terragrunt-generator

The saved excerpt is a snapshot from review. The external source remains the complete and most current version.

---
name: terragrunt-generator
description: Generate/create/scaffold Terragrunt HCL files — root.hcl, terragrunt.hcl, child modules, stacks, multi-env layouts.
---

# Terragrunt Generator

## Overview

Generate production-ready Terragrunt configurations following current best practices, naming conventions, and security standards. All generated configurations are automatically validated.

## Trigger Phrases

Use this skill when the user asks for:
- A new `root.hcl`, `terragrunt.hcl`, or `terragrunt.stack.hcl`
- Multi-environment Terragrunt layouts (`dev/staging/prod`)
- Terragrunt dependency wiring (`dependency` or `dependencies` blocks)
- Terragrunt module source setup (local, Git, Terraform Registry via `tfr:///`)
- Stack catalog unit generation under `catalog/units/*`

**Terragrunt 2025 Features Supported:**
- [Stacks](https://terragrunt.gruntwork.io/docs/features/stacks/) - Infrastructure blueprints with `terragrunt.stack.hcl` (GA since v0.78.0)
- [Feature Flags](https://terragrunt.gruntwork.io/docs/features/feature-flags/) - Runtime control via `feature` blocks
- [Exclude Blocks](https://terragrunt.gruntwork.io/docs/reference/config-blocks-and-attributes/#exclude) - Fine-grained execution control (replaces deprecated `skip`)
- [Errors Blocks](https://terragrunt.gruntwork.io/docs/reference/config-blocks-and-attributes/#errors) - Advanced error handling (replaces deprecated `retryable_errors`)
- [OpenTofu Engine](https://terragrunt.gruntwork.io/docs/features/engine/) - Alternative IaC engine support

## Root Configuration Naming

> **RECOMMENDED**: Use `root.hcl` instead of `terragrunt.hcl` for root files per [migration guide](https://terragrunt.gruntwork.io/docs/migrate/migrating-from-root-terragrunt-hcl).

| Approach | Root File | Include Syntax |
|----------|-----------|----------------|
| **Modern** | `root.hcl` | `find_in_parent_folders("root.hcl")` |
| **Legacy** | `terragrunt.hcl` | `find_in_parent_folders()` |

**Include standard:** Default to `find_in_parent_folders("root.hcl")` in all new examples and generated configs. Use `find_in_parent_folders()` only when explicitly targeting a legacy root file named `terragrunt.hcl`.

## Architecture Patterns

> **CRITICAL:** Before generating ANY configuration, you MUST determine the architecture pattern and understand its constraints.

### Pattern A: Multi-Environment with Environment-Agnostic Root

**Use when:** Managing multiple environments (dev/staging/prod) with shared root configuration.

**Key principle:** `root.hcl` is **environment-agnostic** - it does NOT read environment-specific files.

```
infrastructure/
├── root.hcl              # Environment-AGNOSTIC (no env.hcl references)
├── dev/
│   ├── env.hcl           # Environment variables (locals block)
│   ├── vpc/terragrunt.hcl
│   └── rds/terragrunt.hcl
└── prod/
    ├── env.hcl           # Environment variables (locals block)
    ├── vpc/terragrunt.hcl
    └── rds/terragrunt.hcl
```

**Root.hcl constraints:**
- ❌ CANNOT use `read_terragrunt_config(find_in_parent_folders("env.hcl"))` - env.hcl doesn't exist at root level
- ❌ CANNOT reference `local.environment` or `local.aws_region` that come from env.hcl
- ✅ CAN use static values or `get_env()` for runtime configuration
- ✅ CAN use `${path_relative_to_include()}` for state keys (this works dynamically)

**Child modules read env.hcl:**
```hcl
# dev/vpc/terragrunt.hcl
include "root" {
  path = find_in_parent_folders("root.hcl")
}

locals {
  env = read_terragrunt_config(find_in_parent_folders("env.hcl"))
}

inputs = {
  name = "${local.env.locals.environment}-vpc"  # Works: env.hcl exists in dev/
}
```

### Pattern B: Single Environment or Environment-Aware Root

**Use when:** Single environment OR all environments share the same root with environment detection.

```
infrastructure/
├── root.hcl              # Can be environment-aware via get_env() or directory parsing
├── account.hcl           # Account-level config (optional)
├── region.hcl            # Region-