Anthropic Releases Claude Constitution Under CC0

Anthropic today published the full 'constitution' used in training its Claude Opus 4.5 model, releasing the 35,000-token document under a CC0 license. The constitution — first exposed late last year after researcher Richard Weiss extracted a baked-in document and confirmed by Anthropic staff — details Claude's core values and includes external acknowledgements, including two Catholic clergy reviewers. The release enables public scrutiny and reuse.