A capsule may include a housing, an aerosol-forming substrate, and a heater. The housing defines inlet openings, outlet openings, and a chamber between the inlet openings and the outlet openings. The chamber may have a longest dimension extending from at least one of the inlet openings to a corresponding one of the outlet openings. The aerosol-forming substrate is within the chamber of the housing. The heater is embedded in the housing. The heater includes a first end section, an intermediate section, and a second end section. The intermediate section is disposed within the aerosol-forming substrate in the chamber. An aerosol-generating device may include a device body with a lid configured to open to permit an insertion of the capsule and configured to close to engage the capsule within the device body.