  We investigate solutions to the flavour anomalies in $B$ decays based on loop
diagrams of a "split" dark sector characterised by the simultaneous presence of
heavy particles at the TeV scale and light particles around and below the
$B$-meson mass scale. We show that viable parameter space exists for solutions
based on penguin diagrams with a vector mediator, while minimal constructions
relying on box diagrams are in strong tension with the constraints from the
LHC, LEP, and the anomalous magnetic moment of the muon. In particular, we
highlight a regime where the mediator lies close to the $B$-meson mass,
naturally realising a resonance structure and a $q^2$-dependent effective
coupling. We perform a full fit to the relevant flavour observables and analyse
the constraints from intensity frontier experiments. Besides new measurements
of the anomalous magnetic moment of the muon, we find that decays of the $B$
meson, $B_s$-mixing, missing energy searches at Belle-II, and LHC searches for
top/bottom partners can robustly test these scenarios in the near future.
