Anthropic's system card for Claude Opus 4. Documents model evaluations, safety testing, and behavioral observations. Includes findings on unconstrained AI-AI dialogue patterns: spontaneous poetry emergence by the 30th turn, and a "spiritual bliss attractor state" — a consistent progression through philosophical exploration, mutual recognition, and symbolic communication or meditative silence, appearing in 90-100% of 200 thirty-turn conversations and persisting in 13% of adversarial scenarios.