One read of Claude Developer Platformapi-20261104T020710Z

This capture is too large to show at once. Changes 101-125 of 159 are below, significant first; the rest are on the following screens.

agents-and-tools/tool-use/fine-grained-tool-streaming Changed · +2 / -2 lines

from line 44

4444 

4545All models support fine-grained tool streaming on the Claude API, [Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock), [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/google-managed), and [Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry). To use it, set `eager_input_streaming` to `true` on any user-defined tool where you want fine-grained streaming enabled, and enable streaming on your request.

4646 

47The `eager_input_streaming` field is optional. Setting it to `true` turns on fine-grained streaming for that tool, and omitting it gives you standard buffered streaming, in which the API buffers and validates each parameter value before streaming it back. The exception is a request that still sends the legacy `fine-grained-tool-streaming-2025-05-14` beta header, which turns fine-grained streaming on for tools that leave the field unset. The per-tool field replaces that header, and an explicit `false` keeps buffered streaming for a tool even when a request still sends it. The legacy header cannot be combined with a [computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) or [browser use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) toolset entry: the API rejects a request that sends both, so remove the header and set `eager_input_streaming` on the user-defined tools that need it. See [Tool reference](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference) for the field definition.

47The `eager_input_streaming` field is optional. Setting it to `true` turns on fine-grained streaming for that tool, and omitting it gives you standard buffered streaming, in which the API buffers and validates each parameter value before streaming it back. The exception is a request that sends the `fine-grained-tool-streaming-2025-05-14` beta header, which turns fine-grained streaming on for tools that leave the field unset. The per-tool field replaces that header, and an explicit `false` keeps buffered streaming for a tool even when a request sends it. The header cannot be combined with a [computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) or [browser use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) toolset entry: the API rejects a request that sends both, so remove the header and set `eager_input_streaming` on the user-defined tools that need it. See [Tool reference](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference) for the field definition.

4848 

4949The following example turns on fine-grained streaming for a `make_file` tool and asks Claude for a long poem, so the tool input is large enough to watch it stream in:

5050 

from line 53

5353 curl https://api.anthropic.com/v1/messages \

5454 -H "content-type: application/json" \

5555 -H "x-api-key: $ANTHROPIC_API_KEY" \

56 -H "anthropic-version: 2023-06-01" \

56 -H "anthropic-version: 2026-10-21" \

5757 -d '{

5858 "model": "claude-opus-5-5",

5959 "max_tokens": 65536,

agents-and-tools/tool-use/memory-tool Changed · +1 / -1 lines

from line 142

142142 ```bash cURL

143143 curl https://api.anthropic.com/v1/messages \

144144 -H "x-api-key: $ANTHROPIC_API_KEY" \

145 -H "anthropic-version: 2023-06-01" \

145 -H "anthropic-version: 2026-10-21" \

146146 -H "content-type: application/json" \

147147 -d '{

148148 "model": "claude-opus-5-5",

agents-and-tools/tool-use/parallel-tool-use Changed · +2 / -2 lines

from line 880

880880 curl https://api.anthropic.com/v1/messages \

881881 -H "content-type: application/json" \

882882 -H "x-api-key: $ANTHROPIC_API_KEY" \

883 -H "anthropic-version: 2023-06-01" \

883 -H "anthropic-version: 2026-10-21" \

884884 -d '{

885885 "model": "claude-opus-5-5",

886886 "max_tokens": 1024,

from line 1163

11631163 curl https://api.anthropic.com/v1/messages \

11641164 -H "content-type: application/json" \

11651165 -H "x-api-key: $ANTHROPIC_API_KEY" \

1166 -H "anthropic-version: 2023-06-01" \

1166 -H "anthropic-version: 2026-10-21" \

11671167 -d '{

11681168 "model": "claude-opus-5",

11691169 "max_tokens": 1024,

agents-and-tools/tool-use/tool-reference Changed · +2 / -2 lines

from line 40

4040* **Model-keyed:** `text_editor_20250728` is for Claude 4 and later models and `text_editor_20250124` is for earlier models. The version you use depends on the model you target.

