diff --git a/pkg/covenant/locked_lookup.go b/pkg/covenant/locked_lookup.go
index 32f543c..98c162a 100644
--- a/pkg/covenant/locked_lookup.go
+++ b/pkg/covenant/locked_lookup.go
@@ -44,6 +44,9 @@ var (
 )
 
 // HasLockedName reports whether the JS lockup table contains the name.
+//
+// Lookup is case-insensitive and accepts a canonical `.lthn` suffix in
+// addition to bare labels.
 func HasLockedName(name string) bool {
 	return DefaultLockedCatalog().HasByName(name)
 }
@@ -64,6 +67,9 @@ func HasLockedBinary(name []byte) bool {
 }
 
 // GetLockedName returns the locked-name entry for the provided label.
+//
+// The input is lower-cased before hashing, and canonical `.lthn` suffixes are
+// stripped before lookup.
 func GetLockedName(name string) (LockedName, bool) {
 	return DefaultLockedCatalog().GetByName(name)
 }
@@ -195,8 +201,8 @@ func (c *LockedCatalog) HasByName(name string) bool {
 
 // GetByName returns the locked-name entry for the provided label.
 //
-// The lookup lower-cases ASCII input and hashes it directly, matching the JS
-// reference helper's ASCII encoding behavior.
+// The lookup lower-cases ASCII input, strips canonical `.lthn` suffixes, and
+// hashes the normalized label directly.
 func (c *LockedCatalog) GetByName(name string) (LockedName, bool) {
 	name, ok := asciiLowerName(name)
 	if !ok {
diff --git a/pkg/covenant/locked_lookup_test.go b/pkg/covenant/locked_lookup_test.go
index e1094ae..c42a693 100644
--- a/pkg/covenant/locked_lookup_test.go
+++ b/pkg/covenant/locked_lookup_test.go
@@ -128,6 +128,19 @@ func TestLockedLookupStringAndBinaryAliases(t *testing.T) {
 	if !HasLockedByBinary([]byte("NEC")) {
 		t.Fatal("HasLockedByBinary should report locked catalog labels")
 	}
+
+	item, ok = GetLockedName("nec.lthn")
+	if !ok {
+		t.Fatal("GetLockedName should accept canonical .lthn names")
+	}
+
+	if item.Name != "nec" {
+		t.Fatalf("item.Name = %q, want %q", item.Name, "nec")
+	}
+
+	if !HasLockedName("nec.lthn") {
+		t.Fatal("HasLockedName should accept canonical .lthn names")
+	}
 }
 
 func TestLockedLookupHasByHashAlias(t *testing.T) {
diff --git a/pkg/covenant/name_lookup.go b/pkg/covenant/name_lookup.go
index 322033e..68b5f2d 100644
--- a/pkg/covenant/name_lookup.go
+++ b/pkg/covenant/name_lookup.go
@@ -2,11 +2,13 @@
 
 package covenant
 
+import "bytes"
+
 // asciiLowerName lower-cases ASCII labels without performing Unicode
-// case-folding. The JS reference uses ASCII encoding for these catalog lookups,
-// so non-ASCII input is rejected instead of being hashed differently.
+// case-folding. The helper also strips an optional canonical `.lthn` suffix so
+// the catalog lookups accept the same normalized forms as the top-level LNS API.
 func asciiLowerName(name string) (string, bool) {
-	if len(name) == 0 || len(name) > maxNameSize {
+	if len(name) == 0 {
 		return "", false
 	}
 
@@ -26,5 +28,18 @@ func asciiLowerName(name string) (string, bool) {
 		buf[i] = ch
 	}
 
+	switch {
+	case bytes.HasSuffix(buf, []byte(".lthn.")):
+		buf = buf[:len(buf)-6]
+	case bytes.HasSuffix(buf, []byte(".lthn")):
+		buf = buf[:len(buf)-5]
+	case bytes.HasSuffix(buf, []byte(".")):
+		buf = buf[:len(buf)-1]
+	}
+
+	if len(buf) == 0 || len(buf) > maxNameSize {
+		return "", false
+	}
+
 	return string(buf), true
 }
diff --git a/pkg/covenant/reserved_lookup.go b/pkg/covenant/reserved_lookup.go
index 75b959b..b24bf00 100644
--- a/pkg/covenant/reserved_lookup.go
+++ b/pkg/covenant/reserved_lookup.go
@@ -61,8 +61,8 @@ var (
 
 // HasReservedName reports whether the JS reserved-name table contains the name.
 //
-// Lookup is case-insensitive and matches the reference table's lower-casing
-// behaviour.
+// Lookup is case-insensitive and accepts a canonical `.lthn` suffix in
+// addition to bare labels.
 func HasReservedName(name string) bool {
 	return DefaultReservedCatalog().HasByName(name)
 }
@@ -84,7 +84,8 @@ func HasReservedBinary(name []byte) bool {
 
 // GetReservedName returns the reserved-name entry for the provided label.
 //
-// The input is lower-cased before hashing, matching the JS reference helper.
+// The input is lower-cased before hashing, and canonical `.lthn` suffixes are
+// stripped before lookup.
 func GetReservedName(name string) (ReservedName, bool) {
 	return DefaultReservedCatalog().GetByName(name)
 }
@@ -258,8 +259,8 @@ func (c *ReservedCatalog) HasByName(name string) bool {
 
 // GetByName returns the reserved-name entry for the provided label.
 //
-// The lookup lower-cases ASCII input and hashes it directly, matching the JS
-// reference helper's ASCII encoding behavior.
+// The lookup lower-cases ASCII input, strips canonical `.lthn` suffixes, and
+// hashes the normalized label directly.
 func (c *ReservedCatalog) GetByName(name string) (ReservedName, bool) {
 	name, ok := asciiLowerName(name)
 	if !ok {
diff --git a/pkg/covenant/reserved_lookup_test.go b/pkg/covenant/reserved_lookup_test.go
index 06f9dd4..b1bbc56 100644
--- a/pkg/covenant/reserved_lookup_test.go
+++ b/pkg/covenant/reserved_lookup_test.go
@@ -132,6 +132,19 @@ func TestReservedLookupStringAndBinaryAliases(t *testing.T) {
 	if !HasReservedByBinary([]byte("RESERVED")) {
 		t.Fatal("HasReservedByBinary should report reserved catalog labels")
 	}
+
+	item, ok = GetReservedName("reserved.lthn")
+	if !ok {
+		t.Fatal("GetReservedName should accept canonical .lthn names")
+	}
+
+	if item.Name != "reserved" {
+		t.Fatalf("item.Name = %q, want %q", item.Name, "reserved")
+	}
+
+	if !HasReservedName("reserved.lthn") {
+		t.Fatal("HasReservedName should accept canonical .lthn names")
+	}
 }
 
 func TestReservedLookupHasByHashAlias(t *testing.T) {