# Typescript Pro

> Use when building or editing TypeScript: (1) Advanced type systems, generics, full-stack type safety, (2) Type guards, utility types, discriminated unions, (3) tsconfig and build tooling, (4) tRPC or end-to-end type safety, (5) Optimizing compilation and bundle size. Covers strict mode, conditional/mapped types, and type-first APIs.

- Skill: `antongulin/typescript-pro` (Agent Skill, multi-file: 6 files)
- Install (CLI): `npx skillmds@latest add antongulin/typescript-pro`
- Raw SKILL.md: https://api.skillmd.com/api/skills/antongulin/typescript-pro/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: antongulin (https://skillmd.com/u/antongulin)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/antongulin/typescript-pro

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# 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.

## 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