diff --git a/libs/langchain_v1/langchain/agents/middleware/tool_error_handling.py b/libs/langchain_v1/langchain/agents/middleware/tool_error_handling.py
index 37441d9be59..f165d499385 100644
--- a/libs/langchain_v1/langchain/agents/middleware/tool_error_handling.py
+++ b/libs/langchain_v1/langchain/agents/middleware/tool_error_handling.py
@@ -9,7 +9,7 @@ from __future__ import annotations
 import inspect
 import logging
 import time
-from collections.abc import Callable
+from types import UnionType
 from typing import TYPE_CHECKING, Union, get_args, get_origin, get_type_hints
 
 from langchain_core.messages import ToolMessage
@@ -17,13 +17,10 @@ from langchain_core.messages import ToolMessage
 from langchain.agents.middleware.types import AgentMiddleware
 
 # Import ToolCallResponse locally to avoid circular import
-from langchain.tools.tool_node import ToolCallResponse
+from langchain.tools.tool_node import ToolCallRequest, ToolCallResponse
 
 if TYPE_CHECKING:
-    from collections.abc import Generator
-    from types import UnionType
-
-    from langchain.tools.tool_node import ToolCallRequest, ToolCallResponse
+    from collections.abc import Callable, Generator
 
 logger = logging.getLogger(__name__)
 
@@ -72,13 +69,14 @@ def _infer_retriable_types(
         if first_param.name in type_hints:
             origin = get_origin(first_param.annotation)
             # Handle Union types
-            if origin in [Union, UnionType]:  # type: ignore[has-type]
+            if origin in [Union, UnionType]:
                 args = get_args(first_param.annotation)
                 if all(isinstance(arg, type) and issubclass(arg, Exception) for arg in args):
                     return tuple(args)
                 msg = (
                     "All types in retry predicate annotation must be Exception types. "
-                    "For example, `def should_retry(e: Union[TimeoutError, ConnectionError]) -> bool`. "
+                    "For example, `def should_retry(e: Union[TimeoutError, "
+                    "ConnectionError]) -> bool`. "
                     f"Got '{first_param.annotation}' instead."
                 )
                 raise ValueError(msg)
@@ -260,14 +258,13 @@ class RetryMiddleware(AgentMiddleware):
                     return response
 
                 # If predicate is provided, check if we should retry
-                if self._retry_predicate is not None:
-                    if not self._retry_predicate(exception):
-                        logger.debug(
-                            "Retry predicate returned False for %s in tool %s",
-                            type(exception).__name__,
-                            request.tool_call["name"],
-                        )
-                        return response
+                if self._retry_predicate is not None and not self._retry_predicate(exception):
+                    logger.debug(
+                        "Retry predicate returned False for %s in tool %s",
+                        type(exception).__name__,
+                        request.tool_call["name"],
+                    )
+                    return response
 
                 # Last attempt - return error
                 if attempt > self.max_retries:
diff --git a/libs/langchain_v1/langchain/tools/tool_node.py b/libs/langchain_v1/langchain/tools/tool_node.py
index 56d29fc95ce..6be59457ecc 100644
--- a/libs/langchain_v1/langchain/tools/tool_node.py
+++ b/libs/langchain_v1/langchain/tools/tool_node.py
@@ -152,7 +152,8 @@ ToolCallHandler = Callable[
 """Generator-based handler that intercepts tool execution.
 
 Receives a ToolCallRequest, state, and runtime; yields modified ToolCallRequests;
-receives ToolCallResponses; and returns a final ToolCallResponse. Supports multiple yields for retry logic.
+receives ToolCallResponses; and returns a final ToolCallResponse. Supports multiple
+yields for retry logic.
 """
 
 
@@ -511,7 +512,7 @@ class ToolNode(RunnableCallable):
         input: list[AnyMessage] | dict[str, Any] | BaseModel,
         config: RunnableConfig,
         *,
-        store: Optional[BaseStore],
+        store: BaseStore | None,
     ) -> Any:
         try:
             runtime = get_runtime()
@@ -535,7 +536,7 @@ class ToolNode(RunnableCallable):
         input: list[AnyMessage] | dict[str, Any] | BaseModel,
         config: RunnableConfig,
         *,
-        store: Optional[BaseStore],
+        store: BaseStore | None,
     ) -> Any:
         try:
             runtime = get_runtime()
diff --git a/libs/langchain_v1/tests/unit_tests/tools/test_on_tool_call.py b/libs/langchain_v1/tests/unit_tests/tools/test_on_tool_call.py
index f844aff7352..5a21df58b40 100644
--- a/libs/langchain_v1/tests/unit_tests/tools/test_on_tool_call.py
+++ b/libs/langchain_v1/tests/unit_tests/tools/test_on_tool_call.py
@@ -1,6 +1,7 @@
 """Tests for on_tool_call handler functionality."""
 
 from collections.abc import Generator
+from typing import Any
 
 import pytest
 from langchain_core.messages import AIMessage, ToolMessage
@@ -41,7 +42,7 @@ def test_on_tool_call_passthrough() -> None:
     """Test that a simple passthrough handler works."""
 
     def passthrough_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Simply pass through without modification."""
         response = yield request
@@ -65,14 +66,14 @@ def test_on_tool_call_passthrough() -> None:
     assert tool_message.status != "error"
 
