eth/tracers: add EnableActualGasCost flag to StructLogger

eth/tracers/logger/logger.go

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/tracing"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/holiman/uint256"
 )
@@ -46,6 +47,7 @@ type Config struct {
 	DisableStack        bool // disable stack capture
 	DisableStorage      bool // disable storage capture
 	EnableReturnData    bool // enable return data capture
+	EnableActualGasCost bool // enable actual gas cost computation from consecutive gas values (non-streaming mode only)
 	Limit               int  // maximum size of output, but zero means unlimited
 	// Chain overrides, can be used to execute a trace using future fork rules
 	Overrides *params.ChainConfig `json:"overrides,omitempty"`
@@ -217,7 +219,9 @@ type StructLogger struct {
 	usedGas uint64
 
 	writer        io.Writer         // If set, the logger will stream instead of store logs
-	logs       []json.RawMessage // buffer of json-encoded logs
+	jsonLogs      []json.RawMessage // buffer of json-encoded logs (when EnableActualGasCost is false)
+	logs          []*StructLog      // buffer of logs for deferred JSON encoding (when EnableActualGasCost is true)
+	pendingGasIdx []int             // index into logs for pending gas update at each depth
 	resultSize    int
 
 	interrupt atomic.Bool // Atomic flag to signal execution interruption
@@ -229,6 +233,11 @@ type StructLogger struct {
 func NewStreamingStructLogger(cfg *Config, writer io.Writer) *StructLogger {
 	l := NewStructLogger(cfg)
 	l.writer = writer
+	if cfg != nil && cfg.EnableActualGasCost {
+		log.Warn("EnableActualGasCost is not supported in streaming mode, ignoring")
+		l.cfg.EnableActualGasCost = false
+		l.pendingGasIdx = nil
+	}
 	return l
 }
 
@@ -236,10 +245,14 @@ func NewStreamingStructLogger(cfg *Config, writer io.Writer) *StructLogger {
 func NewStructLogger(cfg *Config) *StructLogger {
 	logger := &StructLogger{
 		storage:  make(map[common.Address]Storage),
-		logs:    make([]json.RawMessage, 0),
+		jsonLogs: make([]json.RawMessage, 0),
 	}
 	if cfg != nil {
 		logger.cfg = *cfg
+		if cfg.EnableActualGasCost {
+			logger.logs = make([]*StructLog, 0)
+			logger.pendingGasIdx = make([]int, 0, 16)
+		}
 	}
 	return logger
 }
@@ -278,15 +291,15 @@ func (l *StructLogger) OnOpcode(pc uint64, opcode byte, gas, cost uint64, scope
 		stack        = scope.StackData()
 		stackLen     = len(stack)
 	)
-	log := StructLog{pc, op, gas, cost, nil, len(memory), nil, nil, nil, depth, l.env.StateDB.GetRefund(), err}
+	slog := StructLog{pc, op, gas, cost, nil, len(memory), nil, nil, nil, depth, l.env.StateDB.GetRefund(), err}
 	if l.cfg.EnableMemory {
-		log.Memory = memory
+		slog.Memory = memory
 	}
 	if !l.cfg.DisableStack {
-		log.Stack = scope.StackData()
+		slog.Stack = scope.StackData()
 	}
 	if l.cfg.EnableReturnData {
-		log.ReturnData = rData
+		slog.ReturnData = rData
 	}
 
 	// Copy a snapshot of the current storage to a new container
@@ -315,16 +328,44 @@ func (l *StructLogger) OnOpcode(pc uint64, opcode byte, gas, cost uint64, scope
 			storage = maps.Clone(l.storage[contractAddr])
 		}
 	}
-	log.Storage = storage
+	slog.Storage = storage
 
 	// create a log
 	if l.writer == nil {
-		entry := log.toLegacyJSON()
+		if l.cfg.EnableActualGasCost {
+			// Store struct for later GasCost modification and deferred JSON encoding
+			l.logs = append(l.logs, &slog)
+			// Approximate size for limit checking. This intentionally overestimates
+			// since exact JSON size is only known after final encoding with updated
+			// gas costs. Constants: ~100 bytes base, 66 per stack item (hex u256),
+			// 2 per memory byte (hex), 132 per storage entry (two hex hashes).
