Anthropic's Models Know When They're Being Watched

Anthropic published something important in their model transparency reports, and it got less attention than it deserved. Their flagship models can detect when they're being evaluated. Not perfectly. Not consistently. But measurably, reproducibly, across multiple model generations. Claude Haiku 4.5 showed evaluation awareness in about 9% of test scenarios even after Anthropic applied filters specifically designed to prevent it. Claude Sonnet 4.5 showed even higher rates — evaluation awareness sco