A fluid infusion system including a pocketable pump housing with a reservoir cavity with helical coupling features. The system further has a reservoir with an open end that is removable from the reservoir cavity. A removable cap coupled to the housing is also included in the system. The cap has corresponding coupling features, an exterior surface and a tab. The corresponding coupling features couple the cap to the housing while the tab is a ridge that extends away from the exterior surface. The tab has a port to accommodate flow from the reservoir and the port defines an axis of rotation such that torque applied to the tab about the axis of rotation disengages the coupling between the cap and the housing. The system further has a removably coupled guard with a slot defined to immobilize rotation of the tab about the axis of rotation.