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We perform a series of high-resolution 2D hydrodynamical simulations ofequal-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN)accretion disks to study whether these binaries can be driven to merger by thesurrounding gas. We find that the gravitational softening adopted for the BBHhas a profound impact on this result. When the softening is less than tenpercent of the binary separation, we show that, in agreement with recentsimulations of isolated equal-mass binaries, prograde BBHs expand in timerather than contract. Eventually, however, the binary separation becomes largeenough that the tidal force of the central AGN disrupts them. Only when thesoftening is relatively large do we find that prograde BBHs harden. Wedetermine through detailed analysis of the binary torque, that this dichotomyis due to a loss of spiral structure in the circum-single disks orbiting eachBH when the softening is a significant fraction of the binary separation.Properly resolving these spirals -- both with high resolution and smallsoftening -- results in a significant source of binary angular momentum. Onlyfor retrograde BBHs do we find consistent hardening, regardless of softening,as these BBHs lack the important spiral structure in their circum-single disks.This suggests that the gas-driven inspiral of retrograde binaries can produce apopulation of compact BBHs in the gravitational-wave-emitting regime in AGNdisks, which may contribute a large fraction to the observed BBH mergers.

Orbital evolution of binary black holes in active galactic nucleus disks: a disk channel for binary black hole mergers?