SN Ia light-curve stretch (x₁), global host mass (log(M_*/M_⊙)_global), and local environmental colour ((g − z)_local) distributions split per redshift origin. SNe Ia with galaxy redshifts are plotted in green (σz ∼ 10⁻⁴), and SNe Ia relying on low-resolution SN spectra (extracted from SEDm, Blagorodnova et al. 2018), either from SNID (Blondin & Tonry 2007) or on host emission lines are plotted in red (σz ∼ 10⁻³). The apparent stretch offset is explained by the selection function associated with galaxy redshifts, which favours high-mass hosts.