Open Source LLM Guardrails: The Libraries Available, Where They Sit, and What They Cannot Replace
Open source LLM guardrails libraries cover prompt-side and response-side filtering inside the application or inference path. Llama Guard, NeMo Guardrails, Guardrails AI, LMQL, and Rebuff each occupy a different position in the stack and produce different control surfaces. This piece walks through the libraries available, the architectural position each one takes, the controls they produce, and the regulatory profile that requires an external inspection layer on top of any of them.