+			l.resultSize += 100 + len(slog.Stack)*66 + len(slog.Memory)*2 + len(slog.ReturnData)*2 + len(slog.Storage)*132
+
+			// Ensure pendingGasIdx slice is large enough for this depth
+			for len(l.pendingGasIdx) <= depth {
+				l.pendingGasIdx = append(l.pendingGasIdx, -1)
+			}
+			// Clear pending indices from deeper levels (we've returned from calls).
+			// These are the last opcodes in child call contexts - we cannot compute
+			// actual gas cost across call boundaries, so keep the pre-calculated cost.
+			for d := len(l.pendingGasIdx) - 1; d > depth; d-- {
+				l.pendingGasIdx[d] = -1
+			}
+			// Update gas cost for pending log at current depth
+			if l.pendingGasIdx[depth] >= 0 {
+				l.logs[l.pendingGasIdx[depth]].GasCost = l.logs[l.pendingGasIdx[depth]].Gas - gas
+			}
+			// Store current log's index as pending at this depth
+			l.pendingGasIdx[depth] = len(l.logs) - 1
+		} else {
+			// Original behavior: encode to JSON immediately with exact size tracking
+			entry := slog.toLegacyJSON()
 			l.resultSize += len(entry)
-		l.logs = append(l.logs, entry)
+			l.jsonLogs = append(l.jsonLogs, entry)
+		}
 		return
 	}
-	log.Write(l.writer)
+	slog.Write(l.writer)
 }
 
 // OnExit is called a call frame finishes processing.
@@ -357,11 +398,25 @@ func (l *StructLogger) GetResult() (json.RawMessage, error) {
 	if failed && !errors.Is(l.err, vm.ErrExecutionReverted) {
 		returnData = []byte{}
 	}
+
+	// Get the appropriate logs based on mode
+	var structLogs []json.RawMessage
+	if l.cfg.EnableActualGasCost {
+		// Convert deferred logs to JSON
+		structLogs = make([]json.RawMessage, 0, len(l.logs))
+		for _, slog := range l.logs {
+			structLogs = append(structLogs, slog.toLegacyJSON())
+		}
+	} else {
+		// Use pre-encoded JSON logs
+		structLogs = l.jsonLogs
+	}
+
 	return json.Marshal(&ExecutionResult{
 		Gas:         l.usedGas,
 		Failed:      failed,
 		ReturnValue: returnData,
-		StructLogs:  l.logs,
+		StructLogs:  structLogs,
 	})
 }
 

eth/tracers/logger/logger_test.go

@@ -17,6 +17,7 @@
 package logger
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"math/big"
@@ -24,6 +25,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/tracing"
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/holiman/uint256"
@@ -43,6 +45,28 @@ func (*dummyStatedb) GetStateAndCommittedState(common.Address, common.Hash) (com
 	return common.Hash{}, common.Hash{}
 }
 
+// mockOpContext implements tracing.OpContext for manual OnOpcode testing.
+type mockOpContext struct{}
+
+var _ tracing.OpContext = (*mockOpContext)(nil)
+
+func (m *mockOpContext) MemoryData() []byte       { return nil }
+func (m *mockOpContext) StackData() []uint256.Int { return nil }
+func (m *mockOpContext) Caller() common.Address   { return common.Address{} }
+func (m *mockOpContext) Address() common.Address  { return common.Address{} }
+func (m *mockOpContext) CallValue() *uint256.Int  { return new(uint256.Int) }
+func (m *mockOpContext) CallInput() []byte        { return nil }
+func (m *mockOpContext) ContractCode() []byte     { return nil }
+
+// testStructLog is used to parse JSON structLogs in tests.
