Two auth commands solve two different problems.
Named configurations switch your whole working context at once.
gcloud auth login
Authenticates you, the human — interactive CLI and console
gcloud auth application-default login
Sets up ADC — what client libraries and Terraform actually use
An engineer's gcloud commands all worked fine — the console showed every project,
gcloud storage ls succeeded. A local Python notebook still failed with DefaultCredentialsError, because only the first command had ever been run.Cloud Shell: free, browser-based, everything preinstalled — great for a quick admin task, a poor fit for anything resembling a production pipeline given its ephemeral compute.