Description

gpshead

opened on Mar 15, 2026

Issue body actions

Bug report

Bug description:

-X lazy_imports, -X thread_inherit_context, and -X context_aware_warnings are not inherited via subprocess._args_from_interpreter_flags() so multiprocessing spawned child processes do not inherit these -X settings unless the user happens to be using the dangerous non-default "fork" start method.

We should consider this for every -X option added. In general the answer should be "yes". There's a list in Lib/subprocess.py to update. (could we automate this by making the list an opt-out instead of a remember-when-adding-a-feature-to-opt-in list?)

Linked PRs

• gh-146004: propagate all -X options to multiprocessing child processes #146005
• [3.14] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) #146552
• gh-146004: fix test_args_from_interpreter_flags #146580
• [3.14] gh-146004: fix test_args_from_interpreter_flags on windows (GH-146580) #146585
• [3.13] gh-146004: propagate all -X options to multiprocessing child processes (GH-146005) #155938
• [3.13] gh-146004: fix test_args_from_interpreter_flags on windows (GH-146580) #155965

Activity

1. gpshead

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   3.15bugs and security fixesbugs and security fixes

   on Mar 15, 2026
2. picnixz

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-multiprocessing

   on Mar 16, 2026
3. gpshead

   self-assigned this

   on Mar 16, 2026
4. gpshead commented on Mar 16, 2026

   

   gpshead

   on Mar 16, 2026

   MemberAuthor

   More actions

   Potentially security relevant for -X disable-remote-debug. though i expect people who really want that off build a python without it or at least use the PYTHON_DISABLE_REMOTE_DEBUG= env var.
5. gpshead

   added a commit that references this issue on Mar 16, 2026

   pythongh-146004: propagate all -X options to subprocesses

   6a115f0
6. gpshead commented on Mar 16, 2026

   

   gpshead

   on Mar 16, 2026

   MemberAuthor

   More actions

   -X options that are not yet being propagated to multiprocessing spawned children that the PR would change:

   ``context_aware_warnings``,
   ``cpu_count``,
   ``disable-remote-debug``,
   ``int_max_str_digits``,
   ``lazy_imports``,
   ``no_debug_ranges``,
   ``pathconfig_warnings``,
   ``perf``,
   ``perf_jit``,
   ``presite``,
   ``pycache_prefix``,
   ``thread_inherit_context``,
   ``warn_default_encoding``.

   thoughts on if any of those should not auto-propagate to non-fork'ed children?
7. gpshead

   assigned

   pablogsal

   on Mar 16, 2026
8. gpshead commented on Mar 16, 2026

   

   gpshead

   on Mar 16, 2026

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   And among those, which ones we should specifically backport propagation as a bugfix?
9. gpshead

   added

   3.14bugs and security fixesbugs and security fixes

   3.13only security fixesonly security fixes

   on Mar 16, 2026
10. vstinner commented on Mar 27, 2026

    

    vstinner

    on Mar 27, 2026

    Member

    More actions

    thoughts on if any of those should not auto-propagate to non-fork'ed children?

    IMO it's safe to propagate all of them to child processes.

    And among those, which ones we should specifically backport propagation as a bugfix?

    I'm fine with backporting your change which propagate the whole sys._xoptions directory.

    Reacted by Gregory P. Smith
11. gpshead

    added a commit that references this issue on Mar 28, 2026

    gh-146004: propagate all -X options to multiprocessing child processes (

    1efe441
12. miss-islington

    added a commit that references this issue on Mar 28, 2026

    pythongh-146004: propagate all -X options to multiprocessing child pr…

    6919ddd
13. gpshead commented on Mar 28, 2026

    

    gpshead

    on Mar 28, 2026

    MemberAuthor

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    status: awaiting a manual backport to 3.13.
14. gpshead

    added a commit that references this issue on Mar 28, 2026

    [3.14] gh-146004: propagate all -X options to multiprocessing child p…

    28d3b9b
15. kumaraditya303

    added a commit that references this issue on Mar 29, 2026

    gh-146004: fix test_args_from_interpreter_flags on windows (#146580)

    1af025d
16. miss-islington

    added a commit that references this issue on Mar 29, 2026

    pythongh-146004: fix test_args_from_interpreter_flags on windows (pyt…

    3ab87af
17. kumaraditya303

    added a commit that references this issue on Mar 29, 2026

    [3.14] gh-146004: fix test_args_from_interpreter_flags on windows (GH…

    525f8e4
18. picnixz

    closed this as completedon Mar 29, 2026
19. maurycy

    added a commit that references this issue on Mar 30, 2026

    Merge remote-tracking branch 'upstream/main' into tachyon-ndjson-kole…

    6a0ea81
20. clin1234

    added 2 commits that reference this issue on Apr 16, 2026

    pythongh-146004: propagate all -X options to multiprocessing child pr…

    de6eb70

    pythongh-146004: fix test_args_from_interpreter_flags on windows (pyt…

    080801e
21. ljfp

    added 2 commits that reference this issue on Apr 25, 2026

    pythongh-146004: propagate all -X options to multiprocessing child pr…

    a1131cb

    pythongh-146004: fix test_args_from_interpreter_flags on windows (pyt…

    56ca205
22. hanlee55

    added 2 commits that reference this issue on Aug 17, 2026

    pythongh-146004: propagate all -X options to multiprocessing child pr…

    1a93745

    pythongh-146004: fix test_args_from_interpreter_flags on windows (pyt…

    197a74a
23. hugovk

    added a commit that references this issue on Aug 17, 2026

    [3.13] gh-146004: propagate all -X options to multiprocessing child p…

    d3f5290
24. zware

    added a commit that references this issue on Aug 18, 2026

    [3.13] gh-146004: fix test_args_from_interpreter_flags on windows (GH…

    2143dcd

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