---
title: "Changes to Send a user message and start a run"
method: POST
path: "/v1/assistant/threads/{threadId}/messages"
---

# Changes to Send a user message and start a run

`POST /v1/assistant/threads/{threadId}/messages`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 2 of 47 revisions.

- **2026-10-27** `7b1871b77854`: 1 breaking, 1 warning, 5 info
- **2026-10-16** `f48e031634f4`: 1 info

## Changes

- **2026-10-27** `7b1871b77854`: 1 breaking, 1 warning, 5 info
  - the request's body type changed from `object` to no type
  - removed the request property `text`
  - added `subschema #1, subschema #2, subschema #3, subschema #4, subschema #5` to the request body `oneOf` list
  - added the optional property `message/parts/items/contentType` to the response with the `201` status
  - added the optional property `message/parts/items/fileName` to the response with the `201` status
  - added the optional property `message/parts/items/pendingAttachmentId` to the response with the `201` status
  - added the optional property `message/parts/items/sizeBytes` to the response with the `201` status
- **2026-10-16** `f48e031634f4`: 1 info
  - endpoint added

---

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