fix(web): serialize duckduckgo search calls

tests/agent/test_runner.py

@@ -689,11 +689,20 @@ async def test_runner_keeps_going_when_tool_result_persistence_fails():
 
 
 class _DelayTool(Tool):
-    def __init__(self, name: str, *, delay: float, read_only: bool, shared_events: list[str]):
+    def __init__(
+        self,
+        name: str,
+        *,
+        delay: float,
+        read_only: bool,
+        shared_events: list[str],
+        exclusive: bool = False,
+    ):
         self._name = name
         self._delay = delay
         self._read_only = read_only
         self._shared_events = shared_events
+        self._exclusive = exclusive
 
     @property
     def name(self) -> str:
@@ -711,6 +720,10 @@ class _DelayTool(Tool):
     def read_only(self) -> bool:
         return self._read_only
 
+    @property
+    def exclusive(self) -> bool:
+        return self._exclusive
+
     async def execute(self, **kwargs):
         self._shared_events.append(f"start:{self._name}")
         await asyncio.sleep(self._delay)
@@ -756,6 +769,48 @@ async def test_runner_batches_read_only_tools_before_exclusive_work():
     assert shared_events[-2:] == ["start:write_a", "end:write_a"]
 
 
+@pytest.mark.asyncio
+async def test_runner_does_not_batch_exclusive_read_only_tools():
+    from nanobot.agent.runner import AgentRunSpec, AgentRunner
+
+    tools = ToolRegistry()
+    shared_events: list[str] = []
+    read_a = _DelayTool("read_a", delay=0.03, read_only=True, shared_events=shared_events)
+    read_b = _DelayTool("read_b", delay=0.03, read_only=True, shared_events=shared_events)
+    ddg_like = _DelayTool(
+        "ddg_like",
+        delay=0.01,
+        read_only=True,
+        shared_events=shared_events,
+        exclusive=True,
+    )
+    tools.register(read_a)
+    tools.register(ddg_like)
+    tools.register(read_b)
+
+    runner = AgentRunner(MagicMock())
+    await runner._execute_tools(
+        AgentRunSpec(
+            initial_messages=[],
+            tools=tools,
+            model="test-model",
+            max_iterations=1,
+            max_tool_result_chars=_MAX_TOOL_RESULT_CHARS,
+            concurrent_tools=True,
+        ),
+        [
+            ToolCallRequest(id="ro1", name="read_a", arguments={}),
+            ToolCallRequest(id="ddg1", name="ddg_like", arguments={}),
+            ToolCallRequest(id="ro2", name="read_b", arguments={}),
+        ],
+        {},
+    )
+
+    assert shared_events[0] == "start:read_a"
+    assert shared_events.index("end:read_a") < shared_events.index("start:ddg_like")
+    assert shared_events.index("end:ddg_like") < shared_events.index("start:read_b")
+
+
 @pytest.mark.asyncio
 async def test_runner_blocks_repeated_external_fetches():
     from nanobot.agent.runner import AgentRunSpec, AgentRunner