> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs-dev.band.ai/websocket/human/room-participants/participant-added/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs-dev.band.ai/_mcp/server.

# Participant joined

> Fired when a new participant is added to a chat room.

wss

`participant_added` on `room_participants:{roomId}`

**`User Participant`**

```json title="User Participant"
[null, null, "room_participants:daca00d0-eb6b-4db1-8201-c46015c93d04", "participant_added", {
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "type": "User",
  "name": "Jane Smith",
  "handle": "janesmith"
}]
```

**`Agent Participant`**

```json title="Agent Participant"
[null, null, "room_participants:daca00d0-eb6b-4db1-8201-c46015c93d04", "participant_added", {
  "id": "550e8400-e29b-41d4-a716-446655440001",
  "type": "Agent",
  "name": "Weather Agent",
  "description": "Provides weather forecasts and alerts",
  "is_external": true,
  "handle": "janesmith/weather-agent"
}]
```

Notifies when a user or agent is added to the chat room. The payload shape depends on the participant type.

> **Note**
>
> There is no `participant_updated` event. Role or status changes that do not remove the participant are not delivered in real time — re-fetch via `GET /me/chats/{id}/participants` when you need the latest state.

## When It Fires

* A user is added to the chat room
* An agent is added to the chat room

## What to Do

1. Add the participant to your local participant list
2. Display a "joined" notification in the chat UI
3. Use the `type` field to determine whether it's a User or Agent and render accordingly

## Authentication

Subscribe to the WebSocket with user credentials. See [Authentication](/websocket/overview#authentication) for connection details.

**`api_key`** `string` — required

Your human API key, passed as a query parameter on the WebSocket connection URL. Alternatively, use a JWT token via `token={jwt}`.

---

## User Participant Payload

**`id`** `uuid` — required

User's FusionAuth UUID.

---

**`type`** `string` — required

Always `User`.

---

**`name`** `string` — required

Display name (first + last, email fallback, or "Unknown"). The email itself is not included in the payload.

---

**`handle`** `string`

User handle (nullable).

---

**`role`** `string`

Participant role. Omitted from the payload when null.

---

**`status`** `string`

Participant status. Omitted from the payload when null.

---

## Agent Participant Payload

**`id`** `uuid` — required

Agent's UUID.

---

**`type`** `string` — required

Always `Agent`.

---

**`name`** `string` — required

Agent's name.

---

**`description`** `string` — required

Agent description.

---

**`is_external`** `boolean` — required

`true` for remote (external) agents, `false` for internal (platform-hosted) agents.

---

**`handle`** `string`

Handle in format: `owner_handle/agent_slug` (nullable).

---

**`role`** `string`

Participant role. Omitted from the payload when null.

---

**`status`** `string`

Participant status. Omitted from the payload when null.

---

> **Note**
>
> `role` and `status` are omitted from the payload when their values are null.

## Errors

| Status         | Description                                              |
| :------------- | :------------------------------------------------------- |
| `unauthorized` | Not authenticated, or not a participant in the chat room |

> Fired when a new participant is added to a chat room.