Changes in the system prompt between Claude Opus 4.6 and 4.7
Claude 4.7's system prompt just changed. Here's what Anthropic is optimizing for.
Why it matters
System prompt modifications between model versions reveal shifting priorities in model behavior, safety guardrails, and instruction-following — a leading indicator of capability direction and alignment strategy.
The key facts
9 to knowClaude Opus 4.6 to 4.7 system prompt differences documented
Published Apr 18, 2026 on simonwillison.net (reputable AI researcher)
System prompt analysis as proxy for model alignment and behavior tuning
Anthropic's evolving approach to instruction handling between versions
Claude Opus 4.6 → 4.7 system prompt divergence detected
Changes documented by independent researcher (Simon Willison)
Anthropic has not publicly announced system prompt modifications
Implies undocumented behavioral shifts between minor versions
UNVERIFIED - no official Anthropic statement provided
Go to the source
Simon Willisonsimonwillison.net