Anthropic has introduced an invisible, machine-detectable watermark for Claude that flags not just text the model fully generates, but anything it processes—including human writing it merely edited. The system, dubbed the 'Scarlet Letter' watermark, extends AI provenance tracking well beyond generated content.
The mark is currently invisible to users, according to the reporting, which frames its concealment as temporary with the qualifier 'for now.' That means creators could find their original work silently flagged as AI-processed, with neither writers nor readers able to tell when the watermark applies.
The implications for disclosure and control are significant. An asymmetry emerges in which platforms or employers could potentially detect the mark while the people whose work is tagged remain unaware, raising broader questions about transparency in how AI-touched content is labeled.