Strecs3D is a specialized desktop application designed to optimize 3D printing infill density through Finite Element Method (FEM) analysis. The software ingests CAD geometry (STEP/STL) and optional stress analysis results (VTU), segments the mesh based on stress thresholds, and exports variable-density 3MF files compatible with major slicers like Cura, Bambu Studio, and PrusaSlicer. It serves as a bridge between structural engineering simulation and additive manufacturing, allowing users to reduce material usage while maintaining structural integrity. The architecture is built on Qt 6 for the user interface and VTK for 3D visualization, compiled via CMake with vcpkg for dependency management. The application follows a modular design with a clear separation between the UI layer, core processing logic, and FEM pipeline integration. It supports a full simulation workflow, converting STEP files to CalculiX input (INP), running the solver, and converting the output (FRD) back to VTK format for visualization and processing. Data flows from geometry import through optional FEM simulation to mesh segmentation and 3MF export. The system relies heavily on external tools (CalculiX, Gmsh, OpenCASCADE) which are integrated via custom ports and wrappers. While the internal C++ code demonstrates professional engineering practices, the heavy coupling to external binary dependencies and platform-specific build configurations introduces maintenance complexity. The codebase is actively maintained with recent commits and a low issue count relative to its popularity. However, technical drift is present due to hardcoded paths for external solvers and custom patches for Gmsh, which require careful version management to prevent breakage in deployment environments.