From 907fefe5191e685b4058d001982b5ccf6a2e35cd Mon Sep 17 00:00:00 2001
From: Christian Bromann <git@bromann.dev>
Date: Tue, 2 Jun 2026 16:57:51 -0700
Subject: [PATCH] cr

---
 libs/langgraph/langgraph/_internal/_typing.py | 12 +++++++++-
 libs/langgraph/langgraph/graph/state.py       | 22 +++++++++++++------
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/libs/langgraph/langgraph/_internal/_typing.py b/libs/langgraph/langgraph/_internal/_typing.py
index 19854d1c8..a708df4ae 100644
--- a/libs/langgraph/langgraph/_internal/_typing.py
+++ b/libs/langgraph/langgraph/_internal/_typing.py
@@ -42,7 +42,17 @@ It can either be a `TypedDict`, `dataclass`, or Pydantic `BaseModel`.
 Note: we cannot use either `TypedDict` or `dataclass` directly due to limitations in type checking.
 """
 
-MISSING = object()
+
+class UnsetSentinel:
+    """Singleton sentinel for unset optional parameters."""
+
+    __slots__ = ()
+
+    def __repr__(self) -> str:
+        return "MISSING"
+
+
+MISSING: UnsetSentinel = UnsetSentinel()
 """Unset sentinel value."""
 
 
diff --git a/libs/langgraph/langgraph/graph/state.py b/libs/langgraph/langgraph/graph/state.py
index 915e89668..ba94c3276 100644
--- a/libs/langgraph/langgraph/graph/state.py
+++ b/libs/langgraph/langgraph/graph/state.py
@@ -47,7 +47,12 @@ from langgraph._internal._fields import (
 from langgraph._internal._pydantic import create_model
 from langgraph._internal._runnable import coerce_to_runnable
 from langgraph._internal._timeout import coerce_timeout_policy
-from langgraph._internal._typing import EMPTY_SEQ, MISSING, DeprecatedKwargs
+from langgraph._internal._typing import (
+    EMPTY_SEQ,
+    MISSING,
+    DeprecatedKwargs,
+    UnsetSentinel,
+)
 from langgraph.channels.base import BaseChannel
 from langgraph.channels.binop import BinaryOperatorAggregate
 from langgraph.channels.delta import DeltaChannel
@@ -669,7 +674,7 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
         metadata: dict[str, Any] | None = None,
         input_schema: type[NodeInputT] | None = None,
         retry_policy: RetryPolicy | Sequence[RetryPolicy] | None = None,
-        cache_policy: CachePolicy | None = MISSING,
+        cache_policy: CachePolicy | None | UnsetSentinel = MISSING,
         error_handler: StateNode[Any, ContextT] | None = None,
         destinations: dict[str, str] | tuple[str, ...] | None = None,
         timeout: float | timedelta | TimeoutPolicy | None = None,
@@ -771,9 +776,12 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
 
         cache_policy_opt_out = False
         if cache_policy is MISSING:
-            cache_policy = None
-        elif cache_policy is None:
+            resolved_cache_policy: CachePolicy | None = None
+        elif isinstance(cache_policy, CachePolicy):
+            resolved_cache_policy = cache_policy
+        else:
             cache_policy_opt_out = True
+            resolved_cache_policy = None
 
         if not isinstance(node, str):
             action = node
@@ -885,7 +893,7 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
                 metadata,
                 input_schema=input_schema,
                 retry_policy=retry_policy,
-                cache_policy=cache_policy,
+                cache_policy=resolved_cache_policy,
                 cache_policy_opt_out=cache_policy_opt_out,
                 error_handler_node=handler_node_name,
                 ends=ends,
@@ -898,7 +906,7 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
                 metadata,
                 input_schema=inferred_input_schema,
                 retry_policy=retry_policy,
-                cache_policy=cache_policy,
+                cache_policy=resolved_cache_policy,
                 cache_policy_opt_out=cache_policy_opt_out,
                 error_handler_node=handler_node_name,
                 ends=ends,
@@ -911,7 +919,7 @@ class StateGraph(Generic[StateT, ContextT, InputT, OutputT]):
                 metadata,
                 input_schema=self.state_schema,
                 retry_policy=retry_policy,
-                cache_policy=cache_policy,
+                cache_policy=resolved_cache_policy,
                 cache_policy_opt_out=cache_policy_opt_out,
                 error_handler_node=handler_node_name,
                 ends=ends,