LangChain
Most widely used framework for building LLM applications. Chains, agents, RAG pipelines, and deep integrations with 300+ tools.
NeMo Guardrails
NVIDIA's open-source toolkit for adding programmable safety, topic, and dialog rails to LLM applications. Define rules in Colang DSL to prevent off-topic responses, enforce output formats, and guard against prompt injection. Standard in enterprise LLM deployments.