Anthropic Details Text Watermark Coming to Future Claude Models Under EU AI Act

Anthropic published a detailed explainer on the watermark that future Claude models will embed in generated text, implemented to comply with the EU AI Act after Anthropic and about 190 other signatories signed the EU Code of Practice on Transparency of AI-Generated Content in July. The method is a variant of Google DeepMind's SynthID-Text: rather than inserting hidden characters or extra tokens, it subtly changes the randomness used when the model chooses among equally good next words, leaving a key-detectable statistical pattern. Anthropic says the watermark carries no identifying information, adds no serving cost, and is applied globally at launch because there is no durable way to scope it by region yet.