Median fraction f_fate of WR–COs that were able to produce BCOs as a function of metallicity. The left-hand (right-hand) plot refers to α_CE = 1 (α_CE = 3). In each set, we consider all WR–CO systems and we count how many of them form any type of BCOs (gray lines, circle markers), only BBHs (purple lines, lower triangle markers), only BHNSs (blue lines, diamond markers), and only BNSs (yellow lines, upper triangle markers). For each (Z, α_CE) pair and BCO type, we consider the distribution of the 12 f_fate fractions of the corresponding simulated sets (combinations of CCSN and natal kick models, see Table 1), and show their median values (scatter points) and 68% credible intervals (error bars).