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457457### Extended thinking not supported
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459Claude 4.7 and later models have removed extended thinking. Sending `thinking: {"type": "enabled"}` to any of these models returns a 400 `invalid_request_error`:
459Claude 4.7 and later models don’t support extended thinking. Sending `thinking: {"type": "enabled"}` to any of these models returns a 400 `invalid_request_error`:
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461461```text wrap
462462"thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.
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509509Claude Haiku 5.5 accepts `thinking: {"type": "disabled"}` and holds it to the same two effort limits that apply to `between_tools`: at `xhigh` or `max` effort, or with a per-message `output_config.effort` that differs from the level in effect, the request returns a 400 `invalid_request_error` with the matching message shown earlier.
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511In both messages, “enable thinking” means adaptive thinking: omit the `thinking` field or send `thinking: {"type": "adaptive"}`. Claude Sonnet 5.5 and Claude Haiku 5.5 reject `"enabled"` with a 400 error. To vary effort for each turn, use adaptive thinking.
511In both messages, “enable thinking” means adaptive thinking: omit the `thinking` field or send `thinking: {"type": "adaptive"}`. Claude Sonnet 5.5 and Claude Haiku 5.5 also reject `"enabled"` with a 400 error. To vary effort for each turn, use adaptive thinking.
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513513Sending `thinking: {"type": "between_tools"}` to any model other than Claude Sonnet 5.5 returns a 400 `invalid_request_error`:
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