Features & Advantages

Here are the key benefits of this x402 +4337 extension:

Token-agnostic Payment — No ERC-3009 Token Required

Traditional x402 models might require a specific “payment token” (e.g., an ERC-3009 token) to simplify settlement. By contrast:

• Since the payment is simply a balance transfer (or arbitrary contract call) wrapped in a UserOperation, we can accept any ERC-20 token (or native token) as payment.

• Supports multi-chain environments (e.g., BSC, Ethereum mainnet, L2s) where a dedicated ERC-3009 token may not exist.

• This greatly broadens flexibility for publishers and users.

Leveraging ERC-4337 / Account Abstraction

By using UserOperations and account abstraction we gain:

• Smart wallet features: e.g., social recovery, multisig, advanced validation logic.

• Potential for paymasters: e.g., DApp or publisher may subsidise gas or accept payment in token rather than native chain gas.

• Better UX: users don’t need native token (ETH etc) just for gas; wallet logic handles that.

• Custom validation logic: e.g., restricting payment to exact token, amount, chain, or even more complex logic (staking, contract calls).

• Improved extensibility and future-proofing as AA becomes more pervasive.

Dual Compatibility: Standard x402 + UserOp

Our facilitator supports both:

• “Standard” x402 where the payment data is a simple transferWithAuthorization signature (e.g., ERC-3009 or another token standard)

• UserOperation-based payment where the data is a signed UserOp. The data type (3009 vs 4337) is encoded in the X-PAYMENT header. This allows the system to interoperate with legacy implementations or mixed markets.

Server-side Agnosticism & Opaque Blob

The server (resource provider) does not need deep awareness of the on-chain mechanics:

• The X-PAYMENT header carries opaque bytes (either token-transfer directive or UserOperation struct)

• The server simply forwards those bytes to the facilitator, which handles verification/settlement

• The server thus remains lightweight and unaware of token types, chains, or wallet logic.

Customised Payment Logic

Since the payment is expressed as a UserOperation, it need not be a plain token transfer. Examples:

• A call to a staking contract (user stakes tokens as access)

• A subscription contract invocation

• Multi-step actions: e.g., approve → transfer in one UserOp

• On-chain logic: e.g., user pays in token A; contract automatically converts to token B; access is granted only if conversion succeeded. This opens up advanced monetisation models beyond “send X tokens”.