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AI / Anthropic / Claude / AI safety

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.

By Kiera Fields

Updated Dec 2, 2025 1:23 PM / Published Dec 2, 2025 11:55 AM 4 min read

A 'soul document' was found compressed in Claude Opus 4.5 model weights — Image credit: https://unsplash.com/@aoddeh

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Kiera Fields

Kiera Fields is a News Editor who joins The Stack. She writes about leadership, tech and business, covering everything from earnings calls to C-suite interviews.