The impact of energy exchange among the three relevant fluid components—baryonic matter, fermionic dark matter (DM), and dark energy (DE)—on the internal structure of neutron stars is investigated. Working with a representative DM mass $m_{\chi }=10\mathrm{GeV}$ and a barotropic DE relation $p_{\mathrm{de}}=\omega {\epsilon }_{\mathrm{de}}$, we embed one or two phenomenological source terms $Q_i$ in the Tolman-Oppenheimer-Volkoff equations and analyze three hierarchical scenarios: (i) coexisting but noninteracting fluids (Model I); (ii) fully interacting fluids with independent baryon–DM and DM–DE exchanges and optional DM self-repulsion (Model II); and (iii) a unified dark sector that couples to baryons through a single exchange term while retaining an internal DM/DE partition (Model III). Across all models two complementary mechanisms dominate; softening by massive, pressure-poor DM, and vacuum softening/binding by the negative pressure of DE. Model I exhibits these effects in their purest form, yielding either softened or self-bound stars depending on the dark composition. In Model II the exchange terms self-regulate, cancelling the explicit dependence on the fluid coupling strength $\alpha$, so that mass-radius curves are nearly invariant when $\alpha$ varies from 0.05 to 1000. Model III breaks this $\alpha$-degeneracy; when the dark sector retains a substantial vacuum fraction, the baryonic pressure gradient is strongly suppressed and both the maximum mass and radii decrease appreciably, whereas a pure-DM core remains almost insensitive to the exchange strength. The study delineates the conditions under which dark interactions can (or cannot) imprint macroscopic signatures, thereby providing a theoretical baseline for future, more strongly constrained, microphysical models.

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• Dark energy
• Dark matter
• Neutron stars & pulsars