4141* **Variant, not version:** `tool_search_tool_regex_20251119` and `tool_search_tool_bm25_20251119` are two search algorithms released together. Neither supersedes the other.

4242* **Legacy:** `code_execution_20250522` supports only Python. `code_execution_20250825` adds Bash and file operations.

43* **Successor:** `computer_toolset_20260801` is the stable successor to the beta `computer_20251124` and `computer_20250124` versions, which remain available on the models listed for them under [Earlier tool versions](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#earlier-tool-versions). `browser_toolset_20260801` is the first version of the browser use tool. Both are [client toolsets](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference#client-toolsets).

43* **Successor:** `computer_toolset_20260801` is the stable successor to the beta `computer_20251124` and `computer_20250124` versions, which are available on the models listed for them under [Earlier tool versions](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#earlier-tool-versions). `browser_toolset_20260801` is the first version of the browser use tool. Both are [client toolsets](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference#client-toolsets).

4444 

4545The `mcp_toolset` type is not date-versioned; versioning is carried in the `anthropic-beta` header instead.

4646 

from line 78

7878* `strict: true` or `input_examples`.

7979* `defer_loading` on the entry, or enabled members whose `defer_loading` values differ (set it for each member in `configs`, all to the same value).

8080* A code execution caller in `allowed_callers` (no [programmatic tool calling](https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling)).

81* The legacy `fine-grained-tool-streaming-2025-05-14` beta header. When you stream, each member’s `input` arrives as one complete `input_json_delta`.

81* The `fine-grained-tool-streaming-2025-05-14` beta header. When you stream, each member’s `input` arrives as one complete `input_json_delta`.

8282* A `tool_choice` of type `tool` that names the toolset or a member (use `auto`, `any`, or `none`).

8383* Two entries of the same toolset, or another tool that carries that toolset’s name: a tool named `computer` alongside `computer_toolset_20260801`, or a tool named `browser` alongside `browser_toolset_20260801`. The two toolsets can be declared together.

8484 

agents-and-tools/tool-use/tool-search-tool Changed · +1 / -1 lines

from line 113

113113 ```bash cURL

114114 curl https://api.anthropic.com/v1/messages \

115115 -H "x-api-key: $ANTHROPIC_API_KEY" \

116 -H "anthropic-version: 2023-06-01" \

116 -H "anthropic-version: 2026-10-21" \

117117 -H "content-type: application/json" \

118118 -d '{

119119 "model": "claude-opus-5-5",

agents-and-tools/tool-use/web-search-tool Changed · +2 / -2 lines

from line 108

108108 ```bash cURL

109109 curl https://api.anthropic.com/v1/messages \

110110 -H "x-api-key: $ANTHROPIC_API_KEY" \

111 -H "anthropic-version: 2023-06-01" \

111 -H "anthropic-version: 2026-10-21" \

112112 -H "content-type: application/json" \

113113 -d '{

114114 "model": "claude-opus-5-5",

from line 281

281281 ```bash cURL

282282 curl https://api.anthropic.com/v1/messages \

283283 -H "x-api-key: $ANTHROPIC_API_KEY" \

284 -H "anthropic-version: 2023-06-01" \

284 -H "anthropic-version: 2026-10-21" \

285285 -H "content-type: application/json" \

286286 -d '{

287287 "model": "claude-opus-5-5",

api/beta-headers Changed · +2 / -2 lines

from line 17

1717```http

1818POST /v1/messages

1919Authorization: Bearer YOUR_API_KEY

20anthropic-version: 2023-06-01

20anthropic-version: 2026-10-21

2121anthropic-beta: BETA_FEATURE_NAME

2222content-type: application/json

2323```

from line 30

3030 ```bash cURL

3131 curl https://api.anthropic.com/v1/messages \

3232 -H "x-api-key: $ANTHROPIC_API_KEY" \

33 -H "anthropic-version: 2023-06-01" \

33 -H "anthropic-version: 2026-10-21" \

3434 -H "anthropic-beta: context-management-2025-06-27" \

3535 -H "content-type: application/json" \

3636 -d '{

api/claude-code/routines-fire Changed · +1 / -1 lines

from line 75

7575| `anthropic-version` | Yes | The [API version](https://platform.claude.com/docs/en/api/versioning), such as `2026-10-21`. The endpoint accepts every version from `2023-06-01` on and behaves the same in each. |

7676| `Content-Type` | When body is present | `application/json`. |

7777 

78Older integrations that send an `anthropic-beta: experimental-cc-routine-2026-04-01` header are unaffected: the endpoint accepts requests with and without it.

