llvmlite llvmlite CI support for Python 3.14

This issue is to document and track the changes required to add initial support for Python 3.14 on CI. Python 3.14 is currently in pre-release (final release scheduled for October 7, 2025) per PEP 745

At present, we are using workarounds to build against pre-release versions. Once official release builds and packages are available, those will be reverted.

The goal is to:

Enable CI jobs against Python 3.14 pre-releases.
Identify and document any failures/required changes.
Ensure CI is ready for Python 3.14 on the official release date.

Sep 09 '25 15:09 swap357

https://github.com/numba/llvmlite/pull/1279 adds CI support for llvmlite build and test GHA workflows.

Follow-up items -

[x] Remove ad-testing/label/py314 dependency once upstream packages are published.
[ ] Re-enable lief dependency in 3.14 test jobs once it has upstream support.

Sep 09 '25 15:09 swap357

The initial part of this was solved with https://github.com/numba/llvmlite/pull/1279

Sep 25 '25 20:09 esc

opened PR https://github.com/numba/llvmlite/pull/1311 to cleanup after official release and conda support for python 3.14.

Oct 01 '25 02:10 swap357

python 3.14t no GIL

(venv314t) PS C:\Users\User_Niki\venv314t> pip install llvmlite==0.46.0b1 Collecting llvmlite==0.46.0b1 Using cached llvmlite-0.46.0b1.tar.gz (185 kB) Installing build dependencies ... done Getting requirements to build wheel ... done Preparing metadata (pyproject.toml) ... done Building wheels for collected packages: llvmlite Building wheel for llvmlite (pyproject.toml) ... error error: subprocess-exited-with-error

× Building wheel for llvmlite (pyproject.toml) did not run successfully. │ exit code: 1 ╰─> [46 lines of output] running bdist_wheel C:\Users\User_Niki\venv314t\Scripts\python.exe C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py Trying generator ('Visual Studio 17 2022', 'x64', 'v143') Running: cmake -G Visual Studio 17 2022 -A x64 -T v143 C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\dummy Traceback (most recent call last): File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 198, in main()

File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 188, in main
main_windows()
~~~~~~~~~~~~^^
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 163, in main_windows
generator = find_windows_generator()
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 130, in find_windows_generator
try_cmake(cmake_dir, build_dir, *generator)
~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 95, in try_cmake
subprocess.check_call(args)
~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "C:\Program Files\Python314\Lib\subprocess.py", line 414, in check_call
retcode = call(*popenargs, **kwargs)
File "C:\Program Files\Python314\Lib\subprocess.py", line 395, in call
with Popen(*popenargs, **kwargs) as p:
~~~~~^^^^^^^^^^^^^^^^^^^^^^
File "C:\Program Files\Python314\Lib\subprocess.py", line 1038, in init
self._execute_child(args, executable, preexec_fn, close_fds,
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pass_fds, cwd, env,
^^^^^^^^^^^^^^^^^^^
...<5 lines>...
gid, gids, uid, umask,
^^^^^^^^^^^^^^^^^^^^^^
start_new_session, process_group)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Program Files\Python314\Lib\subprocess.py", line 1552, in _execute_child
hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
# no special security
^^^^^^^^^^^^^^^^^^^^^
...<4 lines>...
cwd,
^^^^
startupinfo)
^^^^^^^^^^^^
FileNotFoundError: [WinError 2] Не удается найти указанный файл
error: command 'C:\Users\User_Niki\venv314t\Scripts\python.exe' failed with exit code 1
[end of output]

note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed building wheel for llvmlite
Failed to build llvmlite
error: failed-wheel-build-for-install

× Failed to build installable wheels for some pyproject.toml based projects
╰─> llvmlite
(venv314t) PS C:\Users\User_Niki\venv314t> python.exe
Python 3.14.0 free-threading build (tags/v3.14.0:ebf955d, Oct 7 2025, 10:13:09) [MSC v.1944 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.

exit
(venv314t) PS C:\Users\User_Niki\venv314t>

Oct 24 '25 11:10 nikimagic

@nikimagic this issue is about adding CI support for Python 3.14 -- what do you wish to communicate with your comments? It looks like you tried to install 0.46.0b1 -- but the binary could not be installed and compiling from source failed?

