---
title: "Send message"
method: POST
path: "/api/v1/threads/{threadId}/message"
tags: ["messages"]
---

# Send message

`POST /api/v1/threads/{threadId}/message`

## Path parameters

- `threadId` string, required

## Request body

- SendMessageRequest
  - `text` string, required
  - `model` ModelSelection
    - `modelId` string, required
    - `reasoningMode` 'none' | 'instant' | 'minimal' | 'low' | 'medium' | 'high' | 'xhigh' | 'max'
    - `modes` object
      - `fast` boolean
      - `pro` boolean
  - `delivery` 'queue' | 'steer' | 'interrupt'

## Response `200`

AdmitReceipt

- AdmitReceiptEncoded
  - `id` string, required
  - `deduped` boolean, required

## Other responses

- `401` — capy/Unauthorized
- `404` — capy/ThreadNotFound

## Changes

- **2026-08-28** `e9babb6783f3` — 1 info
  - added the new `instant` enum value to the request property `model/reasoningMode`
- **2026-08-11** `792c11dd1007` — 1 info
  - endpoint added

[Change history](https://skmtc.dev/capy/apis/capy-api/changes/api/v1/threads/:threadId/message/post.md)

---

[API](https://skmtc.dev/capy/apis/capy-api.md) · [All operations](https://skmtc.dev/capy/apis/capy-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/capy/capy-api/revisions/e9babb6783f3/schema)