Schematic view, not to scale, of the preferred geometrical configuration for the CSM of SN 2024bch. An outer shell with R_in ≳ 4.4 10¹⁵ cm} is reached by radiation at different times and emits high-ionisation features through the Bowen fluorescence mechanism. This scenario can simultaneously explain the evolution of the luminosities and redshifts of narrow features without the need for ejecta-CSM interaction as an additional source of energy.