Planet metallicity (top; as given in Table 4) and C/O (bottom) vs. stellar mass (left) and metallicity (right) as given by the NASA Exoplanet Archive (J. L. Christiansen et al. 2025). Planets observed with direct spectroscopy are shown as blue circles, planets observed with eclipse spectroscopy as magenta squares, and planets observed with transit spectroscopy as gold diamonds. Ultrahot Jupiters are labeled as stars.