diff --git a/libs/prebuilt/langgraph/prebuilt/tool_node.py b/libs/prebuilt/langgraph/prebuilt/tool_node.py
index 3137309da..f5aa4d86d 100644
--- a/libs/prebuilt/langgraph/prebuilt/tool_node.py
+++ b/libs/prebuilt/langgraph/prebuilt/tool_node.py
@@ -44,7 +44,7 @@ import inspect
 import json
 from collections.abc import Awaitable, Callable
 from copy import copy, deepcopy
-from dataclasses import dataclass, replace
+from dataclasses import dataclass, field, replace
 from types import UnionType
 from typing import (
     TYPE_CHECKING,
@@ -1723,9 +1723,9 @@ class ToolRuntime(_DirectlyInjectedToolArg, Generic[ContextT, StateT]):
     context: ContextT
     config: RunnableConfig
     stream_writer: StreamWriter
-    tools: list[BaseTool]
     tool_call_id: str | None
     store: BaseStore | None
+    tools: list[BaseTool] = field(default_factory=list)
     execution_info: ExecutionInfo | None = None
     server_info: ServerInfo | None = None
 
diff --git a/libs/prebuilt/tests/test_tool_node.py b/libs/prebuilt/tests/test_tool_node.py
index c30787f74..acc5522fa 100644
--- a/libs/prebuilt/tests/test_tool_node.py
+++ b/libs/prebuilt/tests/test_tool_node.py
@@ -2016,6 +2016,19 @@ async def test_tool_node_inject_runtime_dynamic_tool_via_wrap_tool_call_async()
     assert tool_message.tool_call_id == "call_dynamic_2"
 
 
+def test_tool_runtime_defaults_tools_to_empty_list() -> None:
+    runtime = ToolRuntime(
+        state={},
+        context=None,
+        config={},
+        stream_writer=lambda *args, **kwargs: None,
+        tool_call_id=None,
+        store=None,
+    )
+
+    assert runtime.tools == []
+
+
 def test_tool_runtime_forwards_execution_info_server_info_and_tools() -> None:
     """Test that execution_info, server_info, and tools are forwarded from Runtime to ToolRuntime."""
     from langgraph.runtime import ExecutionInfo, ServerInfo