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1414 - claude-opus-5
1515 - claude-opus-4-8
1616 supportedPlatforms:
17 Claude API: stable
17 Claude API:
18 availability: stable
19 note: 'Removal date: November 30, 2026. After removal, requests to `claude-opus-4-8` with `speed: "fast"` will return an error. To continue using fast mode, migrate to Claude Opus 5.5. See [Migrating to Claude Opus 5.5 from Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide#migrating-from-claude-opus-4-8).'
1820 Claude Models on Google Cloud (Anthropic managed): stable
1921 Claude Models on Google Cloud (Google managed): stable
2022 Microsoft Foundry:
2123 availability: stable
22 note: On Microsoft Foundry, fast mode is a separate model whose ID ends in `-fast`. Send requests to a deployment of that model, and leave out `speed`.
24 note: On Microsoft Foundry, fast mode has its own model IDs, which end in `-fast`. Send requests to a deployment of the fast mode model, and leave out `speed`.
2325 details:
24 - 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.
26 - Fast mode is in research preview on Claude Opus 5 and deprecated on Claude Opus 4.8, and needs the `fast-mode-2026-02-01` beta header on both models.
2527---
2628 
2729**API support**: Usage differs by product.
from line 31
2931* **Messages API**: Set `speed: "fast"` on the request.
3032* **Managed Agents**: Set `speed` on the agent’s model object, for example `{"id": "claude-opus-5-5", "speed": "fast"}`.
3133 
32Fast 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 Fable 5.2 and Claude Opus 5.5. Fast mode for Claude Opus 5 and Claude Opus 4.8 is in research preview. Claude Mythos 5.2 supports fast mode too.
34Fast 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 Fable 5.2, Claude Mythos 5.2, and Claude Opus 5.5. Fast mode is in research preview on Claude Opus 5 and deprecated on Claude Opus 4.8.
3335 
3436## How fast mode works
3537 
from line 45
4345 
4446Fast 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.
4547 
46On [Claude in Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry), fast mode is a separate model, such as `claude-opus-5-5-fast`. For Claude Fable 5.2, it is `claude-fable-5-2-fast`. For Claude Mythos 5.2, it is `claude-mythos-5-2-fast`. Send fast mode requests to a deployment of the fast model, and leave out `speed`. A request that sets `speed` on a deployment of the model without `-fast` returns an error.
47 
4848<CodeGroup>
4949 ```bash cURL
5050 curl https://api.anthropic.com/v1/messages \
from line 203
203203 ```
204204</CodeGroup>
205205 
206On [Claude in Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry), fast mode has its own model IDs, and the deployment sets the speed. Send fast mode requests to a deployment of the fast mode model, and leave out `speed`:
207 
208| Model | Fast mode model ID |
209| ----------------- | ------------------------ |
210| Claude Fable 5.2 | `claude-fable-5-2-fast` |
211| Claude Mythos 5.2 | `claude-mythos-5-2-fast` |
212| Claude Opus 5.5 | `claude-opus-5-5-fast` |
213 
214A request that sets `speed` on a deployment of the standard model, such as `claude-opus-5-5`, returns an error.
215 
206216## Rate limits
207217 
208218Fast mode has a dedicated rate limit that is separate from standard rate limits. When you exceed your fast mode rate limit, the API returns a `429` error with a `retry-after` header that says when capacity is available. On [Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/google-managed#rate-limits), Google Cloud manages rate limits and quotas.
209219 
210Claude Opus 5.5 has a default fast mode rate limit in the Start, Build, and Scale [usage tiers](https://platform.claude.com/docs/en/api/rate-limits), so you don’t need to request access to use fast mode with it. Organizations in the Evaluation tier can use fast mode with Claude Opus 5.5 once they move to the Start, Build, or Scale tier. The same applies to Claude Fable 5.2. It also applies to Claude Mythos 5.2.
220Claude Fable 5.2, Claude Mythos 5.2, and Claude Opus 5.5 have a default fast mode rate limit. The default limit applies in the Start, Build, and Scale [usage tiers](https://platform.claude.com/docs/en/api/rate-limits). You don’t need to request fast mode access for these models. Organizations in the Evaluation tier can use fast mode with these models once they move to the Start, Build, or Scale tier.
211221 
212222The response includes headers that indicate your fast mode rate limit status:
213223 
from line 383
373383 
374384### Falling back to standard speed
375385 
376If you’d prefer to fall back to standard speed rather than wait for fast mode capacity, catch the rate limit error and retry without `speed: "fast"`. On Claude in Microsoft Foundry, the deployment sets the speed, so retry on a deployment of the model without `-fast` instead. Set `max_retries` (typescript, php: `maxRetries`; java: `.maxRetries()`; csharp: `MaxRetries`; go: `option.WithMaxRetries()`) to `0` on the initial fast request to skip automatic retries and fail immediately on rate limit errors.
