* With WatchBookmark feature, clients are able to request watch events with BOOKMARK type. Clients should not assume bookmarks are returned at any specific interval, nor may they assume the server will send any BOOKMARK event during a session.

* Introduce API for watch bookmark events. ([#74074](https://github.com/kubernetes/kubernetes/pull/74074), [@wojtek-t](https://github.com/wojtek-t))
    * Introduce Alpha field `AllowWatchBookmarks` in ListOptions for requesting watch bookmarks from apiserver. The implementation in apiserver is hidden behind feature gate `WatchBookmark` (currently in Alpha stage).

### Beta

- Promote WatchBookmark feature to beta and enable it by default.
  With WatchBookmark feature, clients are able to request watch events with BOOKMARK type. Clients should not assume bookmarks are returned at any specific interval, nor may they assume the server will send any BOOKMARK event during a session. ([#79786](https://github.com/kubernetes/kubernetes/pull/79786), [@wojtek-t](https://github.com/wojtek-t))

- Try to send watch bookmarks (if requested) periodically in addition to sending them right before timeout ([#90560](https://github.com/kubernetes/kubernetes/pull/90560), [@wojtek-t](https://github.com/wojtek-t)) [SIG API Machinery]

- The synthetic "Bookmark" event for the watch stream requests will now include a new annotation: `kubernetes.io/initial-events-list-blueprint`. THe annotation contains an empty, versioned list that is encoded in the requested format (such as protobuf, JSON, or CBOR), then...

- Implemented API streaming for the `watch-cache`
  
  When `sendInitialEvents` `ListOption` is set together with `watch=true`, it begins the watch stream with synthetic init events followed by a synthetic "Bookmark" after which the server continues streaming events. ([#110960](https://github.com/kubernetes/kubernetes/pull/110960), [@p0lyn0mial](https://github.com/p0lyn0mial))
- Introduced API for streaming.
  

- Implemented API for streaming for the `etcd` store implementation.
  When `sendInitialEvents ListOption` is set together with `watch=true`, it begins the watch stream with synthetic init events followed by a synthetic `Bookmark`, after which the server continues streaming events. ([#119557](https://github.com/kubernetes/kubernetes/pull/119557), [@p0lyn0mial](https://github.com/p0lyn0mial))

- Removed the `kubernetes.io/initial-events-list-blueprint` annotation from the synthetic "Bookmark" event in watch stream requests. ([#132326](https://github.com/kubernetes/kubernetes/pull/132326), [@p0lyn0mial](https://github.com/p0lyn0mial))

- Client-go/reflector: warns when the bookmark event for initial events hasn't been received ([#124614](https://github.com/kubernetes/kubernetes/pull/124614), [@p0lyn0mial](https://github.com/p0lyn0mial)) [SIG API Machinery]