LangChain

export INFERIT_API_KEY='ik_...'

chat.py

# pip install langchain-openai
import os
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    base_url="https://api-production-c74b9.up.railway.app/v1",
    api_key=os.environ["INFERIT_API_KEY"],
    model="qwen/qwen-2.5-14b-instruct",  # "auto": Inferit picks the model
)

reply = llm.invoke("Say hello in five words.")
print(reply.content)
print(reply.response_metadata.get("model_name"))  # the model that answered

chat.mjs

// npm i @langchain/openai @langchain/core
import { ChatOpenAI } from '@langchain/openai';

const llm = new ChatOpenAI({
  model: 'qwen/qwen-2.5-14b-instruct', // "auto": Inferit picks the model
  apiKey: process.env.INFERIT_API_KEY,
  configuration: { baseURL: 'https://api-production-c74b9.up.railway.app/v1' },
});

const reply = await llm.invoke('Say hello in five words.');
console.log(reply.content);
console.log(reply.response_metadata?.model_name); // the model that answered

chat-x402.mts

// npm i @langchain/openai @langchain/core @x402/fetch @x402/evm viem
import { ChatOpenAI } from '@langchain/openai';
import { wrapFetchWithPayment, x402Client } from '@x402/fetch';
import { ExactEvmScheme } from '@x402/evm/exact/client';
import { generatePrivateKey, privateKeyToAccount } from 'viem/accounts';

const account = privateKeyToAccount((process.env.AGENT_KEY ?? generatePrivateKey()) as `0x${string}`);

// Testnet only: Inferit's faucet gives this address 1,000 free test ITC (the claim costs nothing).
await fetch('https://api-production-c74b9.up.railway.app/v1/faucet', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify({ address: account.address }),
});

// The standard x402 v2 client pays only in tokens it was told about: allow ITC,
// and cap one payment at 1 ITC (1000000 base units, 6 decimals).
const ITC = { network: 'eip155:1874', asset: '0x2E672dFE33EA977FD064E01aDe7d8c73B3Be7fBB' } as const;
const client = new x402Client()
  .register('eip155:*', new ExactEvmScheme(account))
  .setSpendControls({ allowedAssets: [{ ...ITC, maxAmountPerPayment: '1000000' }] });
const paidFetch = wrapFetchWithPayment(fetch, client);

// The OpenAI client always sends an Authorization header. Drop it, so the API
// answers with a 402 quote, which paidFetch pays and retries with PAYMENT-SIGNATURE.
const x402Fetch: typeof fetch = (input, init = {}) => {
  const headers = new Headers(init.headers);
  headers.delete('authorization');
  return paidFetch(input, { ...init, headers });
};

const llm = new ChatOpenAI({
  model: 'qwen/qwen-2.5-14b-instruct',
  apiKey: 'x402', // never sent: x402Fetch removes it
  maxTokens: 64, // the quote is the worst case for this body: a small limit keeps it small
  configuration: { baseURL: 'https://api-production-c74b9.up.railway.app/v1', fetch: x402Fetch },
});
console.log((await llm.invoke('Say hello in five words.')).content);