fast-mode changedbuild-with-claude/fast-mode
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408408### Automatic retries
409409
410When fast mode rate limits are exceeded, the API returns a `429` error with a `retry-after` header. The Anthropic SDKs automatically retry these requests up to 2 times by default (configurable with `max_retries`), waiting for the server-specified delay before each retry. Because fast mode uses continuous token replenishment, the `retry-after` delay is typically short and requests succeed once capacity is available.
410When fast mode rate limits are exceeded, the API returns a `429` error with a `retry-after` header. The Anthropic SDKs automatically retry these requests up to 2 times by default (configurable with `max_retries` (typescript, java, php: `maxRetries`; csharp: `MaxRetries`; go: `option.WithMaxRetries`)), waiting for the server-specified delay before each retry. Because fast mode uses continuous token replenishment, the `retry-after` delay is typically short and requests succeed once capacity is available.
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412412### Falling back to standard speed
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415415 This section covers an opt-in client-side fallback when fast mode is rate limited. It is separate from the behavior on [Claude Opus 4.6](https://platform.claude.com/docs/en/build-with-claude/fast-mode#supported-models), where fast mode is not available and requests run at standard speed automatically.
416416</Note>
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418If 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"`. Set `max_retries` to `0` on the initial fast request to skip automatic retries and fail immediately on rate limit errors.
418If 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"`. Set `max_retries` (typescript, java, php: `maxRetries`; csharp: `MaxRetries`; go: `option.WithMaxRetries`) to `0` on the initial fast request to skip automatic retries and fail immediately on rate limit errors.
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420420<Note>
421421 Falling back from fast to standard speed will result 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.
422422</Note>
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424Because setting `max_retries` to `0` also disables retries for other transient errors (overloaded, internal server errors), the following examples reissue the original request with default retries for those cases.
424Because setting `max_retries` (typescript, java, php: `maxRetries`; csharp: `MaxRetries`; go: `option.WithMaxRetries`) to `0` also disables retries for other transient errors (overloaded, internal server errors), the following examples reissue the original request with default retries for those cases.
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426426<CodeGroup exclude="shell:cURL">
427427 ```bash CLI
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