  We calculate the transverse momentum broadening $\hat q$ and collisional
energy loss $dE/dx$ of hard probes traversing an evolving glasma during the
earliest phase of a relativistic heavy-ion collision. We use a Fokker-Planck
equation and apply a proper time expansion to describe the temporal evolution
of the glasma. The correlators of the chromodynamic fields that determine the
Fokker-Planck collision terms, which in turn provide $\hat q$ and $dE/dx$, are
computed to fifth order. Both transport coefficients are strongly dependent on
time. The maximum values they acquire before the proper time expansion breaks
down are large: $\hat q$ is of the order of a few ${\rm GeV^2/fm}$ and $dE/dx
\sim 1~{\rm GeV/fm}$. Their precise values depend on the probe's velocity ${\bf
v}$, the saturation momentum $Q_s$, and an IR regulator $m$ that is related to
the confinement scale. We study the dependence of our results on these
quantities. Different regularization procedures are analysed and shown to
produce similar results. We also discuss the validity of the proper time
expansion and the compatibility of the approximations that are inherent in the
derivation of the Fokker-Planck equation. We show that hard probes lose a
comparable amount of energy when they propagate through the short-lived glasma
phase, and the long-lasting hydrodynamic phase. The conclusion is that the
glasma plays an important role in jet quenching.
