FrontierAugust 9, 2026via Simon Willison
Quoting Claude Opus 5 system prompt
Why it matters
System prompt disclosure reveals core guardrails, reasoning strategies, and behavioral instructions embedded in Anthropic's most capable model — a rare look inside frontier model architecture and values alignment.
Key signals
- Claude Opus 5 system prompt publicly quoted
- Published Aug 9, 2026 on Simon Willison's site
- Reveals guardrails, reasoning, and behavioral instructions
- Anthropic's alignment and safety strategy exposed in primary source
- Frontier lab internals typically kept confidential
- Published by Simon Willison (trusted AI/tech analyst)
- August 2026 — recent disclosure
- Primary source material on Anthropic model engineering
The hook
Someone just published Claude Opus 5's system prompt in full. Here's what Anthropic is actually telling its flagship model to do.