Left: median P-T profile of HD 209458 b for the three retrievals, free chemistry (orange), equilibrium chemistry (violet), and grid retrieval (pink), performed using STIS+WFC3+NIRCam observations. The shaded region shows 1σ uncertainty on the P-T profile. Right: corresponding mixing ratios of CO₂ (solid) and H₂O (dashed) obtained from the median values of all three retrievals are shown.