From dd0c19862b0e0f500a322894645c008047d10df1 Mon Sep 17 00:00:00 2001
From: root <vaibhav.satheesh03@gmail.com>
Date: Sun, 24 May 2026 01:31:06 +0530
Subject: [PATCH 1/2] gh-132578: Add regression test ensuring Thread subclasses
 can safely define _handle

---
 Lib/test/test_threading.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 3d01804513bde98..ba8084630f38490 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -2847,5 +2847,25 @@ def run_last():
                 err.decode())
 
 
+class ThreadHandleRegressionTest(unittest.TestCase):
+    def test_subclass_can_define_handle(self):
+        # gh-132578: Ensure third-party libraries overriding or defining
+        # a custom `_handle` attribute/method don't clash with CPython internal implementation details.
+        class CustomThread(threading.Thread):
+            def __init__(self):
+                super().__init__()
+                self._handle = "custom_third_party_handle_value"
+
+            def run(self):
+                pass
+
+        t = CustomThread()
+        t.start()
+        t.join()
+        
+        # Assert that our custom handle parameter was preserved and did not break the thread run lifecycle
+        self.assertEqual(t._handle, "custom_third_party_handle_value")
+
+
 if __name__ == "__main__":
     unittest.main()

From 81e7a6c2a8305068dc696a3e8e850865dff57a4c Mon Sep 17 00:00:00 2001
From: root <vaibhav.satheesh03@gmail.com>
Date: Sun, 24 May 2026 01:41:20 +0530
Subject: [PATCH 2/2] gh-132578: Add news blurb to Library and fix test layout
 spacing

---
 Lib/test/test_threading.py                                      | 2 +-
 .../next/Library/2026-05-24-01-30-00.gh-issue-132578.aBcDeF.rst | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2026-05-24-01-30-00.gh-issue-132578.aBcDeF.rst

diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index ba8084630f38490..71756d64068be5d 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -2862,7 +2862,7 @@ def run(self):
         t = CustomThread()
         t.start()
         t.join()
-        
+
         # Assert that our custom handle parameter was preserved and did not break the thread run lifecycle
         self.assertEqual(t._handle, "custom_third_party_handle_value")
 
diff --git a/Misc/NEWS.d/next/Library/2026-05-24-01-30-00.gh-issue-132578.aBcDeF.rst b/Misc/NEWS.d/next/Library/2026-05-24-01-30-00.gh-issue-132578.aBcDeF.rst
new file mode 100644
index 000000000000000..c4c926a97439958
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-24-01-30-00.gh-issue-132578.aBcDeF.rst
@@ -0,0 +1 @@
+Add a regression test to ensure that custom user-defined subclasses of threading.Thread can safely define or override a custom _handle attribute without colliding with internal state-tracking implementations.