386If you’d prefer to fall back to standard speed rather than wait for fast mode capacity, catch the rate limit error and retry without `speed: "fast"`. On Claude in Microsoft Foundry, the deployment sets the speed, so retry on a deployment of the standard model instead. Set `max_retries` (typescript, php: `maxRetries`; java: `.maxRetries()`; csharp: `MaxRetries`; go: `option.WithMaxRetries()`) to `0` on the initial fast request to skip automatic retries and fail immediately on rate limit errors.
377387 
378388<Note>
379389 Falling back from fast to standard speed results in a [prompt cache](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) miss. Requests at different speeds do not share cached prefixes.
from line 610
600610 use Anthropic\Core\Exceptions\RateLimitException;
601611 use Anthropic\Messages\Model;
602612 use Anthropic\RequestOptions;
603 // ...
613 
604614 $client = new Client();
605615 
606616 function createMessageWithFastFallback(
from line 702
692702 
693703## Availability
694704 
695Fast mode is available or in research preview on select models and eligible for zero data retention and HIPAA readiness.
705Fast mode is available or in research preview or deprecated on select models and eligible for zero data retention and HIPAA readiness.
696706 
697707### API support
698708 
from line 710
700710 
701711To access fast mode on Claude Opus 5, contact your account manager or [join the waitlist](https://claude.com/fast-mode).
702712 
703<Warning>
704 Fast mode on Claude Opus 4.8 is deprecated and will be removed on November 30, 2026. After removal, requests to `claude-opus-4-8` with `speed: "fast"` will return an error. To continue using fast mode, migrate to Claude Opus 5.5. See [Migrating to Claude Opus 5.5 from Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide#migrating-from-claude-opus-4-8).
705</Warning>
706 
707713#### [Messages API](https://platform.claude.com/docs/en/build-with-claude/working-with-messages)
708714 
709715* Availability: Available
710716* Usage: Set `speed: "fast"` on the request.
711717 
712| Status | Cloud platforms | Models |
713| --------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
714| 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), [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 5.2](https://platform.claude.com/docs/en/models/fable-5-2/overview), [Claude Mythos 5.2](https://platform.claude.com/docs/en/models/mythos-5-2/overview) |
715| Available<sup>1</sup> | [Microsoft Foundry (hosted on Anthropic)](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry) | [Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/overview), [Claude Mythos 5.2](https://platform.claude.com/docs/en/models/mythos-5-2/overview) |
716| 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) | [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) |
717| Available<sup>1</sup> | [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) |
718| 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) |
718| Status | Cloud platforms | Models |
719| ---------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
720| 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), [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 5.2](https://platform.claude.com/docs/en/models/fable-5-2/overview), [Claude Mythos 5.2](https://platform.claude.com/docs/en/models/mythos-5-2/overview) |
721| Available<sup>1</sup> | [Microsoft Foundry (hosted on Anthropic)](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry) | [Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/overview), [Claude Mythos 5.2](https://platform.claude.com/docs/en/models/mythos-5-2/overview) |
722| 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) | [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) |
723| Available<sup>1</sup> | [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) |
724| Research preview | Claude API | [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) |
725| Deprecated<sup>2</sup> | Claude API | [Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-4-8/overview) |
719726 
7201. On Microsoft Foundry, fast mode is a separate model whose ID ends in `-fast`. Send requests to a deployment of that model, and leave out `speed`.
7271. On Microsoft Foundry, fast mode has its own model IDs, which end in `-fast`. Send requests to a deployment of the fast mode model, and leave out `speed`.
7282. Removal date: November 30, 2026. After removal, requests to `claude-opus-4-8` with `speed: "fast"` will return an error. To continue using fast mode, migrate to Claude Opus 5.5. See [Migrating to Claude Opus 5.5 from Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide#migrating-from-claude-opus-4-8).
721729 
722730#### [Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview)
723731 
from line 732
724732* Availability: Available
725733* Usage: Set `speed` on the agent’s model object, for example `{"id": "claude-opus-5-5", "speed": "fast"}`.
726734 
727| Status | Cloud platforms | Models |
728| ---------------- | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ |
729| Available | Claude API | [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) |
730| 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) |
735| Status | Cloud platforms | Models |
736| ---------------------- | --------------- | ------------------------------------------------------------------------------- |
737| Available | Claude API | [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) |
738| Research preview | Claude API | [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) |
739| Deprecated<sup>1</sup> | Claude API | [Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-4-8/overview) |
740 
7411. Removal date: November 30, 2026. After removal, requests to `claude-opus-4-8` with `speed: "fast"` will return an error. To continue using fast mode, migrate to Claude Opus 5.5. See [Migrating to Claude Opus 5.5 from Claude Opus 4.8](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide#migrating-from-claude-opus-4-8).
731742 
732743### Required beta headers
733744 
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