Star formation histories (SFH) of early (6$<z<$12) galaxies have been foundto be highly stochastic in both simulations and observations, while at$z\lesssim$6 the presence of a main sequence (MS) of star-forming galaxiesimply secular processes at play. In this work, we aim at characterising the SFHvariability of early galaxies as a function of their stellar mass and redshift.We use the JADES public catalogue and derive the physical properties of thegalaxies as well as their SFH using the spectral energy distribution modellingcode CIGALE. To this aim, we implement a non-parametric SFH with a flat priorallowing for as much stochasticity as possible. We use the SFR gradient, anindicator of the movement of galaxies on the SFR-$M_\ast$ plane, linked to therecent SFH of galaxies. This dynamical approach of the relation between the SFRand stellar mass allows us to show that, at $z>9$, 87% of massive galaxies,($\log(M_\ast/M_\odot)\gtrsim$9), have SFR gradients consistent with astochastic star-formation activity during the last 100 Myr, while this fractiondrops to 15% at $z<7$. On the other hand, we see an increasing fraction ofgalaxies with a star-formation activity following a common stream on theSFR-$M_\ast$ plane with cosmic time, indicating that a secular mode ofstar-formation is emerging. We place our results in the context of the observedexcess of UV emission as probed by the UV luminosity function at $z\gtrsim10$,by estimating $\sigma_{UV}$, the dispersion of the UV absolute magnitudedistribution, to be of the order of 1.2mag and compare it with predictions fromthe literature. In conclusion, we find a transition of star-formation modehappening around $z\sim9$: Galaxies with stochastic SFHs dominates at$z\gtrsim9$, although this level of stochasticity is too low to reach thoseinvoked by recent models to reproduce the observed UV luminosity function.