diff --git a/pkg/identity/identity_test.go b/pkg/identity/identity_test.go
index 99d4f68e..d7ed7c28 100644
--- a/pkg/identity/identity_test.go
+++ b/pkg/identity/identity_test.go
@@ -5,6 +5,8 @@ import (
 	"crypto/ed25519"
 	"crypto/rand"
 	"encoding/hex"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"strings"
 	"testing"
 
@@ -766,3 +768,32 @@ func TestAuthorizeInitiatorMessage_NilSignature(t *testing.T) {
 		t.Error("AuthorizeInitiatorMessage() should fail with nil signature")
 	}
 }
+
+func TestVerifyInitiatorMessage_DerivationPathBound(t *testing.T) {
+	pub, priv, _ := generateTestEd25519Key()
+
+	store := &fileStore{
+		initiatorKey: &InitiatorKey{
+			Algorithm: types.EventInitiatorKeyTypeEd25519,
+			Ed25519:   pub,
+		},
+	}
+
+	msg := &types.SignTxMessage{
+		KeyType:             types.KeyTypeSecp256k1,
+		WalletID:            "w",
+		NetworkInternalCode: "ETH",
+		TxID:                "tx",
+		Tx:                  []byte("d"),
+		DerivationPath:      []uint32{44, 60, 0, 0, 0, 1},
+	}
+	raw, err := msg.Raw()
+	require.NoError(t, err)
+	msg.Signature = ed25519.Sign(priv, raw)
+
+	require.NoError(t, store.VerifyInitiatorMessage(msg), "should verify")
+
+	// tamper path
+	msg.DerivationPath = []uint32{44, 60, 0, 0, 0, 999}
+	assert.Error(t, store.VerifyInitiatorMessage(msg), "should not verify")
+}
diff --git a/pkg/types/initiator_msg.go b/pkg/types/initiator_msg.go
index 61004929..f781be1c 100644
--- a/pkg/types/initiator_msg.go
+++ b/pkg/types/initiator_msg.go
@@ -64,17 +64,19 @@ type ResharingMessage struct {
 func (m *SignTxMessage) Raw() ([]byte, error) {
 	// omit the Signature field itself when computing the signed‐over data
 	payload := struct {
-		KeyType             KeyType `json:"key_type"`
-		WalletID            string  `json:"wallet_id"`
-		NetworkInternalCode string  `json:"network_internal_code"`
-		TxID                string  `json:"tx_id"`
-		Tx                  []byte  `json:"tx"`
+		KeyType             KeyType  `json:"key_type"`
+		WalletID            string   `json:"wallet_id"`
+		NetworkInternalCode string   `json:"network_internal_code"`
+		TxID                string   `json:"tx_id"`
+		Tx                  []byte   `json:"tx"`
+		DerivationPath      []uint32 `json:"derivation_path,omitempty"`
 	}{
 		KeyType:             m.KeyType,
 		WalletID:            m.WalletID,
 		NetworkInternalCode: m.NetworkInternalCode,
 		TxID:                m.TxID,
 		Tx:                  m.Tx,
+		DerivationPath:      m.DerivationPath,
 	}
 	return json.Marshal(payload)
 }
diff --git a/pkg/types/initiator_msg_test.go b/pkg/types/initiator_msg_test.go
index 741e577a..6b0e3d25 100644
--- a/pkg/types/initiator_msg_test.go
+++ b/pkg/types/initiator_msg_test.go
@@ -1,6 +1,8 @@
 package types
 
 import (
+	"crypto/ed25519"
+	"crypto/rand"
 	"encoding/json"
 	"testing"
 
@@ -209,3 +211,49 @@ func TestGenerateKeyMessage_EmptyWallet(t *testing.T) {
 	assert.Equal(t, []byte(""), raw)
 	assert.Equal(t, "", msg.InitiatorID())
 }
+
+func TestSignTxMessage_Raw_IncludesDerivationPath(t *testing.T) {
+	msg := &SignTxMessage{
+		KeyType:             KeyTypeSecp256k1,
+		WalletID:            "wallet-123",
+		NetworkInternalCode: "BTC",
+		TxID:                "tx-456",
+		Tx:                  []byte("transaction-data"),
+		Signature:           []byte("signature-data"),
+		DerivationPath:      []uint32{44, 60, 0, 0, 0, 1},
+	}
+	raw, err := msg.Raw()
+	require.NoError(t, err)
+	assert.NotEmpty(t, raw)
+	assert.Contains(t, string(raw), `"derivation_path":[44,60,0,0,0,1]`)
+}
+
+func TestSignTxMessage_DerivationPathIsSignatureBound(t *testing.T) {
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	require.NoError(t, err)
+
+	msg := &SignTxMessage{
+		KeyType:             KeyTypeSecp256k1,
+		WalletID:            "w",
+		NetworkInternalCode: "ETH",
+		TxID:                "tx",
+		Tx:                  []byte("d"),
+		DerivationPath:      []uint32{44, 60, 0, 0, 1},
+	}
+
+	// initiator sign on Raw()
+	raw, err := msg.Raw()
+	require.NoError(t, err)
+	assert.NotEmpty(t, raw)
+	sig := ed25519.Sign(priv, raw)
+
+	// verify pass
+	rawOK, _ := msg.Raw()
+	assert.True(t, ed25519.Verify(pub, rawOK, sig), "original raw should be valid")
+
+	// Attacker: change derivation_path, same sig
+	msg.DerivationPath = []uint32{44, 60, 0, 0, 2}
+	rawTempered, err := msg.Raw()
+	require.NoError(t, err)
+	assert.False(t, ed25519.Verify(pub, rawTempered, sig), "changed derivation_path should invalidate sig")
+}