fix: wrap vector and payload in lists for Langchain.update (#4446)

mem0/vector_stores/langchain.py

@@ -115,7 +115,7 @@ class Langchain(VectorStoreBase):
         Update a vector and its payload.
         """
         self.delete(vector_id)
-        self.insert(vector, payload, [vector_id])
+        self.insert([vector], [payload], [vector_id])
 
     def get(self, vector_id):
         """

tests/vector_stores/test_langchain_vector_store.py

@@ -224,3 +224,24 @@ def test_list_with_exception(langchain_instance):
 
     # Verify that an empty list is returned when an exception occurs
     assert results == []
+
+
+def test_update_wraps_vector_and_payload_in_lists(langchain_instance):
+    """Regression test for Langchain update() type mismatch.
+
+    update() must wrap vector and payload in lists before calling insert(),
+    which expects List[List[float]] and List[Dict] respectively.
+    """
+    langchain_instance.client.delete = Mock()
+    langchain_instance.client.add_embeddings = Mock()
+
+    vector = [0.1, 0.2, 0.3]
+    payload = {"data": "updated text", "name": "updated"}
+    vector_id = "id1"
+
+    langchain_instance.update(vector_id=vector_id, vector=vector, payload=payload)
+
+    langchain_instance.client.delete.assert_called_once_with(ids=[vector_id])
+    langchain_instance.client.add_embeddings.assert_called_once_with(
+        embeddings=[vector], metadatas=[payload], ids=[vector_id]
+    )