Unable to set a custom rejection message for discount code because rejectable property is false

Hello everyone,

I have a fully functional custom discount app that is working. I am trying to incorporate Discount Function support for rejecting discount codes in my app.

At a high-level, my app has two extensions:
1.A UI extension that exposes the surface to create a discount code, rendered in admin.discount-details.function-settings.render.

2.A function that validates and applies/rejects the discount code created by 1.

As mentioned, this is working. I updated my .graphql to include enteredDiscountCodes, and the logs show that this is correctly picked up and is available as the input to the function.

PROBLEM: The rejectable property of the code is false, even though this is a code that is created by my app. Is this a bug, or am I missing something ? Because of this issue, I am unable to return a custom rejection message for the rejected discount code.

API Version for my function is 2026-01

Language: JavaScript / Wasm