Synthetic spectrum of OH (red and purple) and H₂O (blue) for the fiducial model, at typical MIRI-MRS spectral resolution (R = 2500) with (top) and without (bottom, shifted by 0.2 Jy) OH prompt emission. OH is primarily excited by H₂O photodissociation producing highly excited lines down to 9 μm. The OH lines are seen on top of the continuum and embedded in the strong H₂O line forest. The OH prompt emission produces OH in the A′ symmetric states resulting in an imbalance in the four components of each rotational transition. Longward of ≃13.5 μm, we expect OH chemical pumping by O+H₂ to impact the OH lines, a process that is not included in this version of our model.