diff --git a/.claude/guidelines/terraform_style_guide.md b/.claude/guidelines/terraform_style_guide.md
new file mode 100644
index 0000000..e12674f
--- /dev/null
+++ b/.claude/guidelines/terraform_style_guide.md
@@ -0,0 +1,37 @@
+# Terraform Style Guide (Project Overrides)
+
+## Project status
+
+**Legacy compatibility mode.** This code is in production with real clients. It was written before the house Terraform style guide (`<PATH>`) was adopted. A V2 will refactor to current standards; until then, minimize churn.
+
+<!-- TODO(#325): replace `<PATH>` above with the actual location of the house Terraform style guide once it is published. -->
+
+## Style-guide applicability (overrides global)
+
+The Terraform style guide applies to:
+
+- **New files** being added.
+- **Bug fixes** — keep the fix minimal. Do not bundle stylistic cleanup.
+- **Security findings** from checkov / trivy / terrascan — fix or consciously suppress with reason.
+
+The style guide does NOT apply to:
+
+- **Renaming existing resources** (requires `moved {}` blocks or `terraform state mv` — both blast-radius).
+- **Restructuring existing files** to match the strict module layout.
+- **Converting `count` → `for_each`** on existing resources (causes destroy/recreate).
+- **Backfilling `description` / `type` / `sensitive`** on pre-existing variables/outputs unless the user explicitly asks.
+- **Argument ordering changes** inside existing resource/variable/output blocks.
+
+## When a linter flags existing code
+
+1. **Do NOT auto-fix.** Surface the finding with `file:line`.
+2. Propose **suppression first** (inline `# tflint-ignore:<rule>` / `# checkov:skip=<id>: <reason>`), refactor second — and only on explicit user request.
+3. Accumulated suppressions = breadcrumbs for the V2 migration.
+
+## Blast radius — additional rules for this repo
+
+Beyond the global rails:
+
+- `terraform state mv` / `rm` / `import` are **forbidden without a written migration plan in the PR description**.
+- Resource renames require a `moved {}` block AND explicit user confirmation of `terraform plan` output before apply.
+- Any refactor that changes resource addresses (module extraction, renaming, loop-style changes) is a V2 concern and should be flagged, not attempted.
diff --git a/CLAUDE.md b/CLAUDE.md
index db0ed5e..3632b60 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -14,7 +14,7 @@ References in the table below use these prefixes:
 |-----------|----------|
 | ALWAYS DO FOR ALL TASKS | `proj:variable_default_values.md` |
 | Any PR that changes deployer-visible behaviour (variables, component config, components added/removed) | `proj:changelog_protocol.md` |
-| Writing or editing Terraform (`*.tf`, `terraform.tfvars`) | `proj:terraform_conventions.md` |
+| Writing or editing Terraform (`*.tf`, `terraform.tfvars`) | `proj:terraform_conventions.md`, `proj:terraform_style_guide.md` |
 | Writing or editing Python | `proj:python_standards.md` |
 | Running, writing, or analysing tests | `proj:testing_strategy.md`, `proj:testing_commands.md` |
 | Working on security-sensitive code (secrets, IAM, SSM, certificates) | `proj:security_considerations.md` |
@@ -75,7 +75,7 @@ For test commands and structured-logging tooling, see [`proj:testing_commands.md
 ## Project Structure
 
 ### Core Infrastructure (`*.tf` files)
-Sequential numbered files defining infrastructure resources in dependency order.
+Sequential numbered files defining infrastructure resources in (rough) dependency order.
 
 ### Python Scripts (`scripts/`)
 - `scripts/installer/validation/` - Configuration validation