Lasm
Write formally verified webapps in Lean for Node/serverless/edge
Lasm launched on 30 October 2026. It ranked #27 on Daily Launch on 31 October 2026 with a Launch Score of 46, from 36 points on Show HN. It was new in the ranking that day.
What is Lasm?
Lean 4 for the JavaScript and WebAssembly world. Lasm compiles ordinary Lean 4 programs ahead of time to WebAssembly. One Lean code base can become a Node server, a serverless or edge function, a WASI/Fastly module or a browser app. Because it is Lean, you can prove properties of the code you deploy. The flagship example, Conduit, is the RealWorld app with 117 proved theorems. Lasm ships on npm and brings Lean, Lake and its build tools with it; you only need Node (or Bun or Deno).
From its README on GitHub
Lasm is a launch on Show HN. It is written in C and released under the MIT license.
Launch timeline
Launch Score, last 7 days
Ranked on one day so far: 46 of 100 on 31 October.