Terraform "Module source has changed" run terraform init in CI

By Kaveh Alemi·Latchkey

Terraform detected that a module block's source or version differs from what is recorded in the module manifest under .terraform. plan/apply stop until terraform init re-installs the module to match.

What this error means

plan or apply stops with "Error: Module source has changed" and "the source address was changed since this module was installed. Run \"terraform init\" ...".

Error: Module source has changed

  on main.tf line 5, in module "network":
   5:   source = "terraform-aws-modules/vpc/aws"

The source address was changed since this module was installed. Run "terraform init"
to install all modules required by this configuration.

Diagnose it: init, state, or credentials?

Terraform failures in CI are dominated by backend and credential problems rather than configuration errors. Confirm the runner can initialise, authenticate, and lock state before reading the plan.

terraform init -backend=true -input=false
terraform validate
terraform providers
terraform plan -input=false -no-color -detailed-exitcode
#   0 = no changes, 2 = changes, 1 = error

Common causes

A module source or version was edited without re-init

The source or version on a module block changed, but the job restored a cached .terraform from before the change.

CI plans on a stale module manifest

A cache restored the old .terraform/modules/modules.json that no longer matches the edited configuration.

How to fix it

Re-run terraform init

1. Run terraform init so the module manifest is rebuilt for the new source/version.
2. If you cache .terraform, key the cache on the module files so edits bust it.
3. Re-run plan/apply against the freshly installed module.

terraform init -input=false
terraform plan -input=false

Bust the cache on module changes

Include the module configuration and lock file in the cache key so a source change forces a fresh init.

- uses: actions/cache@v4
  with:
    path: .terraform
    key: tf-${{ hashFiles('**/*.tf', '.terraform.lock.hcl') }}

How to prevent it

• Init after any module source or version change.
• Key .terraform caches on the config and lock files.
• Do not carry a stale module manifest across edits.

Frequently asked questions

Related guides

References

• Terraform documentation
• GitHub Actions documentation