Ratio of the ¹²CO₂ Q-branch flux and the fluxes of the 12.40, 15.17, and 17.22 µm H₂O line complexes from our fiducial grid of models, plotted as a function of cavity size, shown with dashed, dotted and solid black lines, respectively. Vertical colored lines, with bars indicating the uncertainty, indicate the same CO₂ /H₂O flux ratios calculated for JWST-MIRI observations of GW Lup (Grant et al. 2023), Sz 98 (Gasman et al. 2023), DR Tau (Temmink et al., in prep.), and CX Tau (Vlasblom et al., in prep.), all taken as a part of the MINDS program.