/**
 * Screen-change detection primitives for the browser auto-answer loop.
 *
 * The loop has to notice that the question/page changed *while a vision call is
 * in flight* (those calls run 50-120s), otherwise a stale answer is applied to
 * the next screen. The in-page MutationObserver is one of the two signals that
 * feed that decision - and it is document-scoped, so it must be RE-INJECTED
 * after every (main-frame) navigation, otherwise the heartbeat's DOM path is
 * dead for the rest of the run.
 *
 * Everything here is pure (no I/O) so it can be unit-tested, and the injected
 * observer script is built from the SAME `observerChangeScore` source so the
 * tested code is literally the code that runs in the page.
 */
/** Score threshold above which the observer reports a material change. */
export declare const SCREEN_CHANGE_THRESHOLD = 15;
/**
 * In-page observer scoring: compares the serialized element texts the
 * MutationObserver watches (`getText()` output) and returns a weighted score.
 * Kept dependency-free so it can be serialized into the injected script via
 * `toString()`.
 *
 * Weights (mirror the Node-side fingerprint): an added or removed element is
 * 10, a shifted/replaced one is 8. A full question swap clears the threshold.
 */
export declare function observerChangeScore(prevText: string, currText: string): number;
/**
 * True only for a MAIN-frame navigation. Subframe/iframe navigations (ads,
 * embedded widgets) must not flag the bound page as changed or trigger a
 * re-inject into an unrelated document.
 */
export declare function isMainFrameNavigation(params: {
    frame?: {
        parentId?: string;
    };
} | null | undefined): boolean;
/**
 * Build the injected MutationObserver script. `observerChangeScore` is embedded
 * from its own source so the unit-tested function is the one that runs in-page.
 * The script is idempotent: it early-returns when its Symbol key already exists
 * on the current document.
 */
export declare function buildObserverScript(): string;