Quoting Claude Opus 5 system prompt
Someone just published Claude Opus 5's system prompt in full. Here's what Anthropic is actually telling its flagship model to do.
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.
The key facts
8 to knowClaude 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
Go to the source
Simon Willisonsimonwillison.net