diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 1aade881745f21..43da804b62beb1 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -831,7 +831,9 @@ Instances of the :class:`Popen` class have the following methods:
 
    If the process does not terminate after *timeout* seconds, a
    :exc:`TimeoutExpired` exception will be raised.  Catching this exception and
-   retrying communication will not lose any output.
+   retrying communication will not lose any output.  Supplying *input* to a
+   subsequent post-timeout :meth:`communicate` call is in undefined behavior
+   and may become an error in the future.
 
    The child process is not killed if the timeout expires, so in order to
    cleanup properly a well-behaved application should kill the child process and
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 79251bd5310223..99e2d0755d7e46 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -2077,6 +2077,10 @@ def _communicate(self, input, endtime, orig_timeout):
                     self.stdin.flush()
                 except BrokenPipeError:
                     pass  # communicate() must ignore BrokenPipeError.
+                except ValueError:
+                    # ignore ValueError: I/O operation on closed file.
+                    if not self.stdin.closed:
+                        raise
                 if not input:
                     try:
                         self.stdin.close()
@@ -2102,10 +2106,13 @@ def _communicate(self, input, endtime, orig_timeout):
             self._save_input(input)
 
             if self._input:
-                input_view = memoryview(self._input)
+                if not isinstance(self._input, memoryview):
+                    input_view = memoryview(self._input)
+                else:
+                    input_view = self._input.cast("b")  # byte input required
 
             with _PopenSelector() as selector:
-                if self.stdin and input:
+                if self.stdin and not self.stdin.closed and self._input:
                     selector.register(self.stdin, selectors.EVENT_WRITE)
                 if self.stdout and not self.stdout.closed:
                     selector.register(self.stdout, selectors.EVENT_READ)
@@ -2138,7 +2145,7 @@ def _communicate(self, input, endtime, orig_timeout):
                                 selector.unregister(key.fileobj)
                                 key.fileobj.close()
                             else:
-                                if self._input_offset >= len(self._input):
+                                if self._input_offset >= len(input_view):
                                     selector.unregister(key.fileobj)
                                     key.fileobj.close()
                         elif key.fileobj in (self.stdout, self.stderr):
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index f0e350c71f60ea..2d717f985a3ac3 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -957,6 +957,48 @@ def test_communicate(self):
         self.assertEqual(stdout, b"banana")
         self.assertEqual(stderr, b"pineapple")
 
+    def test_communicate_memoryview_input(self):
+        # Test memoryview input with byte elements
+        test_data = b"Hello, memoryview!"
+        mv = memoryview(test_data)
+        p = subprocess.Popen([sys.executable, "-c",
+                              'import sys; sys.stdout.write(sys.stdin.read())'],
+                             stdin=subprocess.PIPE,
+                             stdout=subprocess.PIPE)
+        self.addCleanup(p.stdout.close)
+        self.addCleanup(p.stdin.close)
+        (stdout, stderr) = p.communicate(mv)
+        self.assertEqual(stdout, test_data)
+        self.assertIsNone(stderr)
+
+    def test_communicate_memoryview_input_nonbyte(self):
+        # Test memoryview input with non-byte elements (e.g., int32)
+        # This tests the fix for gh-134453 where non-byte memoryviews
+        # had incorrect length tracking on POSIX
+        import array
+        # Create an array of 32-bit integers that's large enough to trigger
+        # the chunked writing behavior (> PIPE_BUF)
+        pipe_buf = getattr(select, 'PIPE_BUF', 512)
+        # Each 'i' element is 4 bytes, so we need more than pipe_buf/4 elements
+        # Add some extra to ensure we exceed the buffer size
+        num_elements = pipe_buf + 1
+        test_array = array.array('i', [0x64306f66 for _ in range(num_elements)])
+        expected_bytes = test_array.tobytes()
+        mv = memoryview(test_array)
+
+        p = subprocess.Popen([sys.executable, "-c",
+                              'import sys; '
+                              'data = sys.stdin.buffer.read(); '
+                              'sys.stdout.buffer.write(data)'],
+                             stdin=subprocess.PIPE,
+                             stdout=subprocess.PIPE)
+        self.addCleanup(p.stdout.close)
+        self.addCleanup(p.stdin.close)
+        (stdout, stderr) = p.communicate(mv)
+        self.assertEqual(stdout, expected_bytes,
+                         msg=f"{len(stdout)=} =? {len(expected_bytes)=}")
+        self.assertIsNone(stderr)
+
     def test_communicate_timeout(self):
         p = subprocess.Popen([sys.executable, "-c",
                               'import sys,os,time;'
@@ -1062,6 +1104,19 @@ def test_writes_before_communicate(self):
         self.assertEqual(stdout, b"bananasplit")
         self.assertEqual(stderr, b"")
 
