# sequence_mismatch

**The event changed since the sequence you sent.**

| | |
|---|---|
| HTTP status | `409` |
| `code` | `sequence_mismatch` |
| Retry? | No, fix the request first |

## What it means

You sent `If-Match` with a `sequence`, but the event now has a different one, or it does not exist yet.

## How to fix it

Read the event again (`GET`), merge your changes and write with the current `sequence`. If you do not need protection against parallel changes, leave out `If-Match`.

## Example

```json
{
  "type": "https://docs.kalender-sync.de/en/api/errors/sequence_mismatch",
  "title": "Conflict",
  "status": 409,
  "code": "sequence_mismatch",
  "detail": "The event changed since the sequence you sent.",
  "request_id": "req_…"
}
```

→ [All error codes](https://docs.kalender-sync.de/en/api/errors/)