Claude's watermarks: a signal, not proof
Anthropic signed the EU code of practice on AI-content transparency and described how it will deliver on it: Claude models launched after August 2 will mark generated text from day one. The watermark is invisible, woven into the text itself, and survives copy-paste and some editing. It's applied at the model level — it will be in the text no matter which product or cloud you use: the app, the API, AWS, Google Cloud. And not just in Europe — everywhere Claude is offered.
The driver is the EU AI Act: transparency obligations became applicable August 2, and about 190 companies signed the code, OpenAI and Google included. Claude's images and files get signed C2PA provenance metadata. Older models are "in progress" — the law provides a transition period; Anthropic names no dates of its own.
How the mark actually works, Anthropic doesn't disclose. What it does state, honestly, is what the mark proves — and what it doesn't.
A mark tells you one thing: the text probably passed through Claude — and no more. "AI wrote it all" and "AI proofread my paragraph" get marked the same, and Anthropic itself calls the mark a signal, not proof. And the reverse: lack of a mark doesn't mean a human wrote it — Anthropic says so itself. The detector, by the way, hasn't shipped yet.
If you work with confidential material — a bank, a law firm, a government body — the question was never the mark. Every request to a cloud model is your document being processed on someone else's server, under someone else's rules. The watermark just made that visible.
The answer is architectural. A model that lives inside your perimeter: documents never leave, the access logs are yours, and you verify that with an infrastructure audit — not with faith in a detector. That's how we deploy assistants: open weights on the client's hardware, retrieval over your corpus, citation to the clause, honest refusal. Plus a quality passport you can re-run yourself.
The question "where does my document go" existed long before watermarks. The watermark just made it visible.