<!-- Extension API v0 — pre-1.0. Interfaces may change without notice until P2 seals the custom-code format. First-party extensions track HEAD. -->

# `order.shipment.cancel`

Cancel a shipment before carrier handoff completes — resets the order to unfulfilled when nothing else is active.

- **scope**: `orders:write`
- **storefront-visible** (bumps the catalog generation): no
- **destructive**: yes — supports dryRun preview

## Payload

| field | type | required | notes |
|---|---|---|---|
| `shipmentId` | string (/^shp_[a-zA-Z0-9]{1,32}$/) | yes |  |

### JSON Schema

```json
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "shipmentId": {
      "type": "string",
      "pattern": "^shp_[a-zA-Z0-9]{1,32}$"
    }
  },
  "required": [
    "shipmentId"
  ],
  "additionalProperties": false
}
```