Recsys Pipeline Architect

If you're building any system that picks "top K items for a user," this skill walks you through designing it as a composable six-stage pipeline: Source, Hydrator, Filter, Scorer, Selector, SideEffect. The pattern comes from xAI's open-sourced For You algorithm, and this is a clean independent reimplementation. It works for feeds, RAG rerankers, notification triage, search reranking, anything with a ranking problem. The skill doesn't just give you theory. It generates runnable scaffolds in TypeScript, Go, or Python, forces you to think through trade-offs like multi-action prediction versus single score, and includes reference implementations that actually pass their test suites. Good for when you need the plumbing around your scoring function, not the scoring function itself.