From 7500655a6883d4eb448ab1b727a188d5e00e3468 Mon Sep 17 00:00:00 2001
From: "Yves.Duprat" <yduprat@gmail.com>
Date: Fri, 21 Aug 2026 00:21:01 +0200
Subject: [PATCH 1/3] Initial commit - Update `Task.__step` , - Update
 `_asyncio` module on the corresponding function, - Add a
 `test_step_dont_swallow_systemexit`  test in  `test_task.py` file.

---
 Lib/asyncio/tasks.py                |  6 +++++-
 Lib/test/test_asyncio/test_tasks.py | 19 +++++++++++++++++++
 Modules/_asynciomodule.c            |  9 +++++++--
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 7889d4793a5dec3..524be6224dc1552 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -268,7 +268,11 @@ def __step(self, exc=None):
             raise exceptions.InvalidStateError(
                 f'__step(): already done: {self!r}, {exc!r}')
         if self._must_cancel:
-            if not isinstance(exc, exceptions.CancelledError):
+            if not isinstance(exc, (exceptions.CancelledError,
+                                   # gh-108549: do not swallow these
+                                   # 2 exceptions
+                                   SystemExit, KeyboardInterrupt)
+                              ):
                 exc = self._make_cancelled_error()
             self._must_cancel = False
         self._fut_waiter = None
diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py
index 9c111da8c27f162..8d11238fbd4449a 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -1891,6 +1891,25 @@ async def notmuch():
             self.loop.run_until_complete(task),
             'ko')
 
+    def test_step_dont_swallow_systemexit(self):
+        # gh-108549: do not swallow
+        # KeybordInterrupt too.
+        async def sub_task():
+            raise SystemExit
+
+        async def gather():
+            try:
+                await asyncio.gather(sub_task(),)
+            except SystemExit:
+                pass
+
+        t = self.new_task(self.loop, gather())
+        with self.assertRaises(SystemExit):
+            self.loop.run_until_complete(t)
+        t.cancel()
+        self.loop.run_until_complete(t)
+        self.assertTrue(t.done())
+
     def test_step_result_future(self):
         # If coroutine returns future, task waits on this future.
 
diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
index 41384b388142ccc..03ea94a6c3ded36 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -3067,8 +3067,13 @@ task_step_impl(asyncio_state *state, TaskObj *task, PyObject *exc)
     if (task->task_must_cancel) {
         assert(exc != Py_None);
 
-        if (!exc || !PyErr_GivenExceptionMatches(exc, state->asyncio_CancelledError)) {
-            /* exc was not a CancelledError */
+        if (!exc ||
+            (!PyErr_GivenExceptionMatches(exc, state->asyncio_CancelledError) &&
+            !PyErr_GivenExceptionMatches(exc, PyExc_KeyboardInterrupt) &&
+            !PyErr_GivenExceptionMatches(exc, PyExc_SystemExit))
+            ) {
+            /* exc was not a CancelledError,
+            neither SystemExit or KeyboardInterrupt (see gh-108549 )*/
             exc = create_cancelled_error(state, (FutureObj*)task);
 
             if (!exc) {

From d66b44f80a18a41a88d48438b714bac1ed1c46ff Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Mon, 24 Aug 2026 14:28:56 +0000
Subject: [PATCH 2/3] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst  | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst

diff --git a/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst b/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
new file mode 100644
index 000000000000000..8d18a14d33a5e40
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
@@ -0,0 +1 @@
+In ``asyncio.Task.__step``, do not cancel the current task when a ``SystemExit``(or a ``KeyboardInterrupt``) exception was just raised.

From a89d0d5c02edee7770359fab43fcf5df43284262 Mon Sep 17 00:00:00 2001
From: "Yves.Duprat" <yduprat@gmail.com>
Date: Mon, 24 Aug 2026 16:42:30 +0200
Subject: [PATCH 3/3] Fix nits in news file.

---
 .../next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst b/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
index 8d18a14d33a5e40..c97425a91921f54 100644
--- a/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
+++ b/Misc/NEWS.d/next/Library/2026-08-24-14-28-47.gh-issue-108549.XZ34WD.rst
@@ -1 +1 @@
-In ``asyncio.Task.__step``, do not cancel the current task when a ``SystemExit``(or a ``KeyboardInterrupt``) exception was just raised.
+In ``asyncio.Task.__step``, do not cancel the current task when a ``SystemExit`` (or a ``KeyboardInterrupt``) exception was just raised.