## Read later

`POST /v1/chats/messages/:messageId/mark`

Marks the message's chat as unread and points the mark at this message — the v2 messenger method `im.v2.Chat.Message.mark`, the "Read later" command in the Bitrix24 interface. The chat is resolved from the message, so no `dialogId` is needed. [Loading a chat](/docs/chats/messages/load) returns the marked message as `data.chat.markedId`: the interface opens the chat at that message.

[`DELETE /v1/chats/:dialogId/unread`](/docs/chats/management/unread) clears the mark together with the pointer. The call is a write: a read-only key gets `403 WRITE_BLOCKED_READONLY_KEY` before any call to Bitrix24.

## Parameters

| Parameter | Type | Required | Default | Description |
|----------|-----|:-----:|-----------|---------|
| `messageId` (path) | number | yes | — | Message ID, a positive integer |

There are no query parameters and no body fields. Any query parameter or body field is rejected with `400 INVALID_PARAMS`.

## Examples

### curl — personal key

```bash
curl -X POST "https://vibecode.bitrix24.com/v1/chats/messages/1002/mark" \
  -H "X-Api-Key: YOUR_API_KEY"
```

### curl — OAuth application

```bash
curl -X POST "https://vibecode.bitrix24.com/v1/chats/messages/1002/mark" \
  -H "X-Api-Key: YOUR_APP_KEY" \
  -H "Authorization: Bearer USER_SESSION_TOKEN"
```

### JavaScript — personal key

```javascript
const res = await fetch('https://vibecode.bitrix24.com/v1/chats/messages/1002/mark', {
  method: 'POST',
  headers: { 'X-Api-Key': 'YOUR_API_KEY' },
})

const { success } = await res.json()
```

### JavaScript — OAuth application

```javascript
const res = await fetch('https://vibecode.bitrix24.com/v1/chats/messages/1002/mark', {
  method: 'POST',
  headers: {
    'X-Api-Key': 'YOUR_APP_KEY',
    'Authorization': 'Bearer USER_SESSION_TOKEN',
  },
})

const { success } = await res.json()
```

## Response fields

| Field | Type | Description |
|------|-----|---------|
| `success` | boolean | Always `true` on success |
| `data` | array | An empty array |

## Response example

```json
{
  "success": true,
  "data": []
}
```

## Error response example

422 — the message's chat is not in the recent dialog list:

```json
{
  "success": false,
  "error": {
    "code": "BITRIX_ERROR",
    "message": "MESSAGE_MARK_FAILED",
    "b24Code": "MESSAGE_MARK_FAILED"
  }
}
```

## Errors

| HTTP | Code | Description |
|------|-----|---------|
| 400 | `INVALID_PARAMS` | `messageId` is not a positive integer, a query parameter or a body field was sent, or the body is not a JSON object. Checked before any call to Bitrix24 |
| 403 | `SCOPE_DENIED` | The API key does not have the `im` scope |
| 403 | `WRITE_BLOCKED_READONLY_KEY` | The key is read-only — the call changes the chat state |
| 401 | `TOKEN_MISSING` | The API key has no Bitrix24 tokens configured |
| 404 | `ENTITY_NOT_FOUND` | Bitrix24 answered "not found"; the portal code is in `error.b24Code` |
| 422 | `BITRIX_ERROR` | Bitrix24 returned an error; the portal code is in `error.b24Code`. A message that does not exist — `MESSAGE_NOT_FOUND`; a chat outside the recent dialog list — `MESSAGE_MARK_FAILED` |
| 502 | `BITRIX_UNAVAILABLE` | Bitrix24 is unavailable or returned a server error |

Full list of common API errors — [Errors](/docs/errors).

## Known specifics

- The mark is set on the chat's row in the recent dialog list. When the chat is hidden from the list, Bitrix24 refuses the call with the code `MESSAGE_MARK_FAILED`; the row returns to the list when a new message arrives in the chat.
- **A marked chat is not re-marked.** When the chat is already marked as unread — by an earlier "read later" or by [`POST /v1/chats/:dialogId/unread`](/docs/chats/management/unread) — Bitrix24 leaves the mark and the pointer as they are and answers with success. To point the mark at another message, first clear it with `DELETE /v1/chats/:dialogId/unread`, then call this endpoint.

## See also

- [Unread mark](/docs/chats/management/unread)
- [Load a chat](/docs/chats/messages/load)
- [Messages around a message](/docs/chats/messages/context)
- [Messages](/docs/chats/messages)