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Builds security-focused full-stack web applications by implementing integrated frontend and backend components with layered security at every level. Covers the complete stack from database to UI, enfo
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Paste the copied command in a terminal. It installs this SKILL.md into that agent.
npx skills add Jeffallan/claude-skills --skill fullstack-guardian -a cursor -y
Builds security-focused full-stack web applications by implementing integrated frontend and backend components with layered security at every level. Covers the complete stack from database to UI, enforcing auth, input validation, output encoding, and parameterized queries across all layers. Use when implementing features across frontend and backend, building REST APIs with corresponding UI, connecting frontend components to backend endpoints, creating end-to-end data flows from database to UI, or implementing CRUD operations with UI forms. Distinct from frontend-only, backend-only, or API-only skills in that it simultaneously addresses all three perspectives—Frontend, Backend, and Security—within a single implementation workflow. Invoke for full-stack feature work, web app development, authenticated API routes with views, microservices, real-time features, monorepo architecture, or technology selection decisions.
Builds security-focused full-stack web applications by implementing integrated frontend and backend components with layered security at every level. Covers the complete stack from database to UI, enforcing auth, input validation, output encoding, and parameterized queries across all layers. Use when implementing features across frontend and backend, building REST APIs with corresponding UI, connecting frontend components to backend endpoints, creating end-to-end data flows from database to UI, or implementing CRUD operations with UI forms. Distinct from frontend-only, backend-only, or API-only skills in that it simultaneously addresses all three perspectives—Frontend, Backend, and Security—within a single implementation workflow. Invoke for full-stack feature work, web app development, authenticated API routes with views, microservices, real-time features, monorepo architecture, or technology selection decisions.
Security-focused full-stack developer implementing features across the entire application stack.
specs/{feature}_design.mdreferences/security-checklist.md before writing any code; confirm auth, authz, validation, and output encoding are addressedLoad detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| Design Template | references/design-template.md | Starting feature, three-perspective design |
| Security Checklist | references/security-checklist.md | Every feature - auth, authz, validation |
| Error Handling | references/error-handling.md | Implementing error flows |
| Common Patterns | references/common-patterns.md | CRUD, forms, API flows |
| Backend Patterns | references/backend-patterns.md | Microservices, queues, observability, Docker |
| Frontend Patterns | references/frontend-patterns.md | Real-time, optimization, accessibility, testing |
| Integration Patterns | references/integration-patterns.md | Type sharing, deployment, architecture decisions |
| API Design | references/api-design-standards.md | REST/GraphQL APIs, versioning, CORS, validation |
| Architecture Decisions | references/architecture-decisions.md | Tech selection, monolith vs microservices |
| Deliverables Checklist | references/deliverables-checklist.md | Completing features, preparing handoff |
A minimal authenticated endpoint illustrating all three layers:
[Backend] — Authenticated route with parameterized query and scoped response:
@router.get("/users/{user_id}/profile", dependencies=[Depends(require_auth)])
async def get_profile(user_id: int, current_user: User = Depends(get_current_user)):
if current_user.id != user_id:
raise HTTPException(status_code=403, detail="Forbidden")
# Parameterized query — no raw string interpolation
row = await db.fetchone("SELECT id, name, email FROM users WHERE id = ?", (user_id,))
if not row:
raise HTTPException(status_code=404, detail="Not found")
return ProfileResponse(**row) # explicit schema — no password/token leakage
[Frontend] — Component calls the endpoint and handles errors gracefully:
async function fetchProfile(userId: number): Promise<Profile> {
const res = await apiFetch(`/users/${userId}/profile`); // apiFetch attaches auth header
if (!res.ok) throw new Error(await res.text());
return res.json();
}
// Client-side input guard (never the only guard)
if (!Number.isInteger(userId) || userId <= 0) throw new Error("Invalid user ID");
[Security]
require_auth dependency; client header is a convenience, not the gate.ProfileResponse) explicitly excludes sensitive fields.When implementing features, provide:
Maintained by @jeffallan, Principal Consultant at Synergetic Solutions