Top panels: center-to-limb variation of observed (symbols) and theoretical EWs derived from the 3D model atmosphere for S_H = 0 (blue dashed), 8/3 (red dotted) and best-fit value (black solid), shown individually for the three triplet components, with wavelength increasing from top to bottom. For each S_H, the corresponding A(O) is defined as the value that minimizes χ² (Eq. (5)) at fixed S_H. Bottom panels: abundance difference , where A(μ) and denote A(O) obtained from line profile fitting at individual μ-angles and at all μ-angles simultaneously. Left and right panels refer to the WCLC and Pereira spectra, respectively.