Ratio of size–mass relations in F444W and F200W at 3 ≤ z < 4: the black line represents rest-frame ∼1 μm and ∼0.5 μm with dashed segments extrapolating to log(M_*/M_⊙) > 11. JWST-based results from Suess et al. (2022) and Martorano et al. (2024) are shown as coloured solid lines and squared points. Star-forming galaxies at log(M_*/M_⊙) > 9.5 are ≳10% smaller in rest-1 μm than in rest-0.5 μm consistent of colour-gradients (see Section 5.3) and lower-z studies.