  We show that high-$p_T$ $R_{AA}$ and $v_2$ are sensitive to the early
expansion dynamics, and that the high-$p_T$ observables prefer delayed onset of
energy loss and transverse expansion. To calculate high-$p_T$ $R_{AA}$ and
$v_2$, we employ our newly developed DREENA-A framework, which combines
state-of-the-art dynamical energy loss model with 3+1-dimensional
hydrodynamical simulations. The model applies to both light and heavy flavor,
and we predict a larger sensitivity of heavy flavor observables to the onset of
transverse expansion. This presents the first time when bulk QGP behavior has
been constrained by high-$p_\perp$ observables and related theory, i.e., by
so-called QGP tomography.