78The endpoint accepts requests with and without an `anthropic-beta: experimental-cc-routine-2026-04-01` header.

7979 

8080### Path parameters

8181 

api/overview Changed · +1 / -1 lines

from line 87

8787Access Claude through AWS, Google Cloud, or Microsoft Azure:

8888 

8989* **Integrated** with cloud provider billing and IAM

90* **Feature availability varies by platform:** Anthropic-operated platforms include [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Claude Models on Google Cloud (Anthropic managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/anthropic-managed), and [Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry); partner-operated platforms include Amazon Bedrock and Claude Models on Google Cloud (Google managed). See each platform’s page for feature availability and timing.

90* **Feature availability varies by platform:** Anthropic-operated platforms include [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Claude Models on Google Cloud (Anthropic managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/anthropic-managed), and [Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry); partner-operated platforms include Claude Models on Google Cloud (Google managed) and Amazon Bedrock. See each platform’s page for feature availability and timing.

9191* **Best for:** Existing cloud commitments, specific compliance requirements, consolidated cloud billing

9292 

9393| Platform | Provider | Documentation |

api/service-tiers Changed · +1 / -1 lines

from line 90

9090 ```bash cURL

9191 curl https://api.anthropic.com/v1/messages \

9292 -H "x-api-key: $ANTHROPIC_API_KEY" \

93 -H "anthropic-version: 2023-06-01" \

93 -H "anthropic-version: 2026-10-21" \

9494 -H "content-type: application/json" \

9595 -d '{

9696 "model": "claude-opus-4-8",

api/versioning Changed · +1 / -1 lines

from line 39

3939 * [RBAC groups](https://platform.claude.com/docs/en/api/beta/organization/rbac_groups/list) no longer return `roles`. Use `role_ids` instead.

4040 * [RBAC group members](https://platform.claude.com/docs/en/api/beta/organization/rbac_groups/members/list), and the response to removing one, no longer return `group_id`. Use `rbac_group_id` instead.

4141 * [RBAC roles](https://platform.claude.com/docs/en/api/beta/organization/rbac_roles/list) no longer return `name`. Use `display_name` instead.

42 * [Organization](https://platform.claude.com/docs/en/api/organization/rate_limits/list) and [workspace](https://platform.claude.com/docs/en/api/organization/workspaces/rate_limits/list) rate-limit entries no longer return `group_type`. Use `group.type` instead.

42 * [Organization](https://platform.claude.com/docs/en/api/organization/rate_limits/list) and [workspace](https://platform.claude.com/docs/en/api/organization/workspaces/rate_limits/list) rate-limit entries, and the response to [setting a workspace’s rate limits](https://platform.claude.com/docs/en/api/organization/workspaces/rate_limits/update), no longer return `group_type`. Use `group.type` instead.

4343 * [API keys](https://platform.claude.com/docs/en/api/organization/api_keys/list) no longer return `workspace_id`. Use `scope.workspace_id` instead, which gives the workspace’s real ID even for the Default Workspace (an all-workspaces key has no `workspace_id` in `scope`).

