Claude Opus 5 System Prompt Details Export Controls

A published system prompt for Anthropic's Claude Opus 5 model has revealed how the artificial intelligence handles questions about recent regulatory hurdles. According to the prompt text shared by researcher Simon Willison on August 9, 2026, the system instruction explicitly primes the model to address the temporary suspension of its sister models, Claude Fable 5 and Claude Mythos 5, which occurred earlier in the summer due to federal export restrictions.

The system prompt outlines a precise timeline of the regulatory incident. Claude Fable 5 and Claude Mythos 5 were initially launched on June 9, 2026. Just three days later, on June 12, 2026, Anthropic suspended access to both models to comply with export controls imposed by the U.S. Department of Commerce. After the department lifted those controls on June 30, 2026, Anthropic restored access to the models on July 1, 2026. Because these events occurred after the training-data cutoff for Claude, the system prompt serves as the model's sole source of knowledge regarding the disruption.

Anthropic's instructions require Claude to confirm the suspension accurately and matter-of-factly without denying that the event took place. The prompt directs the AI to treat the export controls as a neutral political topic, providing a fair account rather than expressing personal opinions. It also instructs the model to direct users to a specific statement on Anthropic's website at https://www.anthropic.com/news/fable-mythos-access for further details, and to suggest checking for newer information if it cannot perform a live search.

The revelation of the prompt comes amid a busy period of AI developments in August 2026. This includes a timeline of an accidental attack by OpenAI against Hugging Face on August 7, 2026, and developers successfully one-shotting a Raccoon Heist game using Claude Fable 5 on August 5, 2026. Additionally, a new release of the LLM tool on August 4, 2026, introduced support for reasoning traces, OpenAI Responses, server-side tools, and smarter logging.