/**
 * The `{$handler}` bridge's Kit half — the mark that tells a Kit control its
 * change handler belongs to a LIVE screen rather than to a one-shot host action.
 *
 * The renderer binds `{$handler: "h3"}` to a callback (`tree/renderer.tsx`). A
 * control cannot tell that callback apart from the plain `onChange` a host or a
 * `$action` binding hands it, and the two want opposite behavior: an action
 * handler leaves the DOM owning the text (`defaultValue`, report the value on
 * change), while a screen handler owns the value itself and re-renders it on
 * every keystroke — so that control has to be CONTROLLED or the two disagree
 * about what is in the box. The mark is what makes the difference visible at the
 * control, which is what keeps every pre-screen payload byte-identical.
 *
 * It lives in `kit/` because the renderer already reaches this direction
 * (`kit/state.ts` is the same shape of shared piece) and the reverse edge would
 * be a cycle.
 */
/** A renderer-bound `{$handler}` callback: the event goes to the screen's VM. */
export type HandlerCallback = (event?: unknown) => void;
/** Stamp a bound handler callback. The renderer is the only caller. */
export declare const markHandlerCallback: (fire: HandlerCallback) => HandlerCallback;
/** A renderer-bound screen handler, as opposed to any other `onChange`. */
export declare const isHandlerCallback: (value: unknown) => value is HandlerCallback;
/**
 * The controlled-mode decision, once, for every text/choice control: a control
 * is controlled only when it has a value to render AND its change handler
 * belongs to a screen. Anything else keeps the uncontrolled DOM it has today.
 */
export declare const controlledHandler: (hasValue: boolean, onChange: unknown) => HandlerCallback | null;
/**
 * Only plain data crosses into a screen: the VM is a different realm, so a host
 * object cannot travel and would fail the crossing instead of the handler.
 *
 * Most Kit callbacks already hand over plain data (a string, a boolean, the
 * `{ target }` a controlled control synthesized). `Form`'s `onSubmit` is the
 * exception — it carries the DOM event, whose `target` is a live element — so it
 * is projected down to the two fields a handler ever reads. `preventDefault` is
 * not one of them: `Form` owns that call itself (forms/form.tsx).
 */
export declare const screenEvent: (event: unknown) => unknown;