feat(openapi): include graphql tag for playground default path

Co-Authored-By: Virgil <virgil@lethean.io>

openapi.go

@@ -191,10 +191,7 @@ func (sb *SpecBuilder) buildPaths(groups []preparedRouteGroup) map[string]any {
 		},
 	}
 
-	graphqlPath := strings.TrimSpace(sb.GraphQLPath)
-	if graphqlPath == "" && sb.GraphQLPlayground {
-		graphqlPath = defaultGraphQLPath
-	}
+	graphqlPath := sb.effectiveGraphQLPath()
 	if graphqlPath != "" {
 		graphqlPath = normaliseOpenAPIPath(graphqlPath)
 		paths[graphqlPath] = graphqlPathItem(graphqlPath, operationIDs)
@@ -619,7 +616,7 @@ func (sb *SpecBuilder) buildTags(groups []preparedRouteGroup) []map[string]any {
 	}
 	seen := map[string]bool{"system": true}
 
-	if graphqlPath := strings.TrimSpace(sb.GraphQLPath); graphqlPath != "" && !seen["graphql"] {
+	if graphqlPath := sb.effectiveGraphQLPath(); graphqlPath != "" && !seen["graphql"] {
 		tags = append(tags, map[string]any{
 			"name":        "graphql",
 			"description": "GraphQL endpoints",
@@ -1624,6 +1621,16 @@ func sseResponseHeaders() map[string]any {
 	}
 }
 
+// effectiveGraphQLPath returns the configured GraphQL path, or the default
+// GraphQL path when playground mode is enabled without an explicit path.
+func (sb *SpecBuilder) effectiveGraphQLPath() string {
+	graphqlPath := strings.TrimSpace(sb.GraphQLPath)
+	if graphqlPath == "" && sb.GraphQLPlayground {
+		return defaultGraphQLPath
+	}
+	return graphqlPath
+}
+
 // documentedResponseHeaders converts route-specific response header metadata
 // into OpenAPI header objects.
 func documentedResponseHeaders(headers map[string]string) map[string]any {

openapi_test.go

@@ -330,6 +330,37 @@ func TestSpecBuilder_Good_GraphQLPlaygroundDefaultsToGraphQLPath(t *testing.T) {
 	}
 }
 
+func TestSpecBuilder_Good_GraphQLPlaygroundDefaultsToGraphQLTag(t *testing.T) {
+	sb := &api.SpecBuilder{
+		Title:             "Test",
+		Version:           "1.0.0",
+		GraphQLPlayground: true,
+	}
+
+	data, err := sb.Build(nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	var spec map[string]any
+	if err := json.Unmarshal(data, &spec); err != nil {
+		t.Fatalf("invalid JSON: %v", err)
+	}
+
+	tags := spec["tags"].([]any)
+	found := false
+	for _, tag := range tags {
+		tm := tag.(map[string]any)
+		if tm["name"] == "graphql" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected graphql tag when playground enables the default GraphQL path")
+	}
+}
+
 func TestSpecBuilder_Good_WebSocketEndpoint(t *testing.T) {
 	sb := &api.SpecBuilder{
 		Title:   "Test",