  Tentative observations of cosmic-ray antihelium by the AMS-02 collaboration
have re-energized the quest to use antinuclei to search for physics beyond the
standard model. However, our transition to a data-driven era requires more
accurate models of the expected astrophysical antinuclei fluxes. We use a
state-of-the-art cosmic-ray propagation model, fit to high-precision antiproton
and cosmic-ray nuclei (B, Be, Li) data, to constrain the antinuclei flux from
both astrophysical and dark matter annihilation models. We show that
astrophysical sources are capable of producing $\mathcal{O}(1)$ antideuteron
events and $\mathcal{O}(0.1)$ antihelium-3 events over 15~years of AMS-02
observations. Standard dark matter models could potentially produce higher
levels of these antinuclei, but showing a different energy-dependence. Given
the uncertainties in these models, dark matter annihilation is still the most
promising candidate to explain preliminary AMS-02 results. Meanwhile, any
robust detection of antihelium-4 events would require more novel dark matter
model building or a new astrophisical production mechanism.