+    def test_communicate_stdin_closed_before_call(self):
+        # gh-70560, gh-74389: stdin.close() before communicate()
+        # should not raise ValueError from stdin.flush()
+        with subprocess.Popen([sys.executable, "-c",
+                               'import sys; sys.exit(0)'],
+                              stdin=subprocess.PIPE,
+                              stdout=subprocess.PIPE,
+                              stderr=subprocess.PIPE) as p:
+            p.stdin.close()  # Close stdin before communicate
+            # This should not raise ValueError
+            (stdout, stderr) = p.communicate()
+            self.assertEqual(p.returncode, 0)
+
     def test_universal_newlines_and_text(self):
         args = [
             sys.executable, "-c",
@@ -1643,6 +1698,40 @@ def test_wait_negative_timeout(self):
 
             self.assertEqual(proc.wait(), 0)
 
+    def test_post_timeout_communicate_sends_input(self):
+        """GH-141473 regression test; the stdin pipe must close"""
+        with subprocess.Popen(
+                [sys.executable, "-uc", """\
+import sys
+while c := sys.stdin.read(512):
+    sys.stdout.write(c)
+print()
+"""],
+                stdin=subprocess.PIPE,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                text=True,
+        ) as proc:
+            try:
+                data = f"spam{'#'*4096}beans"
+                proc.communicate(
+                    input=data,
+                    timeout=0,
+                )
+            except subprocess.TimeoutExpired as exc:
+                pass
+            # Prior to the bugfix, this would hang as the stdin
+            # pipe to the child had not been closed.
+            try:
+                stdout, stderr = proc.communicate(timeout=15)
+            except subprocess.TimeoutExpired as exc:
+                self.fail("communicate() hung waiting on child process that should have seen its stdin pipe close and exit")
+            self.assertEqual(
+                    proc.returncode, 0,
+                    msg=f"STDERR:\n{stderr}\nSTDOUT:\n{stdout}")
+            self.assertStartsWith(stdout, "spam")
+            self.assertIn("beans", stdout)
+
 
 class RunFuncTestCase(BaseTestCase):
     def run_python(self, code, **kwargs):
diff --git a/Misc/NEWS.d/next/Library/2025-05-30-18-37-44.gh-issue-134453.kxkA-o.rst b/Misc/NEWS.d/next/Library/2025-05-30-18-37-44.gh-issue-134453.kxkA-o.rst
new file mode 100644
index 00000000000000..fee975ea70230c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-30-18-37-44.gh-issue-134453.kxkA-o.rst
@@ -0,0 +1,4 @@
+Fixed :func:`subprocess.Popen.communicate` ``input=`` handling of :class:`memoryview`
+instances that were non-byte shaped on POSIX platforms. Those are now properly
+cast to a byte shaped view instead of truncating the input.  Windows platforms
+did not have this bug.
diff --git a/Misc/NEWS.d/next/Library/2025-11-27-20-16-38.gh-issue-141473.Wq4xVN.rst b/Misc/NEWS.d/next/Library/2025-11-27-20-16-38.gh-issue-141473.Wq4xVN.rst
new file mode 100644
index 00000000000000..f6aa592cefda35
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-11-27-20-16-38.gh-issue-141473.Wq4xVN.rst
@@ -0,0 +1,4 @@
+When :meth:`subprocess.Popen.communicate` was called with *input* and a
+*timeout* and is called for a second time after a
+:exc:`~subprocess.TimeoutExpired` exception before the process has died, it
+should no longer hang.
diff --git a/Misc/NEWS.d/next/Library/2025-11-29-04-20-44.gh-issue-74389.pW3URj.rst b/Misc/NEWS.d/next/Library/2025-11-29-04-20-44.gh-issue-74389.pW3URj.rst
new file mode 100644
index 00000000000000..a9bf5f80d80c9f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-11-29-04-20-44.gh-issue-74389.pW3URj.rst
@@ -0,0 +1,3 @@
+When the stdin being used by a :class:`subprocess.Popen` instance is closed,
+this is now ignored in :meth:`subprocess.Popen.communicate` instead of
+leaving the class in an inconsistent state.