- [CustomResourceDefinitions Pruning](#customresourcedefinitions-pruning)
    - [CustomResourceDefinition Defaulting](#customresourcedefinition-defaulting)
    - [CustomResourceDefinition OpenAPI Publishing](#customresourcedefinition-openapi-publishing)
  - [Cluster Lifecycle Stability and Usability Improvements](#cluster-lifecycle-stability-and-usability-improvements)

    The `apiextensions.k8s.io/v1beta1` version of `CustomResourceDefinition` is deprecated and will no longer be served in v1.19. ([#79604](https://github.com/kubernetes/kubernetes/pull/79604), [@liggitt](https://github.com/liggitt))

* 'cj' has been added as a shortname for CronJobs, as in `kubectl get cj` ([#59499](https://github.com/kubernetes/kubernetes/pull/59499), [@soltysh](https://github.com/soltysh))

* `crds` has been added as a shortname for CustomResourceDefinition, as in `kubectl get crds` ([#59061](https://github.com/kubernetes/kubernetes/pull/59061), [@nikhita](https://github.com/nikhita))

  - When registering with a 1.17+ API server, a CustomResourceDefinition conversion webhook can now request that only `v1` ConversionReview requests be sent to them. Previously, conversion webhooks were required to support receiving `v1beta1` ConversionReview requests as well for compatibility with API servers...

- CustomResourceDefinition schemas that use `x-kubernetes-list-map-keys` to specify properties that uniquely identify list items must make those properties required or have a default value, to ensure those properties are present for all list items. See https://kub...

- Introduced OpenAPI format support for `k8s-short-name` and `k8s-long-name` in CustomResourceDefinition schemas. ([#132504](https://github.com/kubernetes/kubernetes/pull/132504), [@jpbetz](https://github.com/jpbetz)) [SIG API Machinery, Architecture, Auth, CLI, Cloud Provider, Cluster Lifecycle, Instrumentation, Network, Node, Scheduling and...

- Alpha support for field selectors on custom resources has been added. With the `CustomResourceFieldSelectors` feature gate enabled, the CustomResourceDefinition API now allows specifying `selectableFields`. Listing a field there enables filtering custom resources for that CustomResourceDefinition in list or watch requests. ([#122717](https://github.com/kubernetes/kubernetes/pull/122717), [@jpbetz](https://github.com/jpbetz))

- CustomResourceDefinition objects created with non-empty `caBundle` fields which are invalid or do not contain any certificates will not appear in discovery or serve endpoints until a valid `caBundle` is provided. Updates to CustomResourceDefinition are no longer allowed to transition a valid `caBundle` field to an invalid `caBundle` field, because this breaks serving of the...

* The deprecated `ThirdPartyResource` (TPR) API was removed.
  To avoid losing your TPR data, [migrate to CustomResourceDefinition](https://kubernetes.io/docs/tasks/access-kubernetes-api/migrate-third-party-resource/).

* The following deprecated flags were removed from `kube-controller-manager`:

* The kube-apiserver openapi doc now includes extensions identifying `APIService` and `CustomResourceDefinition` `kind`s ([#64174](https://github.com/kubernetes/kubernetes/pull/64174), [@liggitt](https://github.com/liggitt))