Setting Up Your Development Environment

Building omnichain smart contracts requires tools that can interact with multiple blockchains and integrate with a messaging protocol such as LayerZero, Axelar, or Wormhole. While most messaging protocols are chain-agnostic, developers typically begin with EVM-compatible networks such as Ethereum, Arbitrum, Avalanche, or Optimism.

The standard development stack includes Solidity for contract development, Hardhat or Foundry for compiling and testing, and messaging SDKs for integration. To streamline development and abstract away boilerplate, frameworks like Thirdweb, Biconomy’s Smart Account SDK, or Safe SDK can be used. These platforms offer tools for deploying and managing smart contracts across chains with shared logic and identity.

Before starting, developers should define the communication flow between contracts. Decide which chains will serve as the origin (where the message is sent), and which will act as the destination (where the message is received and executed). This helps structure the contract deployment strategy and the messaging logic that ties them together.

Connecting to a Smart Account Using Frontend SDKs

Omnichain smart contracts often interact with users via web interfaces that connect to smart accounts—wallets with enhanced capabilities beyond traditional externally owned accounts (EOAs). Smart accounts enable features like gasless transactions, batched calls, and cross-chain execution from a single session.

Frontend SDKs like Thirdweb’s Connect or Biconomy’s Plug and Play Smart Accounts allow developers to integrate these advanced wallets directly into the UI. These SDKs manage wallet connections, session persistence, and gas management. When paired with a messaging protocol, they can also trigger signed transactions that relay instructions across chains.

This connection abstracts much of the complexity for the user. From a single front end, a user can interact with contracts on multiple chains, sign once, and initiate coordinated activity. For example, a user could stake tokens on Optimism and trigger a reward claim on Ethereum, without switching networks or signing multiple transactions.

Customising Your Logic: Gasless Transactions and Whitelisting

Once smart contracts are deployed, the omnichain experience can be enhanced by adding advanced logic. One such enhancement is gas abstraction, which allows users to perform transactions without holding native tokens on the destination chain. This is often implemented through Paymasters or sponsorship services, where the dApp or protocol covers the gas cost.

Gas abstraction is particularly useful in onboarding users to unfamiliar chains or when targeting consumer-grade applications like games and wallets. Messaging protocols like LayerZero or Axelar can integrate with external services or relayers that prepay for execution, enabling gasless interaction on arrival.

Whitelisting is another important function. It restricts access to certain contracts or actions based on wallet addresses or session approvals. In omnichain applications, this logic may need to sync across chains. For example, a contract on Avalanche may need to check if a wallet has previously been approved on Ethereum. This can be achieved by sending a verification message or storing access state on a cross-chain data registry.

Custom logic may also include callback functions, refund handling, rate-limiting, or contract pausing mechanisms. These controls ensure security and user protection while maintaining a seamless omnichain experience.

Simulating and Signing Cross-Chain Transactions

Before deploying to mainnet, it is essential to simulate cross-chain messaging to validate that contracts behave as expected. Testing frameworks like Hardhat or Foundry can be extended using custom scripts that mock the messaging layer.

Some messaging protocols also offer testnets with sandbox environments that replicate the messaging flow between chains. For example, LayerZero’s testnet supports endpoints on Goerli, Fuji (Avalanche testnet), and BNB Chain testnets. Developers can send real messages, track events, and debug interactions between contracts.

The simulation process includes emitting messages from the origin chain, watching how they are encoded and picked up by relayers, and observing how destination contracts parse and execute the payloads. Developers should test edge cases such as invalid payloads, duplicate messages, and failed relays.

Once testing is complete, transactions can be signed and broadcast from the frontend using standard wallet providers like MetaMask, WalletConnect, or smart account SDKs. Signing can also trigger backend functions that instruct relayers to transmit messages, handle retries, or update application state.

Deploying Across Chains and Monitoring Execution

Deploying omnichain smart contracts requires deploying a coordinated set of contracts to multiple chains, with addresses stored and mapped to each other. Each deployment must register the messaging endpoint and identify the destination addresses it communicates with. This mapping is critical for message routing and validation.

For example, if a contract on Ethereum is expected to receive messages from Arbitrum, it must store the address of the sending contract and verify the origin on every incoming message. Most messaging SDKs provide helper functions to register and verify trusted contracts across chains.

Once deployed, monitoring becomes essential. Developers should integrate analytics dashboards, event logs, and error reporting tools to track message status, success/failure rates, and gas usage. Messaging protocols often provide their own explorer tools (e.g., LayerZero Scan, AxelarScan) to inspect cross-chain transactions.

Production systems should include retry logic for failed messages, fallback functions for timeouts, and guardrails to prevent replay or spam attacks. These protections can be embedded directly into the smart contract or handled off-chain through validator logic and relayer controls.

Building Omnichain UX: Frontend Strategies

Omnichain dApps must hide complexity from users. The frontend experience should remain consistent even as logic executes across multiple chains. This involves integrating multiple RPC providers, chain detection tools, and state sync mechanisms that update UI components based on messages received on different networks.

Session-based authentication allows users to connect once and interact across chains without re-signing each transaction. Cross-chain modals, wallet prompts, and confirmation messages should clearly indicate what chain is being used and what action is being performed.

Some dApps also implement progressive loading, showing users real-time status of message delivery and execution. For example, a staking dApp might show a three-step progress bar: “Transaction sent on Arbitrum → Message verified → Rewards distributed on Ethereum.”

To achieve this, developers often use event listeners and subgraph services that watch for relevant on-chain events across multiple chains. These are linked back to the frontend via WebSockets, GraphQL queries, or custom APIs.