Oct 24 '25 11:10 esc

@nikimagic this issue is about adding CI support for Python 3.14 -- what do you wish to communicate with your comments? It looks like you tried to install 0.46.0b1 -- but the binary could not be installed and compiling from source failed?

Venv python3.14 ok Venv python3.14t no gil error install

Oct 24 '25 13:10 nikimagic

@nikimagic this issue is about adding CI support for Python 3.14 -- what do you wish to communicate with your comments? It looks like you tried to install 0.46.0b1 -- but the binary could not be installed and compiling from source failed?

Venv python3.14 ok Venv python3.14t no gil error install

OK, thank you for the report, I have created https://github.com/numba/llvmlite/issues/1338 to track.

Oct 24 '25 15:10 esc

python 3.14t no GIL

(venv314t) PS C:\Users\User_Niki\venv314t> pip install llvmlite==0.46.0b1 Collecting llvmlite==0.46.0b1 Using cached llvmlite-0.46.0b1.tar.gz (185 kB) Installing build dependencies ... done Getting requirements to build wheel ... done Preparing metadata (pyproject.toml) ... done Building wheels for collected packages: llvmlite Building wheel for llvmlite (pyproject.toml) ... error error: subprocess-exited-with-error

× Building wheel for llvmlite (pyproject.toml) did not run successfully. │ exit code: 1 ╰─> [46 lines of output] running bdist_wheel C:\Users\User_Niki\venv314t\Scripts\python.exe C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py Trying generator ('Visual Studio 17 2022', 'x64', 'v143') Running: cmake -G Visual Studio 17 2022 -A x64 -T v143 C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\dummy Traceback (most recent call last): File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 198, in main()
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 188, in main
main_windows()
~~~~~~~~~~~~^^
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 163, in main_windows
generator = find_windows_generator()
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 130, in find_windows_generator
try_cmake(cmake_dir, build_dir, *generator)
~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\User_Niki\AppData\Local\Temp\7\pip-install-hp1qa3xs\llvmlite_8c11503a66174cef9d9dcdd93c04fe8b\ffi\build.py", line 95, in try_cmake
subprocess.check_call(args)
~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "C:\Program Files\Python314\Lib\subprocess.py", line 414, in check_call
retcode = call(*popenargs, **kwargs)
File "C:\Program Files\Python314\Lib\subprocess.py", line 395, in call
with Popen(*popenargs, **kwargs) as p:
~~~~~^^^^^^^^^^^^^^^^^^^^^^
File "C:\Program Files\Python314\Lib\subprocess.py", line 1038, in init
self._execute_child(args, executable, preexec_fn, close_fds,
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pass_fds, cwd, env,
^^^^^^^^^^^^^^^^^^^
...<5 lines>...
gid, gids, uid, umask,
^^^^^^^^^^^^^^^^^^^^^^
start_new_session, process_group)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Program Files\Python314\Lib\subprocess.py", line 1552, in _execute_child
hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
# no special security
^^^^^^^^^^^^^^^^^^^^^
...<4 lines>...
cwd,
^^^^
startupinfo)
^^^^^^^^^^^^
FileNotFoundError: [WinError 2] Не удается найти указанный файл
error: command 'C:\Users\User_Niki\venv314t\Scripts\python.exe' failed with exit code 1
[end of output]

note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed building wheel for llvmlite
Failed to build llvmlite
error: failed-wheel-build-for-install

