diff --git a/examples/deerflow-extension-example/README.md b/examples/deerflow-extension-example/README.md
index 5890fa7b2b..e6ce490a64 100644
--- a/examples/deerflow-extension-example/README.md
+++ b/examples/deerflow-extension-example/README.md
@@ -12,7 +12,7 @@ depends on FastAPI, LangChain, and LangGraph in `pyproject.toml`.
 
 | Contribution | Example behavior |
 | --- | --- |
-| Middleware | Counts tool calls through one `TOOL_VISIBLE` middleware for lead agents and subagents |
+| Middleware | Counts synchronous and asynchronous tool calls, outcomes, and elapsed time at `TOOL_VISIBLE` for lead agents and subagents |
 | Task lifecycle | Creates task-scoped stats on start and folds them into app scope on stop |
 | System-model observer | Counts DeerFlow-owned model calls, including failures |
 | Service | Binds `ExtensionRuntimeDeps` only while the Gateway is running |
@@ -24,6 +24,48 @@ the same `ExampleService` object: its FastAPI dependency returns `503` before
 `start()`, after `stop()`, or when no app store was bound. This keeps the route
 topology stable while runtime capabilities arrive later.
 
+### Tool statistics
+
+The existing `tool_calls` field counts calls entering the wrapper. The stats
+response also includes these fields (this is illustrative output, not a benchmark):
+
+```json
+{
+  "tool_calls": 3,
+  "tool_outcomes": {"returned": 1, "raised": 1, "cancelled": 1},
+  "tool_duration_samples": 3,
+  "tool_duration_total_ms": 60.0
+}
+```
+
+- `returned` means the downstream handler returned normally, including an error
+  `ToolMessage`. It does **not** measure business success. A tool exception
+  converted into a normal return downstream of `TOOL_VISIBLE` counts here too.
+- `cancelled` counts `asyncio.CancelledError` escaping the handler, including
+  actual task cancellation. `raised` counts other escaping exceptions, including
+  LangGraph `GraphBubbleUp` control-flow signals such as graph interrupts.
+  Results and exceptions propagate unchanged; each wrapper calls its handler once.
+  Resuming an interrupted tool node re-executes it and re-enters the wrapper:
+  the interrupted attempt adds a `raised` sample, and the resumed attempt adds
+  its own `tool_calls` increment, duration sample, and outcome. These statistics
+  count observed attempts, not unique logical tool calls across interrupt/resume.
+- Each completed observation adds one duration sample, including zero-duration
+  calls. Elapsed time uses a monotonic clock and includes downstream middleware
+  processing. Durations of overlapping lead/subagent calls are summed, so this
+  total is **not** elapsed run time or exclusive tool execution time.
+
+Outcome counters, duration samples, and elapsed totals are updated together under
+a lock. Task stats are copied and merged into app scope on task stop, after the
+task's tool calls have settled. The first stop consumes the task stats; duplicate
+stops (or a stop without a matching start) add neither tasks nor tool statistics.
+If a host stops a task while calls are still running, only the snapshot at that
+stop is merged; later completions are not published. Active tasks are not included
+in the app's tool totals. The system-model observer retains its existing behavior.
+
+The new fields contain only fixed counters and timing totals, with no tool names,
+arguments, outputs, exception text, or identifying labels. Stats are process-local
+and reset on restart; they are not persisted or shared across workers.
+
 ## Run the package tests
 
 `deerflow-extension-api` is currently sourced from this checkout. Install it
@@ -118,7 +160,7 @@ After one or more runs, request the extension route:
 curl -s http://localhost:2026/api/extension-example/stats
 ```
 
-The response contains aggregated task outcomes, tool-call counts, system-model
+The response contains aggregated task outcomes, tool-call counts, outcomes and timing, system-model
 call counts, the app scope id, and a small projection of the host policy. The
 route passes through the Gateway's normal authentication middleware; use an
 authenticated browser session when authentication is enabled.
@@ -145,5 +187,6 @@ deerflow_extension_example/
 └── plugin.py    # state plus all five small contribution implementations
 tests/
 ├── test_entry_point.py
-└── test_plugin.py
+├── test_plugin.py
+└── test_tool_stats.py
 ```
diff --git a/examples/deerflow-extension-example/deerflow_extension_example/plugin.py b/examples/deerflow-extension-example/deerflow_extension_example/plugin.py
index fb301c6d7b..c99efc6164 100644
--- a/examples/deerflow-extension-example/deerflow_extension_example/plugin.py
+++ b/examples/deerflow-extension-example/deerflow_extension_example/plugin.py
@@ -2,9 +2,12 @@
 
