From 0cbbda24fb2919c21e803580c4c5fe447bab3fed Mon Sep 17 00:00:00 2001
From: Gyanu <gyanum.ug20.cse@nitp.ac.in>
Date: Sun, 30 Aug 2026 11:40:36 +0530
Subject: [PATCH 1/3] Detect asyncio when a loop is running but there is no
 current Task.

Twisted's asyncioreactor (and call_soon callbacks) run on the asyncio loop
without an asyncio.Task, so current_task() is None and sniffio raised
AsyncLibraryNotFoundError.
---
 sniffio/_impl.py               |  9 +++++++++
 sniffio/_tests/test_sniffio.py | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/sniffio/_impl.py b/sniffio/_impl.py
index c1a7bbf..a1eb30f 100644
--- a/sniffio/_impl.py
+++ b/sniffio/_impl.py
@@ -83,6 +83,15 @@ async def generic_sleep(seconds):
                 return "asyncio"
         except RuntimeError:
             pass
+        else:
+            # Running loop, but not inside a Task (Twisted asyncioreactor,
+            # call_soon callbacks, etc.)
+            try:
+                asyncio.get_running_loop()
+            except RuntimeError:
+                pass
+            else:
+                return "asyncio"
 
     # Sniff for curio (for now)
     if 'curio' in sys.modules:
diff --git a/sniffio/_tests/test_sniffio.py b/sniffio/_tests/test_sniffio.py
index 02945a9..b11da3c 100644
--- a/sniffio/_tests/test_sniffio.py
+++ b/sniffio/_tests/test_sniffio.py
@@ -58,6 +58,25 @@ async def this_is_asyncio():
         current_async_library()
 
 
+def test_asyncio_running_loop_without_task():
+    import asyncio
+
+    result = []
+
+    def sync_cb():
+        result.append(current_async_library())
+        loop.stop()
+
+    loop = asyncio.new_event_loop()
+    try:
+        loop.call_soon(sync_cb)
+        loop.run_forever()
+    finally:
+        loop.close()
+
+    assert result == ["asyncio"]
+
+
 @pytest.mark.skipif(
     sys.version_info >= (3, 12),
     reason=

From 98a876b4f8a28a168a61172b5fd81c65e7b1f114 Mon Sep 17 00:00:00 2001
From: Gyanu <gyanum.ug20.cse@nitp.ac.in>
Date: Tue, 1 Sep 2026 11:10:50 +0530
Subject: [PATCH 2/3] Stop the loop if the asyncio fallback test fails.

---
 newsfragments/51.bugfix.rst    | 3 +++
 sniffio/_tests/test_sniffio.py | 6 ++++--
 2 files changed, 7 insertions(+), 2 deletions(-)
 create mode 100644 newsfragments/51.bugfix.rst

diff --git a/newsfragments/51.bugfix.rst b/newsfragments/51.bugfix.rst
new file mode 100644
index 0000000..8bd9665
--- /dev/null
+++ b/newsfragments/51.bugfix.rst
@@ -0,0 +1,3 @@
+``current_async_library`` now reports ``asyncio`` when an event loop is
+running but there is no current Task, such as in ``call_soon`` callbacks
+and Twisted's asyncioreactor.
diff --git a/sniffio/_tests/test_sniffio.py b/sniffio/_tests/test_sniffio.py
index b11da3c..a99f5e8 100644
--- a/sniffio/_tests/test_sniffio.py
+++ b/sniffio/_tests/test_sniffio.py
@@ -64,8 +64,10 @@ def test_asyncio_running_loop_without_task():
     result = []
 
     def sync_cb():
-        result.append(current_async_library())
-        loop.stop()
+        try:
+            result.append(current_async_library())
+        finally:
+            loop.stop()
 
     loop = asyncio.new_event_loop()
     try:

From 84c51c9a073bae30faa1387741708d94a9637e5a Mon Sep 17 00:00:00 2001
From: Gyanu Mayank <gyanum.ug20.cse@nitp.ac.in>
Date: Tue, 1 Sep 2026 22:24:55 +0530
Subject: [PATCH 3/3] Detect asyncio from get_running_loop only.

current_task() already raises outside a loop, so probing it first is
strictly slower and still needs the get_running_loop fallback for
call_soon callbacks.
---
 newsfragments/51.bugfix.rst |  3 ++-
 sniffio/_impl.py            | 16 ++--------------
 2 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/newsfragments/51.bugfix.rst b/newsfragments/51.bugfix.rst
index 8bd9665..8677649 100644
--- a/newsfragments/51.bugfix.rst
+++ b/newsfragments/51.bugfix.rst
@@ -1,3 +1,4 @@
 ``current_async_library`` now reports ``asyncio`` when an event loop is
 running but there is no current Task, such as in ``call_soon`` callbacks
-and Twisted's asyncioreactor.
+and Twisted's asyncioreactor. Detection uses ``asyncio.get_running_loop()``
+only; ``current_task()`` is a slower subset of the same check.
diff --git a/sniffio/_impl.py b/sniffio/_impl.py
index a1eb30f..64d311e 100644
--- a/sniffio/_impl.py
+++ b/sniffio/_impl.py
@@ -75,23 +75,11 @@ async def generic_sleep(seconds):
     if "asyncio" in sys.modules:
         import asyncio
         try:
-            current_task = asyncio.current_task  # type: ignore[attr-defined]
-        except AttributeError:
-            current_task = asyncio.Task.current_task  # type: ignore[attr-defined]
-        try:
-            if current_task() is not None:
-                return "asyncio"
+            asyncio.get_running_loop()
         except RuntimeError:
             pass
         else:
-            # Running loop, but not inside a Task (Twisted asyncioreactor,
-            # call_soon callbacks, etc.)
-            try:
-                asyncio.get_running_loop()
-            except RuntimeError:
-                pass
-            else:
-                return "asyncio"
+            return "asyncio"
 
     # Sniff for curio (for now)
     if 'curio' in sys.modules: