Potential validation issue when using StateLike in Annotation for a tool #32067
Description
Privileged issue
- I am a LangChain maintainer, or was asked directly by a LangChain maintainer to create an issue here.
Issue Content
This code snippet triggers a validation issue. Likely issue in how langchain_core is using Pydantic for the run time validation.
from langgraph.typing import StateLike
@tool(name, description=description)
def handoff_to_agent(
# Annotation is typed as Any instead of StateLike. StateLike
# trigger validation issues from Pydantic / langchain_core interaction.
state: Annotated[StateLike, InjectedState],
tool_call_id: Annotated[str, InjectedToolCallId],
) -> Command:Stack trace:
def create_schema_validator(
schema: CoreSchema,
schema_type: Any,
schema_type_module: str,
schema_type_name: str,
schema_kind: SchemaKind,
config: CoreConfig | None = None,
plugin_settings: dict[str, Any] | None = None,
) -> SchemaValidator | PluggableSchemaValidator:
"""Create a `SchemaValidator` or `PluggableSchemaValidator` if plugins are installed.
Returns:
If plugins are installed then return `PluggableSchemaValidator`, otherwise return `SchemaValidator`.
"""
from . import SchemaTypePath
from ._loader import get_plugins
plugins = get_plugins()
if plugins:
return PluggableSchemaValidator(
schema,
schema_type,
SchemaTypePath(schema_type_module, schema_type_name),
schema_kind,
config,
plugins,
plugin_settings or {},
)
else:
> return SchemaValidator(schema, config)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E pydantic_core._pydantic_core.SchemaError: Error building "model" validator:
E SchemaError: Error building "model-fields" validator:
E SchemaError: Field "state":
E SchemaError: Error building "union" validator:
E SchemaError: Error building "is-instance" validator:
E SchemaError: 'cls' must be valid as the first argument to 'isinstance'
Workaround:
For now implementation will rely on an Any type