Claude Fable 5, Opus 4.8 and Sonnet 5 join the text watermark table

Published 1 October 2026

Anthropic's help article now lists Claude Fable 5, Opus 4.8 and Sonnet 5 with the text watermark, on Anthropic's own surfaces and through the cloud partners, with the rollout on Amazon Bedrock due to complete by 12 October. That makes eight models with the text watermark: Claude Fable 5.1, Fable 5, Mythos 5.1, Opus 5.5, Opus 5, Opus 4.8, Sonnet 5.5 and Sonnet 5. The article also dropped the statement that all models released before 2 August 2026 would be covered by 2 December 2026, and it now gives no date[1].

What changed

The table headed "Which Claude models support watermarking" had listed these three models for Content Credentials on files only. An archived copy from 30 September still shows that; the article's own modification time is 00:01 UTC on 1 October. All three now have ticks in both text watermark columns, and their cloud-partner ticks carry a footnote: "Rollout on Amazon Bedrock will complete by October 12." It replaces an older footnote about Opus 5[1]. The sentence about older models now says only that Anthropic is adding watermarks to outputs from models released before 2 August 2026[1].

What it means

Seven models remain listed for files only: Mythos 5, Opus 4.5, 4.6 and 4.7, Sonnet 4.5 and 4.6, and Haiku 4.5[1]. The 2 December 2026 date still exists in the law: the Commission says providers of AI systems placed on the market before 2 August 2026 must meet the marking and detection obligation from that day[7]. The help article no longer gives Anthropic's own date for finishing. What Anthropic marks, and how.

What is still not known

The table does not say from when the three models' output carries the mark. The footnote names only Amazon Bedrock and says nothing about Google Cloud or Microsoft Foundry. Anthropic has not published detection accuracy for any model, and the detector is still in private preview for organisations obliged to check under EU law[1]. What to do if a detector flags your text.

Last verified against primary sources: 2026-10-01