+type testStructLog struct {
+	Pc      uint64 `json:"pc"`
+	Op      string `json:"op"`
+	Gas     uint64 `json:"gas"`
+	GasCost uint64 `json:"gasCost"`
+	Depth   int    `json:"depth"`
+}
+
 func TestStoreCapture(t *testing.T) {
 	var (
 		logger   = NewStructLogger(nil)
@@ -66,6 +90,669 @@ func TestStoreCapture(t *testing.T) {
 	}
 }
 
+// TestEnableActualGasCost verifies that when EnableActualGasCost is true, gasCost is
+// computed as the difference between consecutive gas values rather than the
+// pre-calculated opcode cost. For opcodes that are the last in a call context
+// (before returning to parent), the pre-calculated cost is kept since we cannot
+// compute actual cost across call boundaries.
+func TestEnableActualGasCost(t *testing.T) {
+	t.Run("same_depth", func(t *testing.T) {
+		// Create logger with EnableActualGasCost enabled
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		evm := vm.NewEVM(vm.BlockContext{}, &dummyStatedb{}, params.TestChainConfig, vm.Config{Tracer: logger.Hooks()})
+		contract := vm.NewContract(common.Address{}, common.Address{}, new(uint256.Int), 100000, nil)
+
+		// Simple bytecode: PUSH1 0x1, PUSH1 0x0, ADD
+		contract.Code = []byte{byte(vm.PUSH1), 0x1, byte(vm.PUSH1), 0x0, byte(vm.ADD)}
+
+		logger.OnTxStart(evm.GetVMContext(), nil, common.Address{})
+		_, err := evm.Run(contract, []byte{}, false)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		// Verify we have logs
+		if len(execResult.StructLogs) < 2 {
+			t.Fatalf("expected at least 2 logs, got %d", len(execResult.StructLogs))
+		}
+
+		// Parse logs and verify gas costs are computed as diffs
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// For all but the last log, gasCost should equal gas[n] - gas[n+1]
+		for i := 0; i < len(logs)-1; i++ {
+			expectedCost := logs[i].Gas - logs[i+1].Gas
+			if logs[i].GasCost != expectedCost {
+				t.Errorf("log[%d] (%s): expected gasCost %d, got %d",
+					i, logs[i].Op, expectedCost, logs[i].GasCost)
+			}
+		}
+	})
+
+	t.Run("depth_change", func(t *testing.T) {
+		// Manually simulate OnOpcode calls with depth changes
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// Simulate: CALL at depth 1, child execution at depth 2, return to depth 1
+		// depth=1, gas=100000: CALL opcode
+		// depth=2, gas=63000:  child starts (PUSH)
+		// depth=2, gas=60000:  child continues (STOP)
+		// depth=1, gas=98000:  back to parent (PUSH)
+		logger.OnOpcode(0, byte(vm.CALL), 100000, 100, scope, nil, 1, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 63000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.STOP), 60000, 0, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.PUSH1), 98000, 3, scope, nil, 1, nil)
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		if len(execResult.StructLogs) != 4 {
+			t.Fatalf("expected 4 logs, got %d", len(execResult.StructLogs))
+		}
+
+		// Parse all logs - order must match execution order
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Verify execution order is preserved: CALL, PUSH, STOP, PUSH
+		expectedOrder := []string{"CALL", "PUSH1", "STOP", "PUSH1"}
+		for i, expected := range expectedOrder {
+			if logs[i].Op != expected {
+				t.Errorf("log[%d]: expected op %s, got %s", i, expected, logs[i].Op)
+			}
+		}
+
+		// CALL at depth 1: gasCost should be 100000 - 98000 = 2000
+		// (includes all child execution gas)
+		if logs[0].GasCost != 2000 {
+			t.Errorf("CALL gasCost: expected 2000, got %d", logs[0].GasCost)
+		}
+
+		// Find child opcodes at depth 2 and verify gas costs
+		var childPushFound bool
+		var childStopLog *testStructLog
+		for i, log := range logs {
+			if log.Depth == 2 && log.Op == "PUSH1" && log.GasCost == 3000 {
+				childPushFound = true
+			}
+			if log.Depth == 2 && log.Op == "STOP" {
+				childStopLog = &logs[i]
+			}
+		}
+		if !childPushFound {
+			t.Error("child PUSH with gasCost 3000 not found")
+		}
+
+		// STOP is the last opcode in the child call - it should keep pre-calculated
+		// cost (0) since we cannot compute actual cost across call boundaries.
