> ## Documentation Index > Fetch the complete documentation index at: https://seilabs-docs-evm-cookbook.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Debugging for EVM > Advanced debugging techniques for EVM transactions on Sei. Learn transaction template generation and analysis using seid and Foundry cast tools. export const RunSnippet = props => { const {method = 'eth_blockNumber', params = [], network = 'testnet', endpoint, label, title, description, decode = 'auto'} = props || ({}); const ENDPOINTS = { testnet: 'https://evm-rpc-testnet.sei-apis.com', mainnet: 'https://evm-rpc.sei-apis.com' }; const rpcUrl = endpoint || ENDPOINTS[network] || ENDPOINTS.testnet; const networkLabel = network === 'mainnet' ? 'Sei Mainnet' : network === 'testnet' ? 'Sei Testnet' : network; const requestBody = { jsonrpc: '2.0', id: 1, method, params }; const requestJson = JSON.stringify(requestBody, null, 2); const [phase, setPhase] = useState('idle'); const [result, setResult] = useState(null); const [errorMsg, setErrorMsg] = useState(null); const [elapsed, setElapsed] = useState(null); const [copied, setCopied] = useState(false); const [btnHover, setBtnHover] = useState(false); const groupThousands = s => s.replace(/\B(?=(\d{3})+(?!\d))/g, ','); const hexToDecimal = value => { if (typeof value !== 'string' || !(/^0x[0-9a-fA-F]+$/).test(value)) return null; if (value.length > 66) return null; try { return groupThousands(BigInt(value).toString(10)); } catch (e) { return null; } }; const run = async () => { setPhase('loading'); setErrorMsg(null); setResult(null); setElapsed(null); const startedAt = typeof performance !== 'undefined' ? performance.now() : null; try { const response = await fetch(rpcUrl, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(requestBody) }); const data = await response.json(); if (startedAt != null && typeof performance !== 'undefined') { setElapsed(Math.round(performance.now() - startedAt)); } if (data && data.error) { setErrorMsg(data.error.message || 'RPC returned an error'); setPhase('error'); return; } setResult(data ? data.result : undefined); setPhase('success'); } catch (err) { setErrorMsg(err && err.message ? err.message : 'Request failed'); setPhase('error'); } }; const resultString = result === undefined ? 'undefined' : JSON.stringify(result, null, 2); const decoded = decode !== 'off' && typeof result === 'string' ? hexToDecimal(result) : null; const copyResult = () => { const flashCopied = () => { setCopied(true); setTimeout(() => setCopied(false), 2000); }; if (typeof navigator !== 'undefined' && navigator.clipboard && navigator.clipboard.writeText) { navigator.clipboard.writeText(resultString).then(flashCopied, () => {}); return; } if (typeof document !== 'undefined') { try { const ta = document.createElement('textarea'); ta.value = resultString; ta.style.position = 'fixed'; ta.style.opacity = '0'; document.body.appendChild(ta); ta.select(); document.execCommand('copy'); document.body.removeChild(ta); flashCopied(); } catch (e) {} } }; const HAIRLINE = 'rgba(128, 128, 128, 0.25)'; const surfaceStyle = { backgroundColor: 'rgba(128, 128, 128, 0.08)' }; const monoStyle = { fontFamily: 'var(--sei-font-mono)' }; const codeStyle = { backgroundColor: 'rgba(128, 128, 128, 0.05)', fontFamily: 'var(--sei-font-mono)' }; const buttonStyle = { backgroundColor: btnHover ? 'var(--sei-maroon-200)' : 'var(--sei-maroon-100)', color: '#ffffff', fontFamily: 'var(--sei-font-mono)', textTransform: 'uppercase', letterSpacing: '0.04em', fontSize: '10px', opacity: phase === 'loading' ? 0.7 : 1, cursor: phase === 'loading' ? 'default' : 'pointer' }; return
{title || method} {networkLabel}
{description ?
{description}
: null}
Request 
				{requestJson}
{phase === 'success' ?
Response{elapsed != null ? ` · ${elapsed} ms` : ''} 
						{resultString}
{decoded ?
= {decoded} (decimal)
: null}
: null} {phase === 'error' ?
