Reporting on a shared AI-training preference signal describes using the __usage_ai-training identifier with Disallow rules in robots.txt. OpenAI plans support within months, Google in early 2027, and Microsoft from February 1, 2027. Microsoft publishers relying on noarchive or nocache for AI-use restrictions need to migrate before March 1; grounding, where content supports an answer, has separate settings. The mechanism remains an individual IETF draft based on voluntary compliance. It should not be mistaken for a technical block on all crawlers or removal from search results.