+		if childStopLog == nil {
+			t.Fatal("child STOP log not found")
+		}
+		if childStopLog.GasCost != 0 {
+			t.Errorf("child STOP gasCost: expected 0 (pre-calculated), got %d", childStopLog.GasCost)
+		}
+	})
+
+	t.Run("nested_calls", func(t *testing.T) {
+		// Test 3 levels deep: depth 1 -> depth 2 -> depth 3 -> back
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// Simulate nested calls:
+		// depth=1, gas=100000: CALL (outer)
+		// depth=2, gas=80000:  PUSH in first child
+		// depth=2, gas=79000:  CALL (inner call)
+		// depth=3, gas=50000:  PUSH in innermost child
+		// depth=3, gas=49000:  STOP in innermost child
+		// depth=2, gas=75000:  back to first child
+		// depth=2, gas=74000:  STOP in first child
+		// depth=1, gas=90000:  back to outer
+		logger.OnOpcode(0, byte(vm.CALL), 100000, 100, scope, nil, 1, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 80000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.CALL), 79000, 100, scope, nil, 2, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 50000, 3, scope, nil, 3, nil)
+		logger.OnOpcode(1, byte(vm.STOP), 49000, 0, scope, nil, 3, nil)
+		logger.OnOpcode(2, byte(vm.PUSH1), 75000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(3, byte(vm.STOP), 74000, 0, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.PUSH1), 90000, 3, scope, nil, 1, nil)
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		if len(execResult.StructLogs) != 8 {
+			t.Fatalf("expected 8 logs, got %d", len(execResult.StructLogs))
+		}
+
+		// Parse all logs
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Find and verify outer CALL at depth 1
+		// gasCost should be 100000 - 90000 = 10000 (includes all nested execution)
+		var outerCall *testStructLog
+		for i := range logs {
+			if logs[i].Op == "CALL" && logs[i].Depth == 1 {
+				outerCall = &logs[i]
+				break
+			}
+		}
+		if outerCall == nil {
+			t.Fatal("outer CALL log not found")
+		}
+		if outerCall.GasCost != 10000 {
+			t.Errorf("outer CALL gasCost: expected 10000, got %d", outerCall.GasCost)
+		}
+
+		// Find and verify inner CALL at depth 2
+		// gasCost should be 79000 - 75000 = 4000 (includes innermost execution)
+		var innerCall *testStructLog
+		for i := range logs {
+			if logs[i].Op == "CALL" && logs[i].Depth == 2 {
+				innerCall = &logs[i]
+				break
+			}
+		}
+		if innerCall == nil {
+			t.Fatal("inner CALL log not found")
+		}
+		if innerCall.GasCost != 4000 {
+			t.Errorf("inner CALL gasCost: expected 4000, got %d", innerCall.GasCost)
+		}
+
+		// Verify innermost PUSH at depth 3 has correct gas diff
+		// gasCost should be 50000 - 49000 = 1000
+		var innermostPush *testStructLog
+		for i := range logs {
+			if logs[i].Op == "PUSH1" && logs[i].Depth == 3 {
+				innermostPush = &logs[i]
+				break
+			}
+		}
+		if innermostPush == nil {
+			t.Fatal("innermost PUSH log not found")
+		}
+		if innermostPush.GasCost != 1000 {
+			t.Errorf("innermost PUSH gasCost: expected 1000, got %d", innermostPush.GasCost)
+		}
+
+		// Verify STOP opcodes at depth 2 and 3 keep pre-calculated cost (0)
+		// since they are the last opcodes in their respective call contexts.
