Which Design Doc Did a Human Write?

Michael Lynch created three design docs for the same open-source web app: one written by hand (16 hours), one generated by Claude Opus 4.6, and one by GPT-5.4. In a reader survey, about 50% correctly identified the human-written version, largely because it contained personal opinions, anecdotal experience, and unconventional technology choices like NixCI. AI-generated docs tended to be more generic and lacked personal voice or opinionated decisions.