From ba99f2e455f29a5b3bd2f12f85e0b8985ec49bb2 Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Sat, 28 Dec 2024 13:00:59 -0800
Subject: [PATCH 1/8] Make _contextvars a builtin module.

---
 Makefile.pre.in                                             | 1 +
 Modules/Setup                                               | 1 -
 Modules/Setup.stdlib.in                                     | 1 -
 Modules/config.c.in                                         | 4 ++++
 PCbuild/pythoncore.vcxproj                                  | 2 +-
 PCbuild/pythoncore.vcxproj.filters                          | 6 +++---
 Modules/_contextvarsmodule.c => Python/_contextvars.c       | 2 +-
 .../clinic/_contextvars.c.h                                 | 0
 configure.ac                                                | 1 -
 9 files changed, 10 insertions(+), 8 deletions(-)
 rename Modules/_contextvarsmodule.c => Python/_contextvars.c (97%)
 rename Modules/clinic/_contextvarsmodule.c.h => Python/clinic/_contextvars.c.h (100%)

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 67acf0fc520087..18484a42abb6e8 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -420,6 +420,7 @@ PARSER_HEADERS= \
 # Python
 
 PYTHON_OBJS=	\
+		Python/_contextvars.o \
 		Python/_warnings.o \
 		Python/Python-ast.o \
 		Python/Python-tokenize.o \
diff --git a/Modules/Setup b/Modules/Setup
index ddf39e0b966610..e01c7bb1a8a45e 100644
--- a/Modules/Setup
+++ b/Modules/Setup
@@ -132,7 +132,6 @@ PYTHONPATH=$(COREPYTHONPATH)
 
 #_asyncio _asynciomodule.c
 #_bisect _bisectmodule.c
-#_contextvars _contextvarsmodule.c
 #_csv _csv.c
 #_datetime _datetimemodule.c
 #_decimal _decimal/_decimal.c
diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 6bb05a06a3465d..174e8339083f7a 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -31,7 +31,6 @@
 @MODULE_ARRAY_TRUE@array arraymodule.c
 @MODULE__ASYNCIO_TRUE@_asyncio _asynciomodule.c
 @MODULE__BISECT_TRUE@_bisect _bisectmodule.c
-@MODULE__CONTEXTVARS_TRUE@_contextvars _contextvarsmodule.c
 @MODULE__CSV_TRUE@_csv _csv.c
 @MODULE__HEAPQ_TRUE@_heapq _heapqmodule.c
 @MODULE__JSON_TRUE@_json _json.c
diff --git a/Modules/config.c.in b/Modules/config.c.in
index c578cd103dc629..704f58506048a3 100644
--- a/Modules/config.c.in
+++ b/Modules/config.c.in
@@ -19,6 +19,7 @@ extern PyObject* PyInit__imp(void);
 extern PyObject* PyInit_gc(void);
 extern PyObject* PyInit__ast(void);
 extern PyObject* PyInit__tokenize(void);
+extern PyObject* PyInit__contextvars(void);
 extern PyObject* _PyWarnings_Init(void);
 extern PyObject* PyInit__string(void);
 
@@ -45,6 +46,9 @@ struct _inittab _PyImport_Inittab[] = {
     /* This lives in gcmodule.c */
     {"gc", PyInit_gc},
 
+    /* This lives in Python/_contextvars.c */
+    {"_contextvars", PyInit__contextvars},
+
     /* This lives in _warnings.c */
     {"_warnings", _PyWarnings_Init},
 
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 9ebf58ae8a9bc4..ef6dbf9f8e4222 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -423,7 +423,6 @@
     </ClCompile>
     <ClCompile Include="..\Modules\_codecsmodule.c" />
     <ClCompile Include="..\Modules\_collectionsmodule.c" />
-    <ClCompile Include="..\Modules\_contextvarsmodule.c" />
     <ClCompile Include="..\Modules\_csv.c" />
     <ClCompile Include="..\Modules\_functoolsmodule.c" />
     <ClCompile Include="..\Modules\_hacl\Hacl_Hash_MD5.c" />
@@ -570,6 +569,7 @@
     <ClCompile Include="..\PC\config.c" />
     <ClCompile Include="..\PC\msvcrtmodule.c" />
     <ClCompile Include="..\Python\pyhash.c" />
+    <ClCompile Include="..\Python\_contextvars.c" />
     <ClCompile Include="..\Python\_warnings.c" />
     <ClCompile Include="..\Python\asdl.c" />
     <ClCompile Include="..\Python\assemble.c" />
diff --git a/PCbuild/pythoncore.vcxproj.filters b/PCbuild/pythoncore.vcxproj.filters
index 6c76a6ab592a84..b661aad2019454 100644
--- a/PCbuild/pythoncore.vcxproj.filters
+++ b/PCbuild/pythoncore.vcxproj.filters
@@ -1262,6 +1262,9 @@
     <ClCompile Include="..\PC\msvcrtmodule.c">
       <Filter>PC</Filter>
     </ClCompile>
+    <ClCompile Include="..\Python\_contextvars.c">
+      <Filter>Python</Filter>
+    </ClCompile>
     <ClCompile Include="..\Python\_warnings.c">
       <Filter>Python</Filter>
     </ClCompile>
@@ -1526,9 +1529,6 @@
     <ClCompile Include="..\Objects\odictobject.c">
       <Filter>Objects</Filter>
     </ClCompile>
-    <ClCompile Include="..\Modules\_contextvarsmodule.c">
-      <Filter>Modules</Filter>
-    </ClCompile>
     <ClCompile Include="$(zlibDir)\adler32.c">
       <Filter>Modules\zlib</Filter>
     </ClCompile>
diff --git a/Modules/_contextvarsmodule.c b/Python/_contextvars.c
similarity index 97%
rename from Modules/_contextvarsmodule.c
rename to Python/_contextvars.c
index 3f96f07909b69a..0f8b8004c1af22 100644
--- a/Modules/_contextvarsmodule.c
+++ b/Python/_contextvars.c
@@ -1,6 +1,6 @@
 #include "Python.h"
 
-#include "clinic/_contextvarsmodule.c.h"
+#include "clinic/_contextvars.c.h"
 
 /*[clinic input]
 module _contextvars
diff --git a/Modules/clinic/_contextvarsmodule.c.h b/Python/clinic/_contextvars.c.h
similarity index 100%
rename from Modules/clinic/_contextvarsmodule.c.h
rename to Python/clinic/_contextvars.c.h
diff --git a/configure.ac b/configure.ac
index cf16e77f0a1503..ce10d518f24c6c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7775,7 +7775,6 @@ dnl always enabled extension modules
 PY_STDLIB_MOD_SIMPLE([array])
 PY_STDLIB_MOD_SIMPLE([_asyncio])
 PY_STDLIB_MOD_SIMPLE([_bisect])
-PY_STDLIB_MOD_SIMPLE([_contextvars])
 PY_STDLIB_MOD_SIMPLE([_csv])
 PY_STDLIB_MOD_SIMPLE([_heapq])
 PY_STDLIB_MOD_SIMPLE([_json])

From 6d00c2aeec9a0e222d8df6383acde2f707f33bf6 Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Fri, 20 Dec 2024 16:23:16 -0800
Subject: [PATCH 2/8] Add 'context' parameter to Thread.

