In the September 2026 Hacker News discussion thread, developers showcased a diverse array of side projects including a weight-training app that optimizes workouts using custom strength curve modeling and an open-source tool for filling out U.S. immigration forms. Other notable builds feature a custom voxel game engine utilizing signed distance fields and a hybrid Zettelkasten notes app for Mac. Additionally, one developer shared the results of an ongoing paper-trading experiment comparing the stock market performance of various AI models against a non-AI control.