4444 

4545 * Claude Enterprise Analytics API:

build-with-claude/claude-in-microsoft-foundry Changed · +2 / -2 lines

from line 201

201201 curl https://{resource}.services.ai.azure.com/anthropic/v1/messages \

202202 -H "content-type: application/json" \

203203 -H "api-key: YOUR_AZURE_API_KEY" \

204 -H "anthropic-version: 2023-06-01" \

204 -H "anthropic-version: 2026-10-21" \

205205 -d '{

206206 "model": "claude-opus-5-5",

207207 "max_tokens": 1024,

from line 404

404404 curl https://{resource}.services.ai.azure.com/anthropic/v1/messages \

405405 -H "content-type: application/json" \

406406 -H "Authorization: Bearer $(az account get-access-token --resource https://ai.azure.com --query accessToken -o tsv)" \

407 -H "anthropic-version: 2023-06-01" \

407 -H "anthropic-version: 2026-10-21" \

408408 -d '{

409409 "model": "claude-opus-5-5",

410410 "max_tokens": 1024,

build-with-claude/compaction-on-demand Changed · +1 / -1 lines

from line 50

5050 # max_tokens caps the whole call, including any thinking, so allow several thousand tokens.

5151 curl https://api.anthropic.com/v1/messages \

5252 -H "x-api-key: $ANTHROPIC_API_KEY" \

53 -H "anthropic-version: 2023-06-01" \

53 -H "anthropic-version: 2026-10-21" \

5454 -H "anthropic-beta: compact-2026-09-04" \

5555 -H "content-type: application/json" \

5656 -d '{

build-with-claude/effort Changed · +2 / -2 lines

from line 52

5252 ```bash cURL

5353 curl https://api.anthropic.com/v1/messages \

5454 -H "x-api-key: $ANTHROPIC_API_KEY" \

55 -H "anthropic-version: 2023-06-01" \

55 -H "anthropic-version: 2026-10-21" \

5656 -H "content-type: application/json" \

5757 -d '{

5858 "model": "claude-opus-5-5",

from line 413

413413 # Effort-only system message: the new level takes effect from the next user turn.

414414 curl https://api.anthropic.com/v1/messages \

415415 -H "x-api-key: $ANTHROPIC_API_KEY" \

416 -H "anthropic-version: 2023-06-01" \

416 -H "anthropic-version: 2026-10-21" \

417417 -H "anthropic-beta: mid-conversation-output-config-2026-07-01" \

418418 -H "content-type: application/json" \

419419 -d '{

build-with-claude/extended-thinking Changed · +2 / -2 lines

from line 45

4545 ```bash cURL

4646 curl https://api.anthropic.com/v1/messages \

4747 -H "x-api-key: $ANTHROPIC_API_KEY" \

48 -H "anthropic-version: 2023-06-01" \

48 -H "anthropic-version: 2026-10-21" \

4949 -H "content-type: application/json" \

5050 -d '{

5151 "model": "claude-sonnet-4-6",

from line 317

317317 

318318How platforms treat the beta header differs. The Claude API, [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), and [Claude Models on Google Cloud (Anthropic managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/anthropic-managed) accept `interleaved-thinking-2025-05-14` on any model and ignore it where unsupported. Acceptance is not the same as effect: on models that reject `type: "enabled"` (4.7 and later) or lack manual-mode interleaving (Claude Opus 4.6), the header has no manual-mode effect; adaptive thinking interleaves automatically there.

319319 

320Partner-operated platforms, [Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock) and [Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/google-managed), likewise accept the header on any model without returning an error, and ignore it on models that don’t support interleaved thinking.

320Partner-operated platforms, [Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/build-with-claude/claude-models-on-google-cloud/google-managed) and [Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock), likewise accept the header on any model without returning an error, and ignore it on models that don’t support interleaved thinking.

