How to Architect for Interoperable Smart Account Deployment

Cross-chain smart account architecture enables a single user identity and asset management logic to function seamlessly across disparate blockchains like Ethereum, Arbitrum, and Polygon. Unlike traditional Externally Owned Accounts (EOAs), which are chain-specific, these accounts are built on smart contract wallets (like Safe, Biconomy, or ERC-4337 accounts) and use interoperability protocols for message passing. The core challenge is maintaining state consistency and executing transactions where the user's assets and the target dApp exist on different chains.

The architecture typically involves three key components: a master account on a 'home' chain (e.g., Ethereum mainnet), satellite account proxies deployed on destination chains, and a cross-chain messaging layer (like Chainlink CCIP, Axelar, or Wormhole) that connects them. The master account holds the primary logic and ownership, while satellite accounts are lightweight contracts that can receive and execute instructions relayed from the home chain. This separation ensures gas efficiency on L2s and keeps complex logic centralized.

Security is paramount in this design. Architects must implement unified signature verification so a user signs once on their home chain, and that signature is valid for actions on satellite chains. This often involves using EIP-1271 for signature validation on contracts. Furthermore, the cross-chain message must be authenticated and include replay protection to prevent the same signed message from being executed multiple times across different networks.

For developers, a common pattern is to use the ERC-4337 EntryPoint contract as the master account's core, extended with cross-chain capabilities. When a user wants to execute an action on Chain B, they submit a UserOperation to the EntryPoint on Chain A. The account contract then initiates a cross-chain message. A relayer or oracle network delivers the payload to the satellite account on Chain B, which finally executes the intended transaction, such as a swap or NFT mint.

Practical deployment requires tools like the Safe{Core} Protocol for modular account management or ZeroDev's Kernel for ERC-4337. Testing is done on cross-chain testnets (e.g., Sepolia and its L2 counterparts) using services like LayerZero's Testnet or Hyperlane's warp routes. The end goal is a non-custodial user experience where interacting with any chain feels like using a single, unified account.

An interoperable smart account system is built on three foundational layers: the account abstraction standard, a cross-chain messaging protocol, and a unified user operation relayer. The most common standard is ERC-4337, which defines the UserOperation struct and separates transaction logic from the Ethereum Virtual Machine (EVM). For cross-chain functionality, protocols like LayerZero, Axelar, or Wormhole are used to pass messages and state between chains. A custom relayer must be architected to receive these messages and submit UserOperation bundles to the destination chain's EntryPoint contract.

The core smart contract architecture requires a Singleton EntryPoint, a Smart Account Factory, and a Cross-Chain Module. The EntryPoint (v0.6) is deployed once per chain and validates & executes bundles. The Factory deploys counterfactual smart accounts using CREATE2, ensuring the same address across all supported EVM chains. The Cross-Chain Module is a smart account plugin that validates messages from your chosen interoperability protocol. It must implement a function like executeFromRemoteChain(bytes calldata payload) that only the designated cross-chain messenger can call.

Key prerequisites include a deep understanding of the UserOperation lifecycle, CREATE2 address derivation, and gas management. Your relayer must handle gas on the destination chain, which can be funded via a paymaster or require users to pre-deposit native tokens. You'll need to set up off-chain infrastructure: a Bundler to package operations, a Paymaster Service for gas sponsorship, and a Message Listener that watches your cross-chain protocol for incoming requests. Development tools like the @account-abstraction SDK and Foundry for contract testing are essential.

A critical design decision is state synchronization. Will your smart account maintain independent states on each chain, or will a 'home chain' act as a source of truth? For simple asset transfers, independent states suffice. For complex, stateful operations, you must implement a system where a state root is passed via cross-chain message, and the receiving chain's module can prove state membership via Merkle proofs. This adds complexity but enables truly unified cross-chain application logic.

Start by deploying the core contracts to a testnet like Sepolia. Use the official EntryPoint address (0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789). Write and deploy a minimal Smart Account Factory and a mock Cross-Chain Module that accepts any call. Simulate a cross-chain message using a local fork and a test relayer script. This validates your gas estimates, message encoding, and security checks before proceeding to a multi-chain test environment like the Axelar testnet or LayerZero's Sepolia-to-Mumbai corridor.

