Temporal evolution of the He Iλ5876 line. Left panel: line-profile evolution in the velocity space. The dashed vertical line marking marks the rest wavelength. Middle panel: evolution of the velocities measured from the P-Cygni absorption minimum of the narrow He I component, formed in the unshocked CSM. Right panel: evolution of the broader He I emission components, reflecting the dynamics of the shocked gas. For clarity, the uncertainties are not shown in the plots, but they can reach values of up to 30%. The comparison data for SNe Ibn are from Pastorello et al. (2016) and Wang et al. (2025).