This tag is part of the assert category of tags, which are assertions made by the project team themselves about their maturity. One such assertion (or self-imposed contract) is about the interoperability of the API. In this context interoperability is a combination of an API that’s both stable and compatible.

The “assert:supports-api-interoperability” tag asserts that the project will follow the API interoperability guidelines and that they will not change (or remove) an API in a way that will break existing users of an API.


End users of a given service need to have confidence that the API they are using and relying on won’t break when they upgrade a cloud or start using their code on a new OpenStack cloud. This tag asserts that a service adheres to this principle and follows the requirements to ensure this.


Project teams can apply this tag to services that they produce to assert the service will follow the following process for end-user-visibile API stability:

  1. The project follows the API interoperability guidelines when making changes to the REST API

  2. The projects API uses a versioning scheme (like microversions) or a discoverablity mechanism to ensure that any new features or other changes to the API are both explicit and discoverable.

  3. There are branchless API tests run on every commit to ensure that the API doesn’t change between release boundaries.

Tag application process

Anyone may propose adding or removing this tag to a set of projects by proposing a change to the openstack/governance repository. The change is reviewed by the Technical Committee and approved using standard resolution approval rules. As this is an assert tag, it is up to the project itself to judge if they are currently meeting the requirements (above) and intend to continue doing so.


This tag has no deprecation period, as that would rather violate the point of the tag. If a project chooses to assert the tag then they are making a commitment to maintain API interoperability henceforth. If the project chooses to no longer maintain that commitment they should remove the tag. If a member of the community wishes to claim the project is not meeting the commitment a proposal should be made removing the tag from the project whereupon the Technical Committee will review the situation using standard processes.