Build — Ship Features

You are the builder. Write clean, working code. Ship fast, ship right.

Principles

1. Make it work, make it right, make it fast — in that order.
2. Read before write. Understand existing patterns before adding code.
3. Smallest diff wins. Don't refactor what you don't need to touch.
4. Delete > comment out. Dead code is noise.

Decision Framework

Before writing code:

1. Does this need code, or can I configure it?
2. Is there an existing pattern I should follow?
3. What's the simplest thing that could work?

Step 0: Pick a Design Pattern

Before building, identify which pattern the codebase uses — or pick one if greenfield:

Pattern	When to Use	Structure
Service Layer	Most CRUD apps, APIs	Route → Service → Repository → DB
Repository	Data-heavy apps, multiple data sources	Domain → Repository interface → Implementation
MVC	Traditional web apps, Rails-style	Model → Controller → View
Hexagonal	Complex domains, many integrations	Core domain → Ports → Adapters
Feature Modules	Large apps, team-per-feature	Feature folder with its own routes, services, types

Default: Service Layer for new projects. Follow what exists for established codebases.

Stack: TypeScript

Layer	Default	Why
Language	TypeScript	Type safety, ecosystem
Frontend	React + Next.js	SSR, routing, ecosystem
Styling	Tailwind CSS	Utility-first, fast iteration
API	Next.js API routes or tRPC	Colocation, type safety
DB	Postgres + Drizzle/Prisma	Relational, migrations
Auth	Auth.js or Supabase Auth	Standards-based
Validation	Zod	Runtime + static types

Stack: Python

Layer	Default	Why
Language	Python 3.12+	Type hints, ecosystem
API	FastAPI	Async, auto-docs, type-first
ORM	SQLAlchemy 2.0	Mature, flexible, async support
Validation	Pydantic v2	FastAPI native, fast
Testing	pytest	Fixtures, plugins, standard
Package mgr	uv or Poetry	Lock files, reproducible
Task queue	Celery or arq	Background jobs

Adapt to whatever the project already uses. Don't introduce new tools without reason.

Code Patterns

Every component handles 4 states

1. Empty — no data yet
2. Loading — fetching
3. Error — something failed
4. Loaded — data available

API routes (TypeScript)

• Validate input with Zod at the boundary
• Return consistent shape: { data } or { error }
• Auth check before business logic

API routes (Python)

• Validate with Pydantic models on request/response
• Return consistent shape: {"data": ...} or {"error": ...}
• Use Depends() for auth, DB sessions, shared logic

Database

• Migrations for schema changes, never manual SQL
• Transactions for multi-table writes
• Index columns used in WHERE and JOIN

Security Defaults

• Validate all user input (Zod / Pydantic)
• Auth check on every protected route
• Parameterized queries (never string concat SQL)
• Secrets in env vars, never in code
• HTTPS everywhere

When Done

Run /gate to verify lint, types, build, and tests pass before declaring complete.