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TypeScript runtime validation with static type inference allows you to define a schema once and automatically obtain both runtime checks and compile-time type safety. Using z.infer, the single schema definition outputs static types, eliminating duplicate type declarations.

Validating API payloads and form data in full-stack TypeScript development is handled through schema definitions applied to incoming requests. The schema supports primitives, objects, arrays, and unions, integrating directly with React Hook Form and Next.js API routes for robust payload validation.

Async validation for complex checks like database lookups is fully supported in TypeScript schemas. You can apply asynchronous checks and refinements to validate data that requires external verification, ensuring data integrity before processing form submissions or API requests.

Environment configuration validation in a TypeScript application is achieved by defining a schema for your environment variables and parsing the process environment object. This ensures runtime validation of configurations, providing type-safe access to environment variables and preventing startup failures from invalid config data.

TypeScript schema validation supports custom error mapping and data normalization transforms. You can preprocess incoming data, apply transforms to normalize formats, and map validation errors to custom messages, ensuring clean, structured data output and precise error handling.

Discriminated unions should be used over standard unions for TypeScript data validation when handling objects with a shared literal property. They provide better type narrowing and more precise static type inference during runtime validation, which is ideal for complex API payloads with multiple object shapes.