Debug Tracing Overview

Requirements

The examples in this guide call the debug JSON-RPC endpoints directly with curl. You do not need an SDK or other libraries. To pretty-print the JSON responses, you can install jq:

# macOS
brew install jq

# Debian/Ubuntu
sudo apt-get install jq

Debug tracing is your primary tool to understand how EVM transactions execute on Sei. With it, you can 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 and 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 a specific transaction	Debugging failed transactions
`debug_traceBlockByNumber`	Trace an entire block	Block-level analysis
`debug_traceCall`	Simulate and trace	Testing before execution
`debug_traceStateAccess`	State access patterns	Performance optimization
`debug_traceTransactionProfile`	Trace plus timing/store-access profiling	Latency breakdown and DB-access analysis

Transaction analysis example

This example traces 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": "0x733214a3e5f551789f7ee58322679a2b141e64533098b8ba41d9e10cf8061a18a777d6ce00000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000001000000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a940000000000000000000000000000000000000000000000000dd26083bfc745570000000000000000000000000000000000000000000000000000000000000160000000000000000000000000000000000000000000000000000000000000000f6a756d7065722e65786368616e67650000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002a30783030303030303030303030303030303030303030303030303030303030303030303030303030303000000000000000000000000000000000000000000000000000000000000000000000fde9ce4e17b650efdca13d524f132876700d806f000000000000000000000000fde9ce4e17b650efdca13d524f132876700d806f0000000000000000000000003894085ef7ff0f0aedf52e2a2704928d1ec074f10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004faaa00000000000000000000000000000000000000000000000000000000000000e0000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000001642646478b0000000000000000000000003894085ef7ff0f0aedf52e2a2704928d1ec074f1000000000000000000000000000000000000000000000000000000000004faaa000000000000000000000000eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee0000000000000000000000000000000000000000000000000dd26083bfc745570000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae00000000000000000000000000000000000000000000000000000000000000c00000000000000000000000000000000000000000000000000000000000000070023894085ef7ff0f0aedf52e2a2704928d1ec074f101ffff015cfa8db453c9904511c4ea9eb0bfc903e36b9f5f01fde9ce4e17b650efdca13d524f132876700d806f01e30fedd158a2e3b13e9badaeabafc5516e95e8c701ffff02001231deb6f5749ef6ce6943a275a1d3e7486f4eae0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
    "calls": [
      {
        "from": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
        "gas": "0x5d03f",
        "gasUsed": "0x3b0cc",
        "to": "0x31a9b1835864706af10103b31ea2b79bdb995f5f",
        "input": "0x733214a3e5f551789f7ee58322679a2b141e64533098b8ba41d9e10cf8061a18a777d6ce00000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000001000000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a940000000000000000000000000000000000000000000000000dd26083bfc745570000000000000000000000000000000000000000000000000000000000000160000000000000000000000000000000000000000000000000000000000000000f6a756d7065722e65786368616e67650000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002a30783030303030303030303030303030303030303030303030303030303030303030303030303030303000000000000000000000000000000000000000000000000000000000000000000000fde9ce4e17b650efdca13d524f132876700d806f000000000000000000000000fde9ce4e17b650efdca13d524f132876700d806f0000000000000000000000003894085ef7ff0f0aedf52e2a2704928d1ec074f10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004faaa00000000000000000000000000000000000000000000000000000000000000e0000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000001642646478b0000000000000000000000003894085ef7ff0f0aedf52e2a2704928d1ec074f1000000000000000000000000000000000000000000000000000000000004faaa000000000000000000000000eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee0000000000000000000000000000000000000000000000000dd26083bfc745570000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae00000000000000000000000000000000000000000000000000000000000000c00000000000000000000000000000000000000000000000000000000000000070023894085ef7ff0f0aedf52e2a2704928d1ec074f101ffff015cfa8db453c9904511c4ea9eb0bfc903e36b9f5f01fde9ce4e17b650efdca13d524f132876700d806f01e30fedd158a2e3b13e9badaeabafc5516e95e8c701ffff02001231deb6f5749ef6ce6943a275a1d3e7486f4eae0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
        "calls": [
          {
            "from": "0x1231deb6f5749ef6ce6943a275a1d3e7486f4eae",
            "gas": "0x5aa48",
            "gasUsed": "0xa724",
            "to": "0x3894085ef7ff0f0aedf52e2a2704928d1ec074f1",
            "input": "0x23b872dd0000000000000000000000004cbee7ad42d33e9d3b41e8b6faca2f6f173c8a940000000000000000000000001231deb6f5749ef6ce6943a275a1d3e7486f4eae000000000000000000000000000000000000000000000000000000000004faaa",
            "output": "0x0000000000000000000000000000000000000000000000000000000000000001",
            "calls": [
              {
                "from": "0x3894085ef7ff0f0aedf52e2a2704928d1ec074f1",
                "gas": "0x54283",
                "gasUsed": "0x4ad6",
                "to": "0x0000000000000000000000000000000000001001",
                "input": "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",
                "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