* Add ``sys.flags.inherit_context``.
* Add ``-X inherit_context`` and :envvar:`PYTHON_INHERIT_CONTEXT`
---
 Doc/library/sys.rst                           | 15 ++++-
 Doc/library/threading.rst                     | 16 +++++-
 Doc/using/cmdline.rst                         | 19 +++++++
 Include/cpython/initconfig.h                  |  1 +
 Lib/test/test_capi/test_config.py             | 10 +++-
 Lib/test/test_context.py                      | 55 +++++++++++++++++++
 Lib/test/test_decimal.py                      |  7 ++-
 Lib/test/test_embed.py                        |  7 ++-
 Lib/test/test_sys.py                          |  5 +-
 Lib/threading.py                              | 24 +++++++-
 ...-01-06-10-55-41.gh-issue-128555.tAK_AY.rst | 16 ++++++
 Python/initconfig.c                           | 51 +++++++++++++++++
 Python/sysmodule.c                            |  2 +
 13 files changed, 216 insertions(+), 12 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 855237e0984972..43bda09323f557 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -535,7 +535,8 @@ always available. Unless explicitly noted otherwise, all variables are read-only
 .. data:: flags
 
    The :term:`named tuple` *flags* exposes the status of command line
-   flags. The attributes are read only.
+   flags.  Flags should only be accessed only by name and not by index.  The
+   attributes are read only.
 
    .. list-table::
 
@@ -594,6 +595,12 @@ always available. Unless explicitly noted otherwise, all variables are read-only
       * - .. attribute:: flags.warn_default_encoding
         - :option:`-X warn_default_encoding <-X>`
 
+      * - .. attribute:: flags.gil
+        - :option:`-X gil <-X>` and :envvar:`PYTHON_GIL`
+
+      * - .. attribute:: flags.inherit_context
+        - :option:`-X inherit_context <-X>` and :envvar:`PYTHON_INHERIT_CONTEXT`
+
    .. versionchanged:: 3.2
       Added ``quiet`` attribute for the new :option:`-q` flag.
 
@@ -620,6 +627,12 @@ always available. Unless explicitly noted otherwise, all variables are read-only
    .. versionchanged:: 3.11
       Added the ``int_max_str_digits`` attribute.
 
+   .. versionchanged:: 3.13
+      Added the ``gil`` attribute.
+
+   .. versionchanged:: 3.14
+      Added the ``inherit_context`` attribute.
+
 
 .. data:: float_info
 
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index 00511df32e4388..65e498aabb8016 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -334,7 +334,7 @@ since it is impossible to detect the termination of alien threads.
 
 
 .. class:: Thread(group=None, target=None, name=None, args=(), kwargs={}, *, \
-                  daemon=None)
+                  daemon=None, context=None)
 
    This constructor should always be called with keyword arguments.  Arguments
    are:
@@ -359,6 +359,17 @@ since it is impossible to detect the termination of alien threads.
    If ``None`` (the default), the daemonic property is inherited from the
    current thread.
 
+   *context* is the :class:`~contextvars.Context` value to use when starting
+   the thread.  The default value is ``None`` which indicates that the
+   :data:`sys.flags.inherit_context` flag controls the behaviour.  If
+   the flag is true, threads will start with a copy of the context of the
+   caller of :meth:`~Thread.start`.  If false, they will start with
+   an empty context.  To explicitly start with an empty context,
+   pass a new instance of :class:`~contextvars.Context()`.  To explicitly
+   start with a copy of the current context, pass the value from
+   :func:`~contextvars.copy_context()`. The flag defaults true on
+   free-threaded builds and false otherwise.
+
    If the subclass overrides the constructor, it must make sure to invoke the
    base class constructor (``Thread.__init__()``) before doing anything else to
    the thread.
@@ -369,6 +380,9 @@ since it is impossible to detect the termination of alien threads.
    .. versionchanged:: 3.10
       Use the *target* name if *name* argument is omitted.
 
+   .. versionchanged:: 3.14
+      Added the *context* parameter.
+
    .. method:: start()
 
       Start the thread's activity.
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index 2a59cf3f62d4c5..be5816f7c8d2b0 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -628,6 +628,15 @@ Miscellaneous options
 
      .. versionadded:: 3.13
 
+   * :samp:`-X inherit_context={0,1}` causes :class:`~threading.Thread`
+     to, by default, use a copy of context of of the caller of
+     ``Thread.start()`` when starting.  Otherwise, threads will start
+     with an empty context.  If unset, the value of this option defaults
+     to ``1`` on free-threaded builds and to ``0`` otherwise.  See also
+     :envvar:`PYTHON_INHERIT_CONTEXT`.
+
+     .. versionadded:: 3.14
+
    It also allows passing arbitrary values and retrieving them through the
    :data:`sys._xoptions` dictionary.
 
@@ -1221,6 +1230,16 @@ conflict.
 
