A cartridge assembly for an aerosol-generating system, including a cartridge including a first compartment having a first air inlet and outlet, a second compartment having a second air inlet and outlet, and a mouthpiece partially surrounding the cartridge and having a third air outlet, the cartridge and the mouthpiece being longitudinally movable relative to one another between a retracted position and an extended position creating a chamber therebetween in fluid communication with the first, second, and third air outlets, the air inlets and the first and second air outlets are obstructed by the mouthpiece in the retracted position, the third air outlet is obstructed by the cartridge, and in the extended position air is drawable into the chamber along first and second airflow pathways extending from the respective air inlet through the compartment to the air outlet, and out of the chamber through the third air outlet.
