  With the expected large increase in data sets, previously not measured decays
will be studied at Belle II. We derive standard model predictions for the $B\to
X_u \tau\bar\nu$ decay rate and distributions. The region in the lepton energy
spectrum where higher-dimension operators in the local OPE need to be resummed
into the $b$-quark light-cone distribution function is a significantly greater
fraction of the phase space than for massless leptons. The finite $\tau$ mass
has the novel effect of shifting and squeezing how the distribution function
enters the lepton energy spectrum. We also derive new predictions for the
$\tau$ polarization.
