What are NeMo Guardrails and Garak — when do you use each?

NeMo Guardrails (Nvidia open-source) — runtime LLM guardrails. Defines conversational rails (topic restrictions, fact-checking, jailbreak detection) using YAML/Colang. Production-deployed alongside LLM apps. Use case: protect production RAG/chatbot from harmful inputs/outputs. Garak (LLM Vulnerability Scanner, Nvidia) — testing-time tool. Probes LLMs with adversarial prompts (jailbreaks, prompt injection, data extraction) and reports vulnerabilities. Use case: security testing during development + before production deployment. Used together: Garak for offensive testing → identify weaknesses → NeMo Guardrails to defend in production. Both critical for AI security engineer toolkit.