The agent network gateway service is private: agents reach it over the WireGuard tunnel, authorised by peer identity, with the cluster as its only target. Only a reverse proxy cluster with private capabilities can serve that, reported per cluster as the `private` capability — the same `supports_private` flag the dashboard gates NetBird-only services on.
A bootstrap could pin an account to a cluster without private capabilities, leaving an immutable dead gateway. Both bootstrap paths now validate the picked cluster: one the account can see must have a connected proxy reporting the capability. Shared and account-owned clusters qualify alike. Known-ness comes from proxy rows, not heartbeat freshness, so a cluster without the capability stays refused while merely offline. A hostname no proxy has declared stays pinnable (address-first). Identity is compared case-insensitively over the account's cluster list.