diff --git a/consensus/tx.go b/consensus/tx.go
index 17ba9ea..2f80ce5 100644
--- a/consensus/tx.go
+++ b/consensus/tx.go
@@ -75,14 +75,16 @@ func ValidateTransaction(tx *types.Transaction, txBlob []byte, forks []config.Ha
 // checkTxVersion validates that the transaction version is appropriate for the
 // current hardfork era.
 //
-// After HF5: transaction version must be >= VersionPostHF5 (3).
+// After HF5: transaction version must be exactly VersionPostHF5 (3) and the
+// embedded hardfork_id must match the active hardfork version.
 // Before HF5: transaction version 3 is rejected (too early).
 func checkTxVersion(tx *types.Transaction, forks []config.HardFork, height uint64) error {
 	hf5Active := config.IsHardForkActive(forks, config.HF5, height)
+	currentFork := config.VersionAtHeight(forks, height)
 
-	if hf5Active && tx.Version < types.VersionPostHF5 {
+	if hf5Active && tx.Version != types.VersionPostHF5 {
 		return coreerr.E("checkTxVersion",
-			fmt.Sprintf("version %d too low after HF5 at height %d", tx.Version, height),
+			fmt.Sprintf("version %d invalid after HF5 at height %d", tx.Version, height),
 			ErrTxVersionInvalid)
 	}
 
@@ -92,6 +94,12 @@ func checkTxVersion(tx *types.Transaction, forks []config.HardFork, height uint6
 			ErrTxVersionInvalid)
 	}
 
+	if hf5Active && tx.HardforkID != currentFork {
+		return coreerr.E("checkTxVersion",
+			fmt.Sprintf("hardfork id %d does not match active fork %d at height %d", tx.HardforkID, currentFork, height),
+			ErrTxVersionInvalid)
+	}
+
 	return nil
 }
 
diff --git a/consensus/tx_version_test.go b/consensus/tx_version_test.go
index 192d499..b7678b9 100644
--- a/consensus/tx_version_test.go
+++ b/consensus/tx_version_test.go
@@ -81,8 +81,20 @@ func TestCheckTxVersion_Bad(t *testing.T) {
 	}{
 		// v2 transaction after HF5 — must be v3.
 		{"v2_after_hf5", validV2Tx(), config.TestnetForks, 250},
+		// v3 transaction after HF5 with wrong hardfork id.
+		{"v3_after_hf5_wrong_hardfork", func() *types.Transaction {
+			tx := validV3Tx()
+			tx.HardforkID = 4
+			return tx
+		}(), config.TestnetForks, 250},
 		// v3 transaction before HF5 — too early.
 		{"v3_before_hf5", validV3Tx(), config.TestnetForks, 150},
+		// future version must be rejected.
+		{"v4_after_hf5", func() *types.Transaction {
+			tx := validV3Tx()
+			tx.Version = types.VersionPostHF5 + 1
+			return tx
+		}(), config.TestnetForks, 250},
 	}
 
 	for _, tt := range tests {
diff --git a/types/asset.go b/types/asset.go
new file mode 100644
index 0000000..db814a6
--- /dev/null
+++ b/types/asset.go
@@ -0,0 +1,40 @@
+// Copyright (c) 2017-2026 Lethean (https://lt.hn)
+//
+// Licensed under the European Union Public Licence (EUPL) version 1.2.
+// SPDX-License-Identifier: EUPL-1.2
+
+package types
+
+// Asset operation types used by the HF5 asset_descriptor_operation variant.
+const (
+	AssetOpRegister   uint8 = 0 // deploy new asset
+	AssetOpEmit       uint8 = 1 // emit additional supply
+	AssetOpUpdate     uint8 = 2 // update asset metadata
+	AssetOpBurn       uint8 = 3 // burn supply with proof
+	AssetOpPublicBurn uint8 = 4 // burn supply publicly
+)
+
+// AssetDescriptorBase holds the core asset metadata referenced by
+// asset_descriptor_operation extra variants.
+type AssetDescriptorBase struct {
+	Ticker         string
+	FullName       string
+	TotalMaxSupply uint64
+	CurrentSupply  uint64
+	DecimalPoint   uint8
+	MetaInfo       string
+	OwnerKey       PublicKey
+	Etc            []byte
+}
+
+// AssetDescriptorOperation represents a deploy/emit/update/burn operation.
+// The wire format is parsed in wire/ as an opaque blob for round-tripping.
+type AssetDescriptorOperation struct {
+	Version       uint8
+	OperationType uint8
+	Descriptor    *AssetDescriptorBase
+	AssetID       Hash
+	AmountToEmit  uint64
+	AmountToBurn  uint64
+	Etc           []byte
+}
diff --git a/types/asset_test.go b/types/asset_test.go
new file mode 100644
index 0000000..f538950
--- /dev/null
+++ b/types/asset_test.go
@@ -0,0 +1,60 @@
+// Copyright (c) 2017-2026 Lethean (https://lt.hn)
+//
+// Licensed under the European Union Public Licence (EUPL) version 1.2.
+// SPDX-License-Identifier: EUPL-1.2
+
+package types
+
+import "testing"
+
+func TestAssetOperationConstants_Good(t *testing.T) {
+	tests := []struct {
+		name string
+		got  uint8
+		want uint8
+	}{
+		{"register", AssetOpRegister, 0},
+		{"emit", AssetOpEmit, 1},
+		{"update", AssetOpUpdate, 2},
+		{"burn", AssetOpBurn, 3},
+		{"public_burn", AssetOpPublicBurn, 4},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.got != tt.want {
+				t.Fatalf("got %d, want %d", tt.got, tt.want)
+			}
+		})
+	}
+}
+
+func TestAssetDescriptorTypes_Good(t *testing.T) {
+	base := AssetDescriptorBase{
+		Ticker:         "LTHN",
+		FullName:       "Lethean",
+		TotalMaxSupply: 1000000,
+		CurrentSupply:  0,
+		DecimalPoint:   12,
+		MetaInfo:       "{}",
+		OwnerKey:       PublicKey{1},
+		Etc:            []byte{1, 2, 3},
+	}
+
+	op := AssetDescriptorOperation{
+		Version:       1,
+		OperationType: AssetOpRegister,
+		Descriptor:    &base,
+		AssetID:       Hash{1},
+		AmountToEmit:  100,
+		AmountToBurn:  10,
+		Etc:           []byte{4, 5, 6},
+	}
+
+	if op.Descriptor == nil || op.Descriptor.Ticker != "LTHN" {
+		t.Fatalf("unexpected descriptor: %+v", op.Descriptor)
+	}
+	if op.OperationType != AssetOpRegister || op.Version != 1 {
+		t.Fatalf("unexpected operation: %+v", op)
+	}
+}