/** Configures backoff curve: initial delay, growth factor, ceiling, and jitter. */
export type BackoffPolicy = {
    initialMs: number;
    maxMs: number;
    factor: number;
    /** Jitter fraction (0–1). Added as `base * jitter * random()` to decorrelate retries. */
    jitter: number;
};
/**
 * Compute the delay for a given attempt number.
 * Formula: `min(maxMs, initialMs * factor^(attempt-1) + jitter)`
 */
export declare function computeBackoff(policy: BackoffPolicy, attempt: number): number;
/** Sleep for `ms` milliseconds, cancellable via AbortSignal. Throws on abort. */
export declare function sleepWithAbort(ms: number, abortSignal?: AbortSignal): Promise<void>;