type-fest: Advanced TypeScript Utility Types

type-fest provides 180+ compile-time utility types with zero runtime overhead for production TypeScript applications. Use it when built-in TypeScript utilities are insufficient for strict type operations, deep transformations, or complex type-level programming.

When to Use This Skill

Activate for:

• API response/request type transformations (snake_case ↔ camelCase)
• Deep configuration merging and partial updates
• Immutable state management with readonly guarantees
• JSON serialization type safety (Date → string, etc.)
• Removing/selecting object properties with strict checking
• Type-safe path access and property selection
• Async function return type extraction
• Conditional type operations