An organization named acme-corp publishes an internal module named vpc for the aws provider to its HCP Terraform private registry. A team wants to call it from a configuration and pin a version. Which source value should the module block use?

Modules in an HCP Terraform private registry use a four-part source: the registry hostname, app.terraform.io, followed by the organization name as the namespace, the module name and the target provider. That address lets the module block use a version constraint, and terraform init authenticates to HCP Terraform with the credentials configured for that hostname. Using registry.terraform.io sends the request to the public registry, where an internal acme-corp module is not published. A three-part address with no hostname is shorthand for the public registry, so it fails the same way, which is the most common mistake when moving modules in-house. Placing the organization last scrambles the segments, and the registry would interpret vpc as the namespace, aws as the module name and acme-corp as the provider. Exam caveat: Terraform Enterprise uses the deployment's own hostname in place of app.terraform.io, and HCP Terraform also accepts the generic localterraform.com hostname for configurations that should run unchanged across instances. Operational check: confirm the CLI has an API token for app.terraform.io, for example from terraform login, run terraform init, and confirm the module downloads at a version satisfying the constraint.