---
title: "Anthropic Adds Export Control Notice to Claude Opus 5 System Prompt"
source: "Simon Willison 博客（Atom）"
source_tier: "t2"
url: "https://simonwillison.net/2026/Aug/9/claude-opus-5-system-prompt/#atom-everything"
permalink: "https://feed.astralor.com/items/itm_741f7f7c4b86cc0e5db3369a"
published: "2026-08-09T23:31:39.000Z"
score: 73
channel: "ai"
tags: ["Anthropic","Claude Fable 5","Claude Mythos 5","Claude Opus 5","Export Controls","System Prompt"]
---

# Anthropic Adds Export Control Notice to Claude Opus 5 System Prompt

## AI commentary

> This is worth watching because it rarely shows how an AI company uses system prompts to 'teach' models to handle politically sensitive events. For AI compliance or model safety practitioners, it's an excellent case study; for general users, it also reminds that model answers may be carefully engineered at the system level.

## At a glance

Simon Willison's blog reveals the system prompt of Claude Opus 5, which includes a notice about Claude Fable 5 and Claude Mythos 5 being temporarily suspended due to U.S. Department of Commerce export controls and restored on July 1, 2026. The prompt ensures the model accurately and matter-of-factly addresses these events, without denying the suspension or sharing personal opinions, and directs users to Anthropic's official statement. This demonstrates how Anthropic manages model awareness of recent policy events via system prompts.

## Key points

- The Claude Opus 5 system prompt includes a notice about the export-control suspension and restoration of Fable 5 and Mythos 5, with a clear timeline.
- The prompt instructs the model to acknowledge the suspension matter-of-factly, avoid personal opinions, and direct users to Anthropic's official statement.
- This design addresses the model's knowledge gap for post-training-cutoff policy events.
- The incident involves U.S. Commerce Department export controls, reflecting the new normal of cross-border AI compliance.

## Full text

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's statement: https://www.anthropic.com/news/fable-mythos-access). 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. Things may have developed since this notice, so Claude checks for newer information when it can search, and otherwise suggests checking Anthropic's site. — Claude Opus 5 system prompt, ensuring Claude doesn't provide incorrect answers about the export controls situation Tags: system-prompts, anthropic, claude, generative-ai, ai, llms, claude-mythos-fable

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Verify against the original before citing; curated by Astral Feed: https://feed.astralor.com/items/itm_741f7f7c4b86cc0e5db3369a