From 35bc8ec276c1d1c7388d418ca9ae73432ffa810f Mon Sep 17 00:00:00 2001
From: Dat Duong <DuongDat.Informatics@rocketmail.com>
Date: Thu, 3 Sep 2026 08:42:33 +0000
Subject: [PATCH] fix(builder): clone MigratedClasses in cloneStateDiff

---
 builder/state.go      |  1 +
 builder/state_test.go | 55 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 builder/state_test.go

diff --git a/builder/state.go b/builder/state.go
index e58e31c44a..fd56c99223 100644
--- a/builder/state.go
+++ b/builder/state.go
@@ -77,6 +77,7 @@ func cloneStateDiff(stateDiff *core.StateDiff) *core.StateDiff {
 		DeclaredV0Classes: slices.Clone(stateDiff.DeclaredV0Classes),
 		DeclaredV1Classes: maps.Clone(stateDiff.DeclaredV1Classes),
 		ReplacedClasses:   maps.Clone(stateDiff.ReplacedClasses),
+		MigratedClasses:   maps.Clone(stateDiff.MigratedClasses),
 	}
 }
 
diff --git a/builder/state_test.go b/builder/state_test.go
new file mode 100644
index 0000000000..a844ac65e8
--- /dev/null
+++ b/builder/state_test.go
@@ -0,0 +1,55 @@
+package builder_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/NethermindEth/juno/builder"
+	"github.com/NethermindEth/juno/core"
+	"github.com/NethermindEth/juno/core/felt"
+	"github.com/NethermindEth/juno/core/pending"
+	"github.com/stretchr/testify/require"
+)
+
+// fullStateDiff populates every StateDiff field for a fixed address with values derived from seed.
+func fullStateDiff(seed uint64) core.StateDiff {
+	address := felt.NewFromUint64[felt.Felt](1)
+	classHash := felt.NewFromUint64[felt.Felt](seed)
+	return core.StateDiff{
+		StorageDiffs:      map[felt.Felt]map[felt.Felt]*felt.Felt{*address: {*classHash: classHash}},
+		Nonces:            map[felt.Felt]*felt.Felt{*address: classHash},
+		DeployedContracts: map[felt.Felt]*felt.Felt{*address: classHash},
+		DeclaredV0Classes: []*felt.Felt{classHash},
+		DeclaredV1Classes: map[felt.Felt]*felt.Felt{*classHash: classHash},
+		ReplacedClasses:   map[felt.Felt]*felt.Felt{*address: classHash},
+		MigratedClasses: map[felt.SierraClassHash]felt.CasmClassHash{
+			felt.SierraClassHash(*classHash): felt.CasmClassHash(*classHash),
+		},
+	}
+}
+
+func TestCloneCopiesEveryStateDiffField(t *testing.T) {
+	original := fullStateDiff(1)
+	// A new StateDiff field must be added to the fixture before the clone can miss it.
+	fields := reflect.ValueOf(original)
+	for i := range fields.NumField() {
+		name := fields.Type().Field(i).Name
+		require.False(t, fields.Field(i).IsZero(), "fixture must populate %s", name)
+	}
+
+	buildState := builder.BuildState{
+		PreConfirmed: &pending.PreConfirmed{
+			Block:       &core.Block{Header: &core.Header{}},
+			StateUpdate: &core.StateUpdate{StateDiff: &original},
+		},
+	}
+	cloned := buildState.Clone().PreConfirmed.StateUpdate.StateDiff
+	require.Equal(t, fullStateDiff(1), *cloned)
+
+	// Same address as original, so Merge writes into the inner storage map instead of adding an entry.
+	extra := fullStateDiff(100)
+	// Merge only appends to DeclaredV0Classes, which never rewrites a shared backing array.
+	original.DeclaredV0Classes[0] = extra.DeclaredV0Classes[0]
+	original.Merge(&extra)
+	require.Equal(t, fullStateDiff(1), *cloned, "clone must not share storage with the original")
+}