TypeScript Advanced Patterns Best Practices Type-level programming, library-author idioms, and feature-implementation patterns that go beyond surface uses of TypeScript 5.x. Contains 40 rules across 5 categories, prioritised by impact on consumer codebases. When to Apply Reference these guidelines when: - Designing a public library or DSL surface (fluent builders, event emitters, route parsers, query builders, schema-derived clients) - Writing type-level algorithms (recursive conditionals, accumulator pattern, key remapping, variadic tuples, type-level string/number ops, type-level tests) - U…