Derived baryon mass fraction of the X-ray-emitting gas within R_vir based on the mean X-ray surface brightness profile of MW-mass central galaxies from Zhang et al. (2024). We evaluate the effects of different assumptions on the inferred baryon fraction, including: n_H profile (Sect. 2.1); isothermal temperature value (Sect. 2.2); lognormal distribution of temperature, ExpCGM model, and TNG-based forward model (Sect. 2.3); halo mass uncertainty (Sect. 2.4); and metallicity (Sect. 2.5). The vertical dashed line indicates the cosmological baryon fraction (f_b = 0.157).