Cost visibility and tag governance for platform changes. Estimates the monthly cost of a Terraform pull request with Infracost, sets up in-cluster cost allocation by namespace and label with OpenCost, and enforces required cost tags in four layers (Terraform default_tags and variable validation, a Conftest gate on the plan, AWS Config REQUIRED_TAGS, and a Kyverno namespace-label policy). Use when asked "what will this cost", "add cost estimates to PRs", "who owns this spend", "enforce cost-center tags", or "set up OpenCost". Cost as one dimension of a full PR review → /platform-skills:pr-review.