> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cope.com/llms.txt
> Use this file to discover all available pages before exploring further.

# community.challenge.joined

> A member joined a challenge.

# community.challenge.joined

> Generated from COPE public event contracts. Do not edit this page by hand.

Fires when a member joins a challenge.

## Delivery Contract

| Field           | Value                                                                                |
| --------------- | ------------------------------------------------------------------------------------ |
| Encoding        | CloudEvents 1.0 structured JSON                                                      |
| Delivery        | At least once                                                                        |
| Idempotency     | Use the CloudEvents `source` + `id` tuple, or COPE `idempotency_key` when available. |
| Source          | `cope.community`                                                                     |
| Subject pattern | `challenge:<identifier>`                                                             |
| Category        | Gamification                                                                         |
| Availability    | Available in the public webhook reference.                                           |
| Schema title    | community.challenge.joined v1 payload                                                |
| Schema ID       | `https://schemas.cope.com/events/community.challenge.joined/v1`                      |

## Payload Fields

| Field          | Required | Type     | Allowed Values | Description |
| -------------- | -------- | -------- | -------------- | ----------- |
| `challenge_id` | yes      | `string` | -              | -           |
| `community_id` | yes      | `string` | -              | -           |
| `user_id`      | yes      | `string` | -              | -           |

## Example CloudEvent

```json theme={"theme":{"light":"github-light","dark":"github-dark"}}
{
  "data": {
    "challenge_id": "example_id",
    "community_id": "example_id",
    "user_id": "example_id"
  },
  "datacontenttype": "application/json",
  "dataschema": "https://schemas.cope.com/events/community.challenge.joined/v1",
  "id": "community.challenge.joined:example",
  "idempotency_key": "community.challenge.joined:example",
  "source": "cope.community",
  "specversion": "1.0",
  "subject": "challenge:example",
  "time": "2026-05-05T12:00:00.000Z",
  "type": "community.challenge.joined"
}
```

## Compatibility

Fields may be added within the same major version. Removing or changing the meaning of a documented field requires a new event version.