On August 11, 2026, Anthropic quietly became the first frontier lab to watermark AI-generated text at production scale, worldwide, across every product. The EU AI Act's Article 50 became enforceable on August 2. Anthropic shipped nine days later. If you build with Claude, this already affects your outputs. Here's what actually changed and what you should do about it. Why This Happened Now Article 50 of the EU AI Act requires providers of generative AI to mark their outputs in machine-readable formats so that downstream users, regulators, and platforms can detect AI-generated content. It became law on August 2, 2026. The penalty for non-compliance isn't trivial. Anthropic didn't watermark just for EU users. The rollout is global: every API call, every Claude.ai session, Claude Code, and hosted instances on AWS, Google Cloud, and Microsoft Foundry. If your models were released after August 2, watermarking is on by default with no opt-out. Older Claude models get the s...