diff --git a/libs/checkpoint/langgraph/checkpoint/memory/__init__.py b/libs/checkpoint/langgraph/checkpoint/memory/__init__.py
index 82361b539..ff6f7b1ca 100644
--- a/libs/checkpoint/langgraph/checkpoint/memory/__init__.py
+++ b/libs/checkpoint/langgraph/checkpoint/memory/__init__.py
@@ -170,8 +170,8 @@ class InMemorySaver(
             return {}
         thread_id = config["configurable"]["thread_id"]
         checkpoint_ns = config["configurable"].get("checkpoint_ns", "")
-        checkpoint_id = config["configurable"].get("checkpoint_id", "")
         ns_storage = self.storage.get(thread_id, {}).get(checkpoint_ns, {})
+        checkpoint_id = get_checkpoint_id(config) or max(ns_storage, default="")
 
         chain: list[str] = []
         target_entry = ns_storage.get(checkpoint_id)
diff --git a/libs/checkpoint/tests/test_memory.py b/libs/checkpoint/tests/test_memory.py
index 51d10a5dd..7c350ab96 100644
--- a/libs/checkpoint/tests/test_memory.py
+++ b/libs/checkpoint/tests/test_memory.py
@@ -420,6 +420,19 @@ class TestInMemorySaverDeltaChannel:
         assert "seed" not in result
         assert result["writes"] == []
 
+    def test_get_channel_writes_without_checkpoint_id_reads_the_latest(self) -> None:
+        saver = InMemorySaver()
+        thread: RunnableConfig = {
+            "configurable": {"thread_id": "t1", "checkpoint_ns": ""}
+        }
+        parent = saver.put(thread, empty_checkpoint(), {}, {})
+        saver.put_writes(parent, [("messages", "hi")], "task1")
+        saver.put(parent, empty_checkpoint(), {}, {})
+
+        result = saver.get_delta_channel_history(config=thread, channels=["messages"])
+
+        assert result == {"messages": {"writes": [("task1", "messages", "hi")]}}
+
 
 class TestBaseFallbackGetChannelWrites:
     """Exercises the `BaseCheckpointSaver.get_delta_channel_history` default