  Common envelope (CE) evolution is a critical but still poorly understood
progenitor phase of many high-energy astrophysical phenomena. Although 3D
global hydrodynamic CE simulations have become more common in recent years,
those involving an asymptotic giant branch (AGB) primary are scarce, due to the
high computational cost from the larger dynamical range compared to red giant
branch (RGB) primaries. But CE evolution with AGB progenitors is desirable to
simulate because such events are the likely progenitors of most bi-polar
planetary nebulae (PNe), and prominent observational testing grounds for CE
physics. Here we present a high resolution global simulation of CE evolution
involving an AGB primary and $1\,\mathrm{M}_\odot$ secondary, evolved for $20$
orbital revolutions. During the last $16$ of these orbits, the envelope unbinds
at an almost constant rate of about
$0.1$-$0.2\,\mathrm{M}_\odot\,\mathrm{yr}^{-1}$. If this rate were maintained,
the envelope would be unbound in less than $10\,\mathrm{yr}$. The dominant
source of this unbinding is consistent with inspiral; we assess the influence
of the ambient medium to be subdominant. We compare this run with a previous
run that used an RGB phase primary evolved from the same $2\,\mathrm{M}_\odot$
main sequence star to assess the influence of the evolutionary state of the
primary. When scaled appropriately, the two runs are quite similar, but with
some important differences.
