Gaming Disorder (GD) has been recognized by the World Health Organization as a behavioral addiction with severe consequences, especially among adolescents. Current prevention approaches are mainly downstream, implemented after video games are released and placing responsibility on players rather than on upstream development choices. To investigate how GD prevention is currently supported upstream, this paper first presents an integrative review of tools and education and training programs in video game development, as these two resources reflect how developers are concretely equipped in their practice. The review highlights a double gap: existing tools improve efficiency, collaboration, and engagement but lack approaches to address GD risks, while education and training provide technical and creative skills but rarely include GD prevention as a learning outcome. Then, to respond to this double gap, this paper presents GameDev MentorHub, an “on-the-job" Technology-Enhanced Learning tool that aims to embed GD prevention directly into the video game development process, providing development support, real-time GD risk evaluation, and context-aware learning grounded in psychological science. By aligning GD prevention with everyday development practice and fostering ongoing knowledge development, the proposed tool seeks to complement existing downstream approaches and advance upstream approaches to prevent GD.