Three different types of mass-transfer evolution found across our binary models, illustrated with cases with M₁ = 30 M_⊙ primaries and different compositions (metallicities). Going from top to bottom, subsequent panels show: mass-transfer rate, envelope mass, surface He abundance, and surface nitrogen enrichment. Bold parts of the curves in the second panel indicate phases of RLOF. Letters mark distinctive events that may occur during the evolution as following. A: a phase of rapid thermal-timescale mass transfer, B: a point when the donor regains thermal equilibrium and the mass transfer transitions to the nuclear timescale, C: phases of detachment, D: temporary mass-transfer rate increase when the donor becomes stripped down to layers that used to be in the intermediate convective zone, and E: mass transfer peak associated with the end of core-He burning and re-expansion of the donor.