One fluid might not rule them all

In this proceeding, we present our recent investigations on hydrodynamic collectivity in high-multiplicity proton--proton collisions at $\sqrt{s}=$ 13 TeV using the VISHNU hybrid model with different initial condition models, called HIJING, super-MC and TRENTo. We find that carefully tuned parameters, simulations can give reasonable descriptions of measured two-particle correlations. However, multi-particle single mixed harmonics cumulants not be described by hydrodynamics these three conditions, even for signs a few cases. Further studies show non-linear response plays an important role expansion p--p systems. Such effect change $c_2\{4\}$ from negative value state to positive final state. The failure description cumulant triggers questions whether rule all collision systems, including LHC.