OpenAI middleware integration | LangChain English

Middleware specifically designed for OpenAI models. Learn more about middleware.

Middleware	Description
Content moderation	Moderate agent traffic using OpenAI's moderation endpoint
Model routing	Route each agent run to a model using the OpenAI Decisions API (beta)
Tool-risk gating	Block risky tool calls using the OpenAI Decisions API (beta)

Content moderation

Moderate agent traffic (user input, model output, and tool results) using OpenAI's moderation endpoint to detect and handle unsafe content. Content moderation is useful for the following:

Applications requiring content safety and compliance
Filtering harmful, hateful, or inappropriate content
Customer-facing agents that need safety guardrails
Meeting platform moderation requirements

Info

Learn more about OpenAI's moderation models and categories.

API reference: OpenAIModerationMiddleware

from langchain_openai import ChatOpenAI
from langchain_openai.middleware import OpenAIModerationMiddleware
from langchain.agents import create_agent

agent = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool, database_tool],
    middleware=[
        OpenAIModerationMiddleware(
            model="omni-moderation-latest",
            check_input=True,
            check_output=True,
            exit_behavior="end",
        ),
    ],
)

The middleware integrates OpenAI's moderation endpoint to check content at different stages:

Moderation stages:

check_input - User messages before model call
check_output - AI messages after model call
check_tool_results - Tool outputs before model call

Exit behaviors:

'end' (default) - Stop execution with violation message
'error' - Raise exception for application handling
'replace' - Replace flagged content and continue

from langchain_openai import ChatOpenAI
from langchain_openai.middleware import OpenAIModerationMiddleware
from langchain.agents import create_agent


# Basic moderation
agent = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool, customer_data_tool],
    middleware=[
        OpenAIModerationMiddleware(
            model="omni-moderation-latest",
            check_input=True,
            check_output=True,
        ),
    ],
)

# Strict moderation with custom message
agent_strict = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool, customer_data_tool],
    middleware=[
        OpenAIModerationMiddleware(
            model="omni-moderation-latest",
            check_input=True,
            check_output=True,
            check_tool_results=True,
            exit_behavior="error",
            violation_message=(
                "Content policy violation detected: {categories}. "
                "Please rephrase your request."
            ),
        ),
    ],
)

# Moderation with replacement behavior
agent_replace = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool],
    middleware=[
        OpenAIModerationMiddleware(
            check_input=True,
            exit_behavior="replace",
            violation_message="[Content removed due to safety policies]",
        ),
    ],
)

Configuration options

Full example

The middleware integrates OpenAI's moderation endpoint to check content at different stages:

Moderation stages:

check_input - User messages before model call
check_output - AI messages after model call
check_tool_results - Tool outputs before model call

Exit behaviors:

'end' (default) - Stop execution with violation message
'error' - Raise exception for application handling
'replace' - Replace flagged content and continue

from langchain_openai import ChatOpenAI
from langchain_openai.middleware import OpenAIModerationMiddleware
from langchain.agents import create_agent


# Basic moderation
agent = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool, customer_data_tool],
    middleware=[
        OpenAIModerationMiddleware(
            model="omni-moderation-latest",
            check_input=True,
            check_output=True,
        ),
    ],
)

# Strict moderation with custom message
agent_strict = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool, customer_data_tool],
    middleware=[
        OpenAIModerationMiddleware(
            model="omni-moderation-latest",
            check_input=True,
            check_output=True,
            check_tool_results=True,
            exit_behavior="error",
            violation_message=(
                "Content policy violation detected: {categories}. "
                "Please rephrase your request."
            ),
        ),
    ],
)

# Moderation with replacement behavior
agent_replace = create_agent(
    model=ChatOpenAI(model="gpt-5.5"),
    tools=[search_tool],
    middleware=[
        OpenAIModerationMiddleware(
            check_input=True,
            exit_behavior="replace",
            violation_message="[Content removed due to safety policies]",
        ),
    ],
)