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EVMDebug TracingOverview

Debug Tracing Overview

Requirements

Install Ethers.js v6.14.4+:

npm install ethers@^6.14.4

All examples use modern ES6 modules and TypeScript patterns.

Debug tracing is your primary tool for understanding EVM transaction execution on Sei. This comprehensive system allows you to analyze transaction flow, optimize gas usage, debug smart contract interactions, and troubleshoot production issues.

What You Can Trace

Transaction Execution

  • Step-by-step opcode execution
  • Contract call hierarchy
  • Gas consumption breakdown
  • State changes and storage access

Contract Interactions

  • Cross-contract calls and returns
  • Event emission analysis
  • Precompile usage tracking
  • External library calls

Performance Analysis

  • Gas optimization opportunities
  • Bottleneck identification
  • Cache hit/miss patterns
  • State access efficiency

Security Analysis

  • Suspicious operation detection
  • Reentrancy pattern analysis
  • Access control verification
  • Vulnerability scanning

Available Tracing Methods

MethodPurposeUse Case
debug_traceTransactionTrace specific transactionDebugging failed transactions
debug_traceBlockByNumberTrace entire blockBlock-level analysis
debug_traceCallSimulate and traceTesting before execution
debug_traceStateAccessState access patternsPerformance optimization

Transaction Analysis Example

Tracing an ERC-20 transfer transaction:

# Real transaction on Sei mainnet
TRANSACTION_HASH="0x75b7ba10248e90db85b224eae587db1728520b6f72c795b9185064f444cee7c3"
 
# Transaction details
 
curl -X POST -H "Content-Type: application/json" \
 --data '{
"jsonrpc": "2.0",
"method": "eth_getTransactionByHash",
"params": ["'$TRANSACTION_HASH'"],
"id": 1
}' \
 https://evm-rpc.sei-apis.com

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "blockHash": "0xbc229fe41605ba2b46fcd7aa7ce328dc2f6da78385dfea84ca8dbef7b4325462",
    "blockNumber": "0x97aefcf",
    "from": "0x4cbee7ad42d33e9d3b41e8b6faca2f6f173c8a94",
    "gas": "0x66f24",
    "gasPrice": "0x565dd756",
    "maxFeePerGas": "0x565dd756",
    "maxPriorityFeePerGas": "0x5e679d6",
    "hash": "0x75b7ba10248e90db85b224eae587db1728520b6f72c795b9185064f444cee7c3",
    "input": "0x733214a3e5f551789f7ee58322679a2b141e64533098b8ba41d9e10cf8061a18a777d6ce00000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000001000000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a940000000000000000000000000000000000000000000000000dd26083bfc745570000000000000000000000000000000000000000000000000000000000000160000000000000000000000000000000000000000000000000000000000000000f6a756d7065722e65786368616e67650000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002a30783030303030303030303030303030303030303030303030303030303030303030303030303030303000000000000000000000000000000000000000000000000000000000000000000000fde9ce4e17b650efdca13d524f132876700d806f000000000000000000000000fde9ce4e17b650efdca13d524f132876700d806f0000000000000000000000003894085ef7ff0f0aedf52e2a2704928d1ec074f10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004faaa00000000000000000000000000000000000000000000000000000000000000e0000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000001642646478b0000000000000000000000003894085ef7ff0f0aedf52e2a2704928d1ec074f1000000000000000000000000000000000000000000000000000000000004faaa000000000000000000000000eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee0000000000000000000000000000000000000000000000000dd26083bfc745570000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae00000000000000000000000000000000000000000000000000000000000000c00000000000000000000000000000000000000000000000000000000000000070023894085ef7ff0f0aedf52e2a2704928d1ec074f101ffff015cfa8db453c9904511c4ea9eb0bfc903e36b9f5f01fde9ce4e17b650efdca13d524f132876700d806f01e30fedd158a2e3b13e9badaeabafc5516e95e8c701ffff02001231deb6f5749ef6ce6943a275a1d3e7486f4eae0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
    "nonce": "0x4",
    "to": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
    "transactionIndex": "0x14",
    "value": "0x0",
    "type": "0x2",
    "accessList": [],
    "chainId": "0x531",
    "v": "0x0",
    "r": "0x3a107aca9cd554a9171a65ea2e8ef56ebeca8cfdc17f4bbecfb0f86837ca90d6",
    "s": "0x426134cf65b701bc8d43162f78bcf787319ff17cc6293188bcbb30fd99feb60",
    "yParity": "0x0"
  }
}