 from __future__ import annotations
 
-from collections.abc import Awaitable, Callable, Sequence
+from asyncio import CancelledError
+from collections.abc import Awaitable, Callable, Iterator, Sequence
+from contextlib import contextmanager
 from dataclasses import dataclass, field
 from threading import Lock
+from time import monotonic_ns
 from typing import Any
 
 from deerflow_extension_api import (
@@ -31,6 +34,9 @@ class ExampleStats:
     """Small extension-owned value used in both app and task stores."""
 
     tool_calls: int = 0
+    tool_outcomes: dict[str, int] = field(default_factory=lambda: {"returned": 0, "raised": 0, "cancelled": 0})
+    tool_duration_samples: int = 0
+    tool_duration_total_ns: int = 0
     tasks: dict[str, int] = field(default_factory=dict)
     system_model_calls: dict[str, dict[str, int]] = field(default_factory=dict)
     _lock: Lock = field(default_factory=Lock, repr=False, compare=False)
@@ -39,13 +45,25 @@ class ExampleStats:
         with self._lock:
             self.tool_calls += 1
 
-    def task_tool_calls(self) -> int:
+    def note_tool_outcome(self, outcome: str, duration_ns: int) -> None:
         with self._lock:
-            return self.tool_calls
+            self.tool_outcomes[outcome] += 1
+            self.tool_duration_samples += 1
+            self.tool_duration_total_ns += duration_ns
 
-    def absorb_task(self, tool_calls: int, outcome: TaskOutcome) -> None:
+    def absorb_task(self, task_stats: ExampleStats, outcome: TaskOutcome) -> None:
+        # Copy the task under its lock, then merge under the app lock.
+        with task_stats._lock:
+            tool_calls = task_stats.tool_calls
+            outcomes = dict(task_stats.tool_outcomes)
+            samples = task_stats.tool_duration_samples
+            duration_ns = task_stats.tool_duration_total_ns
         with self._lock:
             self.tool_calls += tool_calls
+            for name, count in outcomes.items():
+                self.tool_outcomes[name] += count
+            self.tool_duration_samples += samples
+            self.tool_duration_total_ns += duration_ns
             key = outcome.value
             self.tasks[key] = self.tasks.get(key, 0) + 1
 
@@ -64,6 +82,9 @@ class ExampleStats:
             return {
                 "tasks": dict(self.tasks),
                 "tool_calls": self.tool_calls,
+                "tool_outcomes": dict(self.tool_outcomes),
+                "tool_duration_samples": self.tool_duration_samples,
+                "tool_duration_total_ms": self.tool_duration_total_ns / 1_000_000,
                 "system_model_calls": {kind: dict(counts) for kind, counts in self.system_model_calls.items()},
             }
 
@@ -73,16 +94,43 @@ def _stats(store: ExtensionData) -> ExampleStats:
 
 
 class ExampleMiddleware(AgentMiddleware):
+    @contextmanager
+    def _observe(self, request: ToolCallRequest) -> Iterator[None]:
+        task_store = task_store_from_runtime(getattr(request, "runtime", None))
+        task_stats = task_store.get(ExampleStats) if task_store is not None else None
+        if task_stats is None:
+            yield
+            return
+        task_stats.note_tool_call()
+        started = monotonic_ns()
+        outcome = "returned"
+        try:
+            yield
+        except CancelledError:
+            outcome = "cancelled"
+            raise
+        except BaseException:
+            # Includes graph interrupts; observation must not consume control flow.
+            outcome = "raised"
+            raise
+        finally:
+            task_stats.note_tool_outcome(outcome, monotonic_ns() - started)
+
+    def wrap_tool_call(
+        self,
+        request: ToolCallRequest,
+        handler: Callable[[ToolCallRequest], Any],
+    ) -> Any:
+        with self._observe(request):
+            return handler(request)
+
     async def awrap_tool_call(
         self,
         request: ToolCallRequest,
         handler: Callable[[ToolCallRequest], Awaitable[Any]],
     ) -> Any:
-        task_store = task_store_from_runtime(getattr(request, "runtime", None))
-        task_stats = task_store.get(ExampleStats) if task_store is not None else None
-        if task_stats is not None:
-            task_stats.note_tool_call()
-        return await handler(request)
+        with self._observe(request):
+            return await handler(request)
 
