eth/tracers: forward V2 state hooks through mux tracer (#34869)

Fixes the muxTracer to correctly forward events to v2 state
hooks, i.e. `OnCodeChangeV2` and `OnNonceChangeV2`.

eth/tracers/native/mux.go

@@ -63,6 +63,12 @@ func newMuxTracerFromConfig(ctx *tracers.Context, cfg json.RawMessage, chainConf
 //
 // The names parameter associates a label with each tracer, used as keys in
 // the aggregated JSON result returned by GetResult.
+//
+// For hooks that have both a V1 and V2 form (OnCodeChange / OnCodeChangeV2,
+// OnNonceChange / OnNonceChangeV2, OnSystemCallStart / OnSystemCallStartV2),
+// the mux exposes only the V2 variant upward. The fanout then prefers each
+// child's V2 hook and falls back to V1 if only V1 is set, mirroring the
+// precedence already used in core/state_processor.go.
 func NewMuxTracer(names []string, objects []*tracers.Tracer) (*tracers.Tracer, error) {
 	t := &muxTracer{names: names, tracers: objects}
 	return &tracers.Tracer{
@@ -75,8 +81,8 @@ func NewMuxTracer(names []string, objects []*tracers.Tracer) (*tracers.Tracer, e
 			OnFault:             t.OnFault,
 			OnGasChange:         t.OnGasChange,
 			OnBalanceChange:     t.OnBalanceChange,
-			OnNonceChange:       t.OnNonceChange,
-			OnCodeChange:        t.OnCodeChange,
+			OnNonceChangeV2:     t.OnNonceChangeV2,
+			OnCodeChangeV2:      t.OnCodeChangeV2,
 			OnStorageChange:     t.OnStorageChange,
 			OnLog:               t.OnLog,
 			OnSystemCallStartV2: t.OnSystemCallStart,
@@ -151,26 +157,22 @@ func (t *muxTracer) OnBalanceChange(a common.Address, prev, new *big.Int, reason
 	}
 }
 
-func (t *muxTracer) OnNonceChange(a common.Address, prev, new uint64) {
+func (t *muxTracer) OnNonceChangeV2(a common.Address, prev, new uint64, reason tracing.NonceChangeReason) {
 	for _, t := range t.tracers {
-		if t.OnNonceChange != nil {
+		if t.OnNonceChangeV2 != nil {
+			t.OnNonceChangeV2(a, prev, new, reason)
+		} else if t.OnNonceChange != nil {
 			t.OnNonceChange(a, prev, new)
 		}
 	}
 }
 
-func (t *muxTracer) OnCodeChange(a common.Address, prevCodeHash common.Hash, prev []byte, codeHash common.Hash, code []byte) {
-	for _, t := range t.tracers {
-		if t.OnCodeChange != nil {
-			t.OnCodeChange(a, prevCodeHash, prev, codeHash, code)
-		}
-	}
-}
-
 func (t *muxTracer) OnCodeChangeV2(a common.Address, prevCodeHash common.Hash, prev []byte, codeHash common.Hash, code []byte, reason tracing.CodeChangeReason) {
 	for _, t := range t.tracers {
 		if t.OnCodeChangeV2 != nil {
 			t.OnCodeChangeV2(a, prevCodeHash, prev, codeHash, code, reason)
+		} else if t.OnCodeChange != nil {
+			t.OnCodeChange(a, prevCodeHash, prev, codeHash, code)
 		}
 	}
 }

eth/tracers/native/mux_test.go

@@ -0,0 +1,87 @@
+// Copyright 2026 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package native
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/tracing"
+	"github.com/ethereum/go-ethereum/eth/tracers"
+)
+
+// TestMuxForwardsV2StateHooks verifies that the mux tracer fans out the V2
+// variants of state-change hooks to child tracers. A child tracer that only
+// implements OnCodeChangeV2 / OnNonceChangeV2 must still receive events when
+// wrapped behind the mux. The mux must also fall back to the V1 hook when a
+// child only implements V1, mirroring the precedence used in
+// core/state_processor.go.
+func TestMuxForwardsV2StateHooks(t *testing.T) {
+	var (
+		codeV2Calls  int
+		nonceV2Calls int
+		codeV1Calls  int
+		nonceV1Calls int
+	)
+	v2Child := &tracers.Tracer{
+		Hooks: &tracing.Hooks{
+			OnCodeChangeV2: func(addr common.Address, prevCodeHash common.Hash, prevCode []byte, codeHash common.Hash, code []byte, reason tracing.CodeChangeReason) {
+				codeV2Calls++
+			},
+			OnNonceChangeV2: func(addr common.Address, prev, new uint64, reason tracing.NonceChangeReason) {
+				nonceV2Calls++
+			},
+		},
+	}
+	v1Child := &tracers.Tracer{
+		Hooks: &tracing.Hooks{
+			OnCodeChange: func(addr common.Address, prevCodeHash common.Hash, prevCode []byte, codeHash common.Hash, code []byte) {
+				codeV1Calls++
+			},
+			OnNonceChange: func(addr common.Address, prev, new uint64) {
+				nonceV1Calls++
+			},
+		},
+	}
+	mux, err := NewMuxTracer([]string{"v2", "v1"}, []*tracers.Tracer{v2Child, v1Child})
+	if err != nil {
+		t.Fatalf("NewMuxTracer: %v", err)
+	}
+
+	if mux.Hooks.OnCodeChangeV2 == nil {
+		t.Fatal("mux does not expose OnCodeChangeV2; V2-only child tracers will miss code changes")
+	}
+	if mux.Hooks.OnNonceChangeV2 == nil {
+		t.Fatal("mux does not expose OnNonceChangeV2; V2-only child tracers will miss nonce changes")
+	}
+
+	mux.Hooks.OnCodeChangeV2(common.Address{}, common.Hash{}, nil, common.Hash{}, nil, tracing.CodeChangeContractCreation)
+	mux.Hooks.OnNonceChangeV2(common.Address{}, 0, 1, tracing.NonceChangeEoACall)
+
+	if codeV2Calls != 1 {
+		t.Fatalf("V2 child OnCodeChangeV2 got %d calls, want 1", codeV2Calls)
+	}
+	if nonceV2Calls != 1 {
+		t.Fatalf("V2 child OnNonceChangeV2 got %d calls, want 1", nonceV2Calls)
+	}
+	if codeV1Calls != 1 {
+		t.Fatalf("V1 child OnCodeChange got %d calls, want 1 (mux should fall back from V2 to V1)", codeV1Calls)
+	}
+	if nonceV1Calls != 1 {
+		t.Fatalf("V1 child OnNonceChange got %d calls, want 1 (mux should fall back from V2 to V1)", nonceV1Calls)
+	}
+}