Hidden-sector particles with baryon number can give rise to new decay channels of the neutron, mediating apparent baryon violation. The very existence of neutron stars constrains the strength of such effects, and in this talk I develop how precisely determined energy-loss constraints, particularly anomalous binary-pulsar period lengthening, limit not only the total baryon loss rate across the star but also the parameters of the particle physics models that produce such loss. To do this, we compute the new processes in the dense nuclear medium found at the core of a neutron star, employing the techniques of relativistic mean-field theory. Focusing on scenarios in which the dark-sector particles do not accumulate in the star, we extract limits on in-vacuum baryon-number-violating processes, and we determine them for various equations of state. I conclude by noting the implications of our results for models of dark-sector-enabled baryogenesis.