gh-159323: PyREPL on Windows should exit when STDIN is NUL

Lib/_pyrepl/main.py

@@ -9,7 +9,14 @@
 try:
     if sys.platform == "win32" and sys.getwindowsversion().build < 10586:
         raise RuntimeError("Windows 10 TH2 or later required")
-    if not os.isatty(sys.stdin.fileno()):
+    stdin_fd = sys.stdin.fileno()
+    if (
+        not os.isatty(stdin_fd)
+        or (
+            sys.platform == "win32"
+            and os.device_encoding(stdin_fd) is None
+        )
+    ):
         raise OSError(errno.ENOTTY, "tty required", "stdin")
     from .simple_interact import check
     if err := check():

Lib/test/test_pyrepl/test_pyrepl.py

@@ -1099,6 +1099,23 @@ def test_get_completions_sorts_colored_matches_by_visible_text(self):
         )
 
 
+class TestPyReplMain(TestCase):
+    @skipUnless(has_subprocess_support, "test requires subprocess support")
+    @skipUnless(sys.platform == "win32", "Windows-specific test")
+    def test_nul_stdin_exits_cleanly(self):
+        proc = subprocess.run(
+            [sys.executable, "-I"],
+            stdin=subprocess.DEVNULL,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.PIPE,
+            text=True,
+            timeout=SHORT_TIMEOUT,
+        )
+
+        self.assertEqual(proc.returncode, 0, proc.stderr)
+        self.assertIn("tty required", proc.stderr)
+
+
 class TestPyReplReadlineSetup(TestCase):
     def test_setup_ignores_basic_completer_env_when_env_is_disabled(self):
         class FakeFancyCompleter:

Misc/NEWS.d/next/Library/2026-10-13-21-57-48.gh-issue-159323.9S_NE2.rst

@@ -0,0 +1 @@
+PyREPL on Windows now exits when ``NUL`` is passed as ``stdin`` instead of showing stream of tracebacks.