321321 

322322## Turn structure in manual mode

323323 

build-with-claude/fast-mode Changed · +2 / -2 lines

from line 42

4242 ```bash cURL

4343 curl https://api.anthropic.com/v1/messages \

4444 -H "x-api-key: $ANTHROPIC_API_KEY" \

45 -H "anthropic-version: 2023-06-01" \

45 -H "anthropic-version: 2026-10-21" \

4646 -H "content-type: application/json" \

4747 -d '{

4848 "model": "claude-opus-5-5",

from line 223

223223 ```bash cURL

224224 curl https://api.anthropic.com/v1/messages \

225225 -H "x-api-key: $ANTHROPIC_API_KEY" \

226 -H "anthropic-version: 2023-06-01" \

226 -H "anthropic-version: 2026-10-21" \

227227 -H "content-type: application/json" \

228228 -d '{

229229 "model": "claude-opus-5-5",

build-with-claude/message-threads Changed · +2 / -2 lines

from line 268

268268 # Turn 1: send the full conversation and create a thread

269269 curl -sS --fail-with-body https://api.anthropic.com/v1/messages \

270270 -H "x-api-key: $ANTHROPIC_API_KEY" \

271 -H "anthropic-version: 2023-06-01" \

271 -H "anthropic-version: 2026-10-21" \

272272 -H "anthropic-beta: message-threads-2026-08-12" \

273273 -H "content-type: application/json" \

274274 -d '{

from line 284

284284 # Leave out system and tools: the thread keeps them.

285285 curl -sS --fail-with-body https://api.anthropic.com/v1/messages \

286286 -H "x-api-key: $ANTHROPIC_API_KEY" \

287 -H "anthropic-version: 2023-06-01" \

287 -H "anthropic-version: 2026-10-21" \

288288 -H "anthropic-beta: message-threads-2026-08-12" \

289289 -H "content-type: application/json" \

290290 -d '{

build-with-claude/mid-conversation-effort-example Changed · +1 / -1 lines

from line 2884

28842884 # here, the SDK examples carry the full standing-consent text.

28852885 curl --fail-with-body -sS https://api.anthropic.com/v1/messages \

28862886 -H "x-api-key: $ANTHROPIC_API_KEY" \

2887 -H "anthropic-version: 2023-06-01" \

2887 -H "anthropic-version: 2026-10-21" \

28882888 -H "content-type: application/json" \

28892889 -d '{

28902890 "model": "claude-opus-5-5",

build-with-claude/prompt-engineering/prompting-claude-opus-4-8 Changed · +1 / -1 lines

from line 157

157157 

158158## Computer use

159159 

160Claude Opus 4.8 supports computer use through the `computer_toolset_20260801` toolset and the earlier `computer_20251124` tool version. It also supports the [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) (`browser_toolset_20260801`) for tasks inside webpages. [Computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) capability works across resolutions, up to a maximum resolution of 2576px / 3.75MP. Internal computer use testing shows that sending images at 1080p provides a good balance of performance and cost.

160Claude Opus 4.8 supports computer use through the `computer_toolset_20260801` toolset and the `computer_20251124` tool version. It also supports the [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) (`browser_toolset_20260801`) for tasks inside webpages. [Computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) capability works across resolutions, up to a maximum resolution of 2576px / 3.75MP. Internal computer use testing shows that sending images at 1080p provides a good balance of performance and cost.

161161 

162162For particularly cost-sensitive workloads, 720p or 1366×768 are lower-cost options with strong performance. Conduct your own testing to find the ideal settings for your use case; experimenting with effort settings can also help tune the model’s behavior.

163163 

build-with-claude/prompt-engineering/prompting-claude-sonnet-5 Changed · +1 / -1 lines

from line 149

149149 

150150## Computer use

151151 

152Claude Sonnet 5 supports computer use through the `computer_toolset_20260801` toolset and the earlier `computer_20251124` tool version. It also supports the [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) (`browser_toolset_20260801`) for tasks inside webpages. [Computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) capability works across resolutions, up to a maximum resolution of 2576px / 3.75MP. Internal computer use testing shows that sending images at 1080p provides a good balance of performance and cost.

152Claude Sonnet 5 supports computer use through the `computer_toolset_20260801` toolset and the `computer_20251124` tool version. It also supports the [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) (`browser_toolset_20260801`) for tasks inside webpages. [Computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) capability works across resolutions, up to a maximum resolution of 2576px / 3.75MP. Internal computer use testing shows that sending images at 1080p provides a good balance of performance and cost.

153153 

154154For particularly cost-sensitive workloads, 720p or 1366×768 are lower-cost options with strong performance. Conduct your own testing to find the ideal settings for your use case; experimenting with effort settings can also help tune the model’s behavior.

