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briefcase dev fails in Fedora 44 Kinoite Toolbox under Python 3.14 #2988
Description
Describe the bug
Attempting to run podium from main with briefcase dev on a new Linux (Fedora Kinoite 44 Toolbox container) machine, the created virtual environment under .briefcase was missing its Python executables (full traceback shown below) when using Python 3.14.
This could be a compatibility issue with the toolbox image's Python 3.14 installation rather than one with 3.14 in general (switching to a uv-provided standalone build of Python 3.13 made the problem go away, but it's not clear if it's the "python build standalone" vs "Fedora dnf package" aspect that resolved the issue or the "Python 3.13" vs "Python 3.14" aspect).
How to reproduce the bug
- In a Fedora 44 Kinoite Toolbox container, install briefcase using the system Python 3.14 runtime (I tried this with both
python3 -m pip install --user briefcaseanduv tool install briefcase) - Run
briefcase devin a briefcase project (I usedpodium) - Get the exception shown below
Minimum example code
Screenshots
No response
Environment details
- Operating system and version: Fedora 44 Kinoite Toolbox container
- Python version: 3.14 (system DNF package version)
- Software versions:
- Briefcase: 0.4.4
Logs
⬢ [ancoghlan@toolbx podium]$ briefcase dev
Evaluating dynamic project metadata... done
[podium] Activating dev environment...
[podium] Starting in dev mode...
Log saved to /var/home/ancoghlan/devel/podium/logs/briefcase.2026_08_09-15_32_59.dev.log
Traceback (most recent call last):
File "/var/home/ancoghlan/.local/bin/briefcase", line 6, in <module>
sys.exit(main())
~~~~^^
File "/var/home/ancoghlan/.local/lib/python3.14/site-packages/briefcase/__main__.py", line 27, in main
command(**options)
~~~~~~~^^^^^^^^^^^
File "/var/home/ancoghlan/.local/lib/python3.14/site-packages/briefcase/commands/dev.py", line 330, in __call__
return self.run_dev_app(
~~~~~~~~~~~~~~~~^
app,
^^^^
...<3 lines>...
**options,
^^^^^^^^^^
)
^
File "/var/home/ancoghlan/.local/lib/python3.14/site-packages/briefcase/commands/dev.py", line 167, in run_dev_app
app_popen = venv.Popen(
cmdline,
...<5 lines>...
bufsize=1,
)
File "/var/home/ancoghlan/.local/lib/python3.14/site-packages/briefcase/integrations/virtual_environment/base.py", line 172, in Popen
return self.tools.subprocess.Popen(args, **kwargs)
~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
File "/var/home/ancoghlan/.local/lib/python3.14/site-packages/briefcase/integrations/subprocess.py", line 732, in Popen
return self._subprocess.Popen(
~~~~~~~~~~~~~~~~~~~~~~^
[str(arg) for arg in args], **self.final_kwargs(**kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/usr/lib64/python3.14/subprocess.py", line 1039, 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 "/usr/lib64/python3.14/subprocess.py", line 1990, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: '/var/home/ancoghlan/devel/podium/.briefcase/podium/dev.cpython-314-x86_64-linux-gnu/bin/python'
Additional context
No response
Activity
[-]`briefcase dev` fails on Linux under Python 3.14[/-][+]`briefcase dev` fails in Fedora 44 Kinoite Toolbox under Python 3.14[/+]freakboy3742 commentedon Aug 9, 2026
Thanks for the report.
Unfortunately, I haