Ultralow lattice thermal conductivity (${\kappa }_L$) is often found in halide compounds with highly anharmonic lattice frameworks, yet the structural descriptors governing phonon transport remain unclear. Here, we establish a structural framework linking octahedral configurations to phonon dynamics through two key factors: (i) halogen–halogen-related lattice coupling associated with rotational soft modes, leading to phonon spectrum decongestion, enlarged scattering phase spaces, and enhanced anharmonic phonon scattering; and (ii) local octahedral distortions that modify phonon branch separation and dispersion characteristics. Using first-principles calculations on ${\mathrm{CsPbBr}}_3$, we reveal how halogen-mediated rotational dynamics and octahedral distortions reshape the phonon landscape. Guided by these insights, we develop a high-throughput screening strategy that identifies halogen-coordinated octahedral frameworks capable of supporting rotational dynamics and quantifies intrinsic octahedral distortions using a geometric distortion factor $\rho$. This approach uncovers halide compounds with strongly distorted octahedral units and promising ultralow lattice thermal conductivity, establishing rotational soft modes and octahedral distortions as transferable structural descriptors for discovering advanced thermal management materials.

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• Lattice thermal conductivity
• Phonons
• Perovskites
• Boltzmann theory