Light curve and E_peak – E_iso function. Top panel: Background-subtracted 50 keV–2 MeV light curve of GRB 240402B in 0.125-s bins as observed by Glowbug. The two primary peaks at T0+0.5 s and T0+3 s as described in Cheung et al. (2024) are visible, with additional sub-structure in the light curve that is overall consistent with that observed by Konus-Wind (Ridnaia et al. 2024b). Bottom panel: E_peak – E_iso diagram for long (grey) and short GRBs (blue), updated from Dichiara et al. (2021). The position of LXT 240402A/GRB 240402B is shown as a function of redshift, highlighting z = 0.048 and 1.5. The Amati relation (dashed line; Amati et al. 2008) and its 2σ scatter (grey area) are shown.