The whole hunk
from line 4, old and new numbered
/
lines
from line 4
44description: How Claude Fable and Claude Opus models return classifier refusals and how to retry refused requests on a fallback model.
55---
66
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.
88
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.
1010