ANN-based nonparametric reconstructions of the function f(z) and its first three derivatives. The left four panels show the reconstruction using DESI BAO data only, while the right four panels incorporate the DESY5, which significantly stabilizes the reconstruction across all derivative orders. The fiducial reference is a flat ΛCDM model with H₀ = 67.4 km s⁻¹ Mpc⁻¹ and Ω_m,0 = 0.315. Shaded regions denote the 68% confidence intervals.