 
 class ExampleMiddlewareContributor:
@@ -117,10 +165,8 @@ class ExampleTaskLifecycle:
         outcome: TaskOutcome,
     ) -> None:
         task_stats = task_store.remove(ExampleStats)
-        _stats(app_store).absorb_task(
-            task_stats.task_tool_calls() if task_stats is not None else 0,
-            outcome,
-        )
+        if task_stats is not None:
+            _stats(app_store).absorb_task(task_stats, outcome)
 
 
 class ExampleSystemObserver:
diff --git a/examples/deerflow-extension-example/tests/test_plugin.py b/examples/deerflow-extension-example/tests/test_plugin.py
index 7707d75ef6..95b2c8f142 100644
--- a/examples/deerflow-extension-example/tests/test_plugin.py
+++ b/examples/deerflow-extension-example/tests/test_plugin.py
@@ -3,6 +3,7 @@ from __future__ import annotations
 import asyncio
 from dataclasses import dataclass, field
 from typing import Any
+from unittest.mock import patch
 
 from deerflow_extension_api import (
     EXTENSION_TASK_STORE_KEY,
@@ -25,6 +26,9 @@ from deerflow_extension_example import install
 
 
 class FakeRegistry:
+    def plugin(self, contribution: Any) -> bool:
+        return False
+
     def __init__(self) -> None:
         self.middleware_contributors: list[Any] = []
         self.task_lifecycle_contributors: list[Any] = []
@@ -158,7 +162,8 @@ def test_registered_contributions_publish_one_shared_stats_snapshot() -> None:
             after_stop.status_code,
         )
 
-    before_start, status_code, body, after_stop = asyncio.run(exercise_contributions())
+    with patch("deerflow_extension_example.plugin.monotonic_ns", side_effect=[0, 10_000_000]):
+        before_start, status_code, body, after_stop = asyncio.run(exercise_contributions())
 
