### What needs to get done Take an integer value (in `AppMetadata`?) that provides a per-application addendum to the craft-providers compatibility tag, defaulting to zero. Set the `compatibility_tag` keyword argument for the provider base to include that value. ### Why it needs to get done Charmcraft has to override `ProviderService` and `get_base` because it adds custom compatibility tags: https://github.com/canonical/charmcraft/pull/1330/files/84ffcdd7a0731a17fcae83a889ed7e2143f7cfb6#diff-a32511469d8ae4dd52bf0ce115517e3cc980f46568ae386be734af9f2978b7c7 This shouldn't be necessary.