Spicelib really just makes calls to the selected spice engine (in my case ngspice). In this setup spicelib‘s main job is to parse the raw spice data and have a

Spicelib really just makes calls to the selected spice engine (in my case ngspice). In this setup spicelib‘s main job is to parse the raw spice data and have a unified interface regardless which spice engine is selected. But to answer the question: the path to the spice model must currently be set explicitly.