OpenAI implements text watermarking for EU AI Act compliance

OpenAI announced phased text watermarking (textGrain) for ChatGPT and Codex outputs in the EU to meet EU AI Act requirements for machine-readable identification of generated text, with global API opt-in available immediately and detector access limited to approved researchers. This marks a concrete operational response to binding EU provenance rules, establishing technical limits of current watermarking under real-world editing and length constraints. The move directly ties model deployment practices to regulatory mandates affecting one of the largest AI markets.