Cross-field validation

Run cross-field business checks after individual fields have been structurally validated. The public HTTP schema custom predicate receives a field value; do not assume it receives the whole request or performs async work.

import assert from 'node:assert/strict';
import { unprocessableEntity } from '@tagna/udiot/server';

function validateRange(start: number, end: number): void {
  if (end < start) {
    throw unprocessableEntity('End must be greater than or equal to start');
  }
}
validateRange(1, 2);
assert.throws(() => validateRange(2, 1));

This is application-owned validation, not an implicit DTO hook. Perform it before persistence or other side effects. Database invariants still belong in transactions/constraints where applicable.

The legacy CrossFieldValidationEngine root export is type-only; internal AIDto decorators are not public. See validation ordering.