refusals-and-fallback changedbuild-with-claude/refusals-and-fallback
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## Availability ### API support #### [Messages API](https://platform.claude.com/docs/en/build-with-claude/working-with-messages) #### [Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview)
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22title: Refusals and fallback
33url: https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback
44description: How Claude Fable models, Claude Opus models, Claude Sonnet 5.5, and Claude Haiku 5.5 return classifier refusals and how to retry refused requests on a fallback model.
5featureMetadata:
6 supportedModels:
7 - claude-fable-5-1
8 - claude-mythos-5-1
9 - claude-fable-5
10 - claude-opus-5-5
11 - claude-opus-5
12 - claude-sonnet-5-5
13 - claude-haiku-5-5
14 supportedPlatforms:
15 Claude API: ga
16 Claude Platform on AWS: ga
17 Claude Models on Google Cloud (Anthropic managed): ga
18 Amazon Bedrock: ga
19 Claude Models on Google Cloud (Google managed): ga
20 Microsoft Foundry: ga
521---
622
723Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, and Claude Haiku 5.5 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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11781194 Move an existing application to Claude Fable 5.1.
11791195 </Card>
11801196</CardGroup>
1197
1198## Availability
1199
1200Classifier refusals are available or in beta on select models, depending on the API.
1201
1202### API support
1203
1204#### [Messages API](https://platform.claude.com/docs/en/build-with-claude/working-with-messages)
1205
1206* Availability: Always on
1207
1208| Status | Models |
1209| --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
1210| Available | [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview), [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview), [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview), [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview), [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview), [Claude Haiku 5.5](https://platform.claude.com/docs/en/models/haiku-5-5/overview) |
1211
1212#### [Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview)
1213
1214* Availability: Always on
1215
1216| Status | Cloud platforms | Models |
1217| ------ | ------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
1218| Beta | Claude API, [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws) | [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview), [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview), [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview), [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview), [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview), [Claude Haiku 5.5](https://platform.claude.com/docs/en/models/haiku-5-5/overview) |
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