Number of compact binary models containing a white dwarf and a core-collapse remnant for each initial semi-major axis a₀ (immediately post second remnant formation) and delay time T_delay. The shading corresponds to the number of compact binaries produced in each 2D bin per 10⁶ M_⊙. The left column shows results at one-fifth solar metallicity, on the right at half-solar. Top row: WDNS binaries in which the WD forms first. The eccentricity is retained from the supernova, which occurs second, producing a greater range of semi-major axes with a tail extending to higher values at fixed delay time. Middle row: WDNS binaries in which the NS forms first. Bottom row: WDBH binaries in which the BH forms first. We find no WD1-BH2 models. In each case, the vertical dashed line indicates one Hubble time. The vast majority of such binaries merge on much longer timescales (see Table 1). Verbunt et al. (2017) natal kicks are adopted; equivalent plots with Hobbs et al. (2005) and Bray & Eldridge (2016) kicks are given in Appendix A.