<p>Transparent soil model tests are increasingly used to visualize internal soil deformation under dynamic conditions, yet most are conducted under unloading states that deviate from classical stress paths. To support the mechanical interpretation of such tests, this study investigates the undrained horizontal cyclic behavior of nanoscale transparent clay, composed of hydrophilic fumed silica, through cyclic triaxial experiments conducted under unloading conditions, supplemented by advanced constitutive model. The results show that unloading stress ratio plays a critical role in reducing initial confinement, thereby amplifying pore pressure accumulation and stiffness degradation under cyclic loading. The influence of cyclic stress ratio is strongly coupled with unloading stress ratio, as higher cyclic stress ratio under low-confinement conditions further accelerates structural weakening and instability. Tests involving different loading amplitude ratios revealed that stress-path variations induce distinct cyclic responses, underscoring the anisotropic and path-dependent nature of the material. Post-cyclic monotonic tests confirmed significant degradation of residual strength. Numerical simulations using the extended hypoplastic model with a generalized intergranular strain framework showed good capability in capturing the accumulated strain and pore pressure development over thousands of cycles in the tests, providing a foundation for stress-field characterization in future transparent soil experiments.</p>