LangChain

pip install devcaster devcaster_langchain langchain langchain_openai

npm install @devcaster/core @devcaster/langchain @langchain/openai @langchain/langgraph @langchain/core

from devcaster import Devcaster
from devcaster_langchain import LangchainProvider
from langchain.agents import create_agent
from langchain_openai import ChatOpenAI

devcaster = Devcaster(provider=LangchainProvider())
llm = ChatOpenAI(model="gpt-5.2")

# Create a session for your user
session = devcaster.create(user_id="user_123")
tools = session.tools()

agent = create_agent(tools=tools, model=llm)
result = agent.invoke({"messages": [("user", "Send an email to john@example.com with the subject 'Hello' and body 'Hello from Devcaster!'")]})

print(result["messages"][-1].content)

import { ChatOpenAI } from '@langchain/openai';
import { HumanMessage, AIMessage } from '@langchain/core/messages';
import { ToolNode } from '@langchain/langgraph/prebuilt';
import { StateGraph, MessagesAnnotation } from '@langchain/langgraph';
import { Devcaster } from '@devcaster/core';
import { LangchainProvider } from '@devcaster/langchain';

const devcaster = new Devcaster({
  provider: new LangchainProvider(),
});

// Create a session for your user
const session = await devcaster.create("user_123");
const tools = await session.tools();

const toolNode = new ToolNode(tools);

const model = new ChatOpenAI({
  model: 'gpt-5.2',
  temperature: 0,
}).bindTools(tools);

function shouldContinue({ messages }: typeof MessagesAnnotation.State) {
  const lastMessage = messages[messages.length - 1] as AIMessage;
  if (lastMessage.tool_calls?.length) {
    return 'tools';
  }
  return '__end__';
}

async function callModel(state: typeof MessagesAnnotation.State) {
  const response = await model.invoke(state.messages);
  return { messages: [response] };
}

const workflow = new StateGraph(MessagesAnnotation)
  .addNode('agent', callModel)
  .addEdge('__start__', 'agent')
  .addNode('tools', toolNode)
  .addEdge('tools', 'agent')
  .addConditionalEdges('agent', shouldContinue);

const app = workflow.compile();

const finalState = await app.invoke({
  messages: [new HumanMessage("Send an email to john@example.com with the subject 'Hello' and body 'Hello from Devcaster!'")],
});
console.log(finalState.messages[finalState.messages.length - 1].content);