  In this work, we debut a new implementation of IP-Glasma and quantify the
pre-equilibrium longitudinal flow in the IP-Glasma framework. The saturation
physics based IP-Glasma model naturally provides a non-zero initial
longitudinal flow through its pre-equilibrium Yang-Mills evolution. A hybrid
IP-Glasma+MUSIC+UrQMD frame- work is employed to test this new implementation
against experimental data and to make further predictions about hadronic flow
observables in Pb+Pb collisions at 5.02 TeV. Finally, the non-zero
pre-equilibrium longitudinal flow of the IP-Glasma model is quantified, and its
origin is briefly discussed.