    .. versionadded:: 3.13
 
+.. envvar:: PYTHON_INHERIT_CONTEXT
+
+   If this variable is set to ``1`` then :class:`~threading.Thread` will,
+   by default, use a copy of context of of the caller of ``Thread.start()``
+   when starting.  Otherwise, new threads will start with an empty context.
+   If unset, this variable defaults to ``1`` on free-threaded builds and to
+   ``0`` otherwise.  See also :option:`-X inherit_context<-X>`.
+
+   .. versionadded:: 3.14
+
 Debug-mode variables
 ~~~~~~~~~~~~~~~~~~~~
 
diff --git a/Include/cpython/initconfig.h b/Include/cpython/initconfig.h
index 8ef19f677066c2..d8edfa973b96f4 100644
--- a/Include/cpython/initconfig.h
+++ b/Include/cpython/initconfig.h
@@ -179,6 +179,7 @@ typedef struct PyConfig {
     int use_frozen_modules;
     int safe_path;
     int int_max_str_digits;
+    int inherit_context;
 #ifdef __APPLE__
     int use_system_logger;
 #endif
diff --git a/Lib/test/test_capi/test_config.py b/Lib/test/test_capi/test_config.py
index a3179efe4a8235..a54c11377993a8 100644
--- a/Lib/test/test_capi/test_config.py
+++ b/Lib/test/test_capi/test_config.py
@@ -55,6 +55,7 @@ def test_config_get(self):
             ("filesystem_errors", str, None),
             ("hash_seed", int, None),
             ("home", str | None, None),
+            ("inherit_context", int, None),
             ("import_time", bool, None),
             ("inspect", bool, None),
             ("install_signal_handlers", bool, None),
@@ -98,7 +99,7 @@ def test_config_get(self):
         ]
         if support.Py_DEBUG:
             options.append(("run_presite", str | None, None))
-        if sysconfig.get_config_var('Py_GIL_DISABLED'):
+        if support.Py_GIL_DISABLED:
             options.append(("enable_gil", int, None))
             options.append(("tlbc_enabled", int, None))
         if support.MS_WINDOWS:
@@ -170,7 +171,7 @@ def test_config_get_sys_flags(self):
             ("warn_default_encoding", "warn_default_encoding", False),
             ("safe_path", "safe_path", False),
             ("int_max_str_digits", "int_max_str_digits", False),
-            # "gil" is tested below
+            # "gil" and "inherit_context" are tested below
         ):
             with self.subTest(flag=flag, name=name, negate=negate):
                 value = config_get(name)
@@ -182,11 +183,14 @@ def test_config_get_sys_flags(self):
                          config_get('use_hash_seed') == 0
                          or config_get('hash_seed') != 0)
 
-        if sysconfig.get_config_var('Py_GIL_DISABLED'):
+        if support.Py_GIL_DISABLED:
             value = config_get('enable_gil')
             expected = (value if value != -1 else None)
             self.assertEqual(sys.flags.gil, expected)
 
+        expected_inherit_context = 1 if support.Py_GIL_DISABLED else 0
+        self.assertEqual(sys.flags.inherit_context, expected_inherit_context)
+
     def test_config_get_non_existent(self):
         # Test PyConfig_Get() on non-existent option name
         config_get = _testcapi.config_get
diff --git a/Lib/test/test_context.py b/Lib/test/test_context.py
index 82d1797ab3b79e..53ae7b65e1dfbf 100644
--- a/Lib/test/test_context.py
+++ b/Lib/test/test_context.py
@@ -1,3 +1,4 @@
+import sys
 import collections.abc
 import concurrent.futures
 import contextvars
@@ -383,6 +384,60 @@ def sub(num):
             tp.shutdown()
         self.assertEqual(results, list(range(10)))
 
+    @isolated_context
+    @threading_helper.requires_working_threading()
+    def test_context_thread_inherit(self):
+        import threading
+
+        cvar = contextvars.ContextVar('cvar')
+
+        def run_context_none():
+            if sys.flags.inherit_context:
+                expected = 1
+            else:
+                expected = None
+            self.assertEqual(cvar.get(None), expected)
+
+        # By default, context is inherited based on the
+        # sys.flags.inherit_context option.
+        cvar.set(1)
+        thread = threading.Thread(target=run_context_none)
+        thread.start()
+        thread.join()
+
+        # Passing 'None' explicitly should have same behaviour as not
+        # passing parameter.
+        thread = threading.Thread(target=run_context_none, context=None)
+        thread.start()
+        thread.join()
+
+        # An explicit Context value can also be passed
+        custom_ctx = contextvars.Context()
+        custom_var = None
+
+        def setup_context():
+            nonlocal custom_var
+            custom_var = contextvars.ContextVar('custom')
+            custom_var.set(2)
+
+        custom_ctx.run(setup_context)
+
+        def run_custom():
+            self.assertEqual(custom_var.get(), 2)
+
+        thread = threading.Thread(target=run_custom, context=custom_ctx)
+        thread.start()
+        thread.join()
+
+        # You can also pass a new Context() object to start with an empty context
+        def run_empty():
+            with self.assertRaises(LookupError):
+                cvar.get()
+
+        thread = threading.Thread(target=run_empty, context=contextvars.Context())
+        thread.start()
+        thread.join()
+
 
 # HAMT Tests
 
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 02d3fa985e75b9..48a31e5098c1d1 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -44,6 +44,7 @@
 import random
 import inspect
 import threading
+import contextvars
 
 
 if sys.platform == 'darwin':
@@ -1725,8 +1726,10 @@ def test_threading(self):
         self.finish1 = threading.Event()
         self.finish2 = threading.Event()
 
-        th1 = threading.Thread(target=thfunc1, args=(self,))
-        th2 = threading.Thread(target=thfunc2, args=(self,))
+        th1 = threading.Thread(target=thfunc1, args=(self,),
+                               context=contextvars.Context())
+        th2 = threading.Thread(target=thfunc2, args=(self,),
+                               context=contextvars.Context())
 
         th1.start()
         th2.start()
diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index cd65496cafb04d..739e112073d036 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -50,7 +50,7 @@
 INIT_LOOPS = 4
 MAX_HASH_SEED = 4294967295
 
-ABI_THREAD = 't' if sysconfig.get_config_var('Py_GIL_DISABLED') else ''
+ABI_THREAD = 't' if support.Py_GIL_DISABLED else ''
 # PLATSTDLIB_LANDMARK copied from Modules/getpath.py
 if os.name == 'nt':
     PLATSTDLIB_LANDMARK = f'{sys.platlibdir}'
@@ -60,6 +60,10 @@
     PLATSTDLIB_LANDMARK = (f'{sys.platlibdir}/python{VERSION_MAJOR}.'
                            f'{VERSION_MINOR}{ABI_THREAD}/lib-dynload')
 
+if support.Py_GIL_DISABLED:
+    DEFAULT_INHERIT_CONTEXT = 1
+else:
+    DEFAULT_INHERIT_CONTEXT = 0
 
