  Using a successful framework for describing S-wave hadronic decays of light
hyperons induced by a subprocess $s \to u (\bar u d)$, we presented recently a
model-independent calculation of the amplitude and branching ratio for $\Xi^-_b
\to \Lambda_b \pi^-$ in agreement with a LHCb measurement. The same quark
process contributes to $\Xi^0_c \to \Lambda_c \pi^-$, while a second term from
the subprocess $cs \to cd$ has been related by Voloshin to differences among
total decay rates of charmed baryons. We calculate this term and find it to
have a magnitude approximately equal to the $s \to u (\bar u d)$ term. We argue
for a negligible relative phase between these two contributions, potentially
due to final state interactions. However, we do not know whether they interfere
destructively or constructively. For constructive interference one predicts
${\cal B}(\Xi_c^0 \to \Lambda_c \pi^-) = (1.94 \pm 0.70)\times 10^{-3}$ and
${\cal B}(\Xi_c^+ \to \Lambda_c \pi^0) = (3.86 \pm 1.35)\times 10^{-3}$. For
destructive interference, the respective branching fractions are expected to be
less than about $10^{-4}$ and $2 \times 10^{-4}$.
