Anthropic told API customers that text watermarking will be retrofitted to Claude Opus 4.6, Claude Opus 4.5, Claude Sonnet 4.5, and Claude Haiku 4.5 starting November 16, 2026; the rollout on Amazon Bedrock may take several additional days. Claude Opus 4.6 was initially expected to receive the watermark on November 3, but Anthropic confirmed the delay without explaining it. The report says all four models in this wave apply the watermark only when the sampling parameters temperature, top_p, and top_k remain at their defaults. Anthropic says a minor change to any one parameter is enough to avoid the watermark on Claude Opus 4.6 and Claude Sonnet 4.6, and warns developers who rely on watermarking for compliance to keep those settings unchanged. Anthropic says the watermark adds no tokens, does not affect pricing or request and response formats, and contains no information about users, their organizations, or their conversations.