diff --git a/libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_tools.py b/libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_tools.py
index 12274cd3b63fb..d6c3bbfd20a1f 100644
--- a/libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_tools.py
+++ b/libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_tools.py
@@ -1,14 +1,22 @@
 """Test Middleware handling of tools in agents."""
 
 from collections.abc import Callable
+from typing import Any
 
 import pytest
-from langchain_core.messages import AIMessage, HumanMessage, ToolMessage
+from langchain_core.messages import HumanMessage, ToolMessage
 from langchain_core.tools import tool
+from langchain_core.tools.base import BaseTool
 from langgraph.prebuilt.tool_node import ToolNode
 
 from langchain.agents.factory import create_agent
-from langchain.agents.middleware.types import AgentMiddleware, AgentState, ModelRequest
+from langchain.agents.middleware.types import (
+    AgentMiddleware,
+    AgentState,
+    ModelCallResult,
+    ModelRequest,
+    ModelResponse,
+)
 from tests.unit_tests.agents.model import FakeToolCallingModel
 
 
@@ -30,8 +38,8 @@ class RequestCapturingMiddleware(AgentMiddleware):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
             captured_requests.append(request)
             return handler(request)
 
@@ -51,7 +59,15 @@ def wrap_model_call(
     request = captured_requests[0]
     assert isinstance(request.tools, list)
     assert len(request.tools) == 2
-    assert {t.name for t in request.tools} == {"search_tool", "calculator"}
+
+    tools = []
+    for t in request.tools:
+        assert isinstance(t, BaseTool)
+        tools.append(t.name)
+    assert set(tools) == {
+        "search_tool",
+        "calculator",
+    }
 
 
 def test_middleware_can_modify_tools() -> None:
@@ -76,10 +92,14 @@ class ToolFilteringMiddleware(AgentMiddleware):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
             # Only allow tool_a and tool_b
-            filtered_tools = [t for t in request.tools if t.name in {"tool_a", "tool_b"}]
+            filtered_tools: list[BaseTool | dict[str, Any]] = []
+            for t in request.tools:
+                assert isinstance(t, BaseTool)
+                if t.name in {"tool_a", "tool_b"}:
+                    filtered_tools.append(t)
             return handler(request.override(tools=filtered_tools))
 
     # Model will try to call tool_a
@@ -120,8 +140,8 @@ class BadMiddleware(AgentMiddleware):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
             # Add an unknown tool
             return handler(request.override(tools=[*request.tools, unknown_tool]))
 
@@ -149,7 +169,7 @@ def admin_tool(command: str) -> str:
         """Admin-only tool."""
         return f"Admin: {command}"
 
-    class AdminState(AgentState):
+    class AdminState(AgentState[Any]):
         is_admin: bool
 
     class ConditionalToolMiddleware(AgentMiddleware[AdminState]):
@@ -158,11 +178,15 @@ class ConditionalToolMiddleware(AgentMiddleware[AdminState]):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
             # Remove admin_tool if not admin
             if not request.state.get("is_admin", False):
-                filtered_tools = [t for t in request.tools if t.name != "admin_tool"]
+                filtered_tools: list[BaseTool | dict[str, Any]] = []
+                for t in request.tools:
+                    assert isinstance(t, BaseTool)
+                    if t.name != "admin_tool":
+                        filtered_tools.append(t)
                 request = request.override(tools=filtered_tools)
             return handler(request)
 
@@ -197,8 +221,8 @@ class NoToolsMiddleware(AgentMiddleware):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
             # Remove all tools
             request = request.override(tools=[])
             return handler(request)
@@ -240,11 +264,17 @@ class FirstMiddleware(AgentMiddleware):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
-            modification_order.append([t.name for t in request.tools])
-            # Remove tool_c
-            filtered_tools = [t for t in request.tools if t.name != "tool_c"]
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
+            tools: list[str] = []
+            filtered_tools: list[BaseTool | dict[str, Any]] = []
+            for t in request.tools:
+                assert isinstance(t, BaseTool)
+                tools.append(t.name)
+                # Remove tool_c
+                if t.name != "tool_c":
+                    filtered_tools.append(t)
+            modification_order.append(tools)
             request = request.override(tools=filtered_tools)
             return handler(request)
 
@@ -252,13 +282,19 @@ class SecondMiddleware(AgentMiddleware):
         def wrap_model_call(
             self,
             request: ModelRequest,
-            handler: Callable[[ModelRequest], AIMessage],
-        ) -> AIMessage:
-            modification_order.append([t.name for t in request.tools])
-            # Should not see tool_c here
-            assert all(t.name != "tool_c" for t in request.tools)
-            # Remove tool_b
-            filtered_tools = [t for t in request.tools if t.name != "tool_b"]
+            handler: Callable[[ModelRequest], ModelResponse],
+        ) -> ModelCallResult:
+            tools: list[str] = []
+            filtered_tools: list[BaseTool | dict[str, Any]] = []
+            for t in request.tools:
+                assert isinstance(t, BaseTool)
+                # Should not see tool_c here
+                assert t.name != "tool_c"
+                tools.append(t.name)
+                # Remove tool_b
+                if t.name != "tool_b":
+                    filtered_tools.append(t)
+            modification_order.append(tools)
             request = request.override(tools=filtered_tools)
             return handler(request)
 
@@ -317,6 +353,7 @@ class ToolProvidingMiddleware(AgentMiddleware):
     tool_messages = [m for m in messages if isinstance(m, ToolMessage)]
     assert len(tool_messages) == 1
     assert tool_messages[0].name == "middleware_tool"
+    assert isinstance(tool_messages[0].content, str)
     assert "middleware" in tool_messages[0].content.lower()