Cartridge for an aerosol-generating system

An aerosol-generating system, comprising:

• a cartridge comprising:
• a liquid storage container containing a first liquid composition and a second composition,
• a plurality of capsules, each capsule encapsulating the second composition to separate the second composition from the first liquid composition, wherein each capsule comprises a frangible shell encapsulating the second composition,
• a capsule retainer, and
• an outlet in the liquid storage container configured to deliver liquid from the liquid storage container, wherein the capsule retainer substantially prevents any frangible shells, or parts thereof, from exiting the cartridge through the outlet;
• and
• a device configured to receive the cartridge, the device comprising:
• a housing having a cavity configured to receive the cartridge,
• a liquid transport element comprising a first portion insertable into the outlet of the cartridge, and a second portion,
• a heating element adjacent the second portion of the liquid transport element, and
• a power supply configured to supply power to the heating element.