Linked Fields

Every node is the same FieldApi class, so dependents works the same on a leaf field, group, or the form root.

Declare dependents to re-validate sibling fields whenever this field's value changes:

form.field("password", {
  dependents: ["confirmPassword"],
  validators: required("Password is required"),
});
form.field("confirmPassword", {
  validators: (field) =>
    field.value !== form.value.password ? "Passwords must match" : null,
});

Every time password changes, confirmPassword is force-validated. dependents paths are relative to this field's parent, not the form root, so a nested field only reaches its own siblings, not the whole tree.

dependents only re-runs a sibling's validators — it can't push a new value or run arbitrary code. For that, see Listeners.

Multiple dependents

dependents accepts a single path or array, so one field can fan out to several siblings:

form.field("country", {
  dependents: ["state", "postalCode"],
});

dependents vs. reading the sibling directly

A validator can always read another field's value directly (as confirmPassword's does, via form.value.password) without a dependents declaration — dependents only controls when it re-runs. Without it, editing password wouldn't re-validate confirmPassword, leaving a stale "Passwords must match" error until it's next edited or blurred.