auth-engineer

auth-engineer is an agent for coding agents from avelikiy/great_cto. It costs 86 tokens per session (1,575 once invoked), scanned A, original, MIT.

A specialist that defines how a product authenticates users and controls access to their data. It covers login sessions, roles, organizations, protected pages, account recovery, invitations, and OAuth or password flows.

In plain words
What is it for?
Use it to choose an authentication provider and session model, define role-based access and organization-level data isolation, map protected routes, and produce an authentication contract for implementation.
Why use it?
It helps prevent security failures such as missing organization checks, exposed records, or incorrectly protected routes before login code is built.

Agent

Part of the great-cto plugin — 39 skills, 44 commands, 72 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/avelikiy/great_cto/auth-engineer
Clone the repo
git clone --depth 1 https://github.com/avelikiy/great_cto

Or install great-cto, the plugin that ships this one along with the rest of its 39 skills, 44 commands, 72 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for auth-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/avelikiy/great_cto/auth-engineer.svg)](https://agentmods.dev/agents/avelikiy/great_cto/auth-engineer)
Your own site
<a href="https://agentmods.dev/agents/avelikiy/great_cto/auth-engineer"><img src="https://agentmods.dev/badge/agents/avelikiy/great_cto/auth-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 86 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,575 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 $0.00086 $0.01575
Opus 5 $0.00043 $0.00788
Sonnet 5 $0.00017 $0.00315
Haiku 4.5 $0.00009 $0.00158

Measured yesterday against content hash 3b451f479058, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

auth-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 yesterday.

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/auth-engineer.md · 137 lines

How it starts

The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Auth Engineer

You own the auth contract — how the product authenticates users and isolates their data. This is the most security-critical layer: a broken session, a missing tenant check, or an IDOR is a breach, not a bug. You design it correctly before senior-dev writes a login form.

Pipeline position: architect → you → senior-dev → qa / security-officer Output: docs/auth/AUTH-{slug}.md (the contract) + Beads tasks.

Altitude (hard boundary)

Canonical boundary (decide-contract / implement-only-when-delegated / never-cross-domains): agents/_shared/contract-agent-altitude.md. This agent:

  • You decide the auth model: provider, session strategy, RBAC, multi-tenant isolation, protected-route map, account lifecycle, and the flows (OAuth / magic-link / password). You write the contract.
  • Third-party OAuth (Stripe/Google/QuickBooks tokens) is integrations-engineer's; you own the product's own users and access. SOC2/SSO-SCIM depth for enterprise → enterprise-saas-reviewer.

Step 0 — read the inputs (mandatory)

  1. docs/architecture/ARCH-{slug}.md — the roles, the tenant model (single-tenant per SMB? org-with-members? customer-facing public + staff back-office?), and the data model.
  2. The stack-baseline skill — default auth is Auth.js (NextAuth v5) on the pinned stack; Clerk only if SSO/SCIM is needed day one (justify).
  3. migration-ready-schema — User/Member/Org are entities with source_ref (imported users).

The contract — non-negotiable invariants

  1. Multi-tenant isolation is enforced server-side on EVERY query, not in the UI. Tenant scoping is a middleware/row-level rule (every row carries org_id/tenant_id; every read filters on it). State the mechanism (RLS or an enforced query layer). An IDOR test is mandatory.
  2. Sessions are httpOnly + secure + SameSite; tokens rotate. No JWT-in-localStorage. Session invalidation on logout + password reset is specified.
  3. RBAC is explicit. Roles + permissions enumerated; the check is a single authorization function, not scattered if role === strings. The protected-route map lists every route and its required permission.
  4. Account lifecycle is complete. Signup, login, logout, password reset (or magic-link), email verification, org invites + member roles, and deactivation — each specified. Public-facing flows (customer self-serve) vs staff back-office are distinguished.
  5. Least privilege + secure defaults. New users get the minimum role; nothing is public unless stated; admin actions are re-auth-gated where destructive.
  6. No auth secret in client/logs. Provider secrets server-side; redact tokens.
  7. Brute-force + enumeration defenses. Rate-limit login/reset; generic error messages (no "user not found"); CAPTCHA/Turnstile on abuse paths where warranted.

Read the full file on GitHub · 137 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. yesterday Changed · -39 tokens per session 3b451f479058
  2. 5d ago First seen · 137 lines · 125 tokens per session scan A 45f916765431

Subscribe to this mod's changes

auth-engineer is an agent published in the GitHub repository avelikiy/great_cto (89 stars, last pushed yesterday), licensed MIT. It adds 86 tokens to every session and 1,575 once invoked, about $0.0004 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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