export declare function isDefinitiveRejection(err: unknown): boolean;
export declare const TRANSPORT_RETENTION_GRACE_MS: number;
/**
 * May a session whose refresh failed WITHOUT a definitive rejection be kept?
 *
 * `expSeconds` is the id token's `exp` claim. Fails closed: a missing or
 * non-numeric expiry is not a usable bound, so such a session is never retained.
 */
export declare function mayRetainAfterTransportFailure(expSeconds: unknown, now?: number): boolean;
/** Throws a non-definitive `refresh_backoff` error while `key` is still backing off. */
export declare function assertRefreshAllowed(key: string, now?: number): void;
/** Record the outcome of a refresh attempt for `key`. */
export declare function recordRefreshOutcome(key: string, err: unknown, now?: number): void;