Exploitation of our C/O and [M/H] to constrain the formation pathway. Left: comparison of the posterior of the C/O ratio given by ForMoSA (gradient; black: high likelihood) and different scenario of formation as a function of the accreted solid mass. The solid lines correspond to the GI scenario, and the dashed lines correspond to the CA scenario. The blue, green, and purple curves represent a formation within the water-ice line, between the water and CO₂ ice lines, andbetween CO₂ and CO ice lines, respectively. Right: comparison of the bulk enrichment of the NGPPS (red dots) and the estimated properties of HIP 65426 b (blue dot). We show here the NGPPS with a mass higher than 0.05 M_Jup (approximately the mass of Neptune).