Robert Way / Shutterstock.com Kelsey Piper, a writer at Vox's Future Perfect, pasted 125 words of an unpublished political column into Claude Opus 4.7 last week and got her own name back. She hadn't logged in; the test was run in Incognito mode, confirmed through the API, and repeated on a friend's computer. Same result each time. The same model identified her from a school progress report she'd written about a student's Pokémon essays — a genre entirely outside her published work — and from a movie review of a 1942 WWII comedy she'd never publicly reviewed. It took 500 words of unpublished fiction to reach the same conclusion. It took a 15-year-old college application essay. ChatGPT and Gemini mostly guessed wrong, where Opus 4.7 succeeded. Piper writes in The Argument that anyone who has written prolifically under their real name has probably lost meaningful anonymity.…