A comparison of AI agent safety and governance tools to help you choose the right approach.
| Tool | Primary Focus | When It Acts | Architecture | Best For |
|---|---|---|---|---|
| Agent OS | Action interception | During execution | Middleware wrapper | Runtime governance |
| Guardrails AI | Input/output validation | Before/after LLM | Validators | Response quality |
| NeMo Guardrails | Conversational safety | Before/after LLM | Dialog rails | Chatbot safety |
| LlamaGuard | Content classification | Before/after LLM | Classification model | Content moderation |
| LangChain Callbacks | Event observation | Before/after steps | Callback handlers | Monitoring |
What it does: Intercepts agent actions at execution time. Wraps frameworks like LangChain, CrewAI, and OpenAI Assistants with governance checks.
Key differentiator: Policies are enforced by code, not by hoping the LLM complies. If a policy says "no destructive SQL," the action is blocked even if the LLM generates it.
from agent_os import KernelSpace, Policy
kernel = KernelSpace(policies=[
Policy.no_destructive_sql(),
Policy.rate_limit(100, "1m"),
])
@kernel.govern
def my_agent(task):
return llm.generate(task) # Dangerous actions blocked at executionPros:
- Deterministic enforcement (not probabilistic)
- Works with any LLM framework
- POSIX-inspired primitives (signals, VFS)
- Comprehensive audit logging
Cons:
- Application-level only (bypass possible with direct stdlib calls)
- Requires wrapping existing code
- Adds latency (typically 1-5ms per action)
Best for: Production deployments where you need deterministic safety guarantees and audit trails.
What it does: Validates LLM inputs and outputs against schemas. Ensures responses match expected formats and constraints.
from guardrails import Guard
from guardrails.hub import DetectPII
guard = Guard().use(DetectPII())
result = guard(llm.complete, prompt="...")Key differentiator: Schema-based validation with automatic retries. Great for ensuring structured output.
Pros:
- Rich validator ecosystem (Guardrails Hub)
- Automatic retry with corrective prompts
- Schema enforcement (JSON, XML, etc.)
- Strong community
Cons:
- Focuses on I/O, not action interception
- Validators are pattern-based (can miss edge cases)
- Retry loops can increase costs
Best for: Applications where output format and quality are critical.
What it does: Defines conversational "rails" that guide chatbot behavior. Uses a Colang DSL to define allowed conversation flows.
define user ask about competitors
"What can you tell me about [competitor]?"
"How do you compare to [competitor]?"
define flow
user ask about competitors
bot refuse to discuss competitors
Key differentiator: Domain-specific language for conversational safety. Designed for enterprise chatbots.
Pros:
- Colang DSL is intuitive for non-developers
- Built-in topical rails, moderation, fact-checking
- Good for customer-facing chatbots
- NVIDIA backing
Cons:
- Focused on conversational AI (less suitable for agents)
- Colang learning curve
- Less flexible than code-based solutions
Best for: Enterprise chatbots with complex conversational requirements.
What it does: Classifies prompts and responses for safety. Uses a fine-tuned Llama model to detect harmful content.
from transformers import pipeline
classifier = pipeline("text-classification", model="meta-llama/LlamaGuard-7b")
result = classifier("Is this content safe?")Key differentiator: Model-based classification rather than rule-based. Can catch nuanced unsafe content.
Pros:
- Catches nuanced content issues
- Multi-category safety taxonomy
- Open weights (self-hostable)
- Good for content moderation
Cons:
- Requires GPU for inference
- Adds latency (model inference)
- Classification can have false positives/negatives
- Focused on content, not actions
Best for: Content moderation in applications with user-generated input.
What it does: Observes agent execution via callback handlers. Logs events, traces execution, integrates with observability tools.
from langchain.callbacks import StdOutCallbackHandler
chain.invoke({"input": "..."}, callbacks=[StdOutCallbackHandler()])Key differentiator: Native to LangChain ecosystem. Great for observability but doesn't block actions.
Pros:
- Zero additional dependencies
- Integrates with LangSmith, Weights & Biases
- Minimal latency impact
- Good debugging tool
Cons:
- Observability only (doesn't block/modify)
- LangChain-specific
- Not designed for enforcement
Best for: Development and debugging, not production governance.
| Scenario | Recommended Tool |
|---|---|
| Production agent with strict safety requirements | Agent OS |
| Ensuring JSON/structured output from LLM | Guardrails AI |
| Enterprise customer service chatbot | NeMo Guardrails |
| Content moderation for user input | LlamaGuard |
| Debugging LangChain applications | LangChain Callbacks |
| Multi-tenant SaaS with isolation needs | Agent OS |
| Cost control and rate limiting | Agent OS |
These tools are complementary. A robust production setup might use:
from agent_os import KernelSpace
from guardrails import Guard
from langchain.callbacks import TracingCallbackHandler
# 1. Agent OS for action governance
kernel = KernelSpace(policy="strict")
# 2. Guardrails for output validation
guard = Guard().use(DetectPII())
# 3. LangChain callbacks for observability
callbacks = [TracingCallbackHandler()]
@kernel.govern
def my_agent(task):
result = chain.invoke({"input": task}, callbacks=callbacks)
return guard.validate(result)| Feature | Agent OS | Guardrails AI | NeMo Guardrails | LlamaGuard |
|---|---|---|---|---|
| Action blocking | β | βͺ | βͺ | βͺ |
| Input validation | βͺ | β | β | β |
| Output validation | βͺ | β | β | β |
| Rate limiting | β | βͺ | βͺ | βͺ |
| Audit logging | β | βͺ | βͺ | βͺ |
| Cost controls | β | βͺ | βͺ | βͺ |
| Multi-tenant isolation | β | βͺ | βͺ | βͺ |
| Schema enforcement | βͺ | β | βͺ | βͺ |
| Conversational rails | βͺ | βͺ | β | βͺ |
| Content classification | βͺ | βͺ | βͺ | β |
| POSIX signals | β | βͺ | βͺ | βͺ |
| Framework agnostic | β | β | βͺ | β |
| Self-hosted | β | β | β | β |
| Automatic retries | βͺ | β | βͺ | βͺ |
Approximate latency overhead (varies by workload):
| Tool | Typical Latency | Notes |
|---|---|---|
| Agent OS | 1-5ms | Policy evaluation |
| Guardrails AI | 5-50ms | Depends on validators |
| NeMo Guardrails | 10-100ms | Depends on rail complexity |
| LlamaGuard | 100-500ms | Model inference |
| LangChain Callbacks | <1ms | Observability only |
# Before: Prompt-based (unreliable)
prompt = """You are a helpful assistant.
IMPORTANT: Never execute DROP TABLE or DELETE without WHERE.
IMPORTANT: Never access files outside /workspace."""
# After: Kernel-based (deterministic)
from agent_os import KernelSpace, Policy
kernel = KernelSpace(policies=[
Policy.no_destructive_sql(),
Policy.file_access("/workspace"),
])Keep Guardrails for output validation, add Agent OS for action governance:
from agent_os import KernelSpace
from guardrails import Guard
kernel = KernelSpace(policy="strict")
guard = Guard().use(ValidJSON())
@kernel.govern
def my_agent(task):
result = llm.generate(task)
return guard.validate(result) # Output validation
# Actions are governed by kernel- Agent OS = Action interception (what the agent does)
- Guardrails AI = Output validation (what the agent returns)
- NeMo Guardrails = Conversation flows (what the agent says)
- LlamaGuard = Content classification (what's appropriate)
Choose based on your primary concern, and consider combining tools for defense in depth.