Cancels specific line items within a fulfillment order.

Line Item Status Requirements

Only items in pending status (open or allocated) can be cancelled:

• ✅ open - Can be cancelled
• ✅ allocated - Can be cancelled
• ❌ fulfilled - Cannot be cancelled (use unfulfill first)
• ❌ cancelled - Already cancelled
• ❌ closed - Cannot be cancelled

Request Requirements (All Required)

• cancellation_reason (required): One of the predefined enum values
• line_items (required): Array of items to cancel with quantities

Cancellation Reason Values

• CUSTOMER_CANCELLATION - Customer requested cancellation
• AUTO_ALLOCATION_FAILED - Automatic fulfillment allocation failed
• INVENTORY_OUT_OF_STOCK - Items are out of stock
• STAFF_ERROR - Staff made an error
• PAYMENT_ISSUE - Payment problem occurred
• OTHER - Other reason

Cancellation Effects

When items are cancelled:

1. Item status is updated to cancelled with the cancellation reason
2. Order line item's removed_quantities is updated
3. Order status is recalculated
4. Webhooks are triggered

Inventory Impact

If inventory management is enabled and the FO has a location_id:

• reserved is decreased by the cancelled quantity (releasing reserved stock)