Intel / article

Quoting Claude Opus 5 system prompt

Source: simonwillison.net
Date: Published Aug 9, 2026

Terms in this piece · Glossary

system prompt — The standing instructions a model receives before any user input — defining its role, rules, tools, and tone for the whole conversation.
knowledge cutoff — The date after which a model saw no training data — everything later has to reach it through search, tools, or the context window.

Why it matters

Model availability changed under an export-control action and was restored — and the system-prompt text shows the pattern labs use to correct post-cutoff knowledge, which anyone maintaining their own prompts can copy.

Key quotes

“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”

“These events are after Claude's training-data cutoff, so Claude knows about them only from this notice.”

“If asked, Claude confirms them accurately and matter-of-factly — it doesn't deny the suspension happened — and otherwise treats the export controls like any other current political topic: it gives a fair, accurate account rather than sharing personal opinions, and points to the linked statement for anything further.”

Read the source simonwillison.net