  Accretion-induced collapse (AIC) occurs when an O/Ne white dwarf (WD) grows
to nearly the Chandrasekhar mass ($M_{\rm Ch}$), reaching central densities
that trigger electron captures in the core. Using Modules for Experiments in
Stellar Astrophysics ($\texttt{MESA}$), we present the first true binary
simulations of He star + O/Ne WD binaries, focusing on a $1.5 M_\odot$ He star
in a 3 hour orbital period with $1.1-1.3 M_\odot$ O/Ne WDs. The helium star
fills its Roche lobe after core helium burning is completed and donates helium
on its thermal timescale to the WD, $\dot{M}\approx3\times10^{-6} M_\odot$/yr,
a rate high enough that the accreting helium burns stably on the WD. The
accumulated carbon/oxygen ashes from the helium burning undergo an unstable
shell flash that initiates an inwardly moving carbon burning flame. This flame
is only quenched when it runs out of carbon at the surface of the original O/Ne
core. Subsequent accumulation of fresh carbon/oxygen layers also undergo
thermal instabilities, but no mass loss is triggered, allowing $M_{\rm
WD}\rightarrow M_{\rm Ch}$, triggering the onset of AIC. We also discuss the
scenario of accreting C/O WDs that experience shell carbon ignitions to become
O/Ne WDs, and then, under continuing mass transfer, lead to AIC. Studies of the
AIC event rate using binary population synthesis should include all of these
channels, especially this latter channel, which has been previously neglected
but might dominate the rate.