Error 
						{errorMsg}
: null}
; }; ## Overview To debug EVM transactions on Sei, you need to understand both how transactions are created and how to analyze their behavior. This guide covers advanced debugging techniques: transaction template generation, analysis tools, and transaction inspection methods. Use them to find and fix issues in your EVM interactions. ## Transaction template generation The `--generate-only` flag turns any `seid` transaction command into a template generator. The command creates a complete transaction structure but does not broadcast it. With the `--generate-only` flag and Foundry's `cast` tool, you can build, analyze, and debug transactions in the EVM environment. ### Basic command pattern The general command pattern is: ```bash theme={null} seid tx --from --evm-rpc http://url-to-sei-evm-rpc --generate-only ``` ### Generating EVM transaction templates To generate an EVM transaction template, use the `evm` module with `--generate-only`. This example sends SEI to another EVM address: ```bash theme={null} seid tx evm send 0xRecipientAddress 1000000000000000000 \ --gas-fee-cap=100000000000 \ --gas-limit=21000 \ --evm-rpc=http://url-to-sei-evm-rpc \ --from=mykey \ --generate-only ``` This command returns a transaction template that you can analyze before you broadcast it. The template includes all transaction details, but the command does not execute the transaction. *** ## Analyzing EVM transactions with Cast When you have a transaction hash, you can use Foundry's `cast` command to inspect the transaction details: ```bash theme={null} cast tx 0x5010e6600e67f04a9bc3d3b670a7c2de380b180713d9a014a5dbd76b7e2190f1 \ --rpc-url=http://url-to-sei-evm-rpc ``` **Example output:** ```text theme={null} blockHash 0x4696d63a9a9ae88b03bcc94ccbd87f407e994b309d1dff9c0626de51ac57b76e blockNumber 130076639 from 0xAa55a16dD4E73c48C968928983c2bcC98d913d96 transactionIndex 7 effectiveGasPrice 100000000000 accessList [] chainId 1329 gasLimit 2500000 hash 0x5010e6600e67f04a9bc3d3b670a7c2de380b180713d9a014a5dbd76b7e2190f1 input 0xc31d960f0000... maxFeePerGas 100000000000 maxPriorityFeePerGas 100000000000 nonce 3 to 0x000000000000000000000000000000000000100b type 2 value 0 ``` ### Additional analysis commands **Get the transaction receipt:** ```bash theme={null} cast receipt 0x5010e6600e67f04a9bc3d3b670a7c2de380b180713d9a014a5dbd76b7e2190f1 \ --rpc-url=http://url-to-sei-evm-rpc ``` **Decode the transaction input data:** ```bash theme={null} cast 4byte-decode 0xc31d960f0000... ``` All template generation commands create JSON files. You can inspect, modify, and use these files for debugging before you execute the transactions. *** ## RPC consistency Always point `cast` commands to an EVM RPC endpoint (for example, `$EVM_RPC_URL`), not a Cosmos RPC URL. *** ## Tracing and revert reasons If your endpoint supports debug RPC methods, you can get full execution traces and revert reasons: ```bash theme={null} # Full transaction trace cast rpc debug_traceTransaction 0xTX_HASH '{"tracer":"callTracer","timeout":"120s"}' \ --rpc-url=$EVM_RPC_URL # Simulate and trace a call without broadcasting cast rpc debug_traceCall '{"from":"0xFROM","to":"0xTO","data":"0xDATA"}' \ 'latest' '{"tracer":"callTracer","timeout":"120s"}' \ --rpc-url=$EVM_RPC_URL ``` Many public RPC endpoints disable debug methods. If they are disabled, run a local fork and trace there. See the tracing documentation. *** ## Reproduce with a local fork Fork the network locally to reproduce issues deterministically. You can then run traces even if the remote debug RPC is disabled: ```bash theme={null} # Start a local fork anvil --fork-url $EVM_RPC_URL # Re-run calls against the fork cast call 0xContract "method(uint256)" 1 --rpc-url=http://127.0.0.1:8545 # Trace the call on the fork via debug RPC cast rpc debug_traceCall '{"to":"0xContract","data":"0xENCODED_DATA"}' \ 'latest' '{"tracer":"callTracer"}' --rpc-url=http://127.0.0.1:8545 ``` *** ## Event logs and decoding Use the receipt to inspect the logs, and decode them with the contract ABI: ```bash theme={null} # Fetch receipt JSON and view logs cast receipt 0xTX_HASH --rpc-url=$EVM_RPC_URL --json | jq '.logs' # Compute an event signature for topic[0] cast keccak "Transfer(address,address,uint256)" ``` Decode event topics and data with the contract ABI (from your repository or a block explorer). Topic\[0] equals the keccak hash of the event