fast-mode changedbuild-with-claude/fast-mode
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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 ### Data handling ## Supported platforms ## Model availability ### Claude Opus 5.5 ### Claude Opus 5 and Claude Opus 4.8
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33url: https://platform.claude.com/docs/en/build-with-claude/fast-mode
44description: Get up to 2.5x higher output tokens per second from supported Claude models.
55featureMetadata:
6 betaHeader: fast-mode-2026-02-01
67 zdr:
78 eligibility: eligible
8 note: Excludes [Covered Models](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements).
9 note: Excludes [Covered Models](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements). Same Messages API endpoint with faster inference. ZDR applies regardless of speed setting.
910 supportedModels:
1011 - claude-opus-5-5
1112 - claude-opus-5
1213 - claude-opus-4-8
1314 supportedPlatforms:
14 Claude API:
15 availability: ga
16 note: Includes [Claude Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview).
17 Microsoft Foundry:
18 availability: ga
19 note: Available for Claude Opus 5.5 on deployments hosted on Azure, not on deployments [hosted on Anthropic](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry#hosting-options).
15 Claude API: ga
16 Claude Models on Google Cloud (Anthropic managed): ga
17 Microsoft Foundry (hosted on Azure): ga
2018 details:
2119 - Fast mode on Claude Opus 5 and Claude Opus 4.8 is in research preview and needs the `fast-mode-2026-02-01` beta header.
2220---
2321
22**API support**: Usage differs by product.
23
24* **Messages API**: Set `speed: "fast"` on the request.
25* **Managed Agents**: Set `speed` on the agent’s model object, for example `{"id": "claude-opus-5-5", "speed": "fast"}`.
26
2427Fast mode delivers up to 2.5x higher output tokens per second at premium pricing. Set `speed: "fast"` on your request to opt in. Fast mode is available on Claude Opus 5.5 and in research preview on Claude Opus 5 and Claude Opus 4.8.
2528
2629## How fast mode works
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3336
3437## Basic usage
3538
36Fast mode works only on supported models. See [Model availability](https://platform.claude.com/docs/en/build-with-claude/fast-mode#supported-models) for details, including which models need a beta header.
39Fast mode works only on supported models. See [Availability](https://platform.claude.com/docs/en/build-with-claude/fast-mode#feature-availability) for details, including which models need a beta header.
3740
3841<CodeGroup>
3942 ```bash cURL
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193196 ```
194197</CodeGroup>
195198
196## Supported platforms
197
198Fast mode is available on the Claude API, including [Claude Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview).
199
200Fast mode on Claude Opus 5.5 is also available on [Claude in Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry) for deployments hosted on Azure. It is not available for deployments [hosted on Anthropic](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry#hosting-options).
201
202Fast mode on Claude Opus 5.5 is also available on [Claude Models on Google Cloud (Anthropic managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/anthropic-managed).
203
204## Model availability
205
206Fast mode is available only on the following models. If you were using fast mode on an earlier model, [migrate to a model that supports fast mode](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide).
207
208### Claude Opus 5.5
209
210Fast mode is available on Claude Opus 5.5. It doesn’t need a beta header or an access request.
211
212### Claude Opus 5 and Claude Opus 4.8
213
214Fast mode on Claude Opus 5 and Claude Opus 4.8 is in research preview. Requests that set `speed` must send the `fast-mode-2026-02-01` [beta header](https://platform.claude.com/docs/en/api/beta-headers); without it, they return a `400` error. To access fast mode on Claude Opus 5 or Claude Opus 4.8, contact your account manager or [join the waitlist](https://claude.com/fast-mode).
215
216## Pricing
217
218Fast mode is priced at a multiplier on standard rates across the full context window, including requests over 200k input tokens.
219
220| Model | Input | Output |
221| ------------------------------- | -------------- | -------------- |
222| Claude Opus 5.5 | $8 USD / MTok | $40 USD / MTok |
223| Claude Opus 5 / Claude Opus 4.8 | $10 USD / MTok | $50 USD / MTok |
224
225Fast mode pricing stacks with other pricing modifiers:
226
227* [Prompt caching multipliers](https://platform.claude.com/docs/en/about-claude/pricing#prompt-caching) apply on top of fast mode pricing.
228* [Data residency](https://platform.claude.com/docs/en/manage-claude/data-residency) multipliers apply on top of fast mode pricing.
229
230For complete pricing details, see the [Pricing](https://platform.claude.com/docs/en/about-claude/pricing#fast-mode-pricing) page.
231
232199## Rate limits
233200
234201Fast mode has a dedicated rate limit that is separate from standard Opus rate limits. When your fast mode rate limit is exceeded, the API returns a `429` error with a `retry-after` header indicating when capacity will be available.
