# Undo a session

`POST /v1/history/sessions/{sessionId}/undo`

Reverts every change a session made, newest first, as one undoable step. Changes that later edits by others touched are skipped and reported, as are changes that cannot be undone.

Scope: `docs:write`. Undoable.

## Request

```bash
curl -X POST "https://api.lydie.co/v1/history/sessions/01JCQ3V5MZ8G4ZK2X7T9R6N1PB/undo" \
  -H "Authorization: Bearer $LYDIE_TOKEN"
```

## Path parameters

- `sessionId` (string, required): (≥ 1 chars)

## Response

- `undoneIds` (ULID[], required): History entries that were reverted.
- `skipped` (object[], required)
  - `id` (ULID, required)
  - `operation` (string, required)
  - `reason` (string, required): One of: `not_undoable`, `conflict`, `failed`.
  - `message` (string, required)

```json
{
  "undoneIds": [
    "01JCQ3V5MZ8G4ZK2X7T9R6N1PB"
  ],
  "skipped": [
    {
      "id": "01JCQ3V5MZ8G4ZK2X7T9R6N1PB",
      "operation": "string",
      "reason": "not_undoable",
      "message": "string"
    }
  ]
}
```

Errors use the envelope described at https://developers.lydie.co/errors.md.