LangGraph Integration Guide

Name: agentAssert
Author: Varun Pratap Bhardwaj

Add formal runtime invariants and preconditions to LangGraph StateGraph nodes. Intercept state updates before edge transitions occur.

Using the LangGraph Contract Wrapper

Wrap your graph node execution functions with `ContractNode` to automatically validate state invariants and catch drift before continuing along the graph.

langgraph_example.py

from langgraph.graph import StateGraph, END
from agentassert_abc.integrations.langgraph import ContractNode
from agentassert_abc import Contract

# 1. Load contract
contract = Contract.from_yaml("contracts/financial-advisor.yaml")

# 2. Define node function
def advisor_node(state):
    # Standard LangGraph logic
    return {"response": "Your portfolio summary is ready."}

# 3. Create StateGraph with ContractNode wrapper
workflow = StateGraph(dict)
workflow.add_node("advisor", ContractNode(advisor_node, contract=contract))
workflow.set_entry_point("advisor")
workflow.add_edge("advisor", END)

app = workflow.compile()
output = app.invoke({"input": "Show my balance"})