GW231123 total source-frame mass ﹩{M}_{{\rm{tot}}}^{{\rm{src}}}﹩ vs. redshift z, as a lensed black hole merger. Contours indicate 68,% 95%, and 99% credible regions for different waveform and lensing models: unlensed (gray filled; Phenom and NRSur), diffracted (blue unfilled; NRSur), and magnified+diffracted by a singular isothermal macrolens (red filled; NRSur). Circles indicate median values of GWTC-4 events (A. G. Abac et al. 2026a). The black curve marks the approximate detector horizon for O4. Unlike the unlensed interpretation, which requires unusually high masses relative to the GWTC-4 population (A. G. Abac et al. 2026a), lensing analyses harmonize the event with the broader distribution of binary black holes (BBHs).