using StateT as default for InputT

libs/langgraph/langgraph/_typing.py

@@ -0,0 +1,47 @@
+"""Private typing utilities for LangGraph."""
+
+from __future__ import annotations
+
+from dataclasses import Field
+from typing import Any, ClassVar, Protocol, Union
+
+from pydantic import BaseModel
+from typing_extensions import TypeAlias, TypedDict
+
+
+class TypedDictLikeV1(Protocol):
+    """Protocol to represent types that behave like TypedDicts
+
+    Version 1: using `ClassVar` for keys."""
+
+    __required_keys__: ClassVar[frozenset[str]]
+    __optional_keys__: ClassVar[frozenset[str]]
+
+
+class TypedDictLikeV2(Protocol):
+    """Protocol to represent types that behave like TypedDicts
+
+    Version 2: not using `ClassVar` for keys."""
+
+    __required_keys__: frozenset[str]
+    __optional_keys__: frozenset[str]
+
+
+class DataclassLike(Protocol):
+    """Protocol to represent types that behave like dataclasses.
+
+    Inspired by the private _DataclassT from dataclasses that uses a similar protocol as a bound."""
+
+    __dataclass_fields__: ClassVar[dict[str, Field[Any]]]
+
+
+StateLike: TypeAlias = Union[TypedDictLikeV1, TypedDictLikeV2, DataclassLike, BaseModel]
+"""Type alias for state-like types.
+
+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.
+"""
+
+
+class DeprecatedKwargs(TypedDict):
+    """TypedDict to use for extra keyword arguments, enabling type checking warnings for deprecated arguments."""

libs/langgraph/langgraph/func/__init__.py

@@ -19,6 +19,7 @@ from typing import (
 
 from typing_extensions import Unpack
 
+from langgraph._typing import DeprecatedKwargs
 from langgraph.cache.base import BaseCache
 from langgraph.channels.ephemeral_value import EphemeralValue
 from langgraph.channels.last_value import LastValue
@@ -37,7 +38,6 @@ from langgraph.pregel.read import PregelNode
 from langgraph.pregel.write import ChannelWrite, ChannelWriteEntry
 from langgraph.store.base import BaseStore
 from langgraph.types import _DC_KWARGS, CachePolicy, RetryPolicy, StreamMode
-from langgraph.typing import DeprecatedKwargs
 from langgraph.warnings import LangGraphDeprecatedSinceV10
 
 

libs/langgraph/langgraph/graph/state.py

@@ -28,6 +28,7 @@ from langchain_core.runnables import Runnable, RunnableConfig
 from pydantic import BaseModel
 from typing_extensions import Self, TypeAlias, Unpack
 
+from langgraph._typing import DeprecatedKwargs
 from langgraph.cache.base import BaseCache
 from langgraph.channels.base import BaseChannel
 from langgraph.channels.binop import BinaryOperatorAggregate
@@ -77,7 +78,7 @@ from langgraph.types import (
     Send,
     StreamWriter,
 )
-from langgraph.typing import DeprecatedKwargs, InputT, StateT, StateT_contra, Unset
+from langgraph.typing import InputT, StateT, StateT_contra
 from langgraph.utils.fields import (
     get_cached_annotated_keys,
     get_field_default,
@@ -749,32 +750,6 @@ class StateGraph(Generic[StateT, InputT]):
         self.compiled = True
         return self
 
-    @overload
-    def compile(
-        self: StateGraph[StateT, Unset],
-        checkpointer: Checkpointer = None,
-        *,
-        cache: BaseCache | None = None,
-        store: BaseStore | None = None,
-        interrupt_before: All | list[str] | None = None,
-        interrupt_after: All | list[str] | None = None,
-        debug: bool = False,
-        name: str | None = None,
-    ) -> CompiledStateGraph[StateT, StateT]: ...
-
-    @overload
-    def compile(
-        self: StateGraph[StateT, InputT],
-        checkpointer: Checkpointer = None,
-        *,
-        cache: BaseCache | None = None,
-        store: BaseStore | None = None,
-        interrupt_before: All | list[str] | None = None,
-        interrupt_after: All | list[str] | None = None,
-        debug: bool = False,
-        name: str | None = None,
-    ) -> CompiledStateGraph[StateT, InputT]: ...
-
     def compile(
         self,
         checkpointer: Checkpointer = None,
@@ -785,7 +760,7 @@ class StateGraph(Generic[StateT, InputT]):
         interrupt_after: All | list[str] | None = None,
         debug: bool = False,
         name: str | None = None,
-    ) -> CompiledStateGraph[StateT, StateT] | CompiledStateGraph[StateT, InputT]:
+    ) -> CompiledStateGraph[StateT, InputT]:
         """Compiles the state graph into a `CompiledStateGraph` object.
 
