Anthropic is introducing invisible watermarks directly into text produced by newer Claude models as part of its commitments under the EU AI Act's transparency rules. The markings can survive copy-pasting and some editing, although their presence does not necessarily mean that Claude actually authored the underlying text. Anthropic says it has signed the EU AI Act's Article 50(2) Code of Practice on Transparency of AI-Generated Content as a provider of both generative AI models and systems. Its new marking scheme is how the company currently intends to put those commitments into practice, although the company is deploying it worldwide rather than confining it to the bloc responsible for the regulatory impetus. The company says all Claude models launched on or after August 2, 2026, support the technology from launch. Anthropic also intends to extend it to older models over time. According to Anthropic, the watermark is woven directly into Claude’s text output without visibly altering the resulting response. Precisely how Anthropic accomplishes this remains something of a mystery, as the company has declined to publish detailed technical documentation. It nevertheless maintains that the marking does not affect the “meaning, quality, or style” of Claude’s responses. The system extends beyond the consumer-facing Claude chatbot, as supported models produce marked text when accessed through Claude, Claude Code, Cowork, its API and third-party cloud platforms. Anthropic eventually plans to make detection mechanisms available to third parties, although it has yet to divulge how these tools