Anthropic adds text watermarking to four Claude models
What happened
On 1 November 2026, The Decoder reported that Anthropic told API customers by email it will add text watermarking to four models: Claude Mythos 5, Claude Opus 4.7, Claude Opus 4.6 and Claude Sonnet 4.6; rollout on Amazon Bedrock may lag by a few days. The report also said the watermark can be bypassed on two older models by changing sampling parameters. Current status: Anthropic has notified API customers, the watermark rollout for the four models is not yet complete, and there is a delay on the Bedrock channel.
Written by AI from the reports · updated 2 h ago
Timeline
Follow the reports to see the event from each side.
- The DecoderAnthropic's watermark rollout leaves a loophole on two older Claude models
Anthropic is expanding its text watermark to four more Claude models to meet the EU AI Act's December deadline. On the older models Claude Opus 4.6 and Sonnet 4.6, developers can bypass the watermark by tweaking a single sampling parameter. Anthropic addresses the loophole with just a compliance warning.
Heat of this event
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