### **CLI**

*   Swagger 1.2 validation is removed for kubectl. The options `--use-openapi` and `--schema-cache-dir` are also removed because they are no longer needed. ([#53232](https://github.com/kubernetes/kubernetes/pull/53232),[ @apelisse](https://github.com/apelisse))

### **Cluster Lifecycle**

- The PodDisruptionBudget API has been promoted to policy/v1 with no schema changes. The only functional change is that an empty selector (`{}`) written to a policy/v1 PodDisruptionBudget now selects all pods in the namespace. The behavior of the policy/v1beta1 API remains unchanged. The policy/v1beta1 PodDisruptionBudget...

- The list-type of the alpha `resourceClaims` field introduced to `Pods` in `1.26.0` was modified from `set` to `map`, resolving an incompatibility with use of this schema in `CustomResourceDefinitions` and with server-side apply. ([#114585](https://github.com/kubernetes/kubernetes/pull/114585), [@JoelSpeed](https://github.com/JoelSpeed))

- Removed deprecated command `kubectl stop`.

- Kubectl can now use http caching for the OpenAPI schema. The cache
  directory can be configured by passing the `--cache-dir` command line flag to kubectl.
  If set to an empty string, caching is disabled.

- Kubectl now performs validation against OpenAPI schema instead of Swagger 1.2. If
  OpenAPI is not available on the server, it falls back to the old Swagger 1.2.

- Fixed a bug that prevents kubectl to validate CRDs with schema using x-kubernetes-preserve-unknown-fields on object fields.

- Added new `CRDValidationRatcheting` alpha feature. During a PATCH or UPDATE Validation Ratcheting discards errors thrown by unchanged portions of the resource from most OpenAPI schema validations. ([#118990](https://github.com/kubernetes/kubernetes/pull/118990), [@alexzielenski](https://github.com/alexzielenski))

  - The schema for the alpha `CSINodeInfo` CRD has been split into `spec` and `status` fields, and new fields `status.available` and `status.volumePluginMechanism` added. Clusters using the previous alpha schema must delete and recreate the CRD using the new schema. ([#70515](https://github.com/kubernetes/kubernetes/pull/70515), [@davidz627](https://github.com/davidz627))

- CRD writes will generate validation errors if a CEL validation rule references the identifier `oldSelf` on a part of the schema that does not support it. ([#108013](https://github.com/kubernetes/kubernetes/pull/108013), [@benluddy](https://github.com/benluddy))

- Kubernetes is now built using go 1.17. ([#103692](https://github.com/kubernetes/kubernetes/pull/103692), [@justaugustus](https://github.com/justaugustus))
- Performs strict server side schema validation requests via the `fieldValidation=[Strict,Warn,Ignore]`. ([#105916](https://github.com/kubernetes/kubernetes/pull/105916), [@kevindelgado](https://github.com/kevindelgado))
- Promote `IPv6DualStack` feature to stable.

- Fix kubectl SchemaError on CRDs with schema using x-kubernetes-preserve-unknown-fields on array types. ([#94888](https://github.com/kubernetes/kubernetes/pull/94888), [@sttts](https://github.com/sttts)) [SIG API Machinery]