diff --git a/libs/checkpoint/langgraph/checkpoint/base/__init__.py b/libs/checkpoint/langgraph/checkpoint/base/__init__.py
index 7a482a3f9..158962c9f 100644
--- a/libs/checkpoint/langgraph/checkpoint/base/__init__.py
+++ b/libs/checkpoint/langgraph/checkpoint/base/__init__.py
@@ -541,6 +541,9 @@ class BaseCheckpointSaver(Generic[V]):
                 tup = self.get_tuple(cursor_config)
                 if tup is None:
                     break
+                # Pre-delta seed terminator: if the ancestor has a stored
+                # (non-sentinel) value for this channel, that snapshot
+                # subsumes any earlier writes on the chain. Stop here.
                 ancestor_value = tup.checkpoint["channel_values"].get(channel)
                 if ancestor_value is not None and ancestor_value is not DELTA_SENTINEL:
                     if isinstance(ancestor_value, _DeltaSnapshot):
@@ -586,6 +589,7 @@ class BaseCheckpointSaver(Generic[V]):
                 tup = await self.aget_tuple(cursor_config)
                 if tup is None:
                     break
+                # See sync variant for rationale.
                 ancestor_value = tup.checkpoint["channel_values"].get(channel)
                 if ancestor_value is not None and ancestor_value is not DELTA_SENTINEL:
                     if isinstance(ancestor_value, _DeltaSnapshot):