Model-predicted transmission spectrum based on the fiducial model (3× Z_⊙, K_zz = 10⁸ cm² s⁻¹, and T_int = 100 K) presented in Figure 1. The black solid line represents the simulated transmission spectrum including all opacity sources, while the black dashed line shows the same model with the CS₂ abundance adjusted to yield a column density of 10¹⁸ molecules cm⁻² within the observable atmosphere, corresponding to the approximate detectability threshold (refer to Section 3.6). Colored solid lines show simulated transmission spectra computed while excluding the opacity contribution from individual molecular species, as indicated. Light blue symbols with error bars denote the JWST observations presented in the companion observational study by M. Zhang et al. (2026).