Text from Claude Mythos 5, Opus 4.7 and Sonnet 4.6 receives an invisible watermark
According to Anthropic's release notes, text from Claude Mythos 5, Claude Opus 4.7 and Claude Sonnet 4.6 has carried Anthropic's text watermark since 3 November. Previously this applied only to newer models such as Claude Fable 5.1 and Claude Mythos 5.1. For Sonnet 4.6, the watermark may be missing if you set temperature, top_p or top_k to a value other than the default.
What does this mean? If you use Claude for text you submit as your own work, expect it to be recognisable as AI-generated; Anthropic does not mention an opt-out.






