handling-stop-reasons changedbuild-with-claude/handling-stop-reasons
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19411941</CodeGroup>
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19431943<Tip>
1944 If you encounter `refusal` stop reasons frequently while using Claude Sonnet 4.5 or Claude Opus 4.1 (the latter [retired, except on Bedrock and Google Cloud](https://platform.claude.com/docs/en/about-claude/model-deprecations)), you can try updating your API calls to use Haiku 4.5 (`claude-haiku-4-5-20251001`), which has different usage restrictions. Learn more about [understanding Sonnet 4.5's API safety filters](https://support.claude.com/en/articles/12449294-understanding-sonnet-4-5-s-api-safety-filters).
1944 If you encounter `refusal` stop reasons frequently while using Claude Sonnet 4.5 ([deprecated](https://platform.claude.com/docs/en/about-claude/model-deprecations)) or Claude Opus 4.1 (the latter [retired, except on Bedrock and Google Cloud](https://platform.claude.com/docs/en/about-claude/model-deprecations)), you can try updating your API calls to use Haiku 4.5 (`claude-haiku-4-5-20251001`), which has different usage restrictions. Learn more about [understanding Sonnet 4.5's API safety filters](https://support.claude.com/en/articles/12449294-understanding-sonnet-4-5-s-api-safety-filters).
19451945</Tip>
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19471947On a refusal, the `stop_details` object identifies the policy category that triggered it. The categories and the full refusal response shape are covered on [Refusals and fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response). `stop_details` is `null` for all stop reasons other than `refusal`.
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19531953Claude stopped because it reached the model's context window limit. This lets you request the maximum possible tokens without knowing the exact input size.
19541954
19551955<Note>
1956 This stop reason is currently typed only in the SDK's `beta` (csharp, go: `Beta`; java: `beta()`) namespace, so the following examples call `client.beta.messages` (csharp, go: `client.Beta.Messages`; java: `client.beta().messages()`; php: `$client->beta->messages`) and use the `Beta`-prefixed types. On Sonnet 4.5 and newer models the API returns this value without a beta header. For earlier models, add the `model-context-window-exceeded-2025-08-26` beta header to enable it.
1956 This stop reason is currently typed only in the SDK's `beta` (csharp, go: `Beta`; java: `beta()`) namespace, so the following examples call `client.beta.messages` (csharp, go: `client.Beta.Messages`; java: `client.beta().messages()`; php: `$client->beta->messages`) and use the `Beta`-prefixed types. On Sonnet 4.5 (deprecated) and newer models the API returns this value without a beta header. For earlier models, add the `model-context-window-exceeded-2025-08-26` beta header to enable it.
19571957</Note>
19581958
19591959<CodeGroup>
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