Fix

libs/langgraph/langgraph/pregel/algo.py

@@ -30,6 +30,7 @@ from langgraph.checkpoint.base import (
 from langgraph.constants import (
     CONFIG_KEY_CHECKPOINT_MAP,
     CONFIG_KEY_CHECKPOINTER,
+    CONFIG_KEY_GRAPH_COUNT,
     CONFIG_KEY_READ,
     CONFIG_KEY_SEND,
     CONFIG_KEY_TASK_ID,
@@ -429,6 +430,7 @@ def prepare_single_task(
                             manager.get_child(f"graph:step:{step}") if manager else None
                         ),
                         configurable={
+                            CONFIG_KEY_GRAPH_COUNT: 0,
                             CONFIG_KEY_TASK_ID: task_id,
                             # deque.extend is thread-safe
                             CONFIG_KEY_SEND: partial(
@@ -539,6 +541,7 @@ def prepare_single_task(
                                 else None
                             ),
                             configurable={
+                                CONFIG_KEY_GRAPH_COUNT: 0,
                                 CONFIG_KEY_TASK_ID: task_id,
                                 # deque.extend is thread-safe
                                 CONFIG_KEY_SEND: partial(

libs/langgraph/langgraph/pregel/loop.py

@@ -221,11 +221,12 @@ class PregelLoop:
             self.config = patch_configurable(
                 self.config, {"checkpoint_ns": "", "checkpoint_id": None}
             )
-        if config["configurable"].get(CONFIG_KEY_GRAPH_COUNT, 0) > 0:
-            raise ValueError("Detected multiple subgraphs called in a single node.")
-        else:
-            # mutate config so that sibling subgraphs can be detected
-            self.config["configurable"][CONFIG_KEY_GRAPH_COUNT] = 1
+        if self.is_nested:
+            if config["configurable"].get(CONFIG_KEY_GRAPH_COUNT, 0) > 0:
+                raise ValueError("Detected multiple subgraphs called in a single node.")
+            else:
+                # mutate config so that sibling subgraphs can be detected
+                self.config["configurable"][CONFIG_KEY_GRAPH_COUNT] = 1
         if (
             CONFIG_KEY_CHECKPOINT_MAP in self.config["configurable"]
             and self.config["configurable"].get("checkpoint_ns")

libs/langgraph/tests/test_tracing_interops.py

@@ -55,7 +55,7 @@ def wait_for(
     raise ValueError(f"Callable did not return within {total_time}")
 
 
-@pytest.skip("This test times out in CI")
+@pytest.mark.skip("This test times out in CI")
 async def test_nested_tracing():
     lt_py_311 = sys.version_info < (3, 11)
     mock_client = _get_mock_client()