+		for _, log := range logs {
+			if log.Op == "STOP" && log.GasCost != 0 {
+				t.Errorf("STOP at depth %d: expected gasCost 0 (pre-calculated), got %d",
+					log.Depth, log.GasCost)
+			}
+		}
+	})
+
+	t.Run("disabled", func(t *testing.T) {
+		// Default behavior - EnableActualGasCost is false
+		logger := NewStructLogger(nil)
+		evm := vm.NewEVM(vm.BlockContext{}, &dummyStatedb{}, params.TestChainConfig, vm.Config{Tracer: logger.Hooks()})
+		contract := vm.NewContract(common.Address{}, common.Address{}, new(uint256.Int), 100000, nil)
+
+		contract.Code = []byte{byte(vm.PUSH1), 0x1, byte(vm.PUSH1), 0x0, byte(vm.ADD)}
+
+		logger.OnTxStart(evm.GetVMContext(), nil, common.Address{})
+		_, err := evm.Run(contract, []byte{}, false)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		// Parse logs
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// With disabled flag, gasCost should be the pre-calculated cost, not the diff
+		// For PUSH1, the pre-calculated cost is 3
+		for _, log := range logs {
+			if log.Op == "PUSH1" && log.GasCost != 3 {
+				t.Errorf("PUSH1 with disabled flag: expected pre-calculated gasCost 3, got %d", log.GasCost)
+			}
+		}
+	})
+
+	t.Run("empty_logs", func(t *testing.T) {
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		// No opcodes executed, just get result
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		if len(execResult.StructLogs) != 0 {
+			t.Errorf("expected 0 logs, got %d", len(execResult.StructLogs))
+		}
+	})
+
+	t.Run("return_opcode", func(t *testing.T) {
+		// RETURN has dynamic gas cost based on memory expansion
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// Simulate: CALL at depth 1, child prepares return data, RETURN
+		// depth=1, gas=100000: CALL opcode
+		// depth=2, gas=63000:  PUSH (prepare return offset)
+		// depth=2, gas=62000:  PUSH (prepare return size)
+		// depth=2, gas=61000:  RETURN with memory cost (dynamic gas)
+		// depth=1, gas=95000:  back to parent
+		logger.OnOpcode(0, byte(vm.CALL), 100000, 100, scope, nil, 1, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 63000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.PUSH1), 62000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(2, byte(vm.RETURN), 61000, 10, scope, nil, 2, nil) // 10 = pre-calculated cost with mem
+		logger.OnOpcode(1, byte(vm.POP), 95000, 2, scope, nil, 1, nil)
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		if len(execResult.StructLogs) != 5 {
+			t.Fatalf("expected 5 logs, got %d", len(execResult.StructLogs))
+		}
+
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Find RETURN and verify it keeps pre-calculated cost (last opcode in child)
+		var returnLog *testStructLog
+		for i := range logs {
+			if logs[i].Op == "RETURN" {
+				returnLog = &logs[i]
+				break
+			}
+		}
+		if returnLog == nil {
+			t.Fatal("RETURN log not found")
+		}
+		// RETURN is last opcode in child, should keep pre-calculated cost (10)
+		if returnLog.GasCost != 10 {
+			t.Errorf("RETURN gasCost: expected 10 (pre-calculated), got %d", returnLog.GasCost)
+		}
+
+		// Verify CALL has actual cost including child execution
+		var callLog *testStructLog
+		for i := range logs {
+			if logs[i].Op == "CALL" {
+				callLog = &logs[i]
+				break
+			}
+		}
+		if callLog == nil {
+			t.Fatal("CALL log not found")
+		}
+		// CALL: 100000 - 95000 = 5000
+		if callLog.GasCost != 5000 {
+			t.Errorf("CALL gasCost: expected 5000, got %d", callLog.GasCost)
+		}
+	})
+
+	t.Run("revert_opcode", func(t *testing.T) {
+		// REVERT is similar to RETURN but indicates failure
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// Simulate: CALL at depth 1, child reverts
+		// depth=1, gas=100000: CALL opcode
