- `response.patch` and `response.patchType` are not permitted from validating admission webhooks
  - `apiVersion: "admission.k8s.io/v1"` is required
  - `kind: "AdmissionReview"` is required
  - `response.uid: "<value of request.uid>"` is required

  attempted first, and if it fails with a corrupt resource error then it triggers unsafe delete.
  In addition, when this feature is enabled, the 'details' field of 'Status' from the LIST response
  includes information that identifies the corrupt object(s).
  NOTE: unsafe deletion ignores finalizer constraints, and skips precondition checks.

- Improved how the API server responds to **list** requests where the response format negotiates to Protobuf. List responses in Protobuf are marshalled one element at the time, drastically reducing memory needed to serve large collections. Streaming list responses can be disabled via the `StreamingCollectionEncodingToProtobuf` feature gate. ([#129407](https://github.com/kubernetes/kubernetes/pull/129407), [@serath...

- Resolves a spurious "Unknown discovery response content-type" error in client-go discovery requests by tolerating extra content-type parameters in API responses ([#117637](https://github.com/kubernetes/kubernetes/pull/117637), [@seans3](https://github.com/seans3)) [SIG API Machinery]

- Fixed a bug that was blocking extensible error handling when serializing API responses error out. Previously, serialization failures always resulted in the status code of the original response being returned. Now, the following behavior occurs: ([#67041](https://github.com/kubernetes/kubernetes/pull/67041), [@tristanburgess](https://github.com/tristanburgess))

  <mime-type type="application/mbms-msk+xml"/>
  <mime-type type="application/mbms-msk-response+xml"/>
  <mime-type type="application/mbms-protection-description+xml"/>
  <mime-type type="application/mbms-reception-report+xml"/>
  <mime-type type="application/mbms-register+xml"/>
  <mime-type type="application/mbms-register-response+xml"/>
  <mime-type type="application/mbms-user-service-description+xml"/>

  The API Server will no longer proxy non-101 responses for upgrade requests. This could break proxied backends (such as an extension API server) that respond to upgrade requests with a non-101 response code. ([#92941](https://github.com/kubernetes/kubernetes/pull/92941), [@tallclair](https://github.com/tallclair)) [SIG API Machinery]
 
## Changes by Kind

  The API Server will no longer proxy non-101 responses for upgrade requests. This could break proxied backends (such as an extension API server) that respond to upgrade requests with a non-101 response code. ([#92941](https://github.com/kubernetes/kubernetes/pull/92941), [@tallclair](https://github.com/tallclair)) [SIG API Machinery]
 
## Changes by Kind

- Added `apiserver_watch_list_duration_seconds` metrics which will measure response latency distribution in seconds for watchlist requests broken by group, version, resource and scope. ([#120490](https://github.com/kubernetes/kubernetes/pull/120490), [@p0lyn0mial](https://github.com/p0lyn0mial))

### Bug or Regression