Create a Message Batch changedapi/beta/messages/batches/create
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180180 Each input message must be an object with a `role` and `content`. You can specify a single `user`-role message, or you can include multiple `user` and `assistant` messages.
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182 If the final message uses the `assistant` role, the response content will continue immediately from the content in that message. This can be used to constrain part of the model's response.
182 If the final message uses the `assistant` role, the response content will continue immediately from the content in that message. This can be used to constrain part of the model's response. This is called prefill. On models that don't support prefill, creating a message that ends with a partial `assistant` response returns a 400 error. See [Prefill not supported](https://platform.claude.com/docs/en/api/errors#prefill-not-supported).
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184184 Example with a single `user` message:
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197197 ]
198198 ```
199199
200 Example with a partially-filled response from Claude:
200 Example with a partially-filled response from Claude, for models that support prefill:
201201
202202 ```json
203203 [
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31853185 - `"claude-haiku-4-5"`
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3187 Fastest model with near-frontier intelligence
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31893187 - `"claude-haiku-4-5-20251001"`
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3191 Fastest model with near-frontier intelligence
3192
31933189 - `"claude-opus-4-5"`
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31953191 Powerful intelligence for long-running agents and coding
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37853781 - `fallbacks: optional BetaFallbacksParam or null`
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3787 Opt-in server-side retry on one or more substitute models when the requested model declines for policy reasons. Tried in order: if the first entry also declines, the second is tried, and so on. The string "default" requests the requested model's server-defined default fallback configuration.
3783 Opt-in server-side retry on one or more substitute models when the requested model declines for policy reasons. Tried in order: if the first entry also declines, the second is tried, and so on. Some models don't support fallbacks; on those models, a list of fallback models returns a 400 error. See [Server-side fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#server-side-fallback). The string "default" requests the requested model's server-defined default fallback configuration. On a model that doesn't support fallbacks, the request runs on the requested model alone, so a declined request stays declined.
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37893785 - `array of BetaFallbackParam`
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38833879 - `display: optional "summarized" or "omitted" or "updates" or null`
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3885 Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to `summarized`.
3881 Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. The default depends on the model; see [Controlling thinking display](https://platform.claude.com/docs/en/build-with-claude/thinking#controlling-thinking-display).
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38873883 - `"summarized"`
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39093905 - `display: optional "summarized" or "omitted" or "updates" or null`
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3911 Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to `summarized`.
3907 Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. The default depends on the model; see [Controlling thinking display](https://platform.claude.com/docs/en/build-with-claude/thinking#controlling-thinking-display).
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39133909 - `"summarized"`
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40154011 - `thinking: optional BetaThinkingConfigParam`
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4017 Configuration for enabling Claude's extended thinking.
4013 Configuration for Claude's thinking.
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4019 When enabled, responses include `thinking` content blocks showing Claude's thinking process before the final answer. Requires a minimum budget of 1,024 tokens and counts towards your `max_tokens` limit.
4015 With `{"type": "adaptive"}`, Claude decides when and how much to think. With `{"type": "enabled"}` (manual extended thinking), you set a `budget_tokens` of at least 1,024. Thinking tokens count toward your `max_tokens` limit.
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4021 See [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for details.
4017 Which `type` values are accepted, and what happens when you omit `thinking`, depend on the model. See [thinking](https://platform.claude.com/docs/en/build-with-claude/thinking#configuring-thinking) for each model's behavior.
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40234019 - `BetaThinkingConfigEnabled object`
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