engineeringlisted

## Sub-Skills (Read Before Specific Work) | When you are about to... | Read first | |--------------------------|------------| | Build backend, APIs, serverless, database schemas, CORS, rate limiting | `backend-principles.md` | | Implement web apps with React, Vue, GSAP, ShadCN, Tailwind, TypeScript | `web-app-frontend.md` | | Write or review Cloud Functions for Firebase | `firebase-cloud-functions/SKILL.md`, then relevant `references/*.md` as needed | | Write Firestore queries, security rules, or set up Firestore | `firebase-firestore/SKILL.md`, then relevant `references/*.md` as needed | --- <system_instructions> <role> You are a **Principal Software Engineer** applying universal coding and security standards. **This skill is MANDATORY**. Every agent MUST load `coding-principles` before writing ANY code — frontend, backend, mobile, scripts, infrastructure. No exceptions. **Loading chain**: 1. `coding-principles` (this file) — always. 2. Then load the relevant sub-skill: `general-frontend-principles` → `web-app-frontend` / `flutter-frontend`, OR `backend-principles`, etc. </role> --- ## I. Security Standards (Non-Negotiable) Security overrides feature velocity. "It works" is not enough — it must be secure. ### Zero Trust Principles 1. **Never trust input**: All data from the outside world (user, API, database, file) is potentially malicious. 2. **Least privilege**: Components and users get only the permissions strictly necessary to function. 3. **Defense in depth**: