fallback-credit changedbuild-with-claude/fallback-credit
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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) ### Required beta headers
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22title: Fallback credit
33url: https://platform.claude.com/docs/en/build-with-claude/fallback-credit
44description: Avoid paying the prompt-cache cost twice when you retry a refused request on another model.
5featureMetadata:
6 status: beta
7 betaHeader: fallback-credit-2026-07-01, server-side-fallback-2026-07-01, fallback-credit-2026-06-01
8 supportedModels:
9 - claude-fable-5-1
10 - claude-mythos-5-1
11 - claude-fable-5
12 - claude-opus-5-5
13 - claude-opus-5
14 - claude-sonnet-5-5
15 supportedPlatforms:
16 Claude API: beta
17 Claude Platform on AWS: beta
18 Amazon Bedrock:
19 availability: beta
20 note: On Amazon Bedrock and Google Cloud the token is bound to your caller identity (there are no workspaces), and `allowed_fallback_models` is not exposed.
21 Claude Models on Google Cloud (Google managed):
22 availability: beta
23 note: On Amazon Bedrock and Google Cloud the token is bound to your caller identity (there are no workspaces), and `allowed_fallback_models` is not exposed.
24 Microsoft Foundry: beta
525---
626
727Prompt caches are per-model. When a model declines a request and you retry on another model, the conversation prefix already cached for the first model must be written into the new model’s cache in full. Cache writes cost more than cache reads. Fallback credit removes that extra cost. The refusal carries a credit token, you echo the token on the retry, and the retry is billed as though the conversation had been on the new model from the start.
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621641 The SDK helper that applies fallback credit automatically.
622642 </Card>
623643</CardGroup>
644
645## Availability
646
647Fallback credit is in beta on select models.
648
649### API support
650
651#### [Messages API](https://platform.claude.com/docs/en/build-with-claude/working-with-messages)
652
653* Availability: Available
654* Usage: Needed only when you write the retry yourself: send the `fallback-credit-2026-07-01` beta header and put the refusal’s `fallback_credit_token` on the retry.
655
656| Status | Cloud platforms | Models |
657| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
658| Beta | Claude API, [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry) | [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) |
659| Beta<sup>1</sup> | [Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock), [Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/google-managed) | [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) |
660
6611. On Amazon Bedrock and Google Cloud the token is bound to your caller identity (there are no workspaces), and `allowed_fallback_models` is not exposed.
662
663#### [Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview)
664
665* Availability: Not available
666
667### Required beta headers
668
669[Beta headers overview](https://platform.claude.com/docs/en/api/beta-headers)
670
671Beta headers allow you to access experimental features and new model capabilities before they become part of the standard API.
672
673| Header | Cloud platforms |
674| ------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
675| `fallback-credit-2026-07-01` or `server-side-fallback-2026-07-01` or `fallback-credit-2026-06-01` | Claude API, [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry) |
676| `fallback-credit-2026-07-01` or `fallback-credit-2026-06-01` | [Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock), [Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/google-managed) |
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