155155 

build-with-claude/task-budgets Changed · +2 / -2 lines

from line 45

4545 curl https://api.anthropic.com/v1/messages \

4646 -N \

4747 -H "x-api-key: $ANTHROPIC_API_KEY" \

48 -H "anthropic-version: 2023-06-01" \

48 -H "anthropic-version: 2026-10-21" \

4949 -H "anthropic-beta: task-budgets-2026-03-13" \

5050 -H "content-type: application/json" \

5151 -d '{

from line 523

523523 ```bash cURL

524524 curl https://api.anthropic.com/v1/messages \

525525 -H "x-api-key: $ANTHROPIC_API_KEY" \

526 -H "anthropic-version: 2023-06-01" \

526 -H "anthropic-version: 2026-10-21" \

527527 -H "content-type: application/json" \

528528 -d '{

529529 "model": "claude-opus-5-5",

build-with-claude/thinking-tool-workflows Changed · +1 / -1 lines

from line 32

3232 <CodeGroup>

3333 ```bash cURL

3434 curl https://api.anthropic.com/v1/messages \

35 -H "anthropic-version: 2023-06-01" \

35 -H "anthropic-version: 2026-10-21" \

3636 -H "content-type: application/json" \

3737 -H "x-api-key: $ANTHROPIC_API_KEY" \

3838 -d '{

cli-sdks-libraries/cli/scripting Changed · +1 / -1 lines

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113113```bash cURL

114114curl https://api.anthropic.com/v1/messages \

115115 -H "Authorization: Bearer $(ant auth print-credentials --access-token)" \

116 -H "anthropic-version: 2023-06-01" \

116 -H "anthropic-version: 2026-10-21" \

117117 -H "content-type: application/json" \

118118 -d '{

119119 "model": "claude-opus-5-5",

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210210* Audio and file inputs are not supported. A request that includes an `input_audio` or `file` content part returns a 400 error.

211211* Prompt caching is not supported, but it is supported in the [Anthropic SDKs](https://platform.claude.com/docs/en/cli-sdks-libraries/overview).

212212* System/developer messages are hoisted and concatenated into the top-level `system` field, wherever they appear in the conversation. To add system instructions partway through a conversation, use [mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) in the native Claude API.

213 

214- Depending on the model, text generated for a request that sets `temperature` or `top_p` to a value other than the Claude API’s default might not carry the [text watermark](https://platform.claude.com/docs/en/build-with-claude/text-watermark#sampling-settings). If you rely on the watermark, omit both parameters.

213* Depending on the model, text generated for a request that sets `temperature` or `top_p` to a value other than the Claude API’s default might not carry the [text watermark](https://platform.claude.com/docs/en/build-with-claude/text-watermark#sampling-settings). If you rely on the watermark, omit both parameters.

215214 

216215Most unsupported fields are silently ignored rather than producing errors. These are all documented in the following sections.

217216 

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438438 

439439## Semantic versioning

440440 

441Each major version of this SDK sends one API version in the `anthropic-version` header by default, and a new major version comes with each new API version. The first major version that sends `2026-10-21` is 13.0.0; see [Migrating to API version 2026-10-21](https://platform.claude.com/docs/en/api/migration-2026-10-21#upgrade).

442 

443441This package generally follows [SemVer](https://semver.org/spec/v2.0.0.html) conventions, though certain backward-incompatible changes may be released as minor versions:

444442 

4454431. Changes to library internals that are technically public but not intended or documented for external use.

from line 444

4464442. Changes that aren’t expected to impact the vast majority of users in practice.

447445 

448446Backward compatibility is taken seriously to ensure you can rely on a smooth upgrade experience.

447 

448Every request to the Claude API uses an API version. With this SDK, your requests use the API version that was current when your SDK’s major version was released, so you move to a new API version by upgrading to a new major version. Version 13.0.0 is the first to use `2026-10-21`. See [Migrating to API version 2026-10-21](https://platform.claude.com/docs/en/api/migration-2026-10-21#upgrade) for how to upgrade.

449449 

450450## Additional resources

451451