There is provided an aerosol-generating system including an aerosol-generating device and a cartridge assembly, the device including a device inner housing defining a device cavity, an electrical heater, and a device outer housing; and the cartridge assembly including a cartridge assembly inner housing defining a substrate compartment, an aerosol-forming substrate positioned within the substrate compartment, and a cartridge assembly outer housing, and a portion of the cartridge assembly inner housing is configured to be received within the device cavity, and, when the portion of the cartridge assembly inner housing is received within the device cavity, at least a first part of a downstream edge of the device outer housing abuts at least a first part of an upstream edge of the cartridge assembly outer housing so that the cartridge assembly outer housing and the device outer housing form a system outer housing.