- Pods which have an invalid negative `spec.terminationGracePeriodSeconds` value will be treated as having terminationGracePeriodSeconds of 1 ([#115606](https://github.com/kubernetes/kubernetes/pull/115606), [@wzshiming](https://github.com/wzshiming)) [SIG Apps, Node and Testing]

#### Behavioral Changes

 - For all kinds in the API group version, a spec.selector default value is no longer
 available, because it's incompatible with `kubectl
 apply` and strategic merge patch. You must explicitly set the spec.selector value
 in your manifest. An object with a spec.selector value that does not match the labels in
 its spec.template is invalid.

 - Selector mutation is disabled for all kinds in the

- Introduce support for CEL optionals (see [CEL spec proposal 246](https://github.com/google/cel-spec/wiki/proposal-246)).
  This feature will not be fully enabled until a future Kubernetes release (likely to be v1.29), but is added in v1.28 to enable

  of environment variables for containers in Pods. ([#123385](https://github.com/kubernetes/kubernetes/pull/123385), [@HirazawaUi](https://github.com/HirazawaUi))

## Changelog since v1.26.2

## Changes by Kind

### API Change

- Volumes: `resource.claims` gets cleared for PVC specs during create or update of a pod spec with inline PVC template or of a PVC because it has no effect. ([#115928](https://github.com/kubernetes/kubernetes/pull/115928), [@pohly](https://github.com/pohly)) [SIG API Machinery, Apps and Storage]

### Feature

- Setting the `status.loadBalancer` of a Service whose `spec.type` is not `LoadBalancer` was previously allowed, but any update to the `metadata` or `spec` would wipe that field. Setting this field is no longer permitted unless `spec.type` is  `LoadBalancer`.  In the very unlikely event that this has unexpected impact, you can enable the `AllowServiceLBStatusOnNonLB` feature gate, which will restore...