Kubernetes v1.36 marks the graduation of the Mixed Version Proxy (MVP) to Beta status and enables it by default. MVP addresses a long‑standing upgrade problem: when a client contacts an older API server that does not recognize a newly introduced resource, the server previously returned a 404 Not Found, incorrectly suggesting the resource does not exist in the cluster.
With MVP, the request is proxied to a peer API server that knows the resource, returning the correct response. The feature now relies on Aggregated Discovery instead of the StorageVersion API, allowing it to work with CRDs and aggregated APIs. It also adds Peer‑Aggregated Discovery, merging local and peer discovery data so clients see a unified API list regardless of which server they contact.
To operate, MVP requires a few API‑server flags. The feature gate UnknownVersionInteroperabilityProxy is on by default in 1.36, but the --peer-ca-file flag is mandatory for TLS‑authenticated peer communication. Optional flags such as --peer‑advertise‑ip and --peer‑advertise‑port help in complex network topologies. When using kubeadm, these flags can be added under apiServer.extraArgs in the ClusterConfiguration.
Operators of multi‑master clusters are encouraged to verify the peer CA configuration, test MVP in staging environments before upgrading, and provide feedback to SIG API Machinery.