What changed: Anthropic stated that text generated by Claude Mythos 5, Claude Opus 4.7, and Claude Sonnet 4.6 carries Anthropic's text watermark on the platforms listed in 'How Claude marks AI-generated content.' On Claude Sonnet 4.6, text generated for a request that sets temperature, top_p, or top_k to a non-default value might not carry it.
Who is affected
Developers and businesses using the Claude Mythos 5, Claude Opus 4.7, and Claude Sonnet 4.6 models.
What it means for your business
For businesses using these models, this means text they generate may be identifiable as AI-generated via watermark on certain platforms, affecting how that output can be traced to its source.
What to watch
No action is required right now. Once the full list of affected platforms is clarified, review whether your model usage falls within that scope.
Timing
Source gives no separate effective date; the announcement is dated November 3, 2026.
Source: https://platform.claude.com/docs/en/release-notes/overview#november-3-2026
