- Fixed missing delete events on informer re-lists to ensure all delete events were correctly emitted and using the latest known object state, so that all event handlers and stores always reflect the actual apiserver state as best as possible ([#115620](https://github.com/kubernetes/kubernetes/pull/115620), [@odinuge](https://github.com/odinuge))

* kube-apiserver: requests to endpoints handled by unavailable extension API servers (as indicated by an `Available` condition of `false` in the registered APIService) now return `503` errors instead of `404` errors. ([#58070](https://github.com/kubernetes/kubernetes/pull/58070), [@weekface](https://github.com/weekface))

- Fixed an issue with stuck connections handling error responses ([#71412](https://github.com/kubernetes/kubernetes/pull/71412), [@liggitt](https://github.com/liggitt))
- apiserver: fixed handling and logging of panics in REST handlers ([#71076](https://github.com/kubernetes/kubernetes/pull/71076), [@liggitt](https://github.com/liggitt))

- K8s.io/dynamic-resource-allocation/controller: UnsuitableNodes did not handle a mix of allocated and unallocated claims correctly. ([#120338](https://github.com/kubernetes/kubernetes/pull/120338), [@pohly](https://github.com/pohly)) [SIG Node]

- The `baseline` and `restricted` pod security admission levels blocked setting the `host` field on probe and lifecycle handlers. ([#125271](https://github.com/kubernetes/kubernetes/pull/125271), [@tssurya](https://github.com/tssurya)) [SIG Auth, Node and Testing]

- 'Container `preStop` and `postStart` lifecycle handlers using `httpGet` now
  honor the specified `scheme` and `headers` fields. This enables setting custom
  headers and changing the scheme to `HTTPS`, consistent with container
  startup/readiness/liveness probe capabilities. Lifecycle handlers configured
  with `scheme: HTTPS` that encounter errors indicating the endpoint is actually

- The maximum length of the `CSINode` id field has increased to 256 bytes to match the CSI spec. ([#104160](https://github.com/kubernetes/kubernetes/pull/104160), [@pacoxu](https://github.com/pacoxu))
- Troubleshooting: informers log handlers that take more than 100 milliseconds to process an object if the `DeltaFIFO` queue starts to grow beyond 10 elements. ([#103917](https://github.com/kubernetes/kubernetes/pull/103917), [@aojea](https://github.com/aojea))

- `Scheduler` now registers event handlers dynamically. ([#101394](https://github.com/kubernetes/kubernetes/pull/101394), [@Huang-Wei](https://github.com/Huang-Wei))
- `kubectl`: Enable using protocol buffers to request Metrics API. ([#102039](https://github.com/kubernetes/kubernetes/pull/102039), [@serathius](https://github.com/serathius))

- Replaced `apiserver_storage_db_total_size_in_bytes` with `apiserver_storage_size_bytes` metric. ([#118812](https://github.com/kubernetes/kubernetes/pull/118812), [@serathius](https://github.com/serathius))
- Scheduler now waits for handlers to finish syncing before the scheduling cycles start. ([#116729](https://github.com/kubernetes/kubernetes/pull/116729), [@AxeZhan](https://github.com/AxeZhan))

### Other notable changes