/**
 * Optional Google Drive backup for the brains wiki.
 *
 * This module is only activated when DRIVE_BACKUP_ENABLED=true and all
 * required Google OAuth2 credentials are set. When active, every write to
 * local storage is also mirrored to a single Drive folder asynchronously.
 * Failures are logged but never propagated — Drive is backup, not primary.
 */
export declare class DriveBackup {
    private readonly drive;
    private readonly folderId;
    private constructor();
    /**
     * Return a DriveBackup instance if all required env vars are present,
     * or null if backup is disabled or misconfigured.
     */
    static tryCreate(): DriveBackup | null;
    /**
     * Upsert a file to The Drive backup folder.
     * Called fire-and-forget after every local write — errors are swallowed by the caller.
     */
    backup(name: string, content: string): Promise<void>;
}
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