ERC-4337 accounts¶

Each chain's JSON-RPC endpoint, such as https://bruno.mailam.app/sepolia, answers ERC-7769's bundler methods for EntryPoint v0.8 and v0.7. An ERC-4337 library can use it as its bundler: viem's bundler client, ZeroDev's Kernel account client, or anything built on them. No API key or bundler account is needed, nor a paymaster, though an op may use one.

How an op pays¶

An op pays the relay one of three ways:

• In ETH, by its fees, as at any bundler. Set the client up as for any bundler, with the relay as its URL. Whatever fees the client gives the op, the relay's estimate sets its preVerificationGas so that what it's charged comes to the relay's price. Clients that ask their bundler for a gas price get it as Pimlico's and ZeroDev's bundlers answer it (pimlico_getUserOperationGasPrice, zd_getUserOperationGasPrice).
• Through another's paymaster, by its fees. The paymaster pays the op's gas from its deposit in the EntryPoint, which pays the relay in ETH; the paymaster takes its price from the account its own way, such as Circle's in USDC. Give the paymaster's gas limits as it gives them; left out, the relay's estimate measures them, with room to spare. Bruno has no paymaster of its own.
• In a token, by its own calls, holding no ETH. Its fees are zero, so the account needs no ETH, and its last call transfers a token the relay takes, such as USDC, to the relay's payee (from the terms). ERC-4337 has no standard way to pay a bundler in a token, so this takes a few lines beyond the bundler URL. Before signing, prepare the op with a placeholder payment of one unit, and ask the relay its price for it with postpaid_quoteUserOperation. Then send it paying the quoted amount: the client estimates and signs it once. The quote holds until its validUntilBlock. If it's sent later and the price has risen, sending fails as underpaid, with the amount required in the error's data.required.

As with any submission, nothing is included unless the payee receives the payment, and an op that isn't included costs nothing. An op paying by its fees pays for its gas even if its calls fail, as at any bundler: the EntryPoint charges it, or its paymaster. An op paying by its calls pays only if they succeed, since a failing call undoes all of them, the payment included, in Kernel, Coinbase Smart Wallet, Safe and Light Account alike. An account that carries on past a failing call, as ERC-7579's "try" mode does, still pays.

The account can be undeployed: the op's factory and factory data deploy it, as usual. Or it can be an EOA, delegating to a smart account's code by EIP-7702 in its first op.

Which page¶

Each page has one script, complete and tested as it is, for Node 24.

The scripts make a ZeroDev Kernel v3.2, or from an EOA viem's Simple7702 account, ZeroDev's Kernel v3.3, MetaMask's Stateless7702 or Alchemy's Modular Account v2; other smart accounts should work the same way, but only these are tested. The scripts are tested with the current versions of their libraries, viem included. AgentKit's ZeroDevWalletProvider sends through ZeroDev's intents, not a bundler, so with AgentKit, use the AgentKit provider instead.

Methods¶

The specification gives each one's rules, and REST has the same operations under /v1/user-operations. The endpoint isn't a node: other methods, such as eth_getUserOperationByHash or eth_call, are refused, so give your client its own RPC URL for reading the chain.

Each script is run as it is against both relays on a local chain, from an undeployed Kernel v3.2 or a fresh EOA, with the versions listed in support.