Evolution of envelope profiles of temperature (red), total density (solid black), and vapor density (dashed solid) for the standard model (0.2 au, Ṁ_peb = 10⁻⁶ M_⊕ yr, FEOS with Kraus LV-curve, molecular opacities). The CEB is indicated by the vertical solid line, while the vertical dotted linesdenote the boundaries between the frozen zone (region 2b), the well-mixed region 2a, and the saturated region 1. These boundaries expand with time, creating a gradient in the composition. The radiative–convective boundary is indicated by the gray dot. The rate of gas accretion accelerates toward the end, as the crossover mass is reached. The temporal evolution is available as an online movie.