 # If we are running from a build dir, but the stdlib has been installed,
 # some tests need to expect different results.
@@ -586,6 +590,7 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'tracemalloc': 0,
         'perf_profiling': 0,
         'import_time': False,
+        'inherit_context': DEFAULT_INHERIT_CONTEXT,
         'code_debug_ranges': True,
         'show_ref_count': False,
         'dump_refs': False,
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 39857445a02255..d782874fbe80dd 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -1845,8 +1845,9 @@ def test_pythontypes(self):
         # symtable entry
         # XXX
         # sys.flags
-        # FIXME: The +1 will not be necessary once gh-122575 is fixed
-        check(sys.flags, vsize('') + self.P * (1 + len(sys.flags)))
+        # FIXME: The +2 is for the 'gil' and 'inherit_context' flags and
+        # will not be necessary once gh-122575 is fixed
+        check(sys.flags, vsize('') + self.P * (2 + len(sys.flags)))
 
     def test_asyncgen_hooks(self):
         old = sys.get_asyncgen_hooks()
diff --git a/Lib/threading.py b/Lib/threading.py
index da9cdf0b09d83c..eec76a175bfa1e 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -3,6 +3,7 @@
 import os as _os
 import sys as _sys
 import _thread
+import _contextvars
 
 from time import monotonic as _time
 from _weakrefset import WeakSet
@@ -871,7 +872,7 @@ class Thread:
     _initialized = False
 
     def __init__(self, group=None, target=None, name=None,
-                 args=(), kwargs=None, *, daemon=None):
+                 args=(), kwargs=None, *, daemon=None, context=None):
         """This constructor should always be called with keyword arguments. Arguments are:
 
         *group* should be None; reserved for future extension when a ThreadGroup
@@ -888,6 +889,14 @@ class is implemented.
         *kwargs* is a dictionary of keyword arguments for the target
         invocation. Defaults to {}.
 
+        *context* is the contextvars.Context value to use for the thread.
+        The default value is None, which means to check
+        sys.flags.inherit_context.  If that flag is true, use a copy of
+        the context of the caller.  If false, use an empty context.  To
+        explicitly start with an empty context, pass a new instance of
+        contextvars.Context().  To explicitly start with a copy of the
+        current context, pass the value from contextvars.copy_context().
+
         If a subclass overrides the constructor, it must make sure to invoke
         the base class constructor (Thread.__init__()) before doing anything
         else to the thread.
@@ -917,6 +926,7 @@ class is implemented.
             self._daemonic = daemon
         else:
             self._daemonic = current_thread().daemon
+        self._context = context
         self._ident = None
         if _HAVE_THREAD_NATIVE_ID:
             self._native_id = None
@@ -972,6 +982,16 @@ def start(self):
 
         with _active_limbo_lock:
             _limbo[self] = self
+
+        if self._context is None:
+            # No context provided
+            if _sys.flags.inherit_context:
+                # start with a copy of the context of the caller
+                self._context = _contextvars.copy_context()
+            else:
+                # start with an empty context
+                self._context = _contextvars.Context()
+
         try:
             # Start joinable thread
             _start_joinable_thread(self._bootstrap, handle=self._handle,
@@ -1051,7 +1071,7 @@ def _bootstrap_inner(self):
                 _sys.setprofile(_profile_hook)
 
             try:
-                self.run()
+                self._context.run(self.run)
             except:
                 self._invoke_excepthook(self)
         finally:
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
new file mode 100644
index 00000000000000..fd48a047a6d185
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
@@ -0,0 +1,16 @@
+Add the :data:`sys.flags.inherit_context` flag.
+
+* This flag is set to true by default on the free-threaded build
+  and false otherwise.  If the flag is true, starting a new thread using
+  :class:`threading.Thread` will, by default, use a copy of the
+  :class:`contextvars.Context` from the caller of
+  :meth:`threading.Thread.start` rather than using an empty context.
+
+* Add the :option:`-X inherit_context <-X>` command-line option and
+  :envvar:`PYTHON_INHERIT_CONTEXT` environment variable, which set the
+  :data:`~sys.flags.inherit_context` flag.
+
+* Add the ``context`` keyword parameter to :class:`~threading.Thread`.  It can
+  be used to explicitly pass a context value to be used by a new thread.
+
+* Make the :mod:`_contextvars` module built-in.
diff --git a/Python/initconfig.c b/Python/initconfig.c
index 4db77ef47d2362..187796b6c16c1a 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -141,6 +141,7 @@ static const PyConfigSpec PYCONFIG_SPEC[] = {
     SPEC(filesystem_errors, WSTR, READ_ONLY, NO_SYS),
     SPEC(hash_seed, ULONG, READ_ONLY, NO_SYS),
     SPEC(home, WSTR_OPT, READ_ONLY, NO_SYS),
+    SPEC(inherit_context, INT, READ_ONLY, NO_SYS),
     SPEC(import_time, BOOL, READ_ONLY, NO_SYS),
     SPEC(install_signal_handlers, BOOL, READ_ONLY, NO_SYS),
     SPEC(isolated, BOOL, READ_ONLY, NO_SYS),  // sys.flags.isolated
@@ -302,6 +303,9 @@ The following implementation-specific options are available:\n\
 -X importtime: show how long each import takes; also PYTHONPROFILEIMPORTTIME\n\
 -X int_max_str_digits=N: limit the size of int<->str conversions;\n\
          0 disables the limit; also PYTHONINTMAXSTRDIGITS\n\
+-X inherit_context=[0|1]: enable (1) or disable (0) threads inheriting context\n\
+         vars by default;  enabled by default in the free-threaded build and\n\
+         disabled otherwise; also PYTHON_INHERIT_CONTEXT\n\
 -X no_debug_ranges: don't include extra location information in code objects;\n\
          also PYTHONNODEBUGRANGES\n\
 -X perf: support the Linux \"perf\" profiler; also PYTHONPERFSUPPORT=1\n\
@@ -887,6 +891,7 @@ config_check_consistency(const PyConfig *config)
     assert(config->cpu_count != 0);
     // config->use_frozen_modules is initialized later
     // by _PyConfig_InitImportConfig().
+    assert(config->inherit_context >= 0);
 #ifdef __APPLE__
     assert(config->use_system_logger >= 0);
 #endif
@@ -992,6 +997,11 @@ _PyConfig_InitCompatConfig(PyConfig *config)
     config->_is_python_build = 0;
     config->code_debug_ranges = 1;
     config->cpu_count = -1;
+#ifdef Py_GIL_DISABLED
+    config->inherit_context = 1;
+#else
+    config->inherit_context = 0;
+#endif
 #ifdef __APPLE__
     config->use_system_logger = 0;
 #endif