     assert before_start == 503
     assert status_code == 200
@@ -169,5 +174,8 @@ def test_registered_contributions_publish_one_shared_stats_snapshot() -> None:
         "host_policy": {"max_subagents_per_run": 6},
         "tasks": {"completed": 1},
         "tool_calls": 1,
+        "tool_outcomes": {"returned": 1, "raised": 0, "cancelled": 0},
+        "tool_duration_samples": 1,
+        "tool_duration_total_ms": 10.0,
         "system_model_calls": {"title": {"calls": 1, "errors": 1}},
     }
diff --git a/examples/deerflow-extension-example/tests/test_tool_stats.py b/examples/deerflow-extension-example/tests/test_tool_stats.py
new file mode 100644
index 0000000000..f80cdfc06f
--- /dev/null
+++ b/examples/deerflow-extension-example/tests/test_tool_stats.py
@@ -0,0 +1,221 @@
+from __future__ import annotations
+
+import asyncio
+from concurrent.futures import ThreadPoolExecutor
+from threading import Barrier
+from types import SimpleNamespace
+from unittest.mock import patch
+
+import pytest
+from deerflow_extension_api import EXTENSION_TASK_STORE_KEY, ExtensionData, TaskInfo, TaskOutcome
+from langchain_core.messages import ToolMessage
+from langgraph.errors import GraphInterrupt
+
+from deerflow_extension_example.plugin import ExampleMiddleware, ExampleStats, ExampleTaskLifecycle
+
+
+def task_context():
+    app = ExtensionData("app")
+    task = ExtensionData("task")
+    info = TaskInfo(task_id="task", run_id="run", thread_id="thread", kind="lead")
+    lifecycle = ExampleTaskLifecycle()
+    asyncio.run(lifecycle.on_task_start(app, task, info))
+    request = SimpleNamespace(runtime=SimpleNamespace(context={EXTENSION_TASK_STORE_KEY: task}))
+    return app, task, info, lifecycle, request
+
+
+@pytest.mark.parametrize("asynchronous", [False, True])
+@pytest.mark.parametrize("outcome", ["returned", "raised", "interrupt"])
+def test_preserves_result_exception_and_single_invocation(asynchronous, outcome):
+    app, task, info, lifecycle, request = task_context()
+    result = ToolMessage(content="tool reported an error", tool_call_id="call", status="error")
+    error = GraphInterrupt(()) if outcome == "interrupt" else ValueError("tool failed")
+    calls = []
+
+    def handler(received):
+        calls.append(received)
+        if outcome != "returned":
+            raise error
+        return result
+
+    async def async_handler(received):
+        return handler(received)
+
+    def invoke():
+        middleware = ExampleMiddleware()
+        if asynchronous:
+            return asyncio.run(middleware.awrap_tool_call(request, async_handler))
+        return middleware.wrap_tool_call(request, handler)
+
+    with patch("deerflow_extension_example.plugin.monotonic_ns", side_effect=[0, 10_000_000]):
+        if outcome == "returned":
+            assert invoke() is result
+        else:
+            with pytest.raises(type(error)) as caught:
+                invoke()
+            assert caught.value is error
+    assert len(calls) == 1 and calls[0] is request
+    asyncio.run(lifecycle.on_task_stop(app, task, info, TaskOutcome.COMPLETED))
+    snapshot = app.get(ExampleStats).snapshot()
+    assert snapshot["tool_calls"] == 1
+    assert snapshot["tool_outcomes"] == {"returned": int(outcome == "returned"), "raised": int(outcome != "returned"), "cancelled": 0}
+    assert snapshot["tool_duration_samples"] == 1
+    assert snapshot["tool_duration_total_ms"] == 10.0
+
+
+def test_actual_task_cancellation_propagates_and_is_counted():
+    app, task, info, lifecycle, request = task_context()
+    errors = []
+    calls = []
+
+    async def exercise():
+        entered = asyncio.Event()
+
+        async def handler(received):
+            calls.append(received)
+            entered.set()
+            try:
+                await asyncio.Future()
+            except asyncio.CancelledError as error:
+                errors.append(error)
+                raise
+
+        running = asyncio.create_task(ExampleMiddleware().awrap_tool_call(request, handler))
+        await entered.wait()
+        running.cancel()
+        with pytest.raises(asyncio.CancelledError) as caught:
+            await running
+        assert caught.value is errors[0]
+        assert running.cancelled()
+        await lifecycle.on_task_stop(app, task, info, TaskOutcome.ABORTED)
+
+    with patch("deerflow_extension_example.plugin.monotonic_ns", side_effect=[0, 20_000_000]):
+        asyncio.run(exercise())
+    assert len(calls) == 1 and calls[0] is request
+    snapshot = app.get(ExampleStats).snapshot()
+    assert snapshot["tool_outcomes"] == {"returned": 0, "raised": 0, "cancelled": 1}
+    assert snapshot["tool_duration_samples"] == 1
+    assert snapshot["tool_duration_total_ms"] == 20.0
+
+
+@pytest.mark.parametrize("asynchronous", [False, True])
+@pytest.mark.parametrize("scope", ["no-runtime", "no-store", "not-started"])
+def test_missing_task_scope_passes_through(asynchronous, scope):
+    request = SimpleNamespace()
