Thermal emission spectrum for a simulation with surface pressure of 1 bar, redox state of fO₂ − IW = 2, and a_c = 10⁻⁶. Top: comparison between the line-by-line radiative transfer method at R = 60 000 and the correlated-k method at R = 1000, both convolved to R = 200. Bottom: comparison of convolved spectra from both line-by-line and correlated-k methods generated using petitRADTRANS, along with the output spectrum from our framework. All three approaches show negligible differences when predicting photometric fluxes in the JWST MIRI broad-band filters (see text for more details).