When parsing inputs that may be invalid (e.g., string → boolean), do not rely on implicit/unclear failure behavior. Instead, decide explicitly how parse errors should be handled and make it deterministic. Apply this by: - Using a safe fallback for parse errors (e.g., Zod `.catch(...)`) so invalid values consistently map to a chosen boolean. - Ensuring the parsing semantics match your intent: `z.string().boolean()` uses logical string values (like "true"/"false"), which may differ from TypeScript/JS `Boolean()` behavior—use `z.coerce.boolean()` when you want coercion semantics. Example (explicit error recovery to a boolean): ```ts import { z } from "zod"; // Logical boolean parsing with deterministic fallback on error const b = z.string() .boolean() .catch(() => false); // whenever parsing fails b.parse("true"); // true b.parse("False"); // false b.parse("other"); // false (fallback) ``` If you expect JS-like coercion semantics instead of strict logical strings, prefer: ```ts const b = z.coerce.boolean(); ```