Payment Policies

Policies let you control which chain, scheme, or maximum amount the SDK should use when multiple payment options are available.

Available Policies

Policy	Description
preferNetwork(caip2)	Prefer a specific network (e.g. "eip155:8453" for Base)
preferScheme(scheme)	Prefer a payment scheme (e.g. "exact")
maxAmount(amount)	Reject payments above a threshold (in token decimals)

Usage

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)
  ],
});

How Policies Are Applied

When the server returns multiple payment options, the SDK:

1. Filters out options that exceed maxAmount.
2. Sorts remaining options by preferNetwork and preferScheme scores.
3. Selects the highest-scoring option that has a matching wallet.

If no option matches all policies, the SDK falls back to any compatible option.

Common Network IDs (CAIP-2)

Network	CAIP-2 ID
Ethereum Mainnet	eip155:1
Base Mainnet	eip155:8453
Base Sepolia	eip155:84532
Optimism	eip155:10
Arbitrum One	eip155:42161
Polygon	eip155:137
Solana Mainnet	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
Solana Devnet	solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1