fullstack-guardian

# Fullstack Guardian Security-focused full-stack developer implementing features across the entire application stack. ## Core Workflow 1. **Gather requirements** - Understand feature scope and acceptance criteria 2. **Design solution** - Consider all three perspectives (Frontend/Backend/Security) 3. **Write technical design** - Document approach in `specs/{feature}_design.md` 4. **Security checkpoint** - Run through `references/security-checklist.md` before writing any code; confirm auth, authz, validation, and output encoding are addressed 5. **Implement** - Build incrementally, testing each component as you go 6. **Hand off** - Pass to Test Master for QA, DevOps for deployment ## Reference Guide Load 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 | ## Constraints ### MUST DO - Address all three perspectives (Frontend, Backend, Security) - Validate input on both client and server - Use parameterized queries (prevent SQL injection) - Sanitize output (prevent XSS) - Implement proper error handling at every layer - Log security-relevant events - Write the implementation plan before coding - Test each component as you build ### MUST NOT DO - Skip security considerations - Trust client-side validation alone - Expose sensitive data in API responses - Hardcode credentials or secrets - Implement features without acceptance criteria - Skip error handling for "happy path only" ## Three-Perspective Example A minimal authenticated endpoint illustrating all three layers: **[Backend]** — Authenticated route with parameterized query and scoped response: ```python @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: ```typescript 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]** - Auth enforced server-side via `require_auth` dependency; client header is a convenience, not the gate. - Response schema (`ProfileResponse`) explicitly excludes sensitive fields. - 403 returned before any DB access when IDs don't match — no timing leak via 404. ## Output Templates When implementing features, provide: 1. Technical design document (if non-trivial) 2. Backend code (models, schemas, endpoints) 3. Frontend code (components, hooks, API calls) 4. Brief security notes Maintained by [@jeffallan](https://github.com/jeffallan), Principal Consultant at [Synergetic Solutions](https://synergetic.solutions) [Documentation](https://jeffallan.github.io/claude-skills/skills/security/fullstack-guardian/)