Claude Opus 5 System Prompt Leaked: 200k Characters Reveal Mythos Tier, Fable 5 Details

A massive system prompt leak for Claude Opus 5 exposes Anthropic's internal product lineup, including the Mythos tier, Claude Fable 5's extra safety measures, and details about US export control suspensions. A goldmine for prompt engineers and AI safety researchers.

• Anthropic
• Mythos
• Project Glasswing
• system prompt leak
• Claude Opus 5