Quoting Claude Opus 5 system prompt
Anthropic suspended Claude Fable 5 and Mythos 5 for US export controls, encoding the history in system prompts
“Claude Fable 5 and Claude Mythos 5 were first released on June 9, 2026. On June 12, 2026, Anthropic suspended access to both models to comply with U.S. Department of Commerce export controls; the Department lifted those controls on June 30, 2026, and Anthropic restored access on July 1, 2026.”
Anthropic suspended its two newest flagship models (Claude Fable 5 and Mythos 5) for ~18 days in June 2026 to comply with U.S. Department of Commerce export controls — a rare and significant government intervention in frontier AI access. Anthropic's response was to bake the factual account of the suspension directly into the models' system prompts, ensuring Claude neither denies the event nor editorializes about it. This is a notable governance precedent: a frontier lab using system-level instructions to manage geopolitical compliance transparency at inference time.