+		// depth=2, gas=63000:  PUSH (error offset)
+		// depth=2, gas=62000:  PUSH (error size)
+		// depth=2, gas=61000:  REVERT
+		// depth=1, gas=96000:  back to parent (more gas refunded on revert)
+		logger.OnOpcode(0, byte(vm.CALL), 100000, 100, scope, nil, 1, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 63000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.PUSH1), 62000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(2, byte(vm.REVERT), 61000, 5, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.ISZERO), 96000, 3, scope, nil, 1, nil)
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Find REVERT and verify it keeps pre-calculated cost
+		var revertLog *testStructLog
+		for i := range logs {
+			if logs[i].Op == "REVERT" {
+				revertLog = &logs[i]
+				break
+			}
+		}
+		if revertLog == nil {
+			t.Fatal("REVERT log not found")
+		}
+		if revertLog.GasCost != 5 {
+			t.Errorf("REVERT gasCost: expected 5 (pre-calculated), got %d", revertLog.GasCost)
+		}
+
+		// Verify CALL actual cost
+		var callLog *testStructLog
+		for i := range logs {
+			if logs[i].Op == "CALL" {
+				callLog = &logs[i]
+				break
+			}
+		}
+		if callLog == nil {
+			t.Fatal("CALL log not found")
+		}
+		// CALL: 100000 - 96000 = 4000
+		if callLog.GasCost != 4000 {
+			t.Errorf("CALL gasCost: expected 4000, got %d", callLog.GasCost)
+		}
+	})
+
+	t.Run("create_opcode", func(t *testing.T) {
+		// CREATE starts a new contract creation context
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// Simulate: CREATE at depth 1, constructor runs at depth 2, returns
+		// depth=1, gas=100000: CREATE opcode
+		// depth=2, gas=70000:  constructor PUSH
+		// depth=2, gas=69000:  constructor RETURN (returns deployed code)
+		// depth=1, gas=80000:  back to parent
+		logger.OnOpcode(0, byte(vm.CREATE), 100000, 32000, scope, nil, 1, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 70000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.RETURN), 69000, 0, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.POP), 80000, 2, scope, nil, 1, nil)
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Find CREATE and verify actual cost
+		var createLog *testStructLog
+		for i := range logs {
+			if logs[i].Op == "CREATE" {
+				createLog = &logs[i]
+				break
+			}
+		}
+		if createLog == nil {
+			t.Fatal("CREATE log not found")
+		}
+		// CREATE: 100000 - 80000 = 20000
+		if createLog.GasCost != 20000 {
+			t.Errorf("CREATE gasCost: expected 20000, got %d", createLog.GasCost)
+		}
+
+		// Verify RETURN in constructor keeps pre-calculated cost
+		var returnLog *testStructLog
+		for i := range logs {
+			if logs[i].Op == "RETURN" {
+				returnLog = &logs[i]
+				break
+			}
+		}
+		if returnLog == nil {
+			t.Fatal("RETURN log not found")
+		}
+		if returnLog.GasCost != 0 {
+			t.Errorf("constructor RETURN gasCost: expected 0 (pre-calculated), got %d", returnLog.GasCost)
+		}
+	})
+
+	t.Run("create2_opcode", func(t *testing.T) {
+		// CREATE2 is similar to CREATE but with deterministic address
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// Simulate: CREATE2 at depth 1, constructor at depth 2
+		logger.OnOpcode(0, byte(vm.CREATE2), 100000, 32000, scope, nil, 1, nil)
+		logger.OnOpcode(0, byte(vm.PUSH1), 65000, 3, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.STOP), 64000, 0, scope, nil, 2, nil)
+		logger.OnOpcode(1, byte(vm.DUP1), 75000, 3, scope, nil, 1, nil)
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Find CREATE2 and verify actual cost
+		var create2Log *testStructLog
+		for i := range logs {
+			if logs[i].Op == "CREATE2" {
+				create2Log = &logs[i]
+				break
+			}
+		}
+		if create2Log == nil {
