- [API Machinery](#api-machinery)
      - [kube-apiserver](#kube-apiserver)
      - [Dynamic Admission Control](#dynamic-admission-control)
      - [Custom Resource Definitions (CRDs)](#custom-resource-definitions-crds)
      - [Garbage Collector](#garbage-collector)
      - [Monitoring/Prometheus](#monitoringprometheus)
      - [Go Client](#go-client)
  - [External Dependencies](#external-dependencies)

- Removed container name from messages for container created and started events. ([#134043](https://github.com/kubernetes/kubernetes/pull/134043), [@HirazawaUi](https://github.com/HirazawaUi))
- Removed deprecated gogo protocol definitions from `k8s.io/kubelet/pkg/apis/dra` in favor of `google.golang.org/protobuf`. ([#133026](https://github.com/kubernetes/kubernetes/pull/133026), [@saschagrunert](https://github.com/saschagrunert)) [SIG API Machinery and Node]

* CustomResourceDefinitions: OpenAPI v3 validation schemas containing `$ref`references are no longer permitted. Before upgrading, ensure CRD definitions do not include those `$ref` fields. ([#58438](https://github.com/kubernetes/kubernetes/pull/58438), [@carlory](https://github.com/carlory))

            if (this == f) {
                return true;
            }

            /* If uncertain, pathNamesPossiblyEqual returns true.
             * Comparing canonical paths is definitive.
             */
            if (pathNamesPossiblyEqual(url.getPath(), f.url.getPath())) {

                getUncPath0();
                f.getUncPath0();

  - The OpenAPI definitions with the prefix "io.k8s.kubernetes.pkg" (deprecated since 1.9) have been removed. ([#74596](https://github.com/kubernetes/kubernetes/pull/74596), [@sttts](https://github.com/sttts))

- OpenAPI definitions served by kube-apiserver now include enum types by default. ([#108898](https://github.com/kubernetes/kubernetes/pull/108898), [@jiahuif](https://github.com/jiahuif))

- `kubectl rollout restart` now works for DaemonSets and StatefulSets. ([#77423](https://github.com/kubernetes/kubernetes/pull/77423), [@apelisse](https://github.com/apelisse))
- `kubectl get --watch=true` now prints custom resource definitions with custom print columns. ([#76161](https://github.com/kubernetes/kubernetes/pull/76161), [@liggitt](https://github.com/liggitt))

- The `batch/v2alpha1` CronJob type definitions and clients are deprecated and removed. ([#96987](https://github.com/kubernetes/kubernetes/pull/96987), [@soltysh](https://github.com/soltysh)) [SIG API Machinery, Apps, CLI and Testing]

- Validation rules for Custom Resource Definitions can be written in the [CEL expression language](https://github.com/google/cel-spec) using the `x-kubernetes-validations` extension in OpenAPIv3 schemas (alpha). This is gated by the alpha "CustomResourceValidationExpressions" feature gate. ([#1...

- Fixed a regression in `1.27.0` that resulted in `missing metadata in converted object` errors when modifying objects for multi-version custom resource definitions with a conversion strategy of `None`. ([#117301](https://github.com/kubernetes/kubernetes/pull/117301), [@ncdc](https://github.com/ncdc))