diff --git a/tests/agent/test_task_cancel.py b/tests/agent/test_task_cancel.py
index 8894cd973..4902a4c80 100644
--- a/tests/agent/test_task_cancel.py
+++ b/tests/agent/test_task_cancel.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import asyncio
+from types import SimpleNamespace
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -222,6 +223,39 @@ class TestSubagentCancellation:
         assert assistant_messages[0]["reasoning_content"] == "hidden reasoning"
         assert assistant_messages[0]["thinking_blocks"] == [{"type": "thinking", "thinking": "step"}]
 
+    @pytest.mark.asyncio
+    async def test_subagent_exec_tool_not_registered_when_disabled(self, tmp_path):
+        from nanobot.agent.subagent import SubagentManager
+        from nanobot.bus.queue import MessageBus
+        from nanobot.config.schema import ExecToolConfig
+
+        bus = MessageBus()
+        provider = MagicMock()
+        provider.get_default_model.return_value = "test-model"
+        mgr = SubagentManager(
+            provider=provider,
+            workspace=tmp_path,
+            bus=bus,
+            exec_config=ExecToolConfig(enable=False),
+        )
+        mgr._announce_result = AsyncMock()
+
+        async def fake_run(spec):
+            assert spec.tools.get("exec") is None
+            return SimpleNamespace(
+                stop_reason="done",
+                final_content="done",
+                error=None,
+                tool_events=[],
+            )
+
+        mgr.runner.run = AsyncMock(side_effect=fake_run)
+
+        await mgr._run_subagent("sub-1", "do task", "label", {"channel": "test", "chat_id": "c1"})
+
+        mgr.runner.run.assert_awaited_once()
+        mgr._announce_result.assert_awaited_once()
+
     @pytest.mark.asyncio
     async def test_subagent_announces_error_when_tool_execution_fails(self, monkeypatch, tmp_path):
         from nanobot.agent.subagent import SubagentManager