[codex] Fix widget diff traversal for single-child nodes

chatkit/server.py

@@ -158,9 +158,12 @@ def recurse(component: WidgetComponent | WidgetRoot):
                 components[component.id] = component
 
             if hasattr(component, "children"):
-                children = getattr(component, "children", None) or []
-                for child in children:
-                    recurse(child)
+                children = getattr(component, "children", None)
+                if isinstance(children, WidgetComponentBase):
+                    recurse(children)
+                elif isinstance(children, list):
+                    for child in children:
+                        recurse(child)
 
         recurse(component)
         return components

tests/test_widgets.py

@@ -113,6 +113,28 @@
             ),
             ["widget.root.updated"],
         ),
+        # DynamicWidgetRoot with a single-child object
+        (
+            DynamicWidgetRoot(
+                type="Card",
+                children=DynamicWidgetComponent.model_validate({
+                    "type": "Text",
+                    "id": "text",
+                    "value": "Hello",
+                    "streaming": True,
+                }),
+            ),
+            DynamicWidgetRoot(
+                type="Card",
+                children=DynamicWidgetComponent.model_validate({
+                    "type": "Text",
+                    "id": "text",
+                    "value": "Hello, world!",
+                    "streaming": True,
+                }),
+            ),
+            ["widget.streaming_text.value_delta"],
+        ),
     ],
 )
 def test_diff(