Mutation testing, but for LLM evals — early experiment, would love feedback

I write evals for LLM features, wire them into CI, and move on. But a passing eval suite has a blind spot: it tells you nothing about whether it would actually fail if the model quietly got worse. Green isn't the same as good. So I built muteval to measure that directly. It borrows mutation testing from software engineering — you deliberately break the thing under test and check whether your tests catch it. muteval degrades the system (weakens a prompt rule, drops a retrieved doc, swaps in a…