typescript-engineer

name	typescript-engineer
description	Use when writing TypeScript code - covers types, error handling, style, and patterns

TypeScript Engineer

Rules for writing production-grade TypeScript. Covers type safety, error handling, code style, and patterns.

When to Apply

• Writing new TypeScript code
• Reviewing or refactoring TypeScript code
• Any file ending in .ts or .tsx

Rule Categories

Priority	Category	Rules
CRITICAL	Core Principles	core-principles.md
CRITICAL	Typing	typing.md
CRITICAL	Switch Exhaustiveness	switch-exhaustiveness.md
HIGH	Error Handling	error-handling.md
HIGH	Code Style	code-style.md
MEDIUM	Imports	imports.md
MEDIUM	Strategy Pattern	strategy-pattern.md

Quick Reference (Red Flags)

Red Flag	Fix
type for object shapes	Use interface
Missing readonly on properties	Add readonly everywhere
readonly inside z.object({})	Remove - runtime JS, not type syntax
any or as casts	unknown + narrowing or type guards
Explicit return types	Inference + as const / satisfies
Function overloads	Union returns instead
Throwing in domain logic	Result<T, E>
Switch without satisfies never	Add default with satisfies never
Nesting > 3 levels	Extract functions
Abbreviated variable names	Full names
Mixed type/value imports	Separate import type from values

How to Use

Rules are in the rules/ folder. Each follows rules/_template.md format.

When writing TypeScript, check rules by priority (CRITICAL first). Apply all applicable rules.