lint

libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py

@@ -8,6 +8,7 @@ from typing import Any, cast
 
 from langchain_core.runnables import RunnableConfig
 from langgraph.checkpoint.base import (
+    DELTA_SENTINEL,
     WRITES_IDX_MAP,
     ChannelVersions,
     Checkpoint,
@@ -446,8 +447,6 @@ class PostgresSaver(BasePostgresSaver):
             including its configuration, metadata, parent checkpoint (if any),
             and pending writes.
         """
-        from langgraph.checkpoint.base import DELTA_SENTINEL
-
         channel_values = self._load_blobs(value["channel_values"])
         if any(v is DELTA_SENTINEL for v in channel_values.values()):
             cp_config = cast(

libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py

@@ -402,12 +402,7 @@ class AsyncPostgresSaver(BasePostgresSaver):
         cur: Any,
     ) -> list[Any]:
         """Async version of _get_channel_writes_cur — see sync version for rationale."""
-        try:
-            from langgraph.types import (
-                Overwrite,  # type: ignore[import-untyped,import-not-found]
-            )
-        except ImportError:
-            Overwrite = None  # type: ignore[assignment]
+        from langgraph.types import Overwrite  # type: ignore[import-untyped]
 
         await cur.execute(
             "SELECT checkpoint_id, parent_checkpoint_id FROM checkpoints "
@@ -440,7 +435,7 @@ class AsyncPostgresSaver(BasePostgresSaver):
             for type_tag, blob in writes_by_cp.get(cid, []):
                 val = self.serde.loads_typed((type_tag, blob))
                 collected.append(val)
-                if Overwrite is not None and isinstance(val, Overwrite):
+                if isinstance(val, Overwrite):
                     collected.reverse()
                     return collected
         collected.reverse()

libs/checkpoint-postgres/langgraph/checkpoint/postgres/base.py

@@ -235,13 +235,7 @@ class BasePostgresSaver(BaseCheckpointSaver[str]):
         1. Fetch all (checkpoint_id, parent_checkpoint_id) for the thread.
         2. Walk ancestry in Python, then fetch writes with a plain ANY() filter.
         """
-        # Lazy import: mirrors the Send pattern in the serializer.
-        try:
-            from langgraph.types import (
-                Overwrite,  # type: ignore[import-untyped,import-not-found]
-            )
-        except ImportError:
-            Overwrite = None  # type: ignore[assignment]
+        from langgraph.types import Overwrite  # type: ignore[import-untyped]
 
         cur.execute(
             "SELECT checkpoint_id, parent_checkpoint_id FROM checkpoints "
@@ -274,7 +268,7 @@ class BasePostgresSaver(BaseCheckpointSaver[str]):
             for type_tag, blob in writes_by_cp.get(cid, []):
                 val = self.serde.loads_typed((type_tag, blob))
                 collected.append(val)
-                if Overwrite is not None and isinstance(val, Overwrite):
+                if isinstance(val, Overwrite):
                     collected.reverse()
                     return collected
         collected.reverse()