Debug Tracing Overview

Requirements

The examples in this guide call the debug JSON-RPC endpoints directly with curl — no SDK or additional libraries are required. Optionally install jq to pretty-print the JSON responses:

# macOS
brew install jq

# Debian/Ubuntu
sudo apt-get install jq

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

Method	Purpose	Use Case
`debug_traceTransaction`	Trace specific transaction	Debugging failed transactions
`debug_traceBlockByNumber`	Trace entire block	Block-level analysis

When debug_traceBlockByNumber or debug_traceBlockByHash run with the default (struct) tracer — that is, when no custom tracer is specified — Sei can use a parallelized block trace path in which a failed transaction no longer aborts the entire block trace. Instead, each transaction produces its own per-tx entry in the result array: successful transactions include a result field, while failed transactions include an error field. This lets you inspect every transaction in a block even when one or more of them fail.This parallelized path is opt-in and gated by the node config field evm.enable_parallelized_block_trace (default false). When it is disabled, or when an explicit tracer is specified, the legacy trace path is used. Node operators can enable it by setting enable_parallelized_block_trace = true in the [evm] section of app.toml (or via the --evm.enable_parallelized_block_trace flag).

Transaction Analysis Example

Tracing an ERC-20 transfer transaction:

Transaction Details
Basic Trace
Gas Analysis

# 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": "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",
    "nonce": "0x4",
    "to": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
    "transactionIndex": "0x14",
    "value": "0x0",
    "type": "0x2",
    "accessList": [],
    "chainId": "0x531",
    "v": "0x0",
    "r": "0x3a107aca9cd554a9171a65ea2e8ef56ebeca8cfdc17f4bbecfb0f86837ca90d6",
    "s": "0x426134cf65b701bc8d43162f78bcf787319ff17cc6293188bcbb30fd99feb60",
    "yParity": "0x0"
  }
}

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

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "from": "0x4cbee7ad42d33e9d3b41e8b6faca2f6f173c8a94",
    "gas": "0x66f24",
    "gasUsed": "0x40f98",
    "to": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
    "input": "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",
    "calls": [
      {
        "from": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
        "gas": "0x5d03f",
        "gasUsed": "0x3b0cc",
        "to": "0x31a9b1835864706af10103b31ea2b79bdb995f5f",
        "input": "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",
        "calls": [
          {
            "from": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
            "gas": "0x5aa48",
            "gasUsed": "0xa724",
            "to": "0x3894085ef7ff0f0aedf52e2a2704928d1ec074f1",
            "input": "0x23b872dd0000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a940000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae000000000000000000000000000000000000000000000000000000000004faaa",
            "output": "0x0000000000000000000000000000000000000000000000000000000000000001",
            "calls": [
              {
                "from": "0x3894085ef7ff0f0aedf52e2a2704928d1ec074f1",
                "gas": "0x54283",
                "gasUsed": "0x4ad6",
                "to": "0x0000000000000000000000000000000000001001",
                "input": "0x5c05961b0000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a940000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae0000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000004faaa00000000000000000000000000000000000000000000000000000000000000446962632f4341364642464146333939343734413036323633453130443043453541454242453135313839443644344232444439414445363130303745363845423944423000000000000000000000000000000000000000000000000000000000",
                "output": "0x0000000000000000000000000000000000000000000000000000000000000001",
                "value": "0x0",
                "type": "CALL"
              }
            ],
            "logs": [
              {
                "address": "0x3894085ef7ff0f0aedf52e2a2704928d1ec074f1",
                "topics": [
                  "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
                  "0x0000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a94",
                  "0x0000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae"
                ],
                "data": "0x000000000000000000000000000000000000000000000000000000000004faaa",
                "position": "0x1"
              }
            ],
            "value": "0x0",
            "type": "CALL"
          },
          ...
        ]
      }
    ]
  }
}

# Analyze gas usage patterns
curl -X POST -H "Content-Type: application/json" \
  --data '{
    "jsonrpc": "2.0",
    "method": "debug_traceTransaction",
    "params": [
      "0x75b7ba10248e90db85b224eae587db1728520b6f72c795b9185064f444cee7c3",
      {
        "tracer": "{gasUsed: 0, operations: {}, step: function(log, db) { var op = log.op.toString(); var cost = log.getCost(); this.gasUsed += cost; if (!this.operations[op]) { this.operations[op] = { count: 0, totalGas: 0 }; } this.operations[op].count++; this.operations[op].totalGas += cost; }, fault: function(log, db) {}, result: function(ctx, db) { return { totalGas: this.gasUsed, operations: this.operations, efficiency: this.gasUsed / ctx.gasUsed }; }}"
      }
    ],
    "id": 1
  }' \
  https://evm-rpc.sei-apis.com

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "totalGas": 6346011,
    "operations": {
      "PUSH1": {
        "count": 1476,
        "totalGas": 4428
      },
      "MSTORE": {
        "count": 342,
        "totalGas": 1690
      },
      "CALLDATASIZE": {
        "count": 41,
        "totalGas": 82
      },
      "PUSH2": {
        "count": 1400,
        "totalGas": 4200
      },

      ...


      "STOP": {
        "count": 5,
        "totalGas": 0
      },
      "LOG2": {
        "count": 2,
        "totalGas": 5578
      },
      "LOG4": {
        "count": 1,
        "totalGas": 2899
      },
      "LOG1": {
        "count": 1,
        "totalGas": 2542
      }
    },
    "efficiency": 23.84499278564343
  }
}

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)

# Trace transaction with timing/store-access profiling
debug_traceTransactionProfile(hash, {})

Common Tracers

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

Next Steps

JavaScript Tracers - Custom analysis scripts
Troubleshooting - Common issues and solutions

Start with callTracer for general debugging, then use specialized tracers for specific analysis needs.

Overview

Essentials

seid CLI

Frontend Development

Smart Contracts

sei-js Library

Videos

Ecosystem Tutorials

Reference

Hardware Wallets

Debug Tracing Overview

Requirements

What You Can Trace

Transaction Execution

Contract Interactions

Performance Analysis

Security Analysis

Available Tracing Methods

Transaction Analysis Example

Debugging Failed Transactions

Step 1: Identify the Problem

Step 2: Trace the Execution

Step 3: Fix and Test

Common Debugging Scenarios

Transaction Reverted

Out of Gas

Unexpected Behavior

Slow Performance

Quick Reference

Essential Commands

Common Tracers

Next Steps

​Requirements

​What You Can Trace

​Transaction Execution

​Contract Interactions

​Performance Analysis

​Security Analysis

​Available Tracing Methods

​Transaction Analysis Example

​Debugging Failed Transactions

​Step 1: Identify the Problem

​Step 2: Trace the Execution

​Step 3: Fix and Test

​Common Debugging Scenarios

​Transaction Reverted

​Out of Gas

​Unexpected Behavior

​Slow Performance

​Quick Reference

​Essential Commands

​Common Tracers

​Next Steps

Requirements

What You Can Trace

Transaction Execution

Contract Interactions

Performance Analysis

Security Analysis

Available Tracing Methods

Transaction Analysis Example

Debugging Failed Transactions

Step 1: Identify the Problem

Step 2: Trace the Execution

Step 3: Fix and Test

Common Debugging Scenarios

Transaction Reverted

Out of Gas

Unexpected Behavior

Slow Performance

Quick Reference

Essential Commands

Common Tracers

Next Steps