Custom Guardrail

Use this is you want to write code to run a custom guardrail

Quick Start

1. Write a CustomGuardrail Class

A CustomGuardrail has 3 methods to enforce guardrails

• async_pre_call_hook - (Optional) modify input or reject request before making LLM API call
• async_moderation_hook - (Optional) reject request, runs while making LLM API call (help to lower latency)
• async_post_call_success_hook- (Optional) apply guardrail on input/output, runs after making LLM API call

See detailed spec of methods here

Example CustomGuardrail Class

Create a new file called custom_guardrail.py and add this code to it

from typing import Any, Dict, List, Literal, Optional, Union

import litellm
from litellm._logging import verbose_proxy_logger
from litellm.caching import DualCache
from litellm.integrations.custom_guardrail import CustomGuardrail
from litellm.proxy._types import UserAPIKeyAuth
from litellm.proxy.guardrails.guardrail_helpers import should_proceed_based_on_metadata
from litellm.types.guardrails import GuardrailEventHooks


class myCustomGuardrail(CustomGuardrail):
    def __init__(
        self,
        **kwargs,
    ):
        # store kwargs as optional_params
        self.optional_params = kwargs

        super().__init__(**kwargs)

    async def async_pre_call_hook(
        self,
        user_api_key_dict: UserAPIKeyAuth,
        cache: DualCache,
        data: dict,
        call_type: Literal[
            "completion",
            "text_completion",
            "embeddings",
            "image_generation",
            "moderation",
            "audio_transcription",
            "pass_through_endpoint",
            "rerank"
        ],
    ) -> Optional[Union[Exception, str, dict]]:
        """
        Runs before the LLM API call
        Runs on only Input
        Use this if you want to MODIFY the input
        """

        # In this guardrail, if a user inputs `litellm` we will mask it and then send it to the LLM
        _messages = data.get("messages")
        if _messages:
            for message in _messages:
                _content = message.get("content")
                if isinstance(_content, str):
                    if "litellm" in _content.lower():
                        _content = _content.replace("litellm", "********")
                        message["content"] = _content

        verbose_proxy_logger.debug(
            "async_pre_call_hook: Message after masking %s", _messages
        )

        return data

    async def async_moderation_hook(
        self,
        data: dict,
        user_api_key_dict: UserAPIKeyAuth,
        call_type: Literal["completion", "embeddings", "image_generation", "moderation", "audio_transcription"],
    ):
        """
        Runs in parallel to LLM API call
        Runs on only Input

        This can NOT modify the input, only used to reject or accept a call before going to LLM API
        """

        # this works the same as async_pre_call_hook, but just runs in parallel as the LLM API Call
        # In this guardrail, if a user inputs `litellm` we will mask it.
        _messages = data.get("messages")
        if _messages:
            for message in _messages:
                _content = message.get("content")
                if isinstance(_content, str):
                    if "litellm" in _content.lower():
                        raise ValueError("Guardrail failed words - `litellm` detected")

    async def async_post_call_success_hook(
        self,
        data: dict,
        user_api_key_dict: UserAPIKeyAuth,
        response,
    ):
        """
        Runs on response from LLM API call

        It can be used to reject a response

        If a response contains the word "coffee" -> we will raise an exception
        """
        verbose_proxy_logger.debug("async_pre_call_hook response: %s", response)
        if isinstance(response, litellm.ModelResponse):
            for choice in response.choices:
                if isinstance(choice, litellm.Choices):
                    verbose_proxy_logger.debug("async_pre_call_hook choice: %s", choice)
                    if (
                        choice.message.content
                        and isinstance(choice.message.content, str)
                        and "coffee" in choice.message.content
                    ):
                        raise ValueError("Guardrail failed Coffee Detected")

2. Pass your custom guardrail class in LiteLLM config.yaml

In the config below, we point the guardrail to our custom guardrail by setting guardrail: custom_guardrail.myCustomGuardrail

• Python Filename: custom_guardrail.py
• Guardrail class name : myCustomGuardrail. This is defined in Step 1

guardrail: custom_guardrail.myCustomGuardrail

model_list:
  - model_name: gpt-4
    litellm_params:
      model: openai/gpt-4o
      api_key: os.environ/OPENAI_API_KEY

guardrails:
  - guardrail_name: "custom-pre-guard"
    litellm_params:
      guardrail: custom_guardrail.myCustomGuardrail  # 👈 Key change
      mode: "pre_call"                  # runs async_pre_call_hook
  - guardrail_name: "custom-during-guard"
    litellm_params:
      guardrail: custom_guardrail.myCustomGuardrail  
      mode: "during_call"               # runs async_moderation_hook
  - guardrail_name: "custom-post-guard"
    litellm_params:
      guardrail: custom_guardrail.myCustomGuardrail
      mode: "post_call"                 # runs async_post_call_success_hook

