- Add typed fields to all error subclasses (taskId, cycles, field, message, prerequisite, dependent) - Set Object.setPrototypeOf(this, new.target.prototype) in all constructors - Add InvalidInputError.fromTypeBoxError() static factory for TypeBox Value.Errors() output - CircularDependencyError accepts string[][] for cycle paths - 31 unit tests covering instanceof chain, field access, .name property, and error messages