---
format: "aidr-story-markdown/v1"
id: "2bd2c82c67a63cfb1f2fc4108c46d8c35e4be091ef6ff86825ee1b0cc695cc5f"
canonical_url: "https://aidr.today/2bd2c82c?lang=en"
title: "I built the RealWorld app in Lean 4"
lang: "en"
requested_lang: "en"
available_langs: ["en","vi"]
translation_fallback: null
fallback_fields: []
published_at: "2026-10-17T04:20:14.000Z"
category: "Open Source"
topics: ["coding","open-source"]
source_urls: ["https://leangineer.com/blog/realworld-in-lean/","https://lobste.rs/s/xctcdf/i_built_realworld_app_lean_4"]
summary: "A RealWorld full-stack application with official test suites was built entirely in Lean 4. The implementation is somewhat ready for production and can be made more robust than the average full-stack app, though it is only partly correct by construction."
---

# I built the RealWorld app in Lean 4

> [Open the canonical story](<https://aidr.today/2bd2c82c?lang=en>)

**Published:** 2026-10-17T04:20:14.000Z
**Category:** Open Source
**Topics:** coding, open\-source

## Summary

A RealWorld full\-stack application with official test suites was built entirely in Lean 4\. The implementation is somewhat ready for production and can be made more robust than the average full\-stack app, though it is only partly correct by construction\.

## Sources

- [Story source](<https://leangineer.com/blog/realworld-in-lean/>)
- [Discussion](<https://lobste.rs/s/xctcdf/i_built_realworld_app_lean_4>)