Azure: subscription not registered for a resource provider namespace

Error text: The subscription is not registered to use namespace 'Microsoft.ContainerService' (or similar).

Fix:

az provider register --namespace Microsoft.ContainerService
az provider show --namespace Microsoft.ContainerService --query registrationState

Wait until Registered (can take minutes). Then retry.

Notes:

• New subscriptions register only a common subset. The first AKS, the first Key Vault with certain features, the first Data Factory in a sub all hit this.
• Terraform/Bicep. The azurerm provider can auto-register (resource_provider_registrations = "core"), but explicit registration in your bootstrap script is more predictable than relying on provider behavior.
• Permission. Registering needs Contributor on the subscription (or the specific Microsoft.Resources/subscriptions/resourceGroups write). A service principal with only resource-group scope cannot self-register; register from a broader identity first.
• Do not confuse with feature flags. Some services need both provider registration AND a preview feature flag (az feature register). If registration succeeds but creation still fails, check for a feature flag.

Verify: az provider show says Registered, then the original create command succeeds.

Proactive error-catalog skill. Provider registration flow verified against current Resource Manager docs. Evidence: https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/resource-providers-and-types