Use these steps to analyze and fix 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: The transaction failed with a revert. Solution: Use callTracer to find the exact revert reason.

Out of gas

Problem: The transaction ran out of gas. Solution: Use the gas analysis tracer to optimize gas usage.

Unexpected behavior

Problem: The transaction succeeded, but the result is wrong. Solution: Use the opcode tracer for step-by-step analysis.

Slow performance

Problem: The transaction uses too much gas. Solution: Use the 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

Pre-baked trace cache

RPC nodes can optionally pre-compute and cache debug_trace* results in the background. The node then serves trace requests from a local on-disk cache instead of re-executing the block live on every call. You configure this opt-in feature through [evm] fields in app.toml. It is recommended for RPC nodes only. When the feature is enabled, a background worker re-executes each committed block with the configured tracers. It stores the results in a Pebble database at <home>/data/trace_db. These methods serve results from this cache on a cache hit. Otherwise, they fall through to live re-execution:

debug_traceTransaction
debug_traceBlockByNumber and debug_traceBlockByHash

When the cache is used

The node serves a request from the cache only when trace baking is enabled and the request uses a bakeable tracer configuration:

The tracer is one of callTracer, prestateTracer, or flatCallTracer.
The request does not include a custom tracerConfig. A per-call tracerConfig (for example, {"withLog": true}) is not part of the cache key. Any custom tracer config makes the request un-bakeable, so it falls through to live re-execution.

Requests that use the struct logger (no tracer), a JavaScript tracer, or any other named tracer always run live.

Configuration

These [evm] fields in app.toml control trace baking:

Field	Default	Description
`trace_bake_enabled`	`false`	Enables the background trace-baking worker that caches results at `<home>/data/trace_db`. RPC nodes only.
`trace_bake_workers`	`1`	Number of re-execution worker goroutines.
`trace_bake_queue_size`	`4096`	Bounds the in-flight height queue. When the queue is full, heights are dropped so that consensus never blocks. Dropped blocks fall through to live re-execution.
`trace_bake_tracers`	`["callTracer"]`	Which tracers to bake per block. Eligible values: `callTracer`, `prestateTracer`, `flatCallTracer`.
`trace_bake_window_blocks`	`0`	Rolling prune window: blocks older than `(latest - window)` are pruned. `0` disables pruning, so the cache grows without limit.
`trace_bake_use_snapshot`	`false`	Uses in-memory memiavl snapshots as the state backend for trace baking when the store backend supports snapshots.
`trace_bake_snapshot_window`	`64`	Number of recent memiavl snapshots to keep for trace baking.

Trace baking adds a persistent on-disk store at <home>/data/trace_db and increases disk usage. The node flushes the store’s write-ahead log when it shuts down cleanly.

Removed legacy trace filters

The legacy *ExcludeTraceFail endpoints have been removed. For block tracing, use debug_traceBlockByNumber or debug_traceBlockByHash. For EVM receipts, use eth_getTransactionReceipt. There is no block or filter method to discover synthetic logs from Cosmos-originated transactions. If you already know a synthetic transaction hash, enable sei_getTransactionReceipt to get its receipt and logs.

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

Pre-baked trace cache

When the cache is used

Configuration

Removed legacy trace filters

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

​Pre-baked trace cache

​When the cache is used

​Configuration

​Removed legacy trace filters

​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

Pre-baked trace cache

When the cache is used

Configuration

Removed legacy trace filters

Next steps