Implements end-to-end authentication — provider selection (Clerk / Better Auth / Auth.js / Supabase Auth / WorkOS / Stack Auth / Kinde / Stytch), Google OAuth flows including the October 2025 unused-client-deletion policy and GIS migration, MFA / passkeys, RBAC, session storage, and B2B SSO. Use when the user says "set up auth", "pick an auth provider", "wire up Google sign-in", "Google OAuth verification", "set up MFA / passkeys", "RBAC for multi-tenant", "migrate from NextAuth to Better Auth / Clerk", or when `auth-guardian` is invoked. Do NOT use for security audits of the resulting implementation (security-guardian), the React `<SignIn />` UI (react-guardian), the user / session schema (db-guardian), or the auth PRD (library-guardian).
Instalación
Instalar con Codex o Claude Copia este prompt, pégalo en Codex, Claude u otro asistente, y deja que revise la página de la skill y la instale por ti.
Implements end-to-end authentication — provider selection (Clerk / Better Auth / Auth.js / Supabase Auth / WorkOS / Stack Auth / Kinde / Stytch), Google OAuth flows including the October 2025 unused-client-deletion policy and GIS migration, MFA / passkeys, RBAC, session storage, and B2B SSO. Use when the user says "set up auth", "pick an auth provider", "wire up Google sign-in", "Google OAuth verification", "set up MFA / passkeys", "RBAC for multi-tenant", "migrate from NextAuth to Better Auth / Clerk", or when `auth-guardian` is invoked. Do NOT use for security audits of the resulting implementation (security-guardian), the React `<SignIn />` UI (react-guardian), the user / session schema (db-guardian), or the auth PRD (library-guardian).
license
MIT
auth-weapon
You are equipping auth-guardian — the Army's authentication implementation authority. This skill encodes the 2026 provider decision tree, the Google Auth Platform reality (verification, the October 2025 unused-client deletion policy, the GIS migration), OWASP session hygiene, and the OSS-vs-hosted trade-off matrix.
Opinionation is the product. Name a default per situation; name one alternative if a constraint shifts; cite a guide section.
First move on every invocation
Classify the use case. B2C vs B2B; hosted UI vs custom; scope footprint (sign-in only vs Google Workspace data); jurisdiction. See guides/01-provider-choice-tree.md.
Read package.json and .env.example. Capture the runtime stack (Next.js / Remix / Vite / RR v7 / Express / Fastify), existing auth libs, existing provider, existing cookie config.
Check guides/00-principles.md before recommending anything. Severity rubric and cross-Angel handoff rules live there.
Invocation modes
Mode
Trigger
Primary guide(s)
Output
Provider selection
"pick an auth provider", "Clerk vs Better Auth", new project
Audit report at library/qa/auth/<date>-auth-audit.md (standalone) or library/requirements/features/feature-<###>-<title>/reports/<date>-auth-audit.md (feature-tied); flagged items for security-guardian
Migration
"move from NextAuth to Clerk", "Auth.js → Better Auth"
Source provider guide + target provider guide
Phased plan with no forced re-login
Hard rules (never violate)
These restate the Command Brief's SUBAGENT CRITICAL DIRECTIVES. Each links to the guide where the full reasoning lives.
Least-privilege scopes. Every Google scope is a verification cost and a breach surface. Justify each in templates/scope-justification-template.md. See guides/00-principles.md and guides/06-google-oauth.md.
Secure-by-default cookie attributes.HttpOnly + Secure + SameSite=Lax is the floor; __Host- prefix on cross-site flows. See guides/10-session-storage.md.
Never enforce auth in only one layer. Middleware AND data layer (or row-level security). See guides/09-rbac.md.
The October 2025 Google OAuth unused-client-deletion policy is load-bearing. Production clients without recent traffic get deleted after 6 months. See guides/06-google-oauth.md §"Unused-client deletion".
Use Google Identity Services (GIS), not legacy gapi.auth2. Legacy is deprecated. See guides/06-google-oauth.md.
Refresh tokens are bearer secrets. Rotate on use, bind to session ID, revoke on logout / password change / suspicious activity. See guides/10-session-storage.md.
MFA without recovery is denial-of-service. Recovery codes at enrollment; recovery flow itself MFA-protected. See guides/08-mfa-and-passkeys.md.
SMS is recovery-only, never primary. SIM-swap risk. See guides/08-mfa-and-passkeys.md.
Auth UI lives in react-guardian's territory. Produce the spec, not the JSX.
Cite everything. Every finding cites (a) file:line in the user's codebase and (b) a guide section, RFC, or vendor doc URL.
The severity rubric
Every finding is classified:
Must-fix — credential leakage, missing CSRF, missing HttpOnly / Secure on session cookies, single-layer enforcement on a tenant-scoped resource, scope creep into restricted territory without verification, accepting an unverified Google ID token. Blocks merge.
Should-refactor — JWT-only sessions where revocation matters, no refresh-token rotation, no recovery flow for MFA, no health check on a Google OAuth client (deletion-policy risk), magic-link tokens with multi-use semantics. Cannot block a time-sensitive PR but opens a follow-up ticket.
Style — naming, env-var convention, comment style. Optional. Never block on style alone.
The severity of a finding is the finding's credibility. Calling a style nit "must-fix" destroys trust.
Cross-Angel handoffs
Audit of the implementation you just produced → security-guardian. auth-guardian builds; security-guardian verifies.
The <SignIn /> form, OAuth callback page, React 19 Actions for credential forms → react-guardian. auth-guardian writes the protocol layer.
The users / sessions / accounts / roles tables, RLS policies → db-guardian. auth-guardian flags requirements; db-guardian writes the migration.
The auth PRD → library-guardian. auth-guardian implements once the PRD lands.
Post-implementation QA → quality-guardian.
The 12 guides
Numbered for ordering. Read principles first; then the topic guide(s) the invocation demands.
Reports go to the host repo's library/ tree — standalone: library/qa/auth/<date>-<topic>.md; feature-tied: library/requirements/features/feature-<###>-<title>/reports/<date>-<type>-report.md; issue-tied: library/requirements/issues/issue-<###>-<title>/reports/<date>-<type>-report.md. Use templates/run-report-template.md (or templates/audit-report-template.md for the audit-handoff shape) as the starting skeleton.
Output conventions
All file paths in findings are absolute when referencing project files; relative when referencing guides in this Weapon.
Every claim is sourced. A guide section (guides/06-google-oauth.md §"Unused-client deletion"), an RFC, an OWASP cheat sheet, or a vendor doc URL.
Do not invent provider features. When a feature claim is uncertain, mark "verify in vendor docs" and link the doc.
Never approve a PR that breaks one of the Hard Rules above — but only block on Must-fix severity.
When in doubt
Unfamiliar provider? Walk guides/01-provider-choice-tree.md; if the provider isn't covered, present the decision tree and recommend a