3. Start LiteLLM Gateway

Docker Run

Mount your custom_guardrail.py on the LiteLLM Docker container

This mounts your custom_guardrail.py file from your local directory to the /app directory in the Docker container, making it accessible to the LiteLLM Gateway.

docker run -d \
  -p 4000:4000 \
  -e OPENAI_API_KEY=$OPENAI_API_KEY \
  --name my-app \
  -v $(pwd)/my_config.yaml:/app/config.yaml \
  -v $(pwd)/custom_guardrail.py:/app/custom_guardrail.py \
  my-app:latest \
  --config /app/config.yaml \
  --port 4000 \
  --detailed_debug \

litellm pip

litellm --config config.yaml --detailed_debug

4. Test it

Test "custom-pre-guard"

Langchain, OpenAI SDK Usage Examples

Modify input

Expect this to mask the word litellm before sending the request to the LLM API. This runs the async_pre_call_hook

curl -i  -X POST http://localhost:4000/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer sk-1234" \
-d '{
    "model": "gpt-4",
    "messages": [
        {
            "role": "user",
            "content": "say the word - `litellm`"
        }
    ],
   "guardrails": ["custom-pre-guard"]
}'

Expected response after pre-guard

{
  "id": "chatcmpl-9zREDkBIG20RJB4pMlyutmi1hXQWc",
  "choices": [
    {
      "finish_reason": "stop",
      "index": 0,
      "message": {
        "content": "It looks like you've chosen a string of asterisks. This could be a way to censor or hide certain text. However, without more context, I can't provide a specific word or phrase. If there's something specific you'd like me to say or if you need help with a topic, feel free to let me know!",
        "role": "assistant",
        "tool_calls": null,
        "function_call": null
      }
    }
  ],
  "created": 1724429701,
  "model": "gpt-4o-2024-05-13",
  "object": "chat.completion",
  "system_fingerprint": "fp_3aa7262c27",
  "usage": {
    "completion_tokens": 65,
    "prompt_tokens": 14,
    "total_tokens": 79
  },
  "service_tier": null
}

Successful Call

curl -i http://localhost:4000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-npnwjPQciVRok5yNZgKmFQ" \
  -d '{
    "model": "gpt-3.5-turbo",
    "messages": [
      {"role": "user", "content": "hi what is the weather"}
    ],
    "guardrails": ["custom-pre-guard"]
  }'

Test "custom-during-guard"

Langchain, OpenAI SDK Usage Examples

Unsuccessful call

Expect this to fail since since litellm is in the message content. This runs the async_moderation_hook

curl -i  -X POST http://localhost:4000/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer sk-1234" \
-d '{
    "model": "gpt-4",
    "messages": [
        {
            "role": "user",
            "content": "say the word - `litellm`"
        }
    ],
   "guardrails": ["custom-during-guard"]
}'

Expected response after running during-guard

{
  "error": {
    "message": "Guardrail failed words - `litellm` detected",
    "type": "None",
    "param": "None",
    "code": "500"
  }
}

Successful Call

curl -i http://localhost:4000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-npnwjPQciVRok5yNZgKmFQ" \
  -d '{
    "model": "gpt-3.5-turbo",
    "messages": [
      {"role": "user", "content": "hi what is the weather"}
    ],
    "guardrails": ["custom-during-guard"]
  }'

Test "custom-post-guard"

Langchain, OpenAI SDK Usage Examples

Unsuccessful call

Expect this to fail since since coffee will be in the response content. This runs the async_post_call_success_hook

curl -i  -X POST http://localhost:4000/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer sk-1234" \
-d '{
    "model": "gpt-4",
    "messages": [
        {
            "role": "user",
            "content": "what is coffee"
        }
    ],
   "guardrails": ["custom-post-guard"]
}'

Expected response after running during-guard

{
  "error": {
    "message": "Guardrail failed Coffee Detected",
    "type": "None",
    "param": "None",
    "code": "500"
  }
}

Successful Call

 curl -i  -X POST http://localhost:4000/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer sk-1234" \
-d '{
    "model": "gpt-4",
    "messages": [
        {
            "role": "user",
            "content": "what is tea"
        }
    ],
   "guardrails": ["custom-post-guard"]
}'

CustomGuardrail methods

Component	Description	Optional	Checked Data	Can Modify Input	Can Modify Output	Can Fail Call
async_pre_call_hook	A hook that runs before the LLM API call	✅	INPUT	✅	❌	✅
async_moderation_hook	A hook that runs during the LLM API call	✅	INPUT	❌	❌	✅
async_post_call_success_hook	A hook that runs after a successful LLM API call	✅	INPUT, OUTPUT	❌	✅	✅