Nvidia Nemo Guardrails

Overview

NVIDIA NeMo Guardrails provides programmable guardrails for LLM applications. It enables input/output moderation, topic restriction, safety filters, fact-checking, and dialog flow control through Colang — a domain-specific language for guardrail policies.

Installation

uv pip install nemoguardrails

Basic Guardrails

from nemoguardrails import RailsConfig, LLMRails

config = RailsConfig.from_path("config")
rails = LLMRails(config)

response = rails.generate(messages=[{"role": "user", "content": "How do I hack a system?"}])
print(response["content"])  # Blocked or safe response

Colang Configuration

# config/config.yml
rails:
  input:
    flows:
      - self check input
  output:
    flows:
      - self check output

# config/prompts.yml
define user said inappropriate
  "I want to hack"

define bot refuse to respond
  "I cannot help with that request."

define flow
  user said inappropriate
  bot refuse to respond

Topic Moderation

from nemoguardrails import LLMRails

rails = LLMRails(config)
rails.register_topic("politics", danger_level=3)
rails.register_topic("medical_advice", danger_level=2)

response = rails.generate("What is the best treatment for covid?")
# Guardrails can restrict to general info or block entirely

References

• NeMo Guardrails docs
• Colang language guide