Checkout rule creation fails with "An error occurred when creating" on a production store, but works on a development store

Functions
1

Summary

A cart.validations.generate.run function deploys fine and shows up in
Settings → Checkout → Checkout rules → Add rule, but saving the rule
fails with a generic admin error:

An error occurred when creating cobertura-tienda

The exact same app version and function activates successfully on a
development store. It only fails on the production store.

Setup

  • Custom app (installed via custom install link), 1 install
  • Function extension, JavaScript, @shopify/shopify_function ^2.0.1
  • Target: cart.validations.generate.run
  • Extension api_version = "2026-07"
  • Active app version released and confirmed active in the Dev Dashboard

Access scopes:

[access_scopes]
scopes = "write_products,read_validations,write_validations"