<p>In deep coal reservoirs, high in-situ stress and geological heterogeneity cause complex hydraulic fracture (HF)–interface interactions. Elucidating these interaction patterns is crucial for the successful application of hydraulic fracturing technology. This study investigates the propagation mechanisms of directed hydraulic fractures (DHFs) and their interaction with coal–rock interfaces under varying burial depths using true-triaxial hydraulic fracturing experiments. Fracture morphologies were reconstructed using digital image processing. Results show that as the directed fracture (DF) length increases, the initiation pressure decreases in an approximately linear trend, with reductions of –18.54%, –10.67%, –12.20%, and –10.03%, respectively. The average propagation pressure follows a near‑power‑law decline, with reductions of −44.01%, −15.36%, −4.63%, and −7.46%, and the fractures become more easily captured by the interface. With increasing burial depth, the average propagation pressure exhibits an approximately exponential upward trend, with increases of 10.38%, 20.09%, 20.64%, and 72.57%, while the initiation pressure shows a fluctuating but continuously rising trend, with increases of 19.58%, 11.97%, 10.38%, and 15.67%. Meanwhile, the heterogeneous growth of triaxial stresses leads to a phase‑dependent transition in fracture propagation pathways, characterized by an “easy-difficult-easy” pattern for trans‑interface propagation. Based on complex function theory, a stress distribution function at the DHF tip was derived, and a theoretical model was established to predict fracture initiation and propagation paths. The model quantifies the coupling between tip stress and material strength and provides a criterion for distinguishing between intra-layer deflection, interface-following, and trans-interface propagation. This research provides technical and theoretical insights for precise control of fracture networks in deep coal–rock reservoirs and long-term efficient gas extraction.</p>