<![CDATA[Mathematics education in the Merdeka Curriculum era is required to develop students' critical thinking and problem solving skills through real world contexts, one of which is water scarcity and irrigation system efficiency a critical challenge in agriculture. This study aims to develop and validate a teaching module and assessment instrument based on Project-Based Learning (PjBL) with a STEM approach. The developed materials integrate mathematical optimization concepts, specifically the shortest path and network flow, to determine water flow routes in irrigation systems through the "Mini Irrigation Path" project. This study employed a Research and Development (R&D) approach using the ADDIE model, limited to the Development phase, targeting 10th-grade high school students studying linear functions. Data were collected using expert validation sheets for subject matter and media across 35 indicators, which were subsequently analyzed using Aiken's V validity index. The results revealed that 33 out of 35 indicators achieved a V value > 0.80, with 16 indicators reaching absolute agreement (V = 1.0000). The remaining two indicators fell into the moderate validity category but remained statistically significant and were revised by incorporating visual scaffolding and restructuring project instructions. The overall average Aiken's V index was 0.8952, categorizing the products as highly valid. In conclusion, the developed STEM-PjBL based teaching module and assessment instrument are valid and feasible to support contextual mathematics learning, the implementation of Merdeka Curriculum, and the achievement of SDGs 2, 4, and 6.]]>
