Anthropic will watermark text its models generate, at the model level

Anthropic confirmed on 11 August 2026 that every model it released after 2 August automatically watermarks generated text, with C2PA used for files, to comply with the EU AI Act transparency code that took effect that day. The watermark is applied at the model level, so it is present whichever Claude surface the text comes from — API, Claude, Claude Code, Claude Cowork or Claude Tag — and it travels with the text through copy-paste and some editing. The company said it will extend support to older models; how much editing removes the mark is not yet stated.

What it means If you publish, grade or resell model-written text, the provenance mark is now a property of the model rather than an option you switch on — and detection of it becomes a fact of your workflow, not a policy choice.