Donut chart showing the evolutionary state of the donor star (inner ring) and the stability of mass transfer (outer ring) at the onset of the second mass-transfer phase in the fiducial model. The top panel shows systems where the merger remnant becomes the donor, while the bottom panel shows systems where the original tertiary star initiates mass transfer. The inner ring distinguishes between systems that initiate mass transfer on the HG or FGB, and as an SG. The outer ring indicates whether the mass transfer is stable (green), unstable (yellow), or when the accretor is also a post-MS star (purple). The latter outcome is rare, comprising fewer than 2% of systems.