Anthropic's text watermark is easy to bypass on several older Claude models
AI-generated summary Anthropic emailed API customers about a second round of watermark retrofits slated for Claude Opus 4.6, Claude Opus 4.5, Claude Sonnet 4.5, and Claude Haiku 4.5 starting November 16, 2026. Anthropic says the text watermark only applies when temperature, top_p, and top_k are set to their defaults on Claude Opus 4.6 and Claude Sonnet 4.6.