Occurrence of contact phases for models with initial primary masses M_1,  i = 10.2 M_⊙ on the initial mass ratio–separation plane. Models marked with a dot are those for which accretion was limited to 0.1 times the secondary’s global thermal timescale τ_KH (see Sect. 2.2.1). The other ones are marked with a star symbol. The dark-blue quasi-horizontal lines indicate the initial mass transfer cases, which can be read from the right side. Systems on the left of the solid black line are Darwin unstable at the onset of mass transfer according to Eq. (9) and assuming R₁ = R_RL,  1.