LangGraph is a framework that orchestrates workflows with stateful interactions between tools, annotations, and large language models (LLMs). By structuring workflows as state graphs, LangGraph makes it easier to design, debug, and execute complex interactions, such as querying databases and refining responses using LLMs.
LangGraph addresses the problem of building complex, structured workflows for conversational AI and decision-making systems, enabling developers to create flexible, stateful, and dynamic logic flows that integrate with multiple tools and AI models.
Why Use LangGraph with LLMs?
*Structured Workflows: *
Without LangGraph, combining multiple tools and LLMs often involves hard-to-manage code with ad hoc state handling.
LangGraph provides a structured approach using nodes (tools or functions) and edges (dependencies).
State Management:
Tracks the flow of data using annotations, ensuring smooth transitions between nodes.
Avoids repetitive boilerplate code by automating state transitions.
LLM Integration:
Enables chaining of LLMs with tools like Pinecone for vector database querying.
Allows post-processing and response refinement to produce user-specific outputs.
Reusability:
Modular nodes and reusable workflows make LangGraph ideal for scalable applications.
How This Code Works
Problem Statement This application queries a Pinecone vector database to retrieve relevant information (e.g., "Phase 5 deliverables of very long document") and refines the results using an LLM. The user specifies what to query, and the program:
Fetches data from Pinecone.
Summarizes and filters the results using an LLM.
Workflow Overview The workflow is implemented using a StateGraph, which manages the interactions between the following components:
- Nodes:
*pineConeTool: *
Queries Pinecone for relevant results.
*refineResponse: *
Processes and summarizes the results using an LLM.
Edges:
Define the order of execution:
Start → Query Pinecone → Refine Response → End.
- Annotations:
- prompt: The user's query.
- nameSpace: Namespace in the Pinecone index.
- indexName: Pinecone index to query.
- messages: Tracks tool outputs and LLM refinements.-
Code Workflow
- User Query:
The user specifies the prompt, nameSpace, and indexName.
Example: "give me data about phase 5 deliverables do not include phase 6 of the project".
Pinecone Query (pineConeTool):
- Uses embeddings to query Pinecone for relevant results.
- Filters results and returns the matches.
LLM Refinement (refineResponse):
- Passes the raw results to the LLM.
- Instructs the LLM to summarize and filter the results (e.g., exclude Phase 6).
Final Output:
- Returns a refined and concise response to the user.
Key Components ( tools )
Pinecone Tool this tool:
- Embeds the user query using OpenAI embeddings.
- Queries Pinecone for the top 3 matching results.
- Outputs raw matches for further processing.
Refine Response Tool This tool:
- Summarises the results from Pinecone using an LLM.
- Filters and restructures the output based on user constraints.
import { AIMessage, BaseMessage, HumanMessage } from "@langchain/core/messages";
import { ChatOpenAI, OpenAIEmbeddings } from "@langchain/openai";
import {
StateGraph,
MemorySaver,
Annotation,
messagesStateReducer,
START,
END,
} from "@langchain/langgraph";
import { Pinecone as PineconeClient } from "@pinecone-database/pinecone";
import dotenv from "dotenv";
dotenv.config();
const DEBUG = false;
const OPEN_AI_TEXT_EMB_3_SMALL = "text-embedding-3-small";
const MODEL_NAME = "gpt-4o";
const MODEL_TEMP = 0.2;
// create pinecone client connection.
// this is used to run the queries
const pinecone = new PineconeClient({
apiKey: process.env.PINECONE_API_KEY!,
});
// this is the Root Annotation, it will hold
// the state information as the langGraph
// progresses
const StateAnnotations = Annotation.Root({
messages: Annotation<BaseMessage[]>({
reducer: messagesStateReducer, // append new messages
}),
prompt: Annotation<string>(),
nameSpace: Annotation<string>(),
indexName: Annotation<string>(),
});
// this is where we create our tool
// each tool is added to the langGraph
const pineConeTool = async (_state: typeof StateAnnotations.State) => {
if (DEBUG) console.log("In Pinecone Tool");
//create embedding instance of openAI
const embedding = new OpenAIEmbeddings({
openAIApiKey: process.env.OPENAI_API_KEY!,
batchSize: 100,
model: OPEN_AI_TEXT_EMB_3_SMALL,
});
// extract the correct index in pinecone database
const index = pinecone.Index(_state.indexName);
// extract the correct nameSpace in pinecone
const embeddedPrompt = await embedding.embedQuery(_state.prompt);
const result = await index.namespace(_state.nameSpace).query({
vector: embeddedPrompt,
topK: 3,
includeMetadata: true,
});
// iterate over the results from the relevant vectors
const mappedResult = result.matches.map((item) => item.metadata?.text + "\n");
if (DEBUG) console.log("Mapped Result:", mappedResult);
// add the response into the StatAnnotation
return {
messages: [new AIMessage(mappedResult.join(""))],
};
};
// this is the second tool that is called
// within the workflow of the langGraph to
// refine the results
const refineResponse = async (_state: typeof StateAnnotations.State) => {
if (DEBUG) console.log("Processing with LLM...");
// extract the last message on the graph
const lastToolMessage = _state.messages[
_state.messages.length - 1
] as AIMessage;
// Generate a refined prompt with explicit instructions
// this is to refine the results from the extracted vectors
const refinedPrompt = `
Based on the following information, summarize only the deliverables related to Phase 5.
Do not include details about any other phases.
${lastToolMessage.content}
`;
const refinedMessage = new HumanMessage(refinedPrompt);
// Add the refined message to the state
_state.messages.push(refinedMessage);
const response = await model.invoke(_state.messages);
if (DEBUG) console.log("Refined LLM Response:", response.content);
return {
messages: [response],
};
};
//create the LLM
const model = new ChatOpenAI({
model: MODEL_NAME,
temperature: MODEL_TEMP,
});
// define the graph
// this is how the workflow is created
// the tools are added to the nodes StateGraph
// then the order of execution is set
const workflow = new StateGraph(StateAnnotations)
.addNode("__pinecone__", pineConeTool)
.addNode("__refine__", refineResponse)
.addEdge(START, "__pinecone__")
.addEdge("__pinecone__", "__refine__")
.addEdge("__pinecone__", END);
// set the memory between states
const checkpointer = new MemorySaver();
// compile the graph workflow
const app = workflow.compile({ checkpointer });
//finally run a query to start the workflow
async function run() {
// prepare the payload that will be passed between states in
// the langGraph
const payload = {
messages: [],
prompt: "give me data about phase 5 deliverables do not include phase 6",
nameSpace: "emi_pdf",
indexName: "emi-pc-example-index",
};
const finalState = await app.invoke(payload, {
configurable: { thread_id: "emi-77" },
});
//extract results
console.log(finalState.messages[finalState.messages.length - 1].content);
}
// run the graph
run();
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