Supported Assets

Ivorypay x402 supports stablecoins across multiple EVM mainnets. The server automatically selects the on-chain transfer mechanism — either EIP-3009 or Permit2 — based on the chain and token combination.

Chain and Token Matrix

Chain	Network value	Chain ID	USDC	USDT
Base	BASE_MAINNET	8453	EIP-3009	Permit2
Polygon	POLYGON	137	EIP-3009	Permit2
Lisk	LISK_MAINNET	1135	EIP-3009	Permit2
Ethereum	ETHEREUM	1	Permit2	Permit2
BNB Smart Chain	BSC_MAINNET	56	Permit2	Permit2

Strategy Reference

EIP-3009 — No Prior Approval Required

EIP-3009 (transferWithAuthorization) is Circle's native gasless transfer mechanism built into their USDC contracts. The user signs a typed authorization; the server submits the on-chain call.

Applies to: USDC on Base, Polygon, or Lisk.

No ERC-20 approve() call is needed — the transfer is self-contained in the signed authorization.

Permit2 — One-Time Approval Required

Permit2 is Uniswap's universal signature-based transfer standard, deployed at the same address on every EVM chain:

0x000000000022D473030F116dDEE9F6B43aC78BA3

Applies to: Any non-USDC token, USDC on BSC or Ethereum, and all BSC/Ethereum transfers regardless of token.

Before the first Permit2 transfer on a given wallet/token/chain, the payer wallet must grant the Permit2 contract an ERC-20 allowance. This is a one-time transaction per combination — see Permit2 Approval for the step-by-step guide.

How to Tell Which Strategy Applies

After calling POST /api/x402/build, the response includes chain and token. Cross-reference those values against the matrix above. If your combination falls under Permit2, the response will also include a spender field (the gas-payer vault address) that you must include in the Permit2 signed message.

{
  "typedDataHash": "0x...",
  "chain": "BSC_MAINNET",
  "token": "USDT",
  "spender": "0xGasPayerVaultAddress",
  ...
}

If chain is BASE_MAINNET, POLYGON, or LISK_MAINNET and token is USDC, use EIP-3009 signing. Otherwise use Permit2.