@@ -1024,6 +1034,11 @@ config_init_defaults(PyConfig *config)
 #ifdef MS_WINDOWS
     config->legacy_windows_stdio = 0;
 #endif
+#ifdef Py_GIL_DISABLED
+    config->inherit_context = 1;
+#else
+    config->inherit_context = 0;
+#endif
 #ifdef __APPLE__
     config->use_system_logger = 0;
 #endif
@@ -1058,6 +1073,11 @@ PyConfig_InitIsolatedConfig(PyConfig *config)
     config->int_max_str_digits = _PY_LONG_DEFAULT_MAX_STR_DIGITS;
     config->safe_path = 1;
     config->pathconfig_warnings = 0;
+#ifdef Py_GIL_DISABLED
+    config->inherit_context = 1;
+#else
+    config->inherit_context = 0;
+#endif
 #ifdef MS_WINDOWS
     config->legacy_windows_stdio = 0;
 #endif
@@ -1887,6 +1907,32 @@ config_init_cpu_count(PyConfig *config)
                          "n must be greater than 0");
 }
 
+static PyStatus
+config_init_inherit_context(PyConfig *config)
+{
+    const char *env = config_get_env(config, "PYTHON_INHERIT_CONTEXT");
+    if (env) {
+        int enabled;
+        if (_Py_str_to_int(env, &enabled) < 0 || (enabled < 0) || (enabled > 1)) {
+            return _PyStatus_ERR(
+                "PYTHON_INHERIT_CONTEXT=N: N is missing or invalid");
+        }
+        config->inherit_context = enabled;
+    }
+
+    const wchar_t *xoption = config_get_xoption(config, L"inherit_context");
+    if (xoption) {
+        int enabled;
+        const wchar_t *sep = wcschr(xoption, L'=');
+        if (!sep || (config_wstr_to_int(sep + 1, &enabled) < 0) || (enabled < 0) || (enabled > 1)) {
+            return _PyStatus_ERR(
+                "-X inherit_context=n: n is missing or invalid");
+        }
+        config->inherit_context = enabled;
+    }
+    return _PyStatus_OK();
+}
+
 static PyStatus
 config_init_tlbc(PyConfig *config)
 {
@@ -2166,6 +2212,11 @@ config_read_complex_options(PyConfig *config)
     }
 #endif
 
+    status = config_init_inherit_context(config);
+    if (_PyStatus_EXCEPTION(status)) {
+        return status;
+    }
+
     status = config_init_tlbc(config);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index d5cb448eb618e8..6ab9d2b17a8453 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -3141,6 +3141,7 @@ static PyStructSequence_Field flags_fields[] = {
     {"safe_path", "-P"},
     {"int_max_str_digits",      "-X int_max_str_digits"},
     {"gil",                     "-X gil"},
+    {"inherit_context",         "-X inherit_context"},
     {0}
 };
 
@@ -3244,6 +3245,7 @@ set_flags_from_config(PyInterpreterState *interp, PyObject *flags)
 #else
     SetFlagObj(PyLong_FromLong(1));
 #endif
+    SetFlag(config->inherit_context);
 #undef SetFlagObj
 #undef SetFlag
     return 0;

From a868fe97356f97f56468d43b3ca23b4b95636f62 Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Thu, 6 Feb 2025 16:10:34 -0800
Subject: [PATCH 3/8] Tweak blurb markup.

---
 .../2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
index fd48a047a6d185..22c7399bee2204 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
@@ -13,4 +13,4 @@ Add the :data:`sys.flags.inherit_context` flag.
 * Add the ``context`` keyword parameter to :class:`~threading.Thread`.  It can
   be used to explicitly pass a context value to be used by a new thread.
 
-* Make the :mod:`_contextvars` module built-in.
+* Make the ``_contextvars`` module built-in.

From 16fa2c3891e143eca728a84b6942670ff810276d Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Thu, 6 Feb 2025 16:13:00 -0800
Subject: [PATCH 4/8] Doc markup fix.

---
 Doc/library/threading.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index 65e498aabb8016..d333a094f5883e 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -367,7 +367,7 @@ since it is impossible to detect the termination of alien threads.
    an empty context.  To explicitly start with an empty context,
    pass a new instance of :class:`~contextvars.Context()`.  To explicitly
    start with a copy of the current context, pass the value from
-   :func:`~contextvars.copy_context()`. The flag defaults true on
+   :func:`~contextvars.copy_context`. The flag defaults true on
    free-threaded builds and false otherwise.
 
    If the subclass overrides the constructor, it must make sure to invoke the

From 09e72b8d76ec25b1b23477ff7b8beb4218ee26a4 Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Tue, 11 Feb 2025 15:23:37 -0800
Subject: [PATCH 5/8] Rename flag to `thread_inherit_context`.

---
 Doc/library/sys.rst                           |  7 ++--
 Doc/library/threading.rst                     | 13 +++---
 Doc/using/cmdline.rst                         |  8 ++--
 Include/cpython/initconfig.h                  |  2 +-
 Lib/test/test_capi/test_config.py             |  6 +--
 Lib/test/test_context.py                      |  4 +-
 Lib/test/test_embed.py                        |  6 +--
 Lib/test/test_sys.py                          |  2 +-
 Lib/threading.py                              | 10 ++---
 ...-01-06-10-55-41.gh-issue-128555.tAK_AY.rst |  8 ++--
 Python/initconfig.c                           | 40 ++++++++++---------
 Python/sysmodule.c                            |  4 +-
 12 files changed, 56 insertions(+), 54 deletions(-)

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 43bda09323f557..779b179988b935 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -598,8 +598,9 @@ always available. Unless explicitly noted otherwise, all variables are read-only
       * - .. attribute:: flags.gil
         - :option:`-X gil <-X>` and :envvar:`PYTHON_GIL`
 
-      * - .. attribute:: flags.inherit_context
-        - :option:`-X inherit_context <-X>` and :envvar:`PYTHON_INHERIT_CONTEXT`
+      * - .. attribute:: flags.thread_inherit_context
+        - :option:`-X thread_inherit_context <-X>` and
+          :envvar:`PYTHON_THREAD_INHERIT_CONTEXT`
 
    .. versionchanged:: 3.2
       Added ``quiet`` attribute for the new :option:`-q` flag.
@@ -631,7 +632,7 @@ always available. Unless explicitly noted otherwise, all variables are read-only
       Added the ``gil`` attribute.
 
    .. versionchanged:: 3.14
-      Added the ``inherit_context`` attribute.
+      Added the ``thread_inherit_context`` attribute.
 
 
 .. data:: float_info
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index d333a094f5883e..8049f2979f768a 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -361,14 +361,13 @@ since it is impossible to detect the termination of alien threads.
 
    *context* is the :class:`~contextvars.Context` value to use when starting
    the thread.  The default value is ``None`` which indicates that the
-   :data:`sys.flags.inherit_context` flag controls the behaviour.  If
+   :data:`sys.flags.thread_inherit_context` flag controls the behaviour.  If
    the flag is true, threads will start with a copy of the context of the
