Delivery Customization Function - selectedDeliveryOption always null

Functions
1

Hi everyone,

I’m running into an issue with a Delivery Customization Function where the selectedDeliveryOption field is always returning null.

query CartDeliveryOptionsTransformRunInput {
  cart {
    deliveryGroups {
      id
      selectedDeliveryOption {
        title
        handle
      }
      deliveryOptions {
		title
        handle
      }
    }
  }
}

On my store, split shipping is enabled.
When testing with the Checkout UI, I can clearly see the selected delivery method.
In a Discount Function, the selectedDeliveryOption value is also returned correctly.

However, in my Delivery Customization Function, selectedDeliveryOption is always null.

Here’s an example of the response I get:

{
  "cart": {
    "deliveryGroups": [
      {
        "id": "gid://shopify/CartDeliveryGroup/0",
        "selectedDeliveryOption": null,
        "deliveryOptions": [
          {
            "title": "Colissimo en point relais",
            "handle": "ebfa45dac5169495327c7abdeafac7a7-272ed97e3788352a7ce4821feda5fce3",
          },
          {
            "title": "Chrono 18",
            "handle": "ebfa45dac5169495327c7abdeafac7a7-cb11526cde1b630532d5861058b351df",
          }
        ]
      }
    ]
  }
}

I’ve tested this on multiple stores and different API versions (2025-10, 2025-07), and I’m always getting the same result.

Is this expected behavior (a known limitation of Delivery Customization Functions) or could it be a current issue with the API?

Thanks in advance for your help!

4 Likes
Matching DeliveryMethodDefinition to its CartDeliveryOption (GraphQL to Function Input)
3

Also experiencing this issue. It’s blocking development.

2 Likes