import { ComputedRef } from 'vue';
export interface UseElapsedOptions {
    /** Wall-clock origin in epoch ms. Omit (or return undefined) to count from mount. */
    startedAt?: () => number | undefined;
    /** Stops the interval when false — a hidden readout should not schedule work. @default true */
    active?: () => boolean;
    /** @default 100 */
    intervalMs?: number;
}
/**
 * `12.3s` below a minute, `2m 3.0s` above it.
 *
 * Milliseconds are floored to deciseconds before the branch, so the tenth
 * that reads `60.0s` under a naive `toFixed(1)` cannot occur.
 */
export declare function formatElapsed(ms: number): string;
/**
 * Elapsed milliseconds since an origin, refreshed on an interval.
 *
 * The reading is always `Date.now() - origin` rather than a self-incrementing
 * counter: a background tab throttles timers, and a counter that adds a fixed
 * step per fire drifts behind wall clock for as long as the tab stays hidden.
 */
export declare function useElapsed(options?: UseElapsedOptions): ComputedRef<number>;