Merge branch 'nagyv-gitlab-master-patch-36513' into 'master'

Change upgrade and version compatibility

See merge request gitlab-org/gitlab!73583

doc/user/clusters/agent/install/index.md

@@ -350,16 +350,17 @@ Additional management interfaces are planned for the GitLab Kubernetes Agent.
 
 ## Upgrades and version compatibility
 
-As the GitLab Kubernetes Agent is a new product, we are constantly adding new features
-to it. As a result, while shipped features are production ready, its internal API is
-neither stable nor versioned yet. For this reason, GitLab only guarantees compatibility
-between corresponding major.minor (X.Y) versions of GitLab and its cluster side
-component, `agentk`.
+The GitLab Kubernetes Agent is comprised of two major components: `agentk` and `kas`. 
+As we provide `kas` installers built into the various GitLab installation methods, the required `kas` version corresponds to the GitLab `major.minor` (X.Y) versions.
 
-Upgrade your agent installations together with GitLab upgrades. To decide which version of `agentk` to install follow:
+At the same time, `agentk` and `kas` can differ by 1 minor version in either direction. For example,
+`agentk` 14.4 supports `kas` 14.3, 14.4, and 14.5 (regardless of the patch).
 
-1. Open the [`GITLAB_KAS_VERSION`](https://gitlab.com/gitlab-org/gitlab/-/blob/master/GITLAB_KAS_VERSION) file from the GitLab Repository, which contains the latest `agentk` version associated with the `master` branch.
-1. Change the `master` branch and select the Git tag associated with your version. For instance, you could change it to GitLab [v13.5.3-ee release](https://gitlab.com/gitlab-org/gitlab/-/blob/v13.5.3-ee/GITLAB_KAS_VERSION)
+A feature introduced in a given GitLab minor version might work with other `agentk` or `kas` versions.
+To make sure that it works, use at least the same `agentk` and `kas` minor version. For example,
+if your GitLab version is 14.2, use at least `agentk` 14.2 and `kas` 14.2.
+
+We recommend upgrading your `kas` installations together with GitLab instances' upgrades, and to upgrade the `agentk` installations after upgrading GitLab.
 
 The available `agentk` and `kas` versions can be found in
 [the container registry](https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/container_registry/).