prompting-claude-opus-5-5 changedbuild-with-claude/prompt-engineering/prompting-claude-opus-5-5
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7979Claude Opus 5.5 runs safety classifiers, including for biology, cybersecurity, and reasoning extraction.
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8181* **Biology:** The biology safeguards are the same as Claude Fable 5.1's and are new if you're coming from Claude Opus 5. Everyday health and educational questions are unaffected. If the biology classifier gets in the way of your organization's life sciences work, apply to the [Life Sciences Verification Program](https://www.anthropic.com/news/life-sciences-verification-program).
82* **Cybersecurity:** Finding vulnerabilities in source code is allowed. High-risk dual-use cybersecurity activities are not.
82* **Cybersecurity:** Finding vulnerabilities in source code is allowed. High-risk dual-use cybersecurity activities are not. If the cybersecurity classifier gets in the way of your organization's legitimate security work, apply to the [Cyber Verification Program](https://support.claude.com/en/articles/14604842).
8383* **Reasoning extraction:** Requests that push the model to reproduce its internal reasoning in the response text may be declined with the `reasoning_extraction` category. If your prompts ask the model to write out its reasoning in the response, remove those instructions, set `display: "summarized"`, and read the summarized reasoning from the thinking blocks instead; see [Prompts written for thinking disabled](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-opus-5-5#prompts-written-for-thinking-disabled). You can still ask for a short explanation of the answer or a summary of the actions taken; see [Keep reasoning in thinking blocks](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#keep-reasoning-in-thinking-blocks).
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8585A classifier decline arrives as a normal response with `stop_reason: "refusal"` and a `stop_details` object naming the category. You can have the request retried automatically on a fallback model, except for `reasoning_extraction` declines, which server-side fallback returns to you instead of retrying; see [Refusals and fallback](https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5#refusals-and-fallback).
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