • research paths

“The thought, in itself immaterial, clothes itself in the material garment of a sentence and thereby becomes comprehensible to us” — Frege 1956

Tristan Stérin used LLMs to hunt for bugs and inconsistencies in Rocq and Lean. This is actually pretty neat and kind of wild.

Today we honor the life and work of Sir Tony Hoare (1934–2026), one of the giants of computer science. His work shaped algorithms, programming languages, concurrency, and formal verification. 1/7

Some people drink coffee. Others drink coffee and reason about it formally ☕ FP & proof assistant mugs → https://twp.ai/9Pb5eO

Some people drink coffee. Others drink coffee and reason about it formally ☕ FP & proof assistant mugs → https://twp.ai/9PatXs

Some people drink coffee. Others drink coffee and reason about it formally ☕ FP & proof assistant mugs → https://twp.ai/9Pay3E

Some people drink coffee. Others drink coffee and reason about it formally ☕ FP & proof assistant mugs → https://twp.ai/9Payr1

Once we formalize the syntax of a language, the next step is to formalize its semantics: what programs mean and how they behave. There are three classical approaches. 1) Operational semantics Operational semantics defines meaning by describing how programs execute on an abstract machine. 1/8

In a few minutes we are going live on Twitch to watch and discuss selected ICFP talks together. If you are interested in programming languages research, semantics, type systems, and formal methods, join us for a live session of collective viewing and commentary.

going to do some #LeanLang streaming for the first time in a while! i tried to get claude code to add polymorphism to my formalisation of HM. let's see what it managed to do and where it got stuck. join me as i do some forensic analysis 🕵️ starting at 7:30pm UTC today! www.twitch.tv/aronadler

90+ hours interviewing the best minds in type theory. Now you can wear (and sip from) the movement. The Type Theory Forall store is up and running. Apparel and mugs for people who care about foundations. Every purchase helps keep deep PL conversations alive. https://twp.ai/9PbfTY

New semester just started. If your Rocq file already has 37 unsolved goals If your compiler project looks… concerning I’m opening tutoring spots in: • Rocq • Haskell / OCaml • Compilers • Logic & Algebra Strong foundations. No shortcuts. Free intro call 👇

90+ hours interviewing the best minds in type theory. Now you can wear (and sip from) the movement. The Type Theory Forall store is up and running. Apparel and mugs for people who care about foundations. Every purchase helps keep deep PL conversations alive. https://twp.ai/9PbTgF

"Readable formal specifications are not a convenience that AI can replace. They are the foundation of trust."

People often ask: what is type theory and why is it useful? Type Theory is the academic study of type systems: formal frameworks for classifying terms, structuring computation, and specifying the behavior of programs. 🧵 1/9

I’m planning next month’s Type Theory Forall episodes and I’d genuinely love your input. What would you be interested to hear next? Proof theory? Modern Programming Language Semantics? Lean or Rocq? Compilers? AI × formal methods? Is there a paper, idea, or person you think I should talk to?

90+ hours interviewing the best minds in type theory. Now you can wear (and sip from) the movement. The Type Theory Forall store is up and running. Apparel and mugs for people who care about foundations. Every purchase helps keep deep PL conversations alive. https://twp.ai/9PbYfP

An ode to the International PhD Student "To the one living between time zones. Between ambition and homesickness. Between gratitude and guilt. " https://twp.ai/9PbVnL

New semester just started. If your Rocq file already has 37 unsolved goals If your compiler project looks… concerning I’m opening tutoring spots in: • Rocq • Haskell / OCaml • Compilers • Logic & Algebra Strong foundations. No shortcuts. Free intro call 👇

90+ hours interviewing the best minds in type theory. Now you can wear (and sip from) the movement. The Type Theory Forall store is up and running. Apparel and mugs for people who care about foundations. Every purchase helps keep deep PL conversations alive. https://twp.ai/9PbYcf

I was at AmeriHac this past weekend! Decided to write up a blogpost about it :D I did my best to capture the experience. Please let me know if there are any errors or if you have any comments, suggestions or questions thedeveloper101.github.io/posts/2026/0...

ZuriHac 2026 - Registrations are open! ZuriHac is the biggest Haskell community event in the world: a completely free, three-day grassroots coding festival co-organized by the Zürich Friends of Haskell and the OST Eastern Switzerland University of Applied Science. Register: zureg.zfoh.ch/register

ZuriHac also welcomes beginners or people unfamiliar to Haskell who are curious to learn more. There will be an organized beginners’ track, as well as many mentors from the Haskell community happy to answer all your questions.

Your proof assistant is strict. Your type system is expressive. Your coffee mug should be too ☕ FP & ITP mugs (OCaml, Haskell, Lean, Rocq, Isabelle, Agda): store.typetheoryfora...

Type Theory Forall exists because this community exists. If the podcast, the conversations, or the ideas mattered to you, this is one way to support it — and look good doing it 👕 👉 store.typetheoryfora...

New TTFA episode 🎙️ The category-theoretic episode we’ve ever done. A deep dive into Category Theory, Type Theory, and Logic with Valeria de Paiva — co-founder of the Topos Institute and founder of Women in Logic.

Your proof assistant is strict. Your type system is expressive. Your coffee mug should be too ☕ FP & ITP mugs (OCaml, Haskell, Lean, Rocq, Isabelle, Agda): store.typetheoryfora...

Type Theory Forall exists because this community exists. If the podcast, the conversations, or the ideas mattered to you, this is one way to support it — and look good doing it 👕 👉 store.typetheoryfora...

Your proof assistant is strict. Your type system is expressive. Your coffee mug should be too ☕ FP & ITP mugs (OCaml, Haskell, Lean, Rocq, Isabelle, Agda): store.typetheoryfora...

Type Theory Forall exists because this community exists. If the podcast, the conversations, or the ideas mattered to you, this is one way to support it — and look good doing it 👕 👉 store.typetheoryfora...

Your proof assistant is strict. Your type system is expressive. Your coffee mug should be too ☕ FP & ITP mugs (OCaml, Haskell, Lean, Rocq, Isabelle, Agda): store.typetheoryfora...

Type Theory Forall exists because this community exists. If the podcast, the conversations, or the ideas mattered to you, this is one way to support it — and look good doing it 👕 👉 store.typetheoryfora...

Your proof assistant is strict. Your type system is expressive. Your coffee mug should be too ☕ FP & ITP mugs (OCaml, Haskell, Lean, Rocq, Isabelle, Agda): store.typetheoryfora...

Type Theory Forall exists because this community exists. If the podcast, the conversations, or the ideas mattered to you, this is one way to support it — and look good doing it 👕 👉 store.typetheoryfora...

In case you missed it, watch this clip from our interview with Andrej Bauer. I love when CS researchers can articulate a philosophy behind their work, and Andrej DELIVERS www.youtube.com/watch?v=GcTF...