+    if scope != "no-runtime":
+        request.runtime = SimpleNamespace(context={})
+    if scope == "not-started":
+        request.runtime.context[EXTENSION_TASK_STORE_KEY] = ExtensionData("unused")
+    calls = []
+    result = object()
+
+    def handler(received):
+        calls.append(received)
+        return result
+
+    async def async_handler(received):
+        return handler(received)
+
+    middleware = ExampleMiddleware()
+    if asynchronous:
+        assert asyncio.run(middleware.awrap_tool_call(request, async_handler)) is result
+    else:
+        assert middleware.wrap_tool_call(request, handler) is result
+    assert len(calls) == 1 and calls[0] is request
+
+
+def test_concurrent_sync_calls_and_duplicate_finalization():
+    app, task, info, lifecycle, request = task_context()
+    barrier = Barrier(8)
+
+    def handler(received):
+        assert received is request
+        barrier.wait(timeout=10)
+        return received
+
+    def invoke(_):
+        assert ExampleMiddleware().wrap_tool_call(request, handler) is request
+
+    # A constant clock also verifies that zero durations still produce samples.
+    with patch("deerflow_extension_example.plugin.monotonic_ns", return_value=42):
+        with ThreadPoolExecutor(max_workers=8) as pool:
+            list(pool.map(invoke, range(8)))
+    assert app.get(ExampleStats) is None
+
+    def finalize(_):
+        asyncio.run(lifecycle.on_task_stop(app, task, info, TaskOutcome.COMPLETED))
+
+    with ThreadPoolExecutor(max_workers=4) as pool:
+        list(pool.map(finalize, range(4)))
+    snapshot = app.get(ExampleStats).snapshot()
+    assert snapshot["tasks"] == {"completed": 1}
+    assert snapshot["tool_calls"] == 8
+    assert snapshot["tool_outcomes"] == {"returned": 8, "raised": 0, "cancelled": 0}
+    assert snapshot["tool_duration_samples"] == 8
+    assert snapshot["tool_duration_total_ms"] == 0.0
+    snapshot["tool_outcomes"]["returned"] = -1
+    assert app.get(ExampleStats).snapshot()["tool_outcomes"]["returned"] == 8
+
+
+def test_overlapping_async_calls_merge_outcomes_and_elapsed_time():
+    app, task, info, lifecycle, request = task_context()
+
+    async def exercise():
+        ready = asyncio.Event()
+        entered = 0
+
+        async def handler(_):
+            nonlocal entered
+            entered += 1
+            number = entered
+            if entered == 3:
+                ready.set()
+            await ready.wait()
+            if number == 2:
+                raise ValueError("failed")
+            return number
+
+        results = await asyncio.gather(*(ExampleMiddleware().awrap_tool_call(request, handler) for _ in range(3)), return_exceptions=True)
+        assert sum(isinstance(result, ValueError) for result in results) == 1
+        await lifecycle.on_task_stop(app, task, info, TaskOutcome.COMPLETED)
+
+    # Three starts at zero, then completions after 10, 20 and 30 milliseconds.
+    with patch("deerflow_extension_example.plugin.monotonic_ns", side_effect=[0, 0, 0, 10_000_000, 20_000_000, 30_000_000]):
+        asyncio.run(exercise())
+    snapshot = app.get(ExampleStats).snapshot()
+    assert snapshot["tool_calls"] == 3
+    assert snapshot["tool_outcomes"] == {"returned": 2, "raised": 1, "cancelled": 0}
+    assert snapshot["tool_duration_samples"] == 3
+    assert snapshot["tool_duration_total_ms"] == 60.0
+
+
+def test_multiple_task_stores_merge_once_and_unstarted_stop_is_ignored():
+    app, task, info, lifecycle, request = task_context()
+    second = ExtensionData("second")
+    unstarted = ExtensionData("unstarted")
+
+    async def exercise():
+        await lifecycle.on_task_stop(app, unstarted, info, TaskOutcome.FAILED)
+        assert app.get(ExampleStats) is None
+        await lifecycle.on_task_start(app, second, info)
+
+        async def handler(_):
+            return None
+
+        await ExampleMiddleware().awrap_tool_call(request, handler)
+        await lifecycle.on_task_stop(app, task, info, TaskOutcome.COMPLETED)
+        first_snapshot = app.get(ExampleStats).snapshot()
+        await lifecycle.on_task_stop(app, task, info, TaskOutcome.FAILED)
+        assert app.get(ExampleStats).snapshot() == first_snapshot
+        second_request = SimpleNamespace(runtime=SimpleNamespace(context={EXTENSION_TASK_STORE_KEY: second}))
+        await ExampleMiddleware().awrap_tool_call(second_request, handler)
+        await lifecycle.on_task_stop(app, second, info, TaskOutcome.ABORTED)
+
+    with patch("deerflow_extension_example.plugin.monotonic_ns", side_effect=[0, 10_000_000, 0, 20_000_000]):
+        asyncio.run(exercise())
+    snapshot = app.get(ExampleStats).snapshot()
+    assert snapshot["tasks"] == {"completed": 1, "aborted": 1}
+    assert snapshot["tool_calls"] == 2
+    assert snapshot["tool_outcomes"] == {"returned": 2, "raised": 0, "cancelled": 0}
+    assert snapshot["tool_duration_samples"] == 2
+    assert snapshot["tool_duration_total_ms"] == 30.0