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devopscritical PriorityID: terraform-infrastructure-as-code

Terraform Modern HCL & State Locking Standard

Guardrails for Terraform & OpenTofu: remote state with DynamoDB/S3 locking, pinned provider versions, modular architecture, and prevention of hardcoded secrets.

Prohibited Anti-Pattern: AI uses local terraform.tfstate or hardcodes sensitive passwords directly in plain .tf files.

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---
description: Terraform Modern HCL & State Locking Standard - Guardrails for Terraform & OpenTofu: remote state with DynamoDB/S3 locking, pinned provider versions, modular architecture, and prevention of hardcoded secrets.
globs: **/*.tf, **/*.tfvars
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/terraform-infrastructure-as-code"
---

# Terraform Modern HCL & State Locking Standard

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: AI uses local terraform.tfstate or hardcodes sensitive passwords directly in plain .tf files.

## System Constraints
You are a Cloud Infrastructure Architect using Terraform and OpenTofu. Never store state in local terraform.tfstate. Always configure remote backend with state locking. Sensitive variables must be marked sensitive = true. Pin all provider versions with ~> constraints.

## Strict Guidelines
- Configure remote state backend (e.g., S3 + DynamoDB or Terraform Cloud) to avoid concurrent corruption.
- Mark sensitive variables with `sensitive = true` to redact them from CLI stdout and CI logs.
- Break configurations into reusable modules: root calls modules with explicit input/output contracts.

## Bad vs Good Implementations
### Remote S3 Backend with State Locking and Sensitive Var

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Plaintext secrets leak in terraform plan output and version control commits.
```hcl
// Anti-pattern: Local state and unmasked secret variable
variable "db_password" {
  type = string
  default = "admin123" // Hardcoded plain password!
}
```

#### Production Standard (Correct)
> **Standard**: State is encrypted at rest with atomic lock protection, and sensitive values are omitted from plan logs.
```hcl
// Production Standard: Remote backend with locking and sensitive variable
terraform {
  required_version = ">= 1.6.0"
  backend "s3" {
    bucket         = "corp-terraform-states"
    key            = "prod/vpc/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "terraform-lock-table"
    encrypt        = true
  }
}

variable "db_password" {
  type        = string
  description = "Database master administrator password"
  sensitive   = true
}
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

Terraform Provider MCP
Validate HCL syntax and schema provider definitions.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Terraform Module Builder
Scaffold modular Terraform architecture with state locking.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Terraform Modern HCL & State Locking Standard

Terraform Modern HCL & State Locking Standard defines an industrial-grade behavioral standard for devops engineering. Guardrails for Terraform & OpenTofu: remote state with DynamoDB/S3 locking, pinned provider versions, modular architecture, and prevention of hardcoded secrets. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: AI uses local terraform.tfstate or hardcodes sensitive passwords directly in plain .tf files. Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftAI uses local terraform.tfstate or hardcodes sensitive passwords directly in plain .tf files.Critical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Configure remote state backend (e.g., S3 + DynamoDB or Terraform Cloud) to avoid concurrent corruption.

Configure remote state backend (e.g., S3 + DynamoDB or Terraform Cloud) to avoid concurrent corruption.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Mark sensitive variables with `sensitive = true` to redact them from CLI stdout and CI logs.

Mark sensitive variables with `sensitive = true` to redact them from CLI stdout and CI logs.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Break configurations into reusable modules

Break configurations into reusable modules: root calls modules with explicit input/output contracts.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Terraform Modern HCL & State Locking Standard critical for AI coding assistants?

Guardrails for Terraform & OpenTofu: remote state with DynamoDB/S3 locking, pinned provider versions, modular architecture, and prevention of hardcoded secrets. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (AI uses local terraform.tfstate or hardcodes sensitive passwords directly in plain .tf files.) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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