---
title: "Add message to existing thread"
method: POST
path: "/v4/agents/{agent_id}/threads/{thread_ref}/messages/"
tags: ["Agents"]
---

# Add message to existing thread

`POST /v4/agents/{agent_id}/threads/{thread_ref}/messages/`

## Request

- The document declares no server URL.
- Auth: one of:
  - API key in header `Authorization`
  - HTTP bearer

Async add a new message to an existing thread.

## Path parameters

- `agent_id` string, uuid, required: External ID of this agent, used on the simple agent thread API
- `thread_ref` string, required

## Request body

- PublicAgentExecuteRequest: Payload for starting async agent execution.
  - `account_id` integer: Execution account ID. Required for installable agents.
  - `query` string, required: The user's input query
  - `context` object: Optional context data for the agent

## Response `200`

- PublicAgentThreadResponse: Response for async agent execution.
  - `threadId` string, required: External reference ID of the thread
  - `currentAgent` string, uuid, required: External ID of the agent currently responsible for the thread
  - `executionStatus` string, required: Current execution status

## Other responses

- `400`
- `403`
- `404`

## Changes

- **2026-11-03** `84524f38b6c9`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/parcellab/apis/parcellab-api/changes/v4/agents/:agent_id/threads/:thread_ref/messages/post.md)

---

[API](https://skmtc.dev/parcellab/apis/parcellab-api.md) - [All operations](https://skmtc.dev/parcellab/apis/parcellab-api/llms.txt) - [OpenAPI document](https://skmtc.dev/parcellab/apis/parcellab-api/revisions/84524f38b6c9?raw)