Fix Terraform Error: Module Version Requirements Have Changed

terraform init -upgrade

Error: Module version requirements have changed
 
The previously-installed version "3.19.0" of
registry.terraform.io/terraform-aws-modules/vpc/aws no longer matches
the version constraints "~> 5.0".
 
Run terraform init -upgrade to install the new version.

# Re-download modules matching new constraints
terraform init -upgrade

# Delete module cache and re-init
rm -rf .terraform/modules
terraform init

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"      # >= 5.0.0, < 6.0.0 (recommended)
}

# Development — allow minor updates
module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"
}
 
# Production — pin exact version
module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "5.8.1"    # Exact, predictable
}

# 1. Check changelog for breaking changes
# https://github.com/terraform-aws-modules/terraform-aws-vpc/blob/master/CHANGELOG.md
 
# 2. Plan to see what changes
terraform plan
 
# 3. Common breaking changes:
# - Renamed variables
# - Removed outputs
# - Changed resource structure (may recreate resources!)

# Step 1: Update version constraint
module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"    # Was "~> 3.0"
}

# Step 2: Re-init
terraform init -upgrade
 
# Step 3: Plan and review carefully
terraform plan
# ⚠️ Watch for resources being DESTROYED and recreated
 
# Step 4: Apply in non-prod first
terraform apply

# Pin to tag
module "vpc" {
  source = "git::https://github.com/org/modules.git//vpc?ref=v5.0.0"
}
 
# Pin to commit (most stable)
module "vpc" {
  source = "git::https://github.com/org/modules.git//vpc?ref=abc123f"
}