Talos
Open-source WASM interpreter for Lean
Details
- External ID
- 48584761
- Source
- HN
- Company
- —
- Product
- Talos
- Website domain
- github.com
- Launched
- June 18, 2026
- Cohort
- —
- Upvotes
- 106
- Upvotes percentile
- 0.9200819672131147
- Tags
- —
- Fetched at
- Sept. 7, 2026, 9:26 p.m.
- Updated at
- Sept. 7, 2026, 9:26 p.m.
Description
At Cajal (YC W26) we’re excited to share Talos (https://github.com/cajal-technologies/talos), an open source framework for formal verification of WebAssembly modules in Lean.AI is now writing tons of the code that gets pushed to production. As code generation gets cheaper, verification becomes the bottleneck. We believe in a future where every piece of software comes with a mathematical proof that it does what its author intended - in doing so, eliminating many classes of exploits. Talos is part of the foundation for that.Talos provides a Wasm interpreter optimized for reasoning at the binary level, together with a weakest-precondition calculus layer for proving properties about programs. Because we reason directly about WebAssembly, any language with a Wasm backend is in scope: Rust, C++, Go, C, Swift, Kotlin, Zig, C#, and many more.To make this possible, we use Lean: a programming language and theorem prover that lets you both write software and mathematically prove that it's correct - all in one system. That's what lets Talos double as both an executable interpreter and the formal object Lean reasons about. Lean also integrates with modern AI proving tools, discharging goals automatically via both proof search and direct evaluation.To see Talos in action check out a proof for Stein's GCD algorithm, implemented in the popular Rust crate num-integer: https://github.com/cajal-technologies/talos/blob/main/progra....Our roadmap:- Full Wasm coverage by first passing the official W3C testsuite, then later verifying against SpecTec (formal Wasm spec) - Arbitrary crate verification - any Rust crate that compiles to Wasm should be in scope - Building our proof library codelib, to make verifying increasingly complex programs tractableWe would love to hear the community’s feedback on Talos and comments on the state of formal verification right now. Contributions are also welcome!
Enrichment
- Theme
- lightweight and on-device AI runtimes
- Vertical
- Horizontal
- Function
- Dev tools
- Audience
- Developer
- AI stance
- Not AI
- Project type
- Hobby / open-source project
- Normalized one-liner
- wasm interpreter for lean programming language
- Manually corrected
- False
Could you build this?
No Creating a formal WebAssembly interpreter and verification framework in Lean requires deep mathematical logic, formal methods expertise, and intimate knowledge of the WASM specification.
What it would actually take: A real implementation requires formalizing the WebAssembly operational semantics and type system in Lean 4. Developers must write inductive definitions, execution step functions, and mechanize soundness proofs that mirror the official W3C specification. This demands researchers or engineers specialized in dependent type theory, interactive theorem proving, and low-level bytecode semantics.
Discussion
20 comments analyzed.
Competitors mentioned: WasmCert-Isabelle, WasmRef-Isabelle, aeneas (Rust to Lean transpiler), LLVM-IR, RISC-V with Sail formal model
Concerns raised: Modeling nondeterminism in WASM (NaN representation, memory/table grow, stack exhaustion, relaxed SIMD), AI struggles with step-indexed logical relations and proof index shuffling at scale, Rust compiler and assert lowering in trusted base, Reasoning about larger programs with dynamic allocation and address overlap
Feature requests: Formal separation logic API for non-overlapping memory regions, Support for cyclic heap structures with step indexing, Automated transformation from SpecTec to Lean spec generation
Competitors
Other products that read as similar to this one — 133 launches clear the similarity bar, closest 8 shown.
Attention rank: #12 of 134 (itself plus its competitors, highest first — normalized so YC and Product Hunt are compared fairly).
Launched 230 days after the earliest competitor.
- Sandboxing untrusted code using WebAssembly · hn · 2026-02-03 · 76 upvotes · similarity 0.46
- Tangent · hn · 2025-11-20 · 28 upvotes · similarity 0.46
- Formally verified 3D CSG: Trust 93 lines spec, not 1000 lines AI code · hn · 2026-07-28 · 115 upvotes · similarity 0.43
- Optimizing LiteLLM with Rust · hn · 2025-11-18 · 27 upvotes · similarity 0.43
- RiceVM · hn · 2026-04-02 · 7 upvotes · similarity 0.41
- AutoLISP interpreter in Rust/WASM · hn · 2025-12-26 · 137 upvotes · similarity 0.41
- An application stack Claude coded directly in LLVM IR · hn · 2026-03-12 · 10 upvotes · similarity 0.40
- metalean · github · 2026-09-18 · 11 upvotes · similarity 0.40
Other launches for this product
- No other launches for this product.
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