AI A 'soul document' was found compressed in Claude Opus 4.5 model weights Anthropic's staff philosopher confirms the discovery is based on a legitimate document used to train Claude's most recent model. Kiera Fields Dec 02, 2025 - 4 min read Image credit: https://unsplash.com/@aoddeh Get the full story: Subscribe for free Join peers managing over $100 billion in annual IT spend and subscribe to unlock full access to The Stack’s analysis and events. Subscribe now Already a member? Sign in