Envelope shell mass as function of time, interior to 0.3, 0.6, 0.9r_H for the Saturn-mass case. Black curves correspond to run100, labelled as MRS02 (medium resolution, smoothing length r_s ∕r_H = 0.2). The smoothing length is relaxed to its final value over one orbit, corresponding to the initial increase in envelope mass. Further gas accretion is the result of the physical cooling of the envelope. Increasing the resolution even further does not change the accretion rate, as indicated by the orange curve (labelled HRS02). A refined simulation with twice the resolution and half the smoothing length (r_s ∕r_H = 0.1, run100HR) is shown in red. The grey curves represent a test simulation with factor 2 smaller smoothing length, but without the increase in resolution, which results in an unstable envelope.