OpenAI adds opt-in textGrain watermarking to its API and will watermark ChatGPT and Codex text in the EU

Starting Oct 5, API customers anywhere can turn on invisible text watermarking per project or org for select models (off by default), and eligible ChatGPT and Codex users in the EU get it in the coming weeks to meet the EU AI Act. The signal lives in word choice, outputs under ~200 tokens and code snippets aren't required to carry it, and the detector is limited to approved researchers for now.