× Failed to build installable wheels for some pyproject.toml based projects
╰─> llvmlite
(venv314t) PS C:\Users\User_Niki\venv314t> python.exe
Python 3.14.0 free-threading build (tags/v3.14.0:ebf955d, Oct 7 2025, 10:13:09) [MSC v.1944 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.

exit
(venv314t) PS C:\Users\User_Niki\venv314t>

I'm getting this exact same error when trying to install numba 0.45 on a Python .venv, either with uv or pip I get the error FileNotFoundError: [WinError 2] The system cannot find the file specified when Popen tries to find the Python executable although I have already checked that the executable exists in the given directory. For me it looks like this:

        File "C:\Users\anmar\AppData\Roaming\uv\python\cpython-3.14.0-windows-x86_64-none\Lib\subprocess.py", line 1552, in _execute_child
          hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
                             ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
                                   # no special security
                                   ^^^^^^^^^^^^^^^^^^^^^
          ...<4 lines>...
                                   cwd,
                                   ^^^^
                                   startupinfo)
                                   ^^^^^^^^^^^^
      FileNotFoundError: [WinError 2] The system cannot find the file specified
      error: command 'C:\\Users\\anmar\\AppData\\Local\\uv\\cache\\builds-v0\\.tmpvHxnqv\\Scripts\\python.exe' failed with exit code 1

I have already checked that python.exe exists in that path at the time the command runs, and it's a proper executable, not a symlink or a shorcut.

I'm not sure if it's a problem in the subprocess package or in llvmlite src/ffi/build.py that is calling it, but it's annoying that I cannot properly install numba in Python 3.14 because llvmlite fails to build

Nov 04 '25 11:11 toni-neurosc

Nov 04 '25 12:11 nikimagic

I'm getting this exact same error when trying to install numba 0.45 on a Python .venv, either with uv or pip I get the error FileNotFoundError: [WinError 2] The system cannot find the file specified when Popen tries to find the Python executable although I have already checked that the executable exists in the given directory. For me it looks like this:
        File "C:\Users\anmar\AppData\Roaming\uv\python\cpython-3.14.0-windows-x86_64-none\Lib\subprocess.py", line 1552, in _execute_child
          hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
                             ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
                                   # no special security
                                   ^^^^^^^^^^^^^^^^^^^^^
          ...<4 lines>...
                                   cwd,
                                   ^^^^
                                   startupinfo)
                                   ^^^^^^^^^^^^
      FileNotFoundError: [WinError 2] The system cannot find the file specified
      error: command 'C:\\Users\\anmar\\AppData\\Local\\uv\\cache\\builds-v0\\.tmpvHxnqv\\Scripts\\python.exe' failed with exit code 1
I have already checked that python.exe exists in that path at the time the command runs, and it's a proper executable, not a symlink or a shorcut.

I'm not sure if it's a problem in the subprocess package or in llvmlite src/ffi/build.py that is calling it, but it's annoying that I cannot properly install numba in Python 3.14 because llvmlite fails to build

@toni-neurosc : 0.45 does not support 3.14. No binary wheels for 3.14 are available and so you are trying to install from source. Why that fails, I have no idea. I recommend trying the recent beta releases that do support 3.14 (but not 3.14t!):

https://numba.discourse.group/t/ann-numba-0-63-0b1-llvmlite-0-46-0b1-python-3-14-support/3068

Lastly, you can keep up with the 3.14 support of the Numba/llvmlite stack at: https://github.com/numba/numba/issues/9957

Hope that helps?

Nov 04 '25 16:11 esc

@nikimagic this is still llvmlite 0.46.0b1 installation failing on 3.14t?? Or is there something else you wanted to bring our attention to?

Nov 04 '25 16:11 esc

Yes, venv314t, Python 3.14t. Windows server 2025.

Numpy Torch 2.10 nighly (2.8 t version) Matplotlib Pyzmq Jupyter Spyder Pandas 3.0 dev ( t version)

All venv314t work.

Nov 04 '25 22:11 nikimagic