# Apply changes to dataset items

**POST** `/v1/private/datasets/{id}/items/changes`

Apply delta changes (add, edit, delete) to a dataset version with conflict detection.

This endpoint:
- Creates a new version with the applied changes
- Validates that baseVersion matches the latest version (unless override=true)
- Returns 409 Conflict if baseVersion is stale and override is not set

Use `override=true` query parameter to force version creation even with stale baseVersion.

Set 'copy_from_dataset_id' and 'copy_from_version_id' together on the request body to read
carry-forward rows from the supplied (dataset, version) pair instead of the destination's
prior version. When the fields are null, carry-forward rows are read from the destination's
prior version.

Base URL: `https://www.comet.com/opik/api`

Tags: `Datasets`

## Authorization

This operation requires no authorization.

## Path parameters

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `id` | `string` (uuid) | Yes | — |

## Query parameters

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `override` | `boolean` | No | — |

## Request body

Optional. Media type: `application/json`

### Example request body

```json
{}
```

## Responses

| Status | Description | Media type |
| --- | --- | --- |
| `201` | Version created successfully | `application/json` |
| `400` | Bad Request | `application/json` |
| `404` | Dataset or version not found | `application/json` |
| `409` | Version conflict - baseVersion is not the latest | `application/json` |

### Example response: 201 — Version created successfully

```json
{
  "change_description": "string",
  "created_at": "2026-06-09T00:00:00Z",
  "created_by": "string",
  "dataset_id": "00000000-0000-0000-0000-000000000000",
  "evaluators": [
    {
      "config": {},
      "name": "string",
      "type": "code_metric"
    }
  ],
  "execution_policy": {
    "pass_threshold": 0,
    "runs_per_item": 0
  },
  "id": "00000000-0000-0000-0000-000000000000",
  "is_latest": true,
  "items_added": 0,
  "items_deleted": 0,
  "items_modified": 0,
  "items_total": 0,
  "last_updated_at": "2026-06-09T00:00:00Z",
  "last_updated_by": "string",
  "metadata": {
    "additionalProp1": "string"
  },
  "tags": [
    "string"
  ],
  "version_hash": "string",
  "version_name": "string"
}
```

### Example response: 400 — Bad Request

```json
{
  "code": 0,
  "details": "string",
  "message": "string"
}
```

### Example response: 404 — Dataset or version not found

```json
{
  "code": 0,
  "details": "string",
  "message": "string"
}
```

### Example response: 409 — Version conflict - baseVersion is not the latest

```json
{
  "code": 0,
  "details": "string",
  "message": "string"
}
```

## Related pages

- [Activate a pairing session](./activatepairingsession.md)
- [Add blueprint to existing config](./updateagentconfig.md)
- [Add items to annotation queue](./additemstoannotationqueue.md)
- [Add span comment](./addspancomment.md)
- [Add span feedback score](./addspanfeedbackscore.md)
- [Add thread comment](./addthreadcomment.md)
- [Add trace comment](./addtracecomment.md)
- [Add trace feedback score](./addtracefeedbackscore.md)
- [Agent Configs](./tags/agent-configs.md)
- [Agent Insights](./tags/agent-insights.md)

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