An apparatus includes a housing, a platform, a buttress assembly, a retainer member, and a release assembly. The housing defines a gap that is configured to receive a portion of an end effector of a surgical stapler. A portion of the platform is exposed in the gap defined by the housing. The buttress assembly is positioned on the platform and is exposed in the gap defined by the housing. The retainer member is configured to selectively retain the first buttress assembly against the platform. The release assembly is in communication with the retainer member. The release assembly is configured to store energy. The release assembly is further configured to release the stored energy to thereby cause the at least one retainer to release the first buttress assembly from the platform in response to a clamping action of an end effector positioned in the gap defined by the housing.
