Cross-Chain Message Relayer

WHAT IT DOES

Cross-Chain Message Relayer is a developer-focused tool that enables reliable message passing between EVM-compatible blockchain networks. Unlike generic bridge UIs that only show transaction history, this tool actively reads source chain message logs, verifies destination chain message status, checks bridge contract state, estimates relayer fees, validates nonce sequences, and confirms message payload integrity before you submit any relay transaction. It supports Ethereum, Polygon, Arbitrum, Optimism, Avalanche, BNB Chain, and Base, providing a unified interface to monitor and relay cross-chain messages. The tool automatically detects whether a message has already been delivered, is pending, or has failed, and guides you through the relay process with clear status indicators and fee estimates. It is designed for developers building cross-chain applications, bridge operators, and power users who need to manually relay messages when automated relayers fail.

HOW TO USE

Connect your wallet using WalletConnect or a compatible browser extension. Ensure your wallet is on the source chain where the message originated. Enter the bridge contract address that emitted the message—this is the contract you are interacting with, and you are vouching for its safety. Paste the message ID from the source chain's MessageSent event log, along with the complete message payload in hex format. Select the source and destination chains from the dropdown menus. Click "Check message status" to query the bridge contract for the current state of the message—the tool will attempt to determine if it is pending, already delivered, or failed. If the message is pending or unknown, the "Relay message" button appears. Click it to submit the relay transaction. The tool displays a transaction link to your chain's block explorer and logs the final gas cost using receipt.effectiveGasPrice for accurate post-EIP-1559 fee tracking.

ADAPTIVE MESSAGE STATUS RESOLUTION ENGINE

The core technical mechanism that distinguishes this tool is its adaptive message status resolution engine. Different bridge contracts implement different status tracking patterns—some store status in a mapping on the source contract, others require querying the destination contract, and some provide no direct status view at all. This tool implements a multi-strategy resolver: it first attempts to call a messageStatus(bytes32) view function if present, interpreting the return value according to common conventions (0=unknown, 1=pending, 2=delivered, 3=failed). If that fails, it performs a static call simulation of the relay function itself—if the simulation succeeds, the message is likely pending and relayable; if it reverts with a specific error like "already relayed", the message has been delivered; if it reverts for other reasons, the tool marks the status as unknown. The resolver also handles nonce sequences by tracking the last delivered nonce from bridge events when available. Fee estimation uses a layered approach: first checking for a dedicated fee() view, then falling back to eth_estimateGas on the relay transaction multiplied by the current gas price. All RPC calls are wrapped with timeout and retry logic, and the tool automatically falls back to a secondary provider if the primary endpoint fails or rate-limits.

WHAT IT CANNOT SEE

The tool cannot guarantee message delivery if the bridge network fails, destination chain conditions change, or the relayer is front-run by another transaction with a higher nonce. It has no visibility into off-chain bridge relayer status, operator interventions, or governance changes that occur after the relay transaction is submitted. The tool cannot predict the exact confirmation time on destination chains, nor can it detect mempool congestion beyond standard gas price estimates. It does not monitor messages after relay—it is a relayer, not a message tracking service. The tool cannot interact with non-EVM chains, private networks, or bridges that do not implement the standard interface it expects. It also cannot recover funds if you relay an invalid message or send to an incorrect address.

PLEASE NOTE

This tool is designed exclusively for EVM-compatible blockchain networks. It supports Ethereum, Polygon, Arbitrum, Optimism, Avalanche, BNB Chain, Base, and similar chains. Non-EVM networks such as Solana, Cosmos, or Bitcoin are not supported. Always verify the bridge contract address and message payload before relaying—the tool does not validate contract safety or payload correctness. The tool provides estimates only—actual fees and gas costs are determined at the time of transaction execution. Users are responsible for understanding bridge risks, including smart contract vulnerabilities, bridge downtime, and potential front-running attacks.