update

libs/langgraph/langgraph/graph/state.py

@@ -1114,7 +1114,7 @@ def _get_root(input: Any) -> Optional[Sequence[tuple[str, Any]]]:
             else:
                 updates.append(("__root__", i))
         return updates
-    else:
+    elif input is not None:
         return [("__root__", input)]
 
 

libs/langgraph/langgraph/pregel/draw.py

@@ -108,7 +108,8 @@ def draw_graph(
                 for w in task.writers:
                     # apply regular writes
                     if isinstance(w, ChannelWrite):
-                        w.invoke(None, task.config)
+                        empty_input = "" if "__root__" in specs else {}
+                        w.invoke(empty_input, task.config)
                     # apply conditional writes declared for static analysis, only once
                     if w not in static_seen:
                         static_seen.add(w)