Redshift evolution of the dark-energy sector. Left: the dark-energy density ρ_DE(z)/ρ_DE0. Right: the equation of state w_DE(z). The red solid line represents the best-fit MEDE model (CMB+DESI+PantheonPlus). The light-orange region shows the 2σ confidence region derived from MCMC chains, illustrating the posterior distribution of parameters. The green solid line shows the CPL parameterization ((CMB+DESI+PantheonPlus best-fit), and the black dashed line represents ΛCDM. The MEDE model exhibits a smooth transition around z_t ∼ 0.42, crossing the phantom divide w = −1 from phantom-like (w < −1) at high redshifts to quintessence-like (w > −1) at low redshifts.