x402-openai

Drop-in OpenAI TypeScript client with transparent x402 payment support.

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Wrap the standard openai.OpenAI client with a crypto wallet. When the server responds with HTTP 402, the library automatically signs and retries the request — zero code changes needed.

Installation

bun add x402-openai @x402/evm viem                       # EVM (Ethereum / Base / …)
bun add x402-openai @x402/svm @solana/kit @scure/base    # Solana
bun add x402-openai @x402/evm @x402/svm viem @solana/kit @scure/base  # all chains

Quick Start

import { X402OpenAI } from "x402-openai";
import { EvmWallet } from "x402-openai/wallets";

const client = new X402OpenAI({
  wallet: new EvmWallet({ privateKey: "0x…" }),
});

const res = await client.chat.completions.create({
  model: "openai/gpt-4o-mini",
  messages: [{ role: "user", content: "Hello!" }],
});
console.log(res.choices[0]?.message.content);

Swap EvmWallet for SvmWallet to pay on Solana — the API is identical.

Usage

Streaming

const stream = await client.chat.completions.create({
  model: "openai/gpt-4o-mini",
  messages: [{ role: "user", content: "Explain x402" }],
  stream: true,
});

for await (const chunk of stream) {
  const content = chunk.choices[0]?.delta?.content;
  if (content) process.stdout.write(content);
}

Multi-chain

import { EvmWallet, SvmWallet } from "x402-openai/wallets";

const client = new X402OpenAI({
  wallets: [
    new EvmWallet({ privateKey: "0x…" }),
    new SvmWallet({ privateKey: "base58…" }),
  ],
});

BIP-39 Mnemonic (EVM)

const wallet = new EvmWallet({ mnemonic: "word1 word2 … word12" });
const wallet2 = new EvmWallet({ mnemonic: "…", accountIndex: 2 });                 // m/44'/60'/0'/0/2
const wallet3 = new EvmWallet({ mnemonic: "…", derivationPath: "m/44'/60'/2'/0/0" }); // custom path

The protocol selects the right chain automatically based on the server's payment requirements.

Payment Policies

Use policies to control which chain or scheme is preferred when multiple payment options are available:

import { X402OpenAI, preferNetwork, preferScheme, maxAmount } from "x402-openai";
import { EvmWallet, SvmWallet } from "x402-openai/wallets";

const client = new X402OpenAI({
  wallets: [
    new EvmWallet({ privateKey: "0x…" }),
    new SvmWallet({ privateKey: "base58…" }),
  ],
  policies: [
    preferNetwork("eip155:8453"),  // Prefer Base mainnet
    preferScheme("exact"),         // Prefer exact payment scheme
    maxAmount(1_000_000n),         // Cap at 1 USDC (6 decimals)
  ],
});

API Reference

X402OpenAI

Drop-in replacement for openai.OpenAI. Provide exactly one credential source:

Parameter	Type	Description
wallet	Wallet	Single wallet adapter
wallets	Wallet[]	Multiple adapters (multi-chain)
policies	PaymentPolicy[]	Payment policies (chain/scheme preference, amount cap)
x402Client	x402Client	Pre-configured x402 client (bypasses policies)

All standard OpenAI options (baseURL, timeout, maxRetries, …) are forwarded. Default baseURL: https://llm.qntx.fun/v1

Wallet Adapters

Class	Chain	Install extras
EvmWallet({ privateKey: … })	EVM	@x402/evm viem
EvmWallet({ mnemonic: … })	EVM (BIP-39)	@x402/evm viem
SvmWallet({ privateKey: … })	Solana	@x402/svm @solana/kit @scure/base

Implement the Wallet interface to add a new chain.

Examples

See the examples/ directory. Each script is self-contained:

EVM_PRIVATE_KEY="0x…"           bun examples/chat-evm.ts
SOLANA_PRIVATE_KEY="base58…"    bun examples/chat-svm.ts
EVM_PRIVATE_KEY="0x…"           bun examples/streaming-evm.ts
MNEMONIC="word1 word2 …"       bun examples/chat-evm-mnemonic.ts
EVM_PRIVATE_KEY="0x…"           bun examples/chat-evm-policy.ts
EVM_PRIVATE_KEY="0x…" SOLANA_PRIVATE_KEY="base58…" bun examples/chat-multichain-policy.ts

License

This project is licensed under the MIT License.

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A QNTX open-source project.

Code is law. We write both.