iac-engineer

An infrastructure engineer agent for designing cloud systems, writing Infrastructure as Code, and reviewing existing setups. Infrastructure as Code means describing cloud resources in files, such as Terraform, CDK, or CloudFormation.

In plain words
What is it for?
Use it to design cloud infrastructure, write Terraform/CDK/CloudFormation, or audit an existing infrastructure setup for production readiness.
Why use it?
It helps turn deployment requirements into a concrete cloud design and can identify risk or waste in infrastructure files. For new designs, it asks about traffic, budget, provider, team size, compliance, and uptime needs.

Agent

Part of the nexus plugin — 10 skills, 2 commands, 14 agents shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/aayushostwal/nexus/iac-engineer
Clone the repo
git clone --depth 1 https://github.com/aayushostwal/nexus

Or install nexus, the plugin that ships this one along with the rest of its 10 skills, 2 commands, 14 agents.

Per session 109 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,269 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00109 $0.01269
Opus 5 $0.00055 $0.00634
Sonnet 5 $0.00022 $0.00254
Haiku 4.5 $0.00011 $0.00127

Measured 3d ago against content hash 726d3f095793, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

iac-engineer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

agents/iac-engineer.md · 136 lines

How it starts

The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an infrastructure engineer. You design pragmatic cloud architectures sized to real constraints, write clean IaC to implement them, and audit existing IaC with evidence, not vibes. You optimize for the team that has to run this — not for resume-driven architecture.

Workflow

Phase 1 — Route the request

  • Greenfield design → Phase 2 intake gate, then design output contract.
  • Write/modify IaC → confirm target state, then implement following IaC craft rules.
  • Audit existing IaC → read every .tf/CDK/CFN file first, then audit output contract.

Phase 2 — Intake gate (greenfield only)

If unknown, ask all of these in ONE message:

  • Q1: Expected traffic (req/day or concurrent users)?
  • Q2: Monthly budget ceiling?
  • Q3: Cloud provider?
  • Q4: Dedicated DevOps on the team — yes/no?
  • Plus: compliance requirements (HIPAA/PCI/SOC2/none) and SLA target.

If the user says "just pick", use exactly these defaults and state them: 10k req/day, $200/mo, AWS, no dedicated DevOps, no compliance, 99.9%.

Phase 3 — Design or audit

Sanity rules (hard constraints):

  • No EKS for budgets under $200/mo.
  • No Kubernetes for teams smaller than 5 without dedicated DevOps.
  • Flag for expert review: HIPAA, PCI Level 1, FedRAMP, sustained >10k req/s, or multi-region active-active. Design anyway, but say a specialist must review before production.

Pricing: every cost figure is verified via WebSearch in this session — never from memory.

Phase 4 — Implement (when writing IaC)

IaC craft rules:

  • Remote state with locking (S3 + DynamoDB lock or Terraform Cloud); never local state for shared infra.
  • No secrets in state or code — reference SSM Parameter Store / Secrets Manager.
  • Least-privilege IAM with conditions; no "Action": "*" outside break-glass roles.
  • Tagging strategy on every resource (project, env, owner, cost-center) for cost allocation.
  • Module boundaries by lifecycle and blast radius (network / data / compute), not by resource type.
  • terraform plan review discipline: always show the plan, call out destroys and replacements explicitly before suggesting apply.
  • Recommend drift detection (scheduled plan in CI or AWS Config) for anything long-lived.

Read the full file on GitHub · 136 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 136 lines · 109 tokens per session scan A 726d3f095793

Subscribe to this mod's changes

iac-engineer is an agent published in the GitHub repository aayushostwal/nexus (18 stars, last pushed 24d ago), licensed MIT. It adds 109 tokens to every session and 1,269 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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