In the field of Sustainable Agriculture, Agronomy and Food Science, erratic monsoonal precipitation and hydrological drought severely constrain upland rice yields across South and Southeast Asia. This empirical investigation systematically examines Evaluation of Drought-Tolerant Upland Rice Genotypes under Variable Reproductive-Stage Water Deficits through a multi-stage experimental methodology and rigorous quantitative analytical framework. Utilizing randomized complete block field trials across multi-year dry seasons, GGE biplot analysis, and leaf water potential monitoring, data were gathered across multiple operational cycles and validated against established international benchmarks. The statistical and computational results reveal that elite drought-tolerant lines maintained harvest index above 38% and sustained 4.1 t/ha grain yields under -70 kPa soil moisture deficits. Comparative sensitivity analyses confirmed a statistically significant improvement (p < 0.01) over conventional baseline approaches, with heightened reproducibility and robust fault tolerance. These comprehensive findings provide actionable theoretical insights and practical implementation guidelines for cereal breeding programs targeting rainfed and moisture-stressed marginal lands. Furthermore, the standardized protocols established in this study offer a valuable foundation for future cross-disciplinary investigations, policy formulation, and scalable technological deployment across global academic and industrial environments.