Stringify thread_id when of a different type

libs/langgraph/langgraph/constants.py

@@ -69,6 +69,8 @@ CONFIG_KEY_ENSURE_LATEST = sys.intern("__pregel_ensure_latest")
 # (for distributed mode)
 CONFIG_KEY_DELEGATE = sys.intern("__pregel_delegate")
 # holds a boolean indicating whether to delegate subgraphs (for distributed mode)
+CONFIG_KEY_THREAD_ID = sys.intern("thread_id")
+# holds the thread ID for the current invocation
 CONFIG_KEY_CHECKPOINT_MAP = sys.intern("checkpoint_map")
 # holds a mapping of checkpoint_ns -> checkpoint_id for parent graphs
 CONFIG_KEY_CHECKPOINT_ID = sys.intern("checkpoint_id")

libs/langgraph/langgraph/pregel/loop.py

@@ -52,6 +52,7 @@ from langgraph.constants import (
     CONFIG_KEY_SCRATCHPAD,
     CONFIG_KEY_STREAM,
     CONFIG_KEY_TASK_ID,
+    CONFIG_KEY_THREAD_ID,
     EMPTY_SEQ,
     ERROR,
     INPUT,
@@ -285,6 +286,12 @@ class PregelLoop(LoopProtocol):
             )
         else:
             self.checkpoint_config = self.config
+        if thread_id := config[CONF].get(CONFIG_KEY_THREAD_ID):
+            if not isinstance(thread_id, str):
+                self.checkpoint_config = patch_configurable(
+                    self.checkpoint_config,
+                    {CONFIG_KEY_THREAD_ID: str(thread_id)},
+                )
         self.checkpoint_ns = (
             tuple(cast(str, self.config[CONF][CONFIG_KEY_CHECKPOINT_NS]).split(NS_SEP))
             if self.config[CONF].get(CONFIG_KEY_CHECKPOINT_NS)

libs/langgraph/tests/test_pregel.py

@@ -6156,7 +6156,7 @@ def test_falsy_return_from_task(
         falsy_task().result()
         interrupt("test")
 
-    configurable = {"configurable": {"thread_id": str(uuid.uuid4())}}
+    configurable = {"configurable": {"thread_id": uuid.uuid4()}}
     assert [
         chunk for chunk in graph.stream({"a": 5}, configurable, stream_mode="debug")
     ] == [