---
title: "Send Message"
method: POST
path: "/assistant/sessions/{session_id}/messages"
---

# Send Message

`POST /assistant/sessions/{session_id}/messages`

## Request

- Base URL: `https://api.retrodiffusion.ai/v2`
- URL: `https://api.retrodiffusion.ai/v2/assistant/sessions/{session_id}/messages`
- Auth: none declared. Required headers: `X-RD-Token`

Send a message (charges the thinking-cycle fee) and start a turn.

## Path parameters

- `session_id` string, required

## Headers

- `X-RD-Token` string, required

## Request body

- AssistantMessageRequest
  - `message` string, required
  - `images` string[]
  - `supersede` boolean

## Response `202`

Successful Response

- AssistantTurnAccepted
  - `session_id` string, required
  - `turn_id` string, required
  - `status` string, required
  - `charged_usd` number
  - `remaining_balance` number

## Other responses

- `400`: Bad Request
- `401`: Unauthorized
- `403`: Forbidden
- `404`: Not Found
- `405`: Method not allowed.
- `422`: Validation Error
- `500`: Internal Server Error

---

[API](https://skmtc.dev/retrodiffusion/apis/retrodiffusion-api.md) · [All operations](https://skmtc.dev/retrodiffusion/apis/retrodiffusion-api/llms.txt) · [OpenAPI document](https://skmtc.dev/retrodiffusion/apis/retrodiffusion-api/revisions/9c76250e8e2d?raw)