Which Design Doc Did a Human Write?

I created three design docs for the same open-source web app:

• I spent 16 hours writing one of the design docs completely by hand.

• I generated one using Claude Opus 4.6 (medium effort).

• I generated one using GPT-5.4 (high effort).

I generated the AI versions in a few minutes. I fed the agents a prompt that included the design docs chapter of my book and a skeleton design doc structure. The agents who wrote the AI-generated docs did not see the version I wrote.