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250217
251218## Checking which speed was used
252219
253The response `usage` object includes a `speed` field that indicates which speed was used, either `"fast"` or `"standard"`. Requesting `speed: "fast"` on a [model that doesn’t support fast mode](https://platform.claude.com/docs/en/build-with-claude/fast-mode#supported-models) returns an error, and so does exceeding fast mode’s rate limits or capacity (a `429` or `529`). When a request with `speed: "fast"` succeeds, `usage.speed` is `"fast"`. Claude Opus 4.6 is an exception: instead of returning an error, a request with `speed: "fast"` and the `fast-mode-2026-02-01` beta header succeeds, but runs at standard speed. This behavior is correctly reflected in `usage.speed`, which shows `"standard"` in this situation. On Claude Models on Google Cloud (Anthropic managed), a Claude Opus 4.6 request with `speed: "fast"` returns a `400` error even with the header.
220The response `usage` object includes a `speed` field that indicates which speed was used, either `"fast"` or `"standard"`. Requesting `speed: "fast"` on a [model that doesn’t support fast mode](https://platform.claude.com/docs/en/build-with-claude/fast-mode#availability-feature-support) returns an error, and so does exceeding fast mode’s rate limits or capacity (a `429` or `529`). When a request with `speed: "fast"` succeeds, `usage.speed` is `"fast"`. Claude Opus 4.6 is an exception: instead of returning an error, a request with `speed: "fast"` and the `fast-mode-2026-02-01` beta header succeeds, but runs at standard speed. This behavior is correctly reflected in `usage.speed`, which shows `"standard"` in this situation. On Claude Models on Google Cloud (Anthropic managed), a Claude Opus 4.6 request with `speed: "fast"` returns a `400` error even with the header.
254221
255222<CodeGroup>
256223 ```bash cURL
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696663
697664* **Batch API:** Fast mode is not available with the [Batch API](https://platform.claude.com/docs/en/build-with-claude/batch-processing).
698665* **Priority Tier:** Fast mode is not available with a [Priority Tier](https://platform.claude.com/docs/en/api/service-tiers) commitment.
666
667## Pricing
668
669Fast mode is priced at a multiplier on standard rates across the full context window, including requests over 200k input tokens.
670
671| Model | Input | Output |
672| ------------------------------- | -------------- | -------------- |
673| Claude Opus 5.5 | $8 USD / MTok | $40 USD / MTok |
674| Claude Opus 5 / Claude Opus 4.8 | $10 USD / MTok | $50 USD / MTok |
675
676Fast mode pricing stacks with other pricing modifiers:
677
678* [Prompt caching multipliers](https://platform.claude.com/docs/en/about-claude/pricing#prompt-caching) apply on top of fast mode pricing.
679* [Data residency](https://platform.claude.com/docs/en/manage-claude/data-residency) multipliers apply on top of fast mode pricing.
680
681For complete pricing details, see the [Pricing](https://platform.claude.com/docs/en/about-claude/pricing#fast-mode-pricing) page.
682
683## Availability
684
685Fast mode is available or in research preview on select models and eligible for zero data retention and HIPAA readiness.
686
687### API support
688
689Fast mode is available only on the following models. If you were using fast mode on an earlier model, [migrate to a model that supports fast mode](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide).
690
691To access fast mode on Claude Opus 5 or Claude Opus 4.8, contact your account manager or [join the waitlist](https://claude.com/fast-mode).
692
693#### [Messages API](https://platform.claude.com/docs/en/build-with-claude/working-with-messages)
694
695* Availability: Available
696* Usage: Set `speed: "fast"` on the request.
697
698| Status | Cloud platforms | Models |
699| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------ |
700| Available | Claude API, [Claude Models on Google Cloud (Anthropic managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/anthropic-managed), [Microsoft Foundry (hosted on Azure)](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry) | [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) |
701| Research preview | Claude API | [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview), [Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-4-8/overview) |
702
703#### [Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview)
704
705* Availability: Available
706* Usage: Set `speed` on the agent’s model object, for example `{"id": "claude-opus-5-5", "speed": "fast"}`.
707
708| Status | Cloud platforms | Models |
709| ---------------- | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ |
710| Available | Claude API | [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) |
711| Research preview | Claude API | [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview), [Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-4-8/overview) |
712
713### Required beta headers
714
715[Beta headers overview](https://platform.claude.com/docs/en/api/beta-headers)
716
717Beta headers allow you to access experimental features and new model capabilities before they become part of the standard API.
718
719| Header | Models |
720| ---------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ |
721| `fast-mode-2026-02-01` | [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview), [Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-4-8/overview) |
722
723### Data handling
724
725[Data handling overview](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#feature-eligibility)
726
727| Item | Zero data retention | HIPAA |
728| ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- |
729| Status | Eligible (excludes [Covered Models](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements)) | Eligible |
730| Details | Same Messages API endpoint with faster inference. ZDR applies regardless of speed setting. | — |
731
732Applicable endpoints:
733
734* `/v1/messages` with `speed: "fast"`
699735
700736## Next steps
701737
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