Example of a binary model with M_1,  i = 10.2 M_⊙, q_i = 0.2, and a_i = 175.7 R_⊙ going through a phase of (delayed) runaway mass transfer. Panel a is the same as Fig. 3a (‘ign.’ = ‘ignition’). Panel b shows the mass-transfer rate Ṁ_trans (solid black line), thermal mass-transfer rate Ṁ_KH (solid green line) and dynamical mass-transfer rate Ṁ_dyn (solid gold line) for the primary star on the left axis. The right axis shows the component mass evolution as a function of age (dashed blue and orange lines). In panel c, the radius R (solid blue line), Roche lobe radius R_RL (dashed light-blue line), L₂-volume-equivalent radius R_L2 (dahsed green line, Misra et al. 2020, Eq. (15)) and orbital separation a_orb (dashed black line) evolution for the primary are shown as a function of the decreasing primary mass. The blue cross indicates the moment of L₂-overflow.