A quiet failure mode in multi-module Terragrunt setups: someone copies an existing module to bootstrap a new one, forgets to check the region in the provider config, and a resource lands in us-east-1 instead of eu-west-1 — three weeks later, someone's debugging why a Lambda can't reach a VPC that "should" be right there.
This isn't a Terraform bug. It's a consequence of region being just another string that every module has to get right, independently, forever.
The default pattern (and why it's fragile)
Most Terragrunt setups declare region per-project:
# projects/some-service/project.hcl