Debugging Failed Transactions

Steps to analyze and resolve transaction failures:

Step 1: Identify the Problem

# Get transaction receipt
FAILED_TX="0xb2a6f4f7f37d8df728968126c05d1a8b0391003cf375ed5abb1b5e02fe66c717"
 
curl -X POST -H "Content-Type: application/json" \
  --data '{
    "jsonrpc": "2.0",
    "method": "eth_getTransactionReceipt",
    "params": ["'$FAILED_TX'"],
    "id": 1
  }' \
  https://evm-rpc.sei-apis.com

Step 2: Trace the Execution

# Trace to see where it failed
curl -X POST -H "Content-Type: application/json" \
  --data '{
    "jsonrpc": "2.0",
    "method": "debug_traceTransaction",
    "params": [
      "'$FAILED_TX'",
      {
        "tracer": "callTracer",
        "tracerConfig": {
          "withLog": true
        }
      }
    ],
    "id": 1
  }' \
  https://evm-rpc.sei-apis.com

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "from": "0x2c80b1b0473bb765ef536d2526ec63195794d945",
    "gas": "0xc3500",
    "gasUsed": "0x2863d",
    "to": "0xd1efe48b71acd98db16fcb9e7152b086647ef544",
    "input": "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",
    "output": "0x08c379a000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000013546f6f206c6974746c6520726563656976656400000000000000000000000000",
    "error": "execution reverted",
    "revertReason": "Too little received",
    "calls": [
      ...
    ]
  }
}

Step 3: Fix and Test

# Simulate the fix with debug_traceCall
curl -X POST \
  -H "Content-Type: application/json" \
  --data '{
    "jsonrpc": "2.0",
    "method": "debug_traceCall",
    "params": [
      {
        "from": "0x2c80b1b0473bb765ef536d2526ec63195794d945",
        "to": "0xd1efe48b71acd98db16fcb9e7152b086647ef544",
        "gas": "0xc3500",
        "gasPrice": "0x2127ddd32",
        "value": "0x0"
      },
      "0x98a87cc",
      {
        "tracer": "callTracer",
        "tracerConfig": {
          "onlyTopCall": false,
          "withLog": true
        }
      }
    ],
    "id": 1
  }' \
  https://evm-rpc.sei-apis.com

Common Debugging Scenarios

Transaction Reverted

Problem: Transaction failed with revert Solution: Use callTracer to find the exact revert reason

Out of Gas

Problem: Transaction ran out of gas Solution: Use gas analysis tracer to optimize gas usage

Unexpected Behavior

Problem: Transaction succeeded but wrong result Solution: Use opcode tracer for step-by-step analysis

Slow Performance

Problem: Transaction uses too much gas Solution: Use state access tracer to find inefficiencies

Quick Reference

Essential Commands

# Trace transaction
debug_traceTransaction(hash, {tracer: "callTracer"})
 
# Trace block
debug_traceBlockByNumber("latest", {tracer: "callTracer"})
 
# Simulate call
debug_traceCall(tx, "latest", {tracer: "callTracer"})
 
# State access
debug_traceStateAccess(hash)

Common Tracers

  • callTracer: Contract call hierarchy
  • opcodeTracer: Opcode-level execution
  • Custom JS: Custom analysis logic

Next Steps

  1. JavaScript Tracers - Custom analysis scripts
  2. Troubleshooting - Common issues and solutions
Start with callTracer for general debugging, then use specialized tracers for specific analysis needs.
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