---
title: "Changes to Anthropic Messages"
method: POST
path: "/v1/messages"
---

# Changes to Anthropic Messages

`POST /v1/messages`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 8 of 28 revisions.

- **2026-10-31** `2902b7e0a589`: 1 breaking, 1 warning, 1 info
- **2026-10-28** `276756cf8251`: 2 info
- **2026-10-21** `453386b00b9f`: 2 warning, 7 info
- **2026-10-15** `238082f96fd2`: 5 info
- **2026-10-09** `5e602b8ce09d`: 2 info
- **2026-10-02** `7f7cbc891d20`: 1 info
- **2026-10-02** `3238d892d836`: 1 info
- **2026-09-06** `3ab255a22d1b`: 4 info

## Changes

- **2026-10-31** `2902b7e0a589`: 1 breaking, 1 warning, 1 info
  - removed `subschema #7, subschema #8, subschema #9, subschema #10` from the `messages/items/content/anyOf[subschema #2]/items/` request property `anyOf` list
  - added the new `undefined` enum value to the `stop_reason` response property for the response status `200`
  - added `subschema #7, subschema #8, subschema #9, subschema #10` to the `messages/items/content/anyOf[subschema #2]/items/` request property `anyOf` list
- **2026-10-28** `276756cf8251`: 2 info
  - added the new optional request property `messages/items/content/anyOf[subschema #2]/items/anyOf[subschema #11]/tool/anyOf[subschema #2]/definition/eager_input_streaming`
  - added the new optional request property `tools/items/anyOf[subschema #1]/eager_input_streaming`
- **2026-10-21** `453386b00b9f`: 2 warning, 7 info
  - added the new `redacted_thinking` enum value to the `content/items/type` response property for the response status `200`
  - added the new `web_fetch_tool_result` enum value to the `content/items/type` response property for the response status `200`
  - added the new optional request property `tools/items/anyOf[subschema #3]/citations`
  - added the new optional request property `tools/items/anyOf[subschema #3]/max_content_tokens`
  - added `subschema #9` to the `messages/items/content/anyOf[subschema #2]/items/` request property `anyOf` list
  - added the optional property `content/items/citations` to the response with the `200` status
  - added the optional property `content/items/data` to the response with the `200` status
  - added the optional property `content/items/signature` to the response with the `200` status
  - added the optional property `usage/server_tool_use` to the response with the `200` status
- **2026-10-15** `238082f96fd2`: 5 info
  - added the new optional request property `messages/items/content/anyOf[subschema #2]/items/anyOf[subschema #10]/tool/anyOf[subschema #2]/definition/allowed_callers`
  - added the new optional request property `messages/items/content/anyOf[subschema #2]/items/anyOf[subschema #10]/tool/anyOf[subschema #2]/definition/strict`
  - added the new optional request property `tool_choice`
  - added the new optional request property `tools/items/anyOf[subschema #1]/allowed_callers`
  - added the new optional request property `tools/items/anyOf[subschema #1]/strict`
- **2026-10-09** `5e602b8ce09d`: 2 info
  - added the new optional request property `safeguards`
  - added the optional property `safeguard_results` to the response with the `200` status
- **2026-10-02** `7f7cbc891d20`: 1 info
  - added `subschema #10, subschema #11` to the `messages/items/content/anyOf[subschema #2]/items/` request property `anyOf` list
- **2026-10-02** `3238d892d836`: 1 info
  - added the optional property `metadata` to the response with the `200` status
- **2026-09-06** `3ab255a22d1b`: 4 info
  - added the non-success response with the status `408`
  - added the non-success response with the status `413`
  - added the non-success response with the status `415`
  - added the non-success response with the status `529`

---

[Operation](https://skmtc.dev/llmgateway/apis/llmgateway-api/docs/v1/messages/post.md) - [API](https://skmtc.dev/llmgateway/apis/llmgateway-api.md) - [Page](https://skmtc.dev/llmgateway/apis/llmgateway-api/changes/v1/messages/post)