Abstract: Rapid intensification of nearshore tropical cyclones poses a formidable challenge to operational intensity forecasting. Typhoon Maysak (2610) underwent an unexpected intensification over the Beibu Gulf before landfall, subsequently causing severe wind and rainfall impacts across Guangxi, yet the underlying mechanisms remain to be elucidated. Using multi-source data, this study diagnoses the dynamic and thermodynamic processes governing the nearshore intensification of Maysak, focusing on the evolving roles of environmental conditions and inner-core processes. Results reveal that anomalously warm sea surface temperatures exceeding 29℃ and high ocean heat content over the Beibu Gulf provided a critical energy source for intensification, and the deceleration of Maysak near the coast further amplified this oceanic thermal forcing. Dynamically, the eastward expansion of the South Asian High easterly jet enhanced upper-level outflow while simultaneously intensifying deep-layer vertical wind shear, establishing a competing relationship. Nearshore convergence of the boundary layer flow sustained vorticity growth through stretching, dynamically offsetting the adverse effects of strong shear. Thermally, although large-scale moisture transport weakened due to moisture interception by a Bay of Bengal storm, nearshore convergence strengthened ascending motion, drawing deep convection toward the storm center. This reorganization triggered a marked surge in diabatic heating, with a deep heating maximum established in the mid-to-upper troposphere. These processes collectively enhanced moisture utilization efficiency and convective organization, enabling Maysak to achieve intensification despite diminishing external moisture supply. The findings establish a physical framework for understanding nearshore intensification under unfavorable moisture and shear conditions, offering valuable insights for operational intensity forecasting of typhoons in the Beibu Gulf region.