Context

When using OpenTofu with private Spacelift modules, you may encounter a 401 Unauthorized error during module initialization, even after logging in through the CLI. This typically occurs when there are conflicting or outdated authentication credentials stored across different configuration locations.

Answer

To resolve authentication issues with private Spacelift modules, you'll need to perform a complete cleanup of all OpenTofu and Terraform configuration files before re-authenticating. Follow these steps:

1. First, remove all configuration and credential files by running:

   unset TF_CLI_CONFIG_FILE TF_TOKEN_spacelift_io TF_TOKEN_app_spacelift_io
   
   rm -rf \
     ~/.config/opentofu \
     ~/.terraform.d \
     ~/.tofu.d \
     ~/.terraformrc \
     ~/.tofurc \
     ~/.config/terraform

2. Re-authenticate with Spacelift:

   tofu login spacelift.io

3. Follow the browser-based authentication process when prompted

4. Initialize your OpenTofu project:

   tofu init -upgrade

After completing these steps, you should be able to successfully download and use private modules from Spacelift's registry.