The monthly Hacker News "What Are You Working On?" thread for April 2026 showcases side projects from developers across diverse domains. One standout is Caliper, a code quality system specifically designed for AI-generated code that catches convention violations immediately after each agent turn. Early data shows 40% of agent turns produce code that violates project conventions as defined in CLAUDE.md, prompting the founder to build multiple check layers throughout the development cycle rather than relying on final review.

Another project, react.tv, lets users create custom TV channels from YouTube, Twitch, TikTok, and other platforms using an advanced scheduling system with team collaboration and OBS integration for restreaming. One developer built a sophisticated Latin study tool entirely within GNU Emacs, combining gptel, Gemini, local models, yt-dlp, and Voice Activity Detection to transform century-old PDF scans from the Internet Archive into structured Org-mode documents with audio playback and automatic flashcard generation.

The thread also features a quantum photonics experimenter sharing an interactive 3D demo of SPDC for creating entangled photon pairs, a Lotus fan site analyzing over 900 concert setlists to identify song patterns, and an LLM evaluation framework with RAG pipelines for price/accuracy comparisons. The projects reflect developers leveraging AI tools to solve personal problems and explore new technical territories.