Interoperable smart accounts are modular, non-custodial wallets whose logic can execute across different chains. Unlike traditional Externally Owned Accounts (EOAs), their behavior is defined by a smart contract, enabling features like social recovery, batch transactions, and gas sponsorship. The core architectural challenge is designing a system where the account's state, logic, and verification mechanisms remain consistent and secure, regardless of the underlying execution environment. This requires a clear separation between the account abstraction core (ERC-4337, ERC-6900) and the cross-chain messaging layer (like LayerZero, Axelar, or CCIP).

A robust architecture is built on three foundational layers. The Smart Account Layer defines the core contract logic using standards like ERC-4337's Account interface or the more modular ERC-6900. The Interoperability Layer is responsible for secure message passing, employing arbitrary message bridges or general-purpose interoperability protocols. Finally, the Unified EntryPoint Layer acts as a coordinator, often a singleton contract on each supported chain that validates user operations and dispatches them via the interoperability layer. This separation ensures the account logic is chain-agnostic, while cross-chain complexities are abstracted away.

Key design decisions involve state management. You must choose between a unified global state, where a main chain (e.g., Ethereum) acts as the source of truth, and a sharded local state model, where each chain maintains its own state synchronized via light clients or proofs. For most use cases, a hybrid approach is practical: critical security modules (like owner keys) are managed globally, while volatile chain-specific data (like gas token balances) is managed locally. This balances security with performance and cost.

Security is paramount. The interoperability layer becomes a critical trust assumption. Architectures should implement verification at the destination, meaning the receiving chain's EntryPoint must validate the cross-chain message's authenticity. This can be done via native light client verification (e.g., IBC), optimistic fraud proofs, or a decentralized network of attestations. Furthermore, account logic should include rate-limiting and circuit breakers for cross-chain functions to mitigate risks from a compromised bridge or messaging protocol.

For development, start by implementing the core account contract using a framework like Safe{Core} Account Abstraction Kit or ZeroDev Kernel. Then, integrate an interoperability SDK such as LayerZero's Omnichain Contract or Axelar's GMP. A typical cross-chain user operation flow is: 1) User signs a UserOperation on Chain A. 2) A Bundler submits it to Chain A's EntryPoint. 3) The EntryPoint, via a pre-installed module, calls the interoperability protocol to send a message to Chain B. 4) Chain B's EntryPoint verifies the message and executes the intended logic on the user's smart account on Chain B.

Successful deployment requires thorough testing on testnets of multiple chains (e.g., Sepolia, Amoy, BSC Testnet) using tools like Foundry or Hardhat. Monitor for latency in cross-chain finality and gas cost variances. The end goal is a seamless user experience where a single smart account identity can interact with dApps on Ethereum, Polygon, Arbitrum, and beyond, without users managing separate wallets or native gas tokens on each chain.

A deterministic factory contract creates smart accounts at addresses that are predictable and verifiable before deployment. This is achieved by using a CREATE2 opcode with a fixed salt, typically derived from the user's address and a nonce. The primary advantage is interoperability: any service, wallet, or dApp can compute the same future address for a user on any chain, enabling features like gas sponsorship and cross-chain user identity without prior on-chain transactions. This predictability is essential for building seamless multi-chain experiences.

The core architecture involves two key components: a singleton entry point and the factory contract itself. The entry point (like ERC-4337's EntryPoint) handles user operation validation and execution. The factory's sole responsibility is to deploy account contracts using CREATE2. A standard implementation uses abi.encodePacked to create the initcode (constructor code + arguments) and then calls CREATE2 with a salt like keccak256(abi.encodePacked(sender, salt)). The resulting address is keccak256(0xff, factoryAddress, salt, keccak256(initcode)) right-shifted by 96 bits.

Security is paramount in factory design. The contract must immutably enforce that the deployed account's code matches the expected bytecode hash to prevent address collision attacks. This is done by storing a hash of the canonical account initialization code in the factory and verifying it within the deployment function. Furthermore, the factory should include access controls, often allowing only a trusted entry point contract to trigger deployments. This prevents arbitrary users from polluting the address space or deploying malicious accounts at predicted addresses.

