refusals-and-fallback changedbuild-with-claude/refusals-and-fallback
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44description: How Claude Fable and Claude Opus models return classifier refusals and how to retry refused requests on a fallback model.
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7Claude Fable 5.1, Claude Fable 5, and Claude Opus 5 include safety classifiers that can decline a request. When that happens, you receive a normal response, not an error, with `stop_reason: "refusal"`. Its `stop_details.category` names the policy area (see [What a refusal looks like](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response)). You can usually still get an answer by sending the same request to another Claude model. This page shows you how to recognize a refusal and how to set up that retry.
7Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, and Claude Opus 5 include safety classifiers that can decline a request. When that happens, you receive a normal response, not an error, with `stop_reason: "refusal"`. Its `stop_details.category` names the policy area (see [What a refusal looks like](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response)). You can usually still get an answer by sending the same request to another Claude model. This page shows you how to recognize a refusal and how to set up that retry.
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99Read this page when you build on any of these models and want declined requests to fall through to another model automatically. It also applies when you have seen `"refusal"` in a response and want to know what to do next.
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