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

# Changes to Messages

`POST /v1/messages`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 3 of 6 revisions.

- **2026-09-24** `0e5e86e2bae5`: 5 warning, 1 info
- **2026-09-24** `1cffaad2a921`: 2 breaking, 1 warning
- **2026-08-04** `60b6b70202c9`: 1 breaking, 18 info

## Changes

- **2026-09-24** `0e5e86e2bae5`: 5 warning, 1 info
  - removed the request property `effort`
  - removed the request property `models`
  - removed the optional property `pioneer_inference_id` from the response with the `200` status
  - removed the optional property `pioneer_routed_model` from the response with the `200` status
  - removed the optional property `pioneer_savings` from the response with the `200` status
  - added the optional property `fastino_inference_id` to the response with the `200` status
- **2026-09-24** `1cffaad2a921`: 2 breaking, 1 warning
  - added `#/components/schemas/HTTPValidationError, #/components/schemas/AnthropicError` to the response body `oneOf` list for the response status `422`
  - the response's body type changed from `object` to no type for status `422`
  - removed the optional property `detail` from the response with the `422` status
- **2026-08-04** `60b6b70202c9`: 1 breaking, 18 info
  - the response's body type changed from no type to `object` for status `200`
  - added the new optional request property `cache_control`
  - added the new optional request property `effort`
  - added the new optional request property `models`
  - added the new optional request property `output_config`
  - added the new optional request property `speed`
  - added the new optional request property `stop_sequences`
  - added the new optional request property `top_k`
  - added the optional property `pioneer_inference_id` to the response with the `200` status
  - added the optional property `pioneer_routed_model` to the response with the `200` status
  - added the optional property `pioneer_savings` to the response with the `200` status
  - added the optional property `role` to the response with the `200` status
  - added the optional property `stop_reason` to the response with the `200` status
  - added the optional property `stop_sequence` to the response with the `200` status
  - added the optional property `type` to the response with the `200` status
  - added the required property `content` to the response with the `200` status
  - added the required property `id` to the response with the `200` status
  - added the required property `model` to the response with the `200` status
  - added the required property `usage` to the response with the `200` status

---

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