For real-world interoperability, your factory must be deployed at the same address on every network. This is accomplished using the deterministic deployment proxy pattern, where a standardized deployer contract (like the SingletonFactory at 0xce0042B868300000d44A59004Da54A005ffdcf9f) is used. You send a signed deployment transaction with a specific nonce, guaranteeing the same contract address on all EVM chains. Tools like hardhat-deploy or forge create2 scripts automate this process, ensuring your factory is a universal constant for the ecosystem.

Here is a minimal, secure factory contract snippet in Solidity:

solidityCopy
contract SmartAccountFactory {
    address public immutable entryPoint;
    bytes32 public immutable accountInitCodeHash;

    constructor(address _entryPoint, bytes32 _accountInitCodeHash) {
        entryPoint = _entryPoint;
        accountInitCodeHash = _accountInitCodeHash;
    }

    function createAccount(address owner, uint256 salt) public returns (address) {
        require(msg.sender == entryPoint, "Unauthorized");
        bytes memory initCode = abi.encodePacked(
            type(SimpleAccount).creationCode,
            abi.encode(entryPoint, owner)
        );
        require(keccak256(initCode) == accountInitCodeHash, "Invalid init code");
        address account = address(new SimpleAccount{salt: bytes32(salt)}(entryPoint, owner));
        return account;
    }
}

This contract validates the caller and the init code hash before using new ...{salt: ...} (the Solidity shorthand for CREATE2).

Integrating this factory into a user flow requires off-chain address computation. Services use the eth_call RPC to simulate the createAccount function or compute the address locally using libraries like ethers.js (getCreate2Address). This allows a wallet to display a user's smart account address before it's deployed, enabling gasless onboarding. The deterministic pattern is foundational for account abstraction standards like ERC-4337 and is used by major providers including Safe{Wallet} (with its ProxyFactory) and ZeroDev kernels for seamless cross-chain account management.

The Entry Point contract is the core singleton of the ERC-4337 account abstraction standard. All UserOperations from any smart account must be validated and executed through this single, trusted contract on each supported chain. This design enforces critical security invariants, prevents replay attacks across different Entry Point versions, and ensures a consistent execution environment. By standardizing on a single Entry Point per chain, wallet developers and bundlers can build interoperable infrastructure, knowing that a user's smart account logic will be evaluated against a universal set of rules.

Your bundler strategy defines how you submit these UserOperations to the Entry Point. You can run your own bundler node using stacks like skandha or stackup, or rely on a third-party RPC service. The key architectural decision is bundler dependency. A dedicated bundler offers maximum control over transaction ordering, fee management, and censorship resistance, which is crucial for applications requiring high reliability. Third-party services simplify initial setup but introduce a dependency on another entity's infrastructure and economic incentives.

For interoperable deployment, your smart account factory must be chain-aware. It should deploy account proxies with initialization logic that points to the official Entry Point singleton address for that specific network (e.g., 0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789 on Ethereum Mainnet). Use a mapping or a chain ID check within your factory contract. This ensures a user's account, once deployed on multiple chains, interacts with the correct, canonical Entry Point on each one, maintaining security and compatibility across the ecosystem.

Implement a modular validation layer. The Entry Point calls the validateUserOp function on the smart account. Decouple your signature validation and paymaster sponsorship logic from your account's core execution. Use immutable function pointers or delegatecall to modular verifier modules. This allows you to update security rules or payment methods without needing to migrate the user's main account contract, facilitating long-term upgradability and reducing fragmentation.

Finally, design for gas abstraction robustness. A smart account's gas payment flow—whether via a paymaster or the account's own deposit—is managed through the Entry Point. Your architecture must handle edge cases: paymaster postOp failures, insufficient deposit staked in the Entry Point, and volatile gas prices. Implement off-chain simulation in your bundler strategy to reject UserOperations that will fail these checks, protecting users from wasted gas and improving the overall reliability of your deployment.

