Anthropic's watermark rollout leaves a loophole on two older Claude models

Anthropic is expanding its text watermarking system to four older Claude models to meet the EU AI Act deadline. However, API users can bypass the watermark on Claude Opus 4.6 and Claude Sonnet 4.6 by altering default sampling parameters such as temperature, top_p, and top_k. Newer models and certain other older models apply the watermark regardless of these parameter settings. Open article →