Extension only template - problem with function activation

Functions
1

Hey! I created a simple function “paymentCustomization”. I don’t need an admin UI. It’s really simple. On DEV Store it works great. I executed “shopify app dev” and using GrahiQL I sent mutation “paymentCustomizationCreate”.

I met a problem when I wanted to do exactly the same on my production store. I cannot connect to production using “shopify app dev”. I installed GraphiQL as application for Shopify on the PROD, but I got error that my function is not found.

I tried many ways, checked with AI too and I can’t solve the issue. How to active this paymentCustomization on the production store? My app is installed. I chosen “extesion only”, so I can’t use ui.create / ui.details

2

Ok, I found in community issues history the workaround. Seems like extension only is bugged and the temporary solutions is:
query:

{
  shopifyFunctions(first: 250) {
    edges {
      node {
        id
        title
      }
    }
  }
}

To get functionID and then in paymentCustomizationCreate mutation instead of functionHandle use deprecated functionId and it works!

3

Had the same issue to activate a Cart Transform function. Needed to use 2025-07 api with functionId, because in 2025-10 you need to use handle, but that’s not working. Just posting this in case someone from Shopify would take a look.