SlopScan is a small open-source API that checks whether an npm/PyPI package name is real before you install it. The problem it solves is specific and increasingly common: LLMs hallucinate package names — studies put it around 20% of AI-generated code referencing packages that don't exist — and attackers have started pre-registering those exact hallucinated names on the real registries with malicious payloads. It's called slopsquatting, and the nasty part is that ~43% of hallucinated names are consistent across runs of the same model, which makes them systematically guessable and worth squatting on.
SlopScan itself is straightforward: point it at a package name, it scores trust based on registry age, download counts, GitHub signal, and a few other factors, and hands back SAFE / CAUTION / SUSPICIOUS / DANGEROUS. What this post is actually about is wiring it into Claude Code so it checks automatically, before any install runs — and a genuinely interesting bug I hit building the automatic part.
Two pieces, doing different jobs
I built this as a skill plus a hook, and they're not redundant — they solve different problems.
A skill is documentation Claude reads and can act on. It's great for "here's how to do X when you need to" — but it only fires if the model remembers to reach for it. Ask yourself honestly: would you trust an assistant to always remember to check a package before installing it, across every session, forever, with no exceptions? I wouldn't, and I do this daily.