Interoperable smart account deployment requires a relayer network capable of receiving a UserOperation on one chain and executing it on another. The core challenge is managing state and nonce consistency across heterogeneous environments. A primary chain, often the user's home chain, acts as the source of truth for the smart account's nonce and validation logic. The relayer's job is to observe a validated UserOperation on this source chain, then construct and submit a corresponding transaction on the destination chain, ensuring the final execution matches the user's intent.

The architecture typically involves three key components: a listener service, a cross-chain message bridge, and an executor. The listener monitors a mempool or an event log (like a UserOperationEvent) on the source chain. Upon detecting a valid op destined for another chain, it packages the essential data—target address, calldata, and a proof of validation—into a standardized message. This message is then sent via a secure cross-chain messaging protocol such as LayerZero, Axelar, or Wormhole to the destination network.

On the destination chain, an executor contract or a keeper receives the cross-chain message. Its first duty is to verify the message's authenticity and that it originated from the trusted source chain verifier. After verification, it must recreate the execution context. This involves calling the validateUserOp function on the local instance of the user's smart account factory or a proxy to re-validate the operation's signature and nonce against the known state. Only after this validation passes can the executor safely call execute on the smart account.

Critical design considerations include gas management and fee economics. The relayer must prepay gas on the destination chain. Solutions involve having the user pre-fund a gas tank on the destination chain, using a gas abstraction token like ERC-20 for payment, or having the relayer subsidize costs and be reimbursed from the source chain transaction. Furthermore, the system must handle revert scenarios gracefully, ensuring failed executions on the destination chain can trigger a revert or compensation flow on the source chain to maintain atomicity.

For developers, implementing this starts with the Smart Account Factory. A factory deployed on multiple chains should create accounts with the same deterministic address (using CREATE2). The validation module must be aware of its interchain status, checking a nonce that is synchronized via cross-chain messages. A reference flow: a user signs a UserOperation for Chain B, submits it to a bundler on Chain A. The bundler includes it in a block, emitting an event. A relayer picks up the event, sends a message via a bridge to Chain B, where a keeper executes it against the pre-deployed smart account.

Successfully architecting for interoperable smart account deployment requires a layered approach. You must separate the core account logic from the execution environment. The account abstraction core—handling validation, nonce management, and ownership—should be deployed as a singleton on each supported chain. The execution layer, containing your application's specific logic, interacts with this core via standardized interfaces like ERC-4337's IAccount. This separation ensures your business logic remains portable while the foundational account security is chain-native.

For cross-chain user operations, a message relayer is critical. This off-chain service listens for UserOperation events on a source chain, packages them with proofs, and submits them to a verification contract on the destination chain. Implement this using a generalized messaging protocol like LayerZero, Axelar, or Wormhole. Your smart account must implement a function to verify these cross-chain messages and execute the intent. Always include a replay protection mechanism, such as a nonce or a mapping of processed message IDs, to prevent double-spends.

Testing is non-negotiable. Use a development framework like Foundry or Hardhat to simulate a multi-chain environment with forked networks. Write integration tests that deploy your account factory and core logic on two separate forks, then simulate a cross-chain UserOperation via your relayer logic. Tools like Chainlink CCIP Local Simulator or LayerZero's Endpoint mock can streamline this. Audit firms are increasingly focusing on cross-chain vulnerabilities, so factor this into your security budget.

To begin building, explore existing infrastructure. ZeroDev's Kernel and Biconomy's Smart Account are production-ready, modular smart account implementations that support plug-in modules. Pimlico's permissionless.js and Stackup's userop.js bundles simplify interacting with ERC-4337 bundlers and paymasters across chains. Start by forking a template, deploying the core to a testnet like Sepolia, and connecting it to a cross-chain messaging testnet devnet.

The future of this architecture points toward native interoperability. Proposals like EIP-7702 aim to bring AA-like features directly to EOAs, and chains are implementing native cross-chain VM calls. Stay updated by following ERC-4337's Bundler, EntryPoint, and Account Repositories on GitHub and participating in forums like the Ethereum Magicians. Design your system with upgradeable modules to adapt as these standards evolve.