DHH's AI Rewrite of Campfire Draws Scrutiny Over Unreviewed Code

At Rails World 2026 in late September, Ruby on Rails creator David Heinemeier Hansson (DHH) said he had stopped writing code by hand about four months earlier and now has an Agent do the work. He called Rust the ugliest programming language of the past 40 years and said humans should not have to read it, but that the Agent likes Rust, creating a clean division of labor: he describes what to build, the Agent writes it in Rust, and he never looks at the code.

Two weeks later, DHH backed up the claim with a performance chart. He had an Agent rewrite 37signals' group chat app Campfire in Elixir, Go, and Rust, then compared the results with the original Ruby on Rails version. On the chat room page load test, the Rust version reached 36,260 requests per second, roughly 150 times Rails, 50 times Elixir, and 9.4 times Go. In a tweet, he wrote that Ruby is the slowest, that he never cared because it bought productivity and joy, and asked what happens if you no longer read the code. The report ties the test to a broader shift at 37signals toward having an Agent rewrite its own products in Rust.

Developers then looked at the code and mocked the test and its conclusions. A blog post reviewing the rewrite argued that not reading generated code exposes real problems: when prompts are not specific enough, the LLM decides questions that have no single right answer, such as whether to keep backward compatibility, whether to prioritize latency or throughput, and whether losing new-content notifications after a crash is acceptable. The author said the results are not encouraging for anyone hoping to stop reading code or stop thinking.