Evolutionary track of the sdB progenitor calculated with MESA in a binary system with initial stellar masses of 2.7 M_⊙ (primary) and 2.6 M_⊙ (secondary), and an initial orbital period of 3 days. Point 1 marks the start of the simulation at the zero-age main sequence. Point 2 corresponds to the onset of hydrogen shell burning, while circle 3 indicates the beginning of stable mass transfer, which terminates at point 4 At point 5, the stripped primary becomes an sdB star. Finally, point 6 marks the onset of the common envelope phase initiated by the secondary. The color of the track represents the mass evolution of the primary star. The blue star indicates the observed position of the sdB component of PTF1 J2238+7430, as reported by Kupfer et al. (2022).