Hostnames are set with a HostnameConfig document

Talos 1.13 seeds every machine with a HostnameConfig document set to auto: stable, which produces names like talos-d1w-560. The v1alpha1 machine.network.hostname field is refused while that document exists (static hostname is already set in v1alpha1 config), so the fix is to patch the document rather than the legacy field:

apiVersion: v1alpha1
kind: HostnameConfig
hostname: talos-01
auto: off

auto: off is required: auto and hostname are mutually exclusive, and the default stable collides with a static name. The Kubernetes node name follows the hostname and is immutable — renaming a live node registers a brand-new Node and orphans the old one, so the names are pinned before bootstrap.