diff --git a/libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py b/libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py
index f0fe23b4c..926faec0f 100644
--- a/libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py
+++ b/libs/checkpoint-postgres/langgraph/checkpoint/postgres/__init__.py
@@ -453,8 +453,13 @@ class PostgresSaver(BasePostgresSaver):
                   )
                 """,
                 (
-                    thread_id, checkpoint_ns, channel, channel,
-                    thread_id, checkpoint_ns, checkpoint_id,
+                    thread_id,
+                    checkpoint_ns,
+                    channel,
+                    channel,
+                    thread_id,
+                    checkpoint_ns,
+                    checkpoint_id,
                 ),
             )
             row = cur.fetchone()
diff --git a/libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py b/libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py
index be7625566..cf8ed4210 100644
--- a/libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py
+++ b/libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py
@@ -414,8 +414,13 @@ class AsyncPostgresSaver(BasePostgresSaver):
                   )
                 """,
                 (
-                    thread_id, checkpoint_ns, channel, channel,
-                    thread_id, checkpoint_ns, checkpoint_id,
+                    thread_id,
+                    checkpoint_ns,
+                    channel,
+                    channel,
+                    thread_id,
+                    checkpoint_ns,
+                    checkpoint_id,
                 ),
             )
             row = await cur.fetchone()
diff --git a/libs/checkpoint/langgraph/checkpoint/base/__init__.py b/libs/checkpoint/langgraph/checkpoint/base/__init__.py
index 78af858c7..48a8b98c1 100644
--- a/libs/checkpoint/langgraph/checkpoint/base/__init__.py
+++ b/libs/checkpoint/langgraph/checkpoint/base/__init__.py
@@ -36,7 +36,9 @@ class DeltaValue:
     """Returned by DeltaChannel.checkpoint(). Represents one step's writes."""
 
     delta: list[Any]
-    prev_checkpoint_id: str | None  # ID of checkpoint containing previous blob; None = chain root
+    prev_checkpoint_id: (
+        str | None
+    )  # ID of checkpoint containing previous blob; None = chain root
 
 
 @dataclasses.dataclass
diff --git a/libs/checkpoint/tests/test_jsonplus.py b/libs/checkpoint/tests/test_jsonplus.py
index 7533092df..d81475c7e 100644
--- a/libs/checkpoint/tests/test_jsonplus.py
+++ b/libs/checkpoint/tests/test_jsonplus.py
@@ -1004,7 +1004,9 @@ def test_delta_value_serde_round_trip() -> None:
     from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
 
     serde = JsonPlusSerializer()
-    original = DeltaValue(delta=[{"type": "human", "content": "hi"}], prev_checkpoint_id="abc-123")
+    original = DeltaValue(
+        delta=[{"type": "human", "content": "hi"}], prev_checkpoint_id="abc-123"
+    )
     type_tag, blob = serde.dumps_typed(original)
     assert type_tag == "diff"
     loaded = serde.loads_typed((type_tag, blob))
diff --git a/libs/prebuilt/langgraph/prebuilt/tool_node.py b/libs/prebuilt/langgraph/prebuilt/tool_node.py
index d8a1f3182..7ad9d208b 100644
--- a/libs/prebuilt/langgraph/prebuilt/tool_node.py
+++ b/libs/prebuilt/langgraph/prebuilt/tool_node.py
@@ -614,7 +614,6 @@ class _InjectedArgs:
     store: str | None
     runtime: str | None
     all_injected_keys: set[str]
-    _optional_state_args: set[str]
 
 
 class ToolNode(RunnableCallable):
@@ -1336,7 +1335,7 @@ class ToolNode(RunnableCallable):
             return tool_call
 
         tool_call_copy: ToolCall = copy(tool_call)
-        injected_args: dict[str, Any] = {}
+        injected_args = {}
 
         # Inject state
         if injected.state:
@@ -1364,20 +1363,14 @@ class ToolNode(RunnableCallable):
             # Extract state values
             if isinstance(state, dict):
                 for tool_arg, state_field in injected.state.items():
-                    if not state_field:
-                        injected_args[tool_arg] = state
-                    elif state_field in state:
-                        injected_args[tool_arg] = state[state_field]
-                    elif tool_arg not in injected._optional_state_args:
-                        raise KeyError(state_field)
+                    injected_args[tool_arg] = (
+                        state[state_field] if state_field else state
+                    )
             else:
                 for tool_arg, state_field in injected.state.items():
-                    if not state_field:
-                        injected_args[tool_arg] = state
-                    elif hasattr(state, state_field):
-                        injected_args[tool_arg] = getattr(state, state_field)
-                    elif tool_arg not in injected._optional_state_args:
-                        raise AttributeError(state_field)
+                    injected_args[tool_arg] = (
+                        getattr(state, state_field) if state_field else state
+                    )
 
         # Inject store
         if injected.store:
@@ -1870,7 +1863,6 @@ def _get_all_injected_args(tool: BaseTool) -> _InjectedArgs:
     store_arg: str | None = None
     runtime_arg: str | None = None
     all_injected_keys: set[str] = set()
-    _optional_state_args: set[str] = set()
 
     for name, type_ in all_annotations.items():
         # Track all InjectedToolArg-annotated params (including custom subclasses)
@@ -1885,9 +1877,6 @@ def _get_all_injected_args(tool: BaseTool) -> _InjectedArgs:
         if state_inj := _get_injection_from_type(type_, InjectedState):
             if isinstance(state_inj, InjectedState) and state_inj.field:
                 state_args[name] = state_inj.field
-                field_info = full_schema.model_fields.get(name)
-                if field_info and not field_info.is_required():
-                    _optional_state_args.add(name)
             else:
                 state_args[name] = None
 
@@ -1904,5 +1893,4 @@ def _get_all_injected_args(tool: BaseTool) -> _InjectedArgs:
         store=store_arg,
         runtime=runtime_arg,
         all_injected_keys=all_injected_keys,
-        _optional_state_args=_optional_state_args,
     )