-   caller of :meth:`~Thread.start`.  If false, they will start with
-   an empty context.  To explicitly start with an empty context,
-   pass a new instance of :class:`~contextvars.Context()`.  To explicitly
-   start with a copy of the current context, pass the value from
-   :func:`~contextvars.copy_context`. The flag defaults true on
-   free-threaded builds and false otherwise.
+   caller of :meth:`~Thread.start`.  If false, they will start with an empty
+   context.  To explicitly start with an empty context, pass a new instance of
+   :class:`~contextvars.Context()`.  To explicitly start with a copy of the
+   current context, pass the value from :func:`~contextvars.copy_context`. The
+   flag defaults true on free-threaded builds and false otherwise.
 
    If the subclass overrides the constructor, it must make sure to invoke the
    base class constructor (``Thread.__init__()``) before doing anything else to
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index be5816f7c8d2b0..8a4d4fbcd94433 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -628,12 +628,12 @@ Miscellaneous options
 
      .. versionadded:: 3.13
 
-   * :samp:`-X inherit_context={0,1}` causes :class:`~threading.Thread`
+   * :samp:`-X thread_inherit_context={0,1}` causes :class:`~threading.Thread`
      to, by default, use a copy of context of of the caller of
      ``Thread.start()`` when starting.  Otherwise, threads will start
      with an empty context.  If unset, the value of this option defaults
      to ``1`` on free-threaded builds and to ``0`` otherwise.  See also
-     :envvar:`PYTHON_INHERIT_CONTEXT`.
+     :envvar:`PYTHON_THREAD_INHERIT_CONTEXT`.
 
      .. versionadded:: 3.14
 
@@ -1230,13 +1230,13 @@ conflict.
 
    .. versionadded:: 3.13
 
-.. envvar:: PYTHON_INHERIT_CONTEXT
+.. envvar:: PYTHON_THREAD_INHERIT_CONTEXT
 
    If this variable is set to ``1`` then :class:`~threading.Thread` will,
    by default, use a copy of context of of the caller of ``Thread.start()``
    when starting.  Otherwise, new threads will start with an empty context.
    If unset, this variable defaults to ``1`` on free-threaded builds and to
-   ``0`` otherwise.  See also :option:`-X inherit_context<-X>`.
+   ``0`` otherwise.  See also :option:`-X thread_inherit_context<-X>`.
 
    .. versionadded:: 3.14
 
diff --git a/Include/cpython/initconfig.h b/Include/cpython/initconfig.h
index d8edfa973b96f4..202f4a8964736e 100644
--- a/Include/cpython/initconfig.h
+++ b/Include/cpython/initconfig.h
@@ -179,7 +179,7 @@ typedef struct PyConfig {
     int use_frozen_modules;
     int safe_path;
     int int_max_str_digits;
-    int inherit_context;
+    int thread_inherit_context;
 #ifdef __APPLE__
     int use_system_logger;
 #endif
diff --git a/Lib/test/test_capi/test_config.py b/Lib/test/test_capi/test_config.py
index a54c11377993a8..21c66a7b613335 100644
--- a/Lib/test/test_capi/test_config.py
+++ b/Lib/test/test_capi/test_config.py
@@ -55,7 +55,7 @@ def test_config_get(self):
             ("filesystem_errors", str, None),
             ("hash_seed", int, None),
             ("home", str | None, None),
-            ("inherit_context", int, None),
+            ("thread_inherit_context", int, None),
             ("import_time", bool, None),
             ("inspect", bool, None),
             ("install_signal_handlers", bool, None),
@@ -171,7 +171,7 @@ def test_config_get_sys_flags(self):
             ("warn_default_encoding", "warn_default_encoding", False),
             ("safe_path", "safe_path", False),
             ("int_max_str_digits", "int_max_str_digits", False),
-            # "gil" and "inherit_context" are tested below
+            # "gil" and "thread_inherit_context" are tested below
         ):
             with self.subTest(flag=flag, name=name, negate=negate):
                 value = config_get(name)
@@ -189,7 +189,7 @@ def test_config_get_sys_flags(self):
             self.assertEqual(sys.flags.gil, expected)
 
         expected_inherit_context = 1 if support.Py_GIL_DISABLED else 0
-        self.assertEqual(sys.flags.inherit_context, expected_inherit_context)
+        self.assertEqual(sys.flags.thread_inherit_context, expected_inherit_context)
 
     def test_config_get_non_existent(self):
         # Test PyConfig_Get() on non-existent option name
diff --git a/Lib/test/test_context.py b/Lib/test/test_context.py
index 53ae7b65e1dfbf..b026f5cb64a571 100644
--- a/Lib/test/test_context.py
+++ b/Lib/test/test_context.py
@@ -392,14 +392,14 @@ def test_context_thread_inherit(self):
         cvar = contextvars.ContextVar('cvar')
 
         def run_context_none():
-            if sys.flags.inherit_context:
+            if sys.flags.thread_inherit_context:
                 expected = 1
             else:
                 expected = None
             self.assertEqual(cvar.get(None), expected)
 
         # By default, context is inherited based on the
-        # sys.flags.inherit_context option.
+        # sys.flags.thread_inherit_context option.
         cvar.set(1)
         thread = threading.Thread(target=run_context_none)
         thread.start()
diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index 739e112073d036..772d62320a5ba9 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -61,9 +61,9 @@
                            f'{VERSION_MINOR}{ABI_THREAD}/lib-dynload')
 
 if support.Py_GIL_DISABLED:
-    DEFAULT_INHERIT_CONTEXT = 1
+    DEFAULT_THREAD_INHERIT_CONTEXT = 1
 else:
-    DEFAULT_INHERIT_CONTEXT = 0
+    DEFAULT_THREAD_INHERIT_CONTEXT = 0
 
 # If we are running from a build dir, but the stdlib has been installed,
 # some tests need to expect different results.
@@ -590,7 +590,7 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'tracemalloc': 0,
         'perf_profiling': 0,
         'import_time': False,
-        'inherit_context': DEFAULT_INHERIT_CONTEXT,
+        'thread_inherit_context': DEFAULT_THREAD_INHERIT_CONTEXT,
         'code_debug_ranges': True,
         'show_ref_count': False,
         'dump_refs': False,
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index d782874fbe80dd..b58355700f2c6d 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -1845,7 +1845,7 @@ def test_pythontypes(self):
         # symtable entry
         # XXX
         # sys.flags
-        # FIXME: The +2 is for the 'gil' and 'inherit_context' flags and
+        # FIXME: The +2 is for the 'gil' and 'thread_inherit_context' flags and
         # will not be necessary once gh-122575 is fixed
         check(sys.flags, vsize('') + self.P * (2 + len(sys.flags)))
 
diff --git a/Lib/threading.py b/Lib/threading.py
index eec76a175bfa1e..fc27de3f7a2d79 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -891,11 +891,11 @@ class is implemented.
 
