Core masses (solid lines) and envelope masses (dashed lines) as a function of time. Gray lines: model without planetesimal fragmentation. Black lines: model without planetesimal fragmentation but considering grain opacities reduction (G.O.R). Red lines: baseline model. Pink lines: model taking into account all the improvements in the calculation of (the dependencies of with the planetesimal impact velocities and compositions), pebble accretion rates, and considering reduced grain opacities.