CoolingPolicy
Anthropic extends Claude text watermarking to older models, with a sampling loophole
Anthropic's help page says Claude text watermarks apply at the model level and lists models back to Opus 4.5, and that it signed the EU AI Act Article 50(2) transparency code. Detection is in private preview. The Decoder reports that on Opus 4.6 and Sonnet 4.6 the mark applies only at default temperature, top_p and top_k; Anthropic's page does not address this.
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Made the five · #2 on Sunday, November 1, 2026
Anthropic watermarks older Claude models, with a gap
Primary source
Anthropicsupport.claude.com/en/articles/16266773-how-claude-marks-ai-generated-contentCoverage · 2 articles, oldest first
Saturday, October 31, 2026