signature. *** ## Nonce, balance, and gas diagnostics Check common failure points quickly: ```bash theme={null} cast nonce 0xYourAddress --rpc-url=$EVM_RPC_URL cast balance 0xYourAddress --rpc-url=$EVM_RPC_URL cast gas-price --rpc-url=$EVM_RPC_URL cast block latest baseFeePerGas --rpc-url=$EVM_RPC_URL cast chain-id --rpc-url=$EVM_RPC_URL ``` **Checklist:** * Incorrect nonce (a pending transaction in the mempool) * Insufficient native balance for gas * Underpriced `maxFeePerGas` or `maxPriorityFeePerGas` * Chain ID mismatch ## Try it live Each `cast` diagnostic above is a plain read-only JSON-RPC call. Run four of them against Sei Mainnet here. The example address (`0xAa55…3d96`) is the sender from the `cast tx` output earlier on this page. *** ## Offline workflow with --generate-only Generate, inspect, sign, and broadcast a transaction safely: ```bash theme={null} # 1) Generate a template (no broadcast) seid tx evm send 0xTO 1000000000000000000 \ --from=$WALLET_NAME --evm-rpc=$EVM_RPC_URL --generate-only > tx.json # 2) Sign offline with your key seid tx sign tx.json --from $WALLET_NAME --chain-id $CHAIN_ID > signed.json # 3) Broadcast the signed tx seid tx broadcast signed.json ``` Never commit signed transactions or private keys. Use environment variables and `.gitignore` for sensitive data. *** ## Precompile awareness Calls to system precompiles (for example, addresses such as `0x...100b`) may have specific input and output formats and error behavior. * See [EVM precompiles](/evm/precompiles/example-usage) and [CosmWasm precompiles](/evm/precompiles/cosmwasm-precompiles/example-usage) * Cross-check expected selectors, parameter encoding, and revert messages *** ## Storage inspection When you debug state changes, check the on-chain state directly: ```bash theme={null} cast storage 0xContract 0xSLOT --rpc-url=$EVM_RPC_URL ``` *** ## Transaction analysis When you analyze transactions, follow these practices: * Always verify EVM transactions thoroughly * Use `cast` to decode the input data of EVM transactions * Keep track of gas parameters * Monitor the transaction status on the EVM layer **Analysis tips:** ```bash theme={null} # Use Foundry's cast tool for detailed transaction inspection cast tx 0x5010e6600e67f04a9bc3d3b670a7c2de380b180713d9a014a5dbd76b7e2190f1 \ --rpc-url=$EVM_RPC_URL # Get transaction receipt to verify success cast receipt 0x5010e6600e67f04a9bc3d3b670a7c2de380b180713d9a014a5dbd76b7e2190f1 \ --rpc-url=$EVM_RPC_URL # Decode transaction input data cast 4byte-decode 0xa9059cbb000000... ``` Transaction analysis checklist: Always verify that a transaction succeeded before you continue. Check gas usage to optimize future transactions. Use Foundry's `cast` tool for detailed transaction inspection. *** ## Error handling Monitor EVM transactions so that you can handle potential issues: ```javascript theme={null} try { // Check EVM transaction status const evmStatus = await checkEvmStatus(txHash); if (!evmStatus.success) { const evmError = await cast.call(['tx', txHash, '--rpc-url', evmRpcUrl]); console.error('EVM transaction failed:', evmError); } } catch (error) { console.error('Transaction analysis failed:', error); } ``` **Best practices for error handling:** * Always check the transaction status on both the Cosmos and EVM layers * Use detailed error logging to debug failed transactions * Implement retry logic for network-related failures * Monitor gas usage and adjust limits accordingly *** ## Security guidelines Critical security requirements: Keep private keys secure, and never include them in templates. When you work with wallet keys or mnemonics, use an `.env` file or other environment variables. Never commit sensitive information to version control. Always verify transaction details before you sign. **Environment variable setup:** ```bash theme={null} # Create .env file for sensitive data WALLET_NAME=mykey EVM_RPC_URL=http://url-to-sei-evm-rpc PRIVATE_KEY=your_private_key_here # Add .env to .gitignore echo ".env" >> .gitignore ``` **Secure transaction execution:** ```bash theme={null} # Use environment variables in commands seid tx evm send 0x1234567890abcdef... 1000000000000000000 \ --from=$WALLET_NAME \ --evm-rpc=$EVM_RPC_URL # Generate transaction template first to verify details seid tx evm send 0x1234567890abcdef... 1000000000000000000 \ --from=$WALLET_NAME \ --evm-rpc=$EVM_RPC_URL \ --generate-only ``` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.