Opcode Tracer

Log every instruction with gas, stack, memory, and storage at each step.

The opcode tracer records every EVM instruction executed, along with gas costs, stack state, memory, and storage changes. This is the default tracer when you pass --trace without specifying --tracer.

Usage

mega-evme run 0x60016000526001601ff3 --trace --tracer opcode

Options

These flags control what the opcode tracer captures. Disabling memory and stack capture significantly reduces trace size for large executions.

Flag	Default	Description
--trace.opcode.disable-memory	false	Omit memory snapshots from each step
--trace.opcode.disable-stack	false	Omit stack snapshots from each step
--trace.opcode.disable-storage	false	Omit storage change records
--trace.opcode.enable-return-data	false	Include return data in each step (off by default for size)

Output Format

The opcode tracer emits Geth-compatible JSON. The top-level object wraps the trace:

Schema

Field	Type	Description
failed	bool	Whether the transaction reverted
gas	number	Total gas used
returnValue	hex string	Return data from the transaction
structLogs	array	Array of per-opcode step objects

Each entry in structLogs:

Field	Type	Description
pc	number	Program counter
op	string	Opcode name (e.g., PUSH1, SSTORE)
gas	number	Gas remaining before this step
gasCost	number	Gas consumed by this step
depth	number	Call depth
stack	array	Stack contents as hex strings (unless disabled)
memory	array	Memory contents as 32-byte hex chunks (unless disabled)
storage	object	Storage changes as key-value hex pairs (unless disabled)
returnData	hex string	Return data at this step (only if enabled)

Example Output

Running mega-evme run 0x60016000526001601ff3 --trace --tracer opcode produces:

{
  "failed": false,
  "gas": 60018,
  "returnValue": "0x01",
  "structLogs": [
    {
      "pc": 0,
      "op": "PUSH1",
      "gas": 9940000,
      "gasCost": 3,
      "depth": 1,
      "stack": [],
      "memory": []
    },
    {
      "pc": 2,
      "op": "PUSH1",
      "gas": 9939997,
      "gasCost": 3,
      "depth": 1,
      "stack": ["0x1"],
      "memory": []
    },
    {
      "pc": 4,
      "op": "MSTORE",
      "gas": 9939994,
      "gasCost": 6,
      "depth": 1,
      "stack": ["0x1", "0x0"],
      "memory": []
    },
    {
      "pc": 5,
      "op": "PUSH1",
      "gas": 9939988,
      "gasCost": 3,
      "depth": 1,
      "stack": [],
      "memory": [
        "0000000000000000000000000000000000000000000000000000000000000001"
      ]
    },
    {
      "pc": 7,
      "op": "PUSH1",
      "gas": 9939985,
      "gasCost": 3,
      "depth": 1,
      "stack": ["0x1"],
      "memory": [
        "0000000000000000000000000000000000000000000000000000000000000001"
      ]
    },
    {
      "pc": 9,
      "op": "RETURN",
      "gas": 9939982,
      "gasCost": 0,
      "depth": 1,
      "stack": ["0x1", "0x1f"],
      "memory": [
        "0000000000000000000000000000000000000000000000000000000000000001"
      ]
    }
  ]
}

Examples

Minimal trace (no memory or stack, for compact output):

mega-evme run 0x60016000526001601ff3 \
  --trace --tracer opcode \
  --trace.opcode.disable-memory \
  --trace.opcode.disable-stack

Full trace to file with return data:

mega-evme run 0x60016000526001601ff3 \
  --trace --tracer opcode \
  --trace.opcode.enable-return-data \
  --trace.output trace.json