/**
 * Marks an experiment as completed in local storage.
 * @param slug The slug of the experiment
 */
export declare function markExperimentCompleted(slug: string): void;
/**
 * Checks if an experiment has been completed.
 * @param slug The slug of the experiment
 * @returns True if completed, false otherwise
 */
export declare function isExperimentCompleted(slug: string): boolean;
/**
 * Clears the completion state for an experiment.
 * @param slug The slug of the experiment
 */
export declare function clearExperimentCompletion(slug: string): void;
/**
 * Validates a completion token from the URL.
 * For V1, this is a simple check for ?completed=true.
 * In V2, this would verify a signed JWT.
 * @param url The current URL
 * @returns True if the token is valid
 */
export declare function validateCompletionToken(url: URL): boolean;