Messages changedapi/messages
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5656 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.
5757
58 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.
58 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).
5959
6060 Example with a single `user` message:
6161
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7373 ]
7474 ```
7575
76 Example with a partially-filled response from Claude:
76 Example with a partially-filled response from Claude, for models that support prefill:
7777
7878 ```json
7979 [
from line 1135
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11361136 - `"claude-haiku-4-5"`
11371137
1138 Fastest model with near-frontier intelligence
1139
11401138 - `"claude-haiku-4-5-20251001"`
11411139
1142 Fastest model with near-frontier intelligence
1143
11441140 - `"claude-opus-4-5"`
11451141
11461142 Powerful intelligence for long-running agents and coding
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13171313
13181314- `thinking: optional ThinkingConfigParam`
13191315
1320 Configuration for enabling Claude's extended thinking.
1316 Configuration for Claude's thinking.
13211317
1322 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.
1318 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.
13231319
1324 See [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for details.
1320 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.
13251321
13261322 - `ThinkingConfigEnabled object`
13271323
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13391335
13401336 - `display: optional "summarized" or "omitted" or null`
13411337
1342 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`.
1338 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).
13431339
13441340 - `"summarized"`
13451341
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13601356 - `display: optional "summarized" or "omitted" or null`
13611357
1362 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`.
1358 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).
13631359
13641360 - `"summarized"`
13651361
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39853981 - `"claude-haiku-4-5"`
39863982
3987 Fastest model with near-frontier intelligence
3988
39893983 - `"claude-haiku-4-5-20251001"`
39903984
3991 Fastest model with near-frontier intelligence
3992
39933985 - `"claude-opus-4-5"`
39943986
39953987 Powerful intelligence for long-running agents and coding
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45614553 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.
45624554
4563 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.
4555 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).
45644556
45654557 Example with a single `user` message:
45664558
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45784570 ]
45794571 ```
45804572
4581 Example with a partially-filled response from Claude:
4573 Example with a partially-filled response from Claude, for models that support prefill:
45824574
45834575 ```json
45844576 [
from line 5632
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56415633 - `"claude-haiku-4-5"`
56425634
5643 Fastest model with near-frontier intelligence
5644
56455635 - `"claude-haiku-4-5-20251001"`
56465636
5647 Fastest model with near-frontier intelligence
5648
56495637 - `"claude-opus-4-5"`
56505638
56515639 Powerful intelligence for long-running agents and coding
from line 5720
57325720
57335721- `thinking: optional ThinkingConfigParam`
57345722
5735 Configuration for enabling Claude's extended thinking.
5723 Configuration for Claude's thinking.
57365724
5737 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.
5725 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.
57385726
5739 See [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for details.
5727 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.
57405728
57415729 - `ThinkingConfigEnabled object`
57425730
from line 5742
57545742
57555743 - `display: optional "summarized" or "omitted" or null`
57565744
5757 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`.
5745 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).
57585746
57595747 - `"summarized"`
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57755763 - `display: optional "summarized" or "omitted" or null`
57765764
5777 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`.
5765 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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57795767 - `"summarized"`
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86158603
86168604- `BrowserHoverInput object`
86178605
8618 Move the cursor to a coordinate or element without clicking.
8619
8620 - `target: BrowserClickTarget`
8621
8622 Where to act: either a viewport coordinate or an element reference.
8623
8624 - `BrowserCoordinateTarget object`
8625
8626 A point in the browser viewport, in viewport pixels (the same frame as a
8627 full-viewport screenshot).
8628
8629 - `type: "coordinate"`
8630
8631 - `x: number`
8632
8633 Pixels from the left edge of the viewport.
8634
8635 minimum: 0
8636
8637 - `y: number`
8638
8639 Pixels from the top edge of the viewport.
8640
8641 minimum: 0
8642
8643 - `BrowserRefTarget object`
8644
8645 An element on the page, identified by a reference from a prior `read_page` or
8646 `find` result. References are scoped to the tab that produced them and become
8647 stale after navigation or a major re-render.
8648
8649 - `type: "ref"`
8650
8651 - `ref: string`
8652
8653 An element reference (e.g. "ref_7") returned by a prior `read_page` or `find` result.
8654
8655 - `tab_id: optional string or null`
8656
8657 Tab to act on. Defaults to the active tab when omitted.
8658
8659### Browser Hover Tool Use Block
8660
8661- `BrowserH
8606 Move the cursor to a coordinate or ele
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