https://simonwillison.net/2026/Apr/18/opus-system-prompt/
Article
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Simon Willison analyzed diff between Opus 4.6 and 4.7 system prompts.
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New acting_vs_clarifying section: Claude should attempt tasks rather than ask clarifying questions.
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Eating disorder safety section added; new knowledge cutoff date.
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Prompt now exceeds 60,000 words (~80k tokens), nearly 10% of 1M context window.
Discussion
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acting_vs_clarifying change widely noticed: 4.7 just picks an interpretation and goes, less friction.
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4.7 reportedly over-aggressive flagging security/scraping work as malware risk.
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sigmoid10 flagged 80k-token system prompt cost: “you haven’t even had any user input yet.”
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Mixed quality verdict: some prefer 4.6, others find 4.7 significantly better.
Discuss on HN