Heavy-ion collisions produce far-from-equilibrium QCD matter which rapidly becomes a hydrodynamic medium. In this talk, I discuss how jets are shaped by the initial stage of such collisions. Most importantly, I show that anisotropic momentum broadening of jets at early times leads to net spin in emitted gluons. This means that there is net spin polarization of jet partons which is constant at all energy scales. I furthermore discuss jet broadening in the later hydrodynamic stage. Using tools of non-equilibrium field theory, I show that momentum broadening is substantially reduced at lower transverse momenta compared with a medium in thermal equilibrium.