  The black hole candidate XTE J2012+381 underwent an outburst at the end of
2022. We analyzed 105 NICER observations and 2 NuSTAR observations of the
source during the outburst. The NuSTAR observations of the $M \sim10M_\odot$
black hole indicate clear signs of relativistic disk reflection, which we
modeled to measure a BH spin of $a=0.988^{+0.008}_{-0.030}$ and an inclination
of $\theta=68^{+6}_{-11}$ degrees ($1\sigma$ statistical errors). In our
analysis, we test an array of models and examine the effect of fitting NuSTAR
spectra alone versus fitting simultaneously with NICER. We find that when the
underlying continuum emission is properly accounted for, the reflected emission
is similarly characterized by multiple models. We combined 52 NICER spectra to
obtain a spectrum with an effective exposure of 190 ks in order to probe the
presence of absorption lines that would be suggestive of disk winds, but the
resulting features were not statistically significant. We discuss the
implications of this measurement in relation to the overall BH spin
distribution in X-ray binary systems.
