DD4hep is a software framework for providing a complete solution for full detector description (geometry, materials, visualization, readout, alignment, calibration, etc.) for high energy physics experiments. It uses the ROOT geometry package and adds support for detector alignment, conditions, and simulation with Geant4. Built here with +ddg4 +ddcad +edm4hep +g4hepem +hepmc3 +xercesc, matching the EIC (eic_xl) variant set -- part of hep-forge's EIC Phase 1 simulation-chain build-out (geant -> g4hepem -> dd4hep -> epic -> npsim, plus acts).