xAI will switch on invisible statistical watermarking across its Grok API text models by default beginning November 7, 2026, the company announced on October 31. The watermark covers several Grok model versions and applies to the api.x.ai endpoint, the Responses API and the Chat Completions API. It nudges token selection toward a statistical pattern while leaving the visible text unaltered.

Team administrators can disable the watermark for each model through the xAI Console, and consumer-facing Grok products are not affected — the change is API-only. Developers who do nothing will be shipping watermarked text from November 7.

The move marks a shift in xAI's stated position: the company had previously argued that AI text output should remain unaltered. It aligns Grok with the transparency demands of the EU AI Act — and it lands the same week Anthropic extended its own Claude text watermark to four more models.