 
-def test_on_tool_call_retry_success():
+def test_on_tool_call_retry_success() -> None:
     """Test that retry handler can recover from transient errors."""
     # Reset counter
     if hasattr(rate_limit_tool, "_call_count"):
         rate_limit_tool._call_count = 0
 
     def retry_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Retry up to 3 times."""
         max_retries = 3
@@ -97,7 +98,8 @@ def test_on_tool_call_retry_success():
                     status="error",
                 ),
             )
-        raise AssertionError("Unreachable code")
+        msg = "Unreachable code"
+        raise AssertionError(msg)
 
     tool_node = ToolNode([rate_limit_tool], on_tool_call=retry_handler, handle_tool_errors=False)
     result = tool_node.invoke(
@@ -117,11 +119,11 @@ def test_on_tool_call_retry_success():
     assert tool_message.status != "error"
 
 
-def test_on_tool_call_convert_error_to_message():
+def test_on_tool_call_convert_error_to_message() -> None:
     """Test that handler can convert raised errors to error messages."""
 
     def error_to_message_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Convert any error to a user-friendly message."""
         response = yield request
@@ -161,11 +163,11 @@ def test_on_tool_call_convert_error_to_message():
     assert tool_message.status == "error"
 
 
-def test_on_tool_call_let_error_raise():
+def test_on_tool_call_let_error_raise() -> None:
     """Test that handler can let errors propagate."""
 
     def let_raise_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Just return the response as-is, letting errors raise."""
         response = yield request
@@ -173,7 +175,7 @@ def test_on_tool_call_let_error_raise():
 
     tool_node = ToolNode([error_tool], on_tool_call=let_raise_handler, handle_tool_errors=False)
 
-    with pytest.raises(ValueError) as exc_info:
+    with pytest.raises(ValueError, match=r"Error with value: 5"):
         tool_node.invoke(
             {
                 "messages": [
@@ -185,15 +187,13 @@ def test_on_tool_call_let_error_raise():
             }
         )
 
-    assert "Error with value: 5" in str(exc_info.value)
 
-
-def test_on_tool_call_with_handled_errors():
+def test_on_tool_call_with_handled_errors() -> None:
     """Test interaction between on_tool_call and handle_tool_errors."""
     call_count = {"count": 0}
 
     def counting_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Count how many times we're called."""
         call_count["count"] += 1
@@ -221,19 +221,19 @@ def test_on_tool_call_with_handled_errors():
     assert "Please fix your mistakes" in tool_message.content
 
 
-def test_on_tool_call_must_return_value():
+def test_on_tool_call_must_return_value() -> None:
     """Test that handler must return a ToolCallResponse."""
 
     def no_return_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Handler that doesn't return anything."""
-        response = yield request
+        _ = yield request
         # Implicit return None
 
     tool_node = ToolNode([success_tool], on_tool_call=no_return_handler)
 
-    with pytest.raises(ValueError) as exc_info:
+    with pytest.raises(ValueError, match=r"must explicitly return a ToolCallResponse"):
         tool_node.invoke(
             {
                 "messages": [
@@ -245,14 +245,12 @@ def test_on_tool_call_must_return_value():
             }
         )
 
-    assert "must explicitly return a ToolCallResponse" in str(exc_info.value)
 
-
-def test_on_tool_call_request_modification():
+def test_on_tool_call_request_modification() -> None:
     """Test that handler can modify the request before execution."""
 
     def double_input_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Double the input value."""
         # Modify the tool call args
@@ -286,17 +284,15 @@ def test_on_tool_call_request_modification():
     assert tool_message.content == "20"
 
 
-def test_on_tool_call_response_validation():
+def test_on_tool_call_response_validation() -> None:
     """Test that ToolCallResponse validates action and required fields."""
     # Test action="return" requires result
-    with pytest.raises(ValueError) as exc_info:
+    with pytest.raises(ValueError, match=r"action='return' requires a result"):
         ToolCallResponse(action="return")
-    assert "action='return' requires a result" in str(exc_info.value)
 
     # Test action="raise" requires exception
-    with pytest.raises(ValueError) as exc_info:
+    with pytest.raises(ValueError, match=r"action='raise' requires an exception"):
         ToolCallResponse(action="raise")
-    assert "action='raise' requires an exception" in str(exc_info.value)
 
     # Valid responses should work
     ToolCallResponse(
@@ -306,7 +302,7 @@ def test_on_tool_call_response_validation():
     ToolCallResponse(action="raise", exception=ValueError("test"))
 
 
-def test_on_tool_call_without_handler_backward_compat():
+def test_on_tool_call_without_handler_backward_compat() -> None:
     """Test that tools work without on_tool_call handler (backward compatibility)."""
     # Success case
     tool_node = ToolNode([success_tool])
@@ -324,7 +320,7 @@ def test_on_tool_call_without_handler_backward_compat():
 
     # Error case with handle_tool_errors=False
     tool_node_error = ToolNode([error_tool], handle_tool_errors=False)
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match=r"Error with value: 5"):
         tool_node_error.invoke(
             {
                 "messages": [
@@ -351,12 +347,12 @@ def test_on_tool_call_without_handler_backward_compat():
     assert result["messages"][0].status == "error"
 
 
-def test_on_tool_call_multiple_yields():
+def test_on_tool_call_multiple_yields() -> None:
     """Test that handler can yield multiple times for retries."""
     attempts = {"count": 0}
 
     def multi_yield_handler(
-        request: ToolCallRequest, state, runtime
+        request: ToolCallRequest, _state: Any, _runtime: Any
     ) -> Generator[ToolCallRequest, ToolCallResponse, ToolCallResponse]:
         """Yield multiple times to track attempts."""
         max_attempts = 3
@@ -373,7 +369,7 @@ def test_on_tool_call_multiple_yields():
 
     tool_node = ToolNode([error_tool], on_tool_call=multi_yield_handler, handle_tool_errors=False)
 
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match=r"Error with value: 5"):
         tool_node.invoke(
             {
                 "messages": [