Anthropic claims Chinese AI firms secretly use Claude. Is it true?

Anthropic has alleged that Chinese AI companies secretly used its Claude model to advance their own systems, an accusation now echoed in a joint advisory from the National Security Agency, FBI, and Cybersecurity and Infrastructure Security Agency issued last month stating that Chinese AI developers have been systematically extracting capabilities from US frontier models to cut their own computing and electricity costs. The claims have not been substantiated in the available reporting, leaving open whether Chinese firms actually tapped US models.