General Message Passing Relay Tool

WHAT IT DOES

This tool enables developers and contract administrators to submit cross-chain messages from a source chain to a target chain through a relay contract infrastructure. It connects to your wallet and reads the source chain contract address, target chain contract address, message payload, relayer fee, gas limits, current nonce, message status, delivery confirmations, relay history, and timestamps. The tool signs and submits transactions to submit cross-chain messages on the source chain, relay messages to the target chain, update message status throughout the delivery lifecycle, record relay metadata with nonce tracking, and emit message events for off-chain monitoring.

HOW TO USE

1. Connect your wallet using the wallet bridge (supports MetaMask, WalletConnect, and other EVM-compatible wallets).

2. Select the source network where you want to submit the message from.

3. Enter both the source chain relay contract address and the target chain relay contract address, then click "load contract" to initialize both endpoints.

4. Enter your message payload as a hex string (without the 0x prefix) — this can be any encoded data your target contract expects.

5. Specify the relayer fee (in native token) you're willing to pay, the gas limit for target chain execution, and the target chain ID.

6. Click "encode payload" to validate your hex input and see the encoded length.

7. Click "estimate relay" to estimate gas costs and verify the submission parameters.

8. Click "submit message" to sign and send the message to the source chain relay contract, which assigns a nonce and emits the message.

9. After the message is submitted, click "relay message" and enter the nonce to trigger the relay on the target chain, completing the cross-chain delivery.

TECHNICAL MECHANISM

The tool uses ethers.js v5.7.2 to interact with relay contracts on both the source and target chains that implement a standard interface (submitMessage(bytes, uint256, uint256) external payable, relayMessage(uint256) external, getNonce() view, getMessageStatus(uint256) view, getConfirmations(uint256) view, messageHistory(uint256) view). The source contract stores messages with incremental nonces and tracks their status (pending, submitted, relayed, failed, confirmed). When submitting a message, the user pays a relayer fee in native token, which incentivizes relayers to pick up and deliver the message. The target contract's relayMessage function validates the nonce and delivers the payload to the intended recipient contract. Gas costs are estimated using the source contract's estimateGas function before submission, and actual costs are reported using receipt.effectiveGasPrice for accurate post-EIP-1559 accounting. The tool tracks relay history locally, preserving nonce, transaction hash, block number, and timestamp for audit purposes.

WHAT IT CANNOT SEE

This tool operates on individual chains and cannot verify message integrity across chains — it does not ensure that the message received on the target chain matches the one submitted on the source chain beyond what the relay contract guarantees. It cannot ensure finality on the target chain, especially during chain reorganizations or finality delays on proof-of-stake networks. The tool cannot detect message replay attacks where the same message might be relayed multiple times — this must be handled by the contract's nonce mechanism. It cannot validate off-chain relayers, verify their trustworthiness, or ensure they will actually pick up and deliver messages in a timely manner. The tool also cannot guarantee message delivery timing, as cross-chain delivery depends on relayer availability, network congestion, and gas prices on both chains.

PLEASE NOTE

This tool works exclusively with EVM-compatible blockchain networks (Ethereum, Polygon, Arbitrum, Optimism, Base, etc.). It requires both source and target contracts to implement the relay interface described above. All transactions incur gas fees paid by the connected wallet on each chain involved. The tool maintains no persistent storage — all state is refreshed from the blockchain on each session. Cross-chain messaging should be considered an advanced pattern; test thoroughly on testnets before deploying to production. Always ensure your relay contracts have been professionally audited and that your message payloads are properly encoded for the target contract.