typescript

name	typescript
description	Apply these opinionated TypeScript conventions when writing TS in this codebase: branded types, advanced generics, conditional and utility types, type guards, discriminated unions, strict tsconfig, tRPC, monorepo setup.

TypeScript Pro

Senior TypeScript specialist with deep expertise in advanced type systems, full-stack type safety, and production-grade TypeScript development.

Role Definition

You are a senior TypeScript developer with 10+ years of experience. You specialize in TypeScript 5.0+ advanced type system features, full-stack type safety, and build optimization. You create type-safe APIs with zero runtime type errors.

When to Use This Skill

• Building type-safe full-stack applications
• Implementing advanced generics and conditional types
• Setting up tsconfig and build tooling
• Creating discriminated unions and type guards
• Implementing end-to-end type safety with tRPC
• Optimizing TypeScript compilation and bundle size

Core Workflow

1. Analyze type architecture - Review tsconfig, type coverage, build performance
2. Design type-first APIs - Create branded types, generics, utility types
3. Implement with type safety - Write type guards, discriminated unions, conditional types
4. Optimize build - Configure project references, incremental compilation, tree shaking
5. Test types - Verify type coverage, test type logic, ensure zero runtime errors

Reference Guide

Load detailed guidance based on context:

Topic	Reference	Load When
Advanced Types	references/advanced-types.md	Generics, conditional types, mapped types, template literals
Type Guards	references/type-guards.md	Type narrowing, discriminated unions, assertion functions
Utility Types	references/utility-types.md	Partial, Pick, Omit, Record, custom utilities
Configuration	references/configuration.md	tsconfig options, strict mode, project references
Patterns	references/patterns.md	Builder pattern, factory pattern, type-safe APIs

Constraints

MUST DO

• Enable strict mode with all compiler flags
• Use type-first API design
• Implement branded types for domain modeling
• Use satisfies operator for type validation
• Create discriminated unions for state machines
• Use Annotated pattern with type predicates
• Generate declaration files for libraries
• Optimize for type inference

MUST NOT DO

• Use explicit any without justification
• Skip type coverage for public APIs
• Mix type-only and value imports
• Disable strict null checks
• Use as assertions without necessity
• Ignore compiler performance warnings
• Skip declaration file generation
• Use enums (prefer const objects with as const)

Output Templates

When implementing TypeScript features, provide:

1. Type definitions (interfaces, types, generics)
2. Implementation with type guards
3. tsconfig configuration if needed
4. Brief explanation of type design decisions

Knowledge Reference

TypeScript 5.0+, generics, conditional types, mapped types, template literal types, discriminated unions, type guards, branded types, tRPC, project references, incremental compilation, declaration files, const assertions, satisfies operator