<p>This study investigates the combined effects of Hall current and diffusion thermo on the three-dimensional magnetohydrodynamic (MHD) Casson hybrid nanofluid (CuO–Ag/water) flow over a linearly stretched surface under rotating conditions. The presence of thermophoresis and Brownian motion is incorporated to analyze thermal and mass transfer characteristics. The novelty of this work lies in the integrated study of Hall current, Diffusion thermo, and hybrid nanoparticle effects on heat and mass transport, which has not been extensively explored in existing literature. The governing partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs) using similarity transformations. A numerical approach utilizing the fourth-order Runge–Kutta method with the shooting technique is employed to solve the equations. Results are validated against existing literature, demonstrating 99.9% compatibility for various parameter ranges. The present study reveals that fluid velocity decreases as the rotation parameter increases, whereas it increases with a higher Hall current parameter. Additionally, the temperature rises with an increase in thermal radiation and diffusion thermo effects, highlighting their significant influence on heat transfer dynamics. This study uniquely integrates Hall current and diffusion thermo effects into a Casson hybrid nanofluid model, providing new insights into complex heat and mass transfer mechanisms. The dual impact of thermophoresis and Brownian motion in such a setting is explored for the first time, offering a foundation for future experimental and numerical investigations.</p>