         The compiled graph implements the `Runnable` interface and can be invoked,
@@ -837,8 +812,7 @@ class StateGraph(Generic[StateT, InputT]):
             ]
         )
 
-        ResolvedInputT: type[InputT] | type[StateT] = self.input or self.schema
-        compiled = CompiledStateGraph[StateT, ResolvedInputT](  # type: ignore[valid-type]
+        compiled = CompiledStateGraph[StateT, InputT](
             builder=self,
             schema_to_mapper={},
             config_type=self.config_schema,
@@ -886,7 +860,7 @@ class StateGraph(Generic[StateT, InputT]):
         return compiled.validate()
 
 
-class CompiledStateGraph(Pregel[InputT], Generic[StateT, InputT]):
+class CompiledStateGraph(Pregel[StateT, InputT], Generic[StateT, InputT]):
     builder: StateGraph[StateT, InputT]
     schema_to_mapper: dict[type[Any], Callable[[Any], Any] | None]
 

libs/langgraph/langgraph/pregel/__init__.py

@@ -107,7 +107,7 @@ from langgraph.types import (
     StreamChunk,
     StreamMode,
 )
-from langgraph.typing import InputT
+from langgraph.typing import InputT, StateT
 from langgraph.utils.config import (
     ensure_config,
     merge_configs,
@@ -298,7 +298,7 @@ class NodeBuilder:
         )
 
 
-class Pregel(PregelProtocol[InputT], Generic[InputT]):
+class Pregel(PregelProtocol[StateT, InputT], Generic[StateT, InputT]):
     """Pregel manages the runtime behavior for LangGraph applications.
 
     ## Overview

libs/langgraph/langgraph/pregel/protocol.py

@@ -9,11 +9,11 @@ from langchain_core.runnables.graph import Graph as DrawableGraph
 from typing_extensions import Self
 
 from langgraph.pregel.types import All, StateSnapshot, StateUpdate, StreamMode
-from langgraph.typing import InputT
+from langgraph.typing import InputT, StateT
 
 
 # TODO: remove Runnable inheritance here!
-class PregelProtocol(Runnable[InputT, Any], Generic[InputT], ABC):
+class PregelProtocol(Runnable[InputT, Any], Generic[StateT, InputT], ABC):
     @abstractmethod
     def with_config(
         self, config: RunnableConfig | None = None, **kwargs: Any

libs/langgraph/langgraph/typing.py

@@ -1,57 +1,10 @@
 from __future__ import annotations
 
-from dataclasses import Field
-from typing import (
-    Any,
-    ClassVar,
-    Protocol,
-    Union,
-)
+from typing import Union
 
-from pydantic import BaseModel
-from typing_extensions import TypeAlias, TypedDict, TypeVar
+from typing_extensions import TypeVar
 
-
-class _TypedDictLikeV1(Protocol):
-    """Protocol to represent types that behave like TypedDicts
-
-    Version 1: using `ClassVar` for keys."""
-
-    __required_keys__: ClassVar[frozenset[str]]
-    __optional_keys__: ClassVar[frozenset[str]]
-
-
-class _TypedDictLikeV2(Protocol):
-    """Protocol to represent types that behave like TypedDicts
-
-    Version 2: not using `ClassVar` for keys."""
-
-    __required_keys__: frozenset[str]
-    __optional_keys__: frozenset[str]
-
-
-class _DataclassLike(Protocol):
-    """Protocol to represent types that behave like dataclasses.
-
-    Inspired by the private _DataclassT from dataclasses that uses a similar protocol as a bound."""
-
-    __dataclass_fields__: ClassVar[dict[str, Field[Any]]]
-
-
-StateLike: TypeAlias = Union[
-    _TypedDictLikeV1, _TypedDictLikeV2, _DataclassLike, BaseModel
-]
-"""Type alias for state-like types.
-
-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."""
-
-
-class Unset:
-    """Sentinel representing an unset value."""
-
-
-UNSET = Unset()
+from langgraph._typing import StateLike
 
 StateT = TypeVar("StateT", bound=StateLike)
 """Type variable used to represent the state in a graph."""
@@ -60,15 +13,18 @@ StateT_co = TypeVar("StateT_co", bound=StateLike, covariant=True)
 
 StateT_contra = TypeVar("StateT_contra", bound=StateLike, contravariant=True)
 
-InputT = TypeVar("InputT", bound=Union[StateLike, Unset], default=Unset)
-"""Type variable used to represent the input to a graph.
+InputT = TypeVar("InputT", bound=StateLike, default=StateT)
+"""Type variable used to represent the input to a state graph.
 
-In practice, InputT might be represented by either the `input_type` or `state_type` of a graph.
-If `input_type` is not specified, it defaults to `StateType`."""
+Defaults to `StateT`.
+"""
 
-OutputT = TypeVar("OutputT", bound=Union[StateLike, Unset], default=Unset)
-"""Type variable used to represent the output of a graph."""
+ResolvedInputT = TypeVar("ResolvedInputT", bound=StateLike)
+"""Type variable used to represent the resolved input to a state graph.
+
+No default.
+"""
 
 
-class DeprecatedKwargs(TypedDict):
-    """TypedDict to use for extra keyword arguments, enabling type checking warnings for deprecated arguments."""
+OutputT = TypeVar("OutputT", bound=Union[StateLike, None], default=StateT)
+"""Type variable used to represent the output of a state graph."""