         *context* is the contextvars.Context value to use for the thread.
         The default value is None, which means to check
-        sys.flags.inherit_context.  If that flag is true, use a copy of
-        the context of the caller.  If false, use an empty context.  To
+        sys.flags.thread_inherit_context.  If that flag is true, use a copy
+        of the context of the caller.  If false, use an empty context.  To
         explicitly start with an empty context, pass a new instance of
-        contextvars.Context().  To explicitly start with a copy of the
-        current context, pass the value from contextvars.copy_context().
+        contextvars.Context().  To explicitly start with a copy of the current
+        context, pass the value from contextvars.copy_context().
 
         If a subclass overrides the constructor, it must make sure to invoke
         the base class constructor (Thread.__init__()) before doing anything
@@ -985,7 +985,7 @@ def start(self):
 
         if self._context is None:
             # No context provided
-            if _sys.flags.inherit_context:
+            if _sys.flags.thread_inherit_context:
                 # start with a copy of the context of the caller
                 self._context = _contextvars.copy_context()
             else:
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
index 22c7399bee2204..e0b468e76a062b 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-06-10-55-41.gh-issue-128555.tAK_AY.rst
@@ -1,4 +1,4 @@
-Add the :data:`sys.flags.inherit_context` flag.
+Add the :data:`sys.flags.thread_inherit_context` flag.
 
 * This flag is set to true by default on the free-threaded build
   and false otherwise.  If the flag is true, starting a new thread using
@@ -6,9 +6,9 @@ Add the :data:`sys.flags.inherit_context` flag.
   :class:`contextvars.Context` from the caller of
   :meth:`threading.Thread.start` rather than using an empty context.
 
-* Add the :option:`-X inherit_context <-X>` command-line option and
-  :envvar:`PYTHON_INHERIT_CONTEXT` environment variable, which set the
-  :data:`~sys.flags.inherit_context` flag.
+* Add the :option:`-X thread_inherit_context <-X>` command-line option and
+  :envvar:`PYTHON_THREAD_INHERIT_CONTEXT` environment variable, which set the
+  :data:`~sys.flags.thread_inherit_context` flag.
 
 * Add the ``context`` keyword parameter to :class:`~threading.Thread`.  It can
   be used to explicitly pass a context value to be used by a new thread.
diff --git a/Python/initconfig.c b/Python/initconfig.c
index 187796b6c16c1a..02d43c0236c28e 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -141,7 +141,7 @@ static const PyConfigSpec PYCONFIG_SPEC[] = {
     SPEC(filesystem_errors, WSTR, READ_ONLY, NO_SYS),
     SPEC(hash_seed, ULONG, READ_ONLY, NO_SYS),
     SPEC(home, WSTR_OPT, READ_ONLY, NO_SYS),
-    SPEC(inherit_context, INT, READ_ONLY, NO_SYS),
+    SPEC(thread_inherit_context, INT, READ_ONLY, NO_SYS),
     SPEC(import_time, BOOL, READ_ONLY, NO_SYS),
     SPEC(install_signal_handlers, BOOL, READ_ONLY, NO_SYS),
     SPEC(isolated, BOOL, READ_ONLY, NO_SYS),  // sys.flags.isolated
@@ -303,9 +303,6 @@ The following implementation-specific options are available:\n\
 -X importtime: show how long each import takes; also PYTHONPROFILEIMPORTTIME\n\
 -X int_max_str_digits=N: limit the size of int<->str conversions;\n\
          0 disables the limit; also PYTHONINTMAXSTRDIGITS\n\
--X inherit_context=[0|1]: enable (1) or disable (0) threads inheriting context\n\
-         vars by default;  enabled by default in the free-threaded build and\n\
-         disabled otherwise; also PYTHON_INHERIT_CONTEXT\n\
 -X no_debug_ranges: don't include extra location information in code objects;\n\
          also PYTHONNODEBUGRANGES\n\
 -X perf: support the Linux \"perf\" profiler; also PYTHONPERFSUPPORT=1\n\
@@ -329,6 +326,9 @@ The following implementation-specific options are available:\n\
          PYTHON_TLBC\n"
 #endif
 "\
+-X thread_inherit_context=[0|1]: enable (1) or disable (0) threads inheriting\n\
+         context vars by default; enabled by default in the free-threaded\n\
+         build and disabled otherwise; also PYTHON_THREAD_INHERIT_CONTEXT\n\
 -X tracemalloc[=N]: trace Python memory allocations; N sets a traceback limit\n \
          of N frames (default: 1); also PYTHONTRACEMALLOC=N\n\
 -X utf8[=0|1]: enable (1) or disable (0) UTF-8 mode; also PYTHONUTF8\n\
@@ -416,6 +416,8 @@ static const char usage_envvars[] =
 #ifdef Py_GIL_DISABLED
 "PYTHON_TLBC     : when set to 0, disables thread-local bytecode (-X tlbc)\n"
 #endif
+"PYTHON_THREAD_INHERIT_CONTEXT: threads inherit context vars if 1\n"
+"                   (-X thread_inherit_context)\n"
 "PYTHONTRACEMALLOC: trace Python memory allocations (-X tracemalloc)\n"
 "PYTHONUNBUFFERED: disable stdout/stderr buffering (-u)\n"
 "PYTHONUTF8      : control the UTF-8 mode (-X utf8)\n"
@@ -891,7 +893,7 @@ config_check_consistency(const PyConfig *config)
     assert(config->cpu_count != 0);
     // config->use_frozen_modules is initialized later
     // by _PyConfig_InitImportConfig().
-    assert(config->inherit_context >= 0);
+    assert(config->thread_inherit_context >= 0);
 #ifdef __APPLE__
     assert(config->use_system_logger >= 0);
 #endif
@@ -998,9 +1000,9 @@ _PyConfig_InitCompatConfig(PyConfig *config)
     config->code_debug_ranges = 1;
     config->cpu_count = -1;
 #ifdef Py_GIL_DISABLED
-    config->inherit_context = 1;
+    config->thread_inherit_context = 1;
 #else
-    config->inherit_context = 0;
+    config->thread_inherit_context = 0;
 #endif
 #ifdef __APPLE__
     config->use_system_logger = 0;
@@ -1035,9 +1037,9 @@ config_init_defaults(PyConfig *config)
     config->legacy_windows_stdio = 0;
 #endif
 #ifdef Py_GIL_DISABLED
-    config->inherit_context = 1;
+    config->thread_inherit_context = 1;
 #else
-    config->inherit_context = 0;
+    config->thread_inherit_context = 0;
 #endif
 #ifdef __APPLE__
     config->use_system_logger = 0;
@@ -1074,9 +1076,9 @@ PyConfig_InitIsolatedConfig(PyConfig *config)
     config->safe_path = 1;
     config->pathconfig_warnings = 0;
 #ifdef Py_GIL_DISABLED
-    config->inherit_context = 1;
+    config->thread_inherit_context = 1;
 #else
-    config->inherit_context = 0;
+    config->thread_inherit_context = 0;
 #endif
 #ifdef MS_WINDOWS
     config->legacy_windows_stdio = 0;
@@ -1908,27 +1910,27 @@ config_init_cpu_count(PyConfig *config)
 }
 
 static PyStatus
-config_init_inherit_context(PyConfig *config)
+config_init_thread_inherit_context(PyConfig *config)
 {
-    const char *env = config_get_env(config, "PYTHON_INHERIT_CONTEXT");
+    const char *env = config_get_env(config, "PYTHON_THREAD_INHERIT_CONTEXT");
