perf(kv): skip merge of absent context/user/tenant maps in snapshot

error.go

@@ -744,8 +744,12 @@ func (o OopsError) ToMap() map[string]any { //nolint:gocyclo
 
 	if s.userID != "" || len(s.userData) > 0 {
 		// snapshot() owns s.userData (freshly merged in mergeMaps), so it can
-		// be used directly instead of copying.
+		// be used directly instead of copying. It is nil when only the user
+		// ID was set.
 		user := s.userData
+		if user == nil {
+			user = map[string]any{}
+		}
 		if s.userID != "" {
 			user["id"] = s.userID
 		}
@@ -754,8 +758,12 @@ func (o OopsError) ToMap() map[string]any { //nolint:gocyclo
 
 	if s.tenantID != "" || len(s.tenantData) > 0 {
 		// snapshot() owns s.tenantData (freshly merged in mergeMaps), so it can
-		// be used directly instead of copying.
+		// be used directly instead of copying. It is nil when only the tenant
+		// ID was set.
 		tenant := s.tenantData
+		if tenant == nil {
+			tenant = map[string]any{}
+		}
 		if s.tenantID != "" {
 			tenant["id"] = s.tenantID
 		}

kv.go

@@ -303,9 +303,17 @@ func snapshot(o OopsError) OopsError { //nolint:gocyclo
 	}
 
 	s.tags = lo.Uniq(s.tags)
-	s.context = dereferencePointers(lazyMapEvaluation(mergeMaps(contextMaps)))
-	s.userData = dereferencePointers(lazyMapEvaluation(mergeMaps(userDataMaps)))
-	s.tenantData = dereferencePointers(lazyMapEvaluation(mergeMaps(tenantDataMaps)))
+	// Only merge when the chain actually carries maps: mergeMaps allocates
+	// even for empty input, and consumers only ever check len() on these.
+	if len(contextMaps) > 0 {
+		s.context = dereferencePointers(lazyMapEvaluation(mergeMaps(contextMaps)))
+	}
+	if len(userDataMaps) > 0 {
+		s.userData = dereferencePointers(lazyMapEvaluation(mergeMaps(userDataMaps)))
+	}
+	if len(tenantDataMaps) > 0 {
+		s.tenantData = dereferencePointers(lazyMapEvaluation(mergeMaps(tenantDataMaps)))
+	}
 
 	return s
 }