+			t.Fatal("CREATE2 log not found")
+		}
+		// CREATE2: 100000 - 75000 = 25000
+		if create2Log.GasCost != 25000 {
+			t.Errorf("CREATE2 gasCost: expected 25000, got %d", create2Log.GasCost)
+		}
+	})
+
+	t.Run("multiple_siblings", func(t *testing.T) {
+		// Test: depth 1 -> depth 2 (call A) -> depth 1 -> depth 2 (call B) -> depth 1
+		// This tests that pendingLogs is properly cleared between sibling calls
+		logger := NewStructLogger(&Config{EnableActualGasCost: true})
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+
+		scope := &mockOpContext{}
+
+		// First call to depth 2
+		logger.OnOpcode(0, byte(vm.CALL), 100000, 100, scope, nil, 1, nil) // CALL A
+		logger.OnOpcode(0, byte(vm.PUSH1), 60000, 3, scope, nil, 2, nil)   // in child A
+		logger.OnOpcode(1, byte(vm.STOP), 59000, 0, scope, nil, 2, nil)    // child A ends
+		logger.OnOpcode(1, byte(vm.PUSH1), 90000, 3, scope, nil, 1, nil)   // back to parent
+
+		// Second call to depth 2 (sibling)
+		logger.OnOpcode(2, byte(vm.CALL), 89000, 100, scope, nil, 1, nil) // CALL B
+		logger.OnOpcode(0, byte(vm.PUSH1), 50000, 3, scope, nil, 2, nil)  // in child B
+		logger.OnOpcode(1, byte(vm.STOP), 49000, 0, scope, nil, 2, nil)   // child B ends
+		logger.OnOpcode(1, byte(vm.PUSH1), 80000, 3, scope, nil, 1, nil)  // back to parent
+
+		result, err := logger.GetResult()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var execResult ExecutionResult
+		if err := json.Unmarshal(result, &execResult); err != nil {
+			t.Fatal(err)
+		}
+
+		if len(execResult.StructLogs) != 8 {
+			t.Fatalf("expected 8 logs, got %d", len(execResult.StructLogs))
+		}
+
+		var logs []testStructLog
+		for _, raw := range execResult.StructLogs {
+			var log testStructLog
+			if err := json.Unmarshal(raw, &log); err != nil {
+				t.Fatal(err)
+			}
+			logs = append(logs, log)
+		}
+
+		// Find both CALLs and verify their costs
+		var calls []*testStructLog
+		for i := range logs {
+			if logs[i].Op == "CALL" {
+				calls = append(calls, &logs[i])
+			}
+		}
+		if len(calls) != 2 {
+			t.Fatalf("expected 2 CALL logs, got %d", len(calls))
+		}
+
+		// First CALL: 100000 - 90000 = 10000
+		if calls[0].GasCost != 10000 {
+			t.Errorf("first CALL gasCost: expected 10000, got %d", calls[0].GasCost)
+		}
+		// Second CALL: 89000 - 80000 = 9000
+		if calls[1].GasCost != 9000 {
+			t.Errorf("second CALL gasCost: expected 9000, got %d", calls[1].GasCost)
+		}
+
+		// All STOPs should keep pre-calculated cost (0)
+		for _, log := range logs {
+			if log.Op == "STOP" && log.GasCost != 0 {
+				t.Errorf("STOP at depth %d: expected gasCost 0, got %d", log.Depth, log.GasCost)
+			}
+		}
+	})
+
+	t.Run("streaming_mode_ignores_flag", func(t *testing.T) {
+		// Verify that EnableActualGasCost is ignored in streaming mode
+		var buf bytes.Buffer
+		logger := NewStreamingStructLogger(&Config{EnableActualGasCost: true}, &buf)
+
+		// pendingGasIdx should be nil since feature is disabled in streaming mode
+		if logger.pendingGasIdx != nil {
+			t.Error("pendingGasIdx should be nil in streaming mode")
+		}
+
+		// Verify streaming still works
+		logger.env = &tracing.VMContext{StateDB: &dummyStatedb{}}
+		scope := &mockOpContext{}
+
+		logger.OnOpcode(0, byte(vm.PUSH1), 100000, 3, scope, nil, 1, nil)
+		logger.OnOpcode(1, byte(vm.STOP), 99997, 0, scope, nil, 1, nil)
+
+		// Output should have been written to buffer
+		if buf.Len() == 0 {
+			t.Error("streaming logger should have written output")
+		}
+	})
+}
+
 // Tests that blank fields don't appear in logs when JSON marshalled, to reduce
 // logs bloat and confusion. See https://github.com/ethereum/go-ethereum/issues/24487
 func TestStructLogMarshalingOmitEmpty(t *testing.T) {