     if (env) {
         int enabled;
         if (_Py_str_to_int(env, &enabled) < 0 || (enabled < 0) || (enabled > 1)) {
             return _PyStatus_ERR(
-                "PYTHON_INHERIT_CONTEXT=N: N is missing or invalid");
+                "PYTHON_THREAD_INHERIT_CONTEXT=N: N is missing or invalid");
         }
-        config->inherit_context = enabled;
+        config->thread_inherit_context = enabled;
     }
 
-    const wchar_t *xoption = config_get_xoption(config, L"inherit_context");
+    const wchar_t *xoption = config_get_xoption(config, L"thread_inherit_context");
     if (xoption) {
         int enabled;
         const wchar_t *sep = wcschr(xoption, L'=');
         if (!sep || (config_wstr_to_int(sep + 1, &enabled) < 0) || (enabled < 0) || (enabled > 1)) {
             return _PyStatus_ERR(
-                "-X inherit_context=n: n is missing or invalid");
+                "-X thread_inherit_context=n: n is missing or invalid");
         }
-        config->inherit_context = enabled;
+        config->thread_inherit_context = enabled;
     }
     return _PyStatus_OK();
 }
@@ -2212,7 +2214,7 @@ config_read_complex_options(PyConfig *config)
     }
 #endif
 
-    status = config_init_inherit_context(config);
+    status = config_init_thread_inherit_context(config);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
     }
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 6ab9d2b17a8453..71285c074be066 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -3141,7 +3141,7 @@ static PyStructSequence_Field flags_fields[] = {
     {"safe_path", "-P"},
     {"int_max_str_digits",      "-X int_max_str_digits"},
     {"gil",                     "-X gil"},
-    {"inherit_context",         "-X inherit_context"},
+    {"thread_inherit_context",  "-X thread_inherit_context"},
     {0}
 };
 
@@ -3245,7 +3245,7 @@ set_flags_from_config(PyInterpreterState *interp, PyObject *flags)
 #else
     SetFlagObj(PyLong_FromLong(1));
 #endif
-    SetFlag(config->inherit_context);
+    SetFlag(config->thread_inherit_context);
 #undef SetFlagObj
 #undef SetFlag
     return 0;

From 872920d525f3938bd22c623d4e0041f012688aba Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Tue, 11 Feb 2025 12:41:50 -0800
Subject: [PATCH 6/8] Regenerate 'configure' script.

---
 configure | 28 ----------------------------
 1 file changed, 28 deletions(-)

diff --git a/configure b/configure
index d46bc563a67245..260a49fc83149b 100755
--- a/configure
+++ b/configure
@@ -801,8 +801,6 @@ MODULE__HEAPQ_FALSE
 MODULE__HEAPQ_TRUE
 MODULE__CSV_FALSE
 MODULE__CSV_TRUE
-MODULE__CONTEXTVARS_FALSE
-MODULE__CONTEXTVARS_TRUE
 MODULE__BISECT_FALSE
 MODULE__BISECT_TRUE
 MODULE__ASYNCIO_FALSE
@@ -30727,28 +30725,6 @@ then :
 
 
 
-fi
-
-
-        if test "$py_cv_module__contextvars" != "n/a"
-then :
-  py_cv_module__contextvars=yes
-fi
-   if test "$py_cv_module__contextvars" = yes; then
-  MODULE__CONTEXTVARS_TRUE=
-  MODULE__CONTEXTVARS_FALSE='#'
-else
-  MODULE__CONTEXTVARS_TRUE='#'
-  MODULE__CONTEXTVARS_FALSE=
-fi
-
-  as_fn_append MODULE_BLOCK "MODULE__CONTEXTVARS_STATE=$py_cv_module__contextvars$as_nl"
-  if test "x$py_cv_module__contextvars" = xyes
-then :
-
-
-
-
 fi
 
 
@@ -33599,10 +33575,6 @@ if test -z "${MODULE__BISECT_TRUE}" && test -z "${MODULE__BISECT_FALSE}"; then
   as_fn_error $? "conditional \"MODULE__BISECT\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
-if test -z "${MODULE__CONTEXTVARS_TRUE}" && test -z "${MODULE__CONTEXTVARS_FALSE}"; then
-  as_fn_error $? "conditional \"MODULE__CONTEXTVARS\" was never defined.
-Usually this means the macro was only invoked conditionally." "$LINENO" 5
-fi
 if test -z "${MODULE__CSV_TRUE}" && test -z "${MODULE__CSV_FALSE}"; then
   as_fn_error $? "conditional \"MODULE__CSV\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5

From 2c48fc5122522a8aaefa358c1b7e860bc0d268de Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Wed, 19 Feb 2025 09:53:11 -0800
Subject: [PATCH 7/8] Add comment about why 'context' is passed in test.

---
 Lib/test/test_decimal.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 48a31e5098c1d1..884b272482e72d 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -1726,6 +1726,9 @@ def test_threading(self):
         self.finish1 = threading.Event()
         self.finish2 = threading.Event()
 
+        # This test wants to start threads with an empty context, no matter
+        # the setting of sys.flags.thread_inherit_context.  We pass the
+        # 'context' argument explicitly with an empty context instance.
         th1 = threading.Thread(target=thfunc1, args=(self,),
                                context=contextvars.Context())
         th2 = threading.Thread(target=thfunc2, args=(self,),

From 53eb72d5511ab0f6e2cd6c0c8b8ea6c52db45c6b Mon Sep 17 00:00:00 2001
From: Neil Schemenauer <nas@arctrix.com>
Date: Fri, 21 Feb 2025 12:07:59 -0800
Subject: [PATCH 8/8] Revise "decimal' docs, adding note about flag.

---
 Doc/library/decimal.rst | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst
index 9318af60b60f95..2111ff67edaa3d 100644
--- a/Doc/library/decimal.rst
+++ b/Doc/library/decimal.rst
@@ -1884,13 +1884,20 @@ the current thread.
 
 If :func:`setcontext` has not been called before :func:`getcontext`, then
 :func:`getcontext` will automatically create a new context for use in the
-current thread.
-
-The new context is copied from a prototype context called *DefaultContext*. To
-control the defaults so that each thread will use the same values throughout the
-application, directly modify the *DefaultContext* object. This should be done
-*before* any threads are started so that there won't be a race condition between
-threads calling :func:`getcontext`. For example::
+current thread.  New context objects have default values set from the
+:data:`decimal.DefaultContext` object.
+
+The :data:`sys.flags.thread_inherit_context` flag affects the context for
+new threads.  If the flag is false, new threads will start with an empty
+context.  In this case, :func:`getcontext` will create a new context object
+when called and use the default values from *DefaultContext*.  If the flag
+is true, new threads will start with a copy of context from the caller of
+:meth:`Thread.start`.
+
+To control the defaults so that each thread will use the same values throughout
+the application, directly modify the *DefaultContext* object. This should be
+done *before* any threads are started so that there won't be a race condition
+between threads calling :func:`getcontext`. For example::
 
    # Set applicationwide defaults for all threads about to be launched
    DefaultContext.prec = 12

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