NaB(CN)${}_4$ exhibits giant negative thermal expansion (NTE) that is closely associated with low-frequency phonons with large negative Grüneisen parameters. Although compression-induced softening of negative-Grüneisen phonons can modify lattice thermal conductivity (${\kappa }_{\mathrm{L}}$), how NTE-active phonon modes differently influence the population (${\kappa }_{\mathrm{pop}}$) and coherence (${\kappa }_{\mathrm{coh}}$) contributions to ${\kappa }_{\mathrm{L}}$ remains unclear. Here, we combine perturbative high-order anharmonic lattice dynamics and homogeneous nonequilibrium molecular dynamics (HNEMD) simulations accelerated by a neuroevolution potential (NEP) to investigate compression-dependent thermal transport in NaB(CN)${}_4$. Both approaches capture a compression-induced decrease in ${\kappa }_{\mathrm{L}}$. At 300 K, NEP–HNEMD simulations show that ${\kappa }_{\mathrm{L}}$ decreases from $1.05\pm 0.03$ to $0.49\pm 0.01\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ over the structurally intact strain range examined up to $4\%$. In the weak-compression regime, the reduction is dominated by the suppression of ${\kappa }_{\mathrm{pop}}$. NTE-active framework modes near 2.5 THz soften under compression, reducing phonon group velocities and increasing the three-phonon scattering phase space. By contrast, the compression-induced difference in ${\kappa }_{\mathrm{coh}}$ is mainly concentrated near 7.5 THz, where the relevant phonon pairs harden. Nevertheless, ${\kappa }_{\mathrm{coh}}$ increases only slightly and remains secondary to ${\kappa }_{\mathrm{pop}}$. These contrasting responses reveal a nonuniform phonon-spectrum reconstruction under compression in which strain selectively reshapes the population and coherence channels of heat transport, linking NTE-active phonons to anomalous thermal transport in NaB(CN)${}_4$.

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• Lattice thermal conductivity
• Mechanical & acoustical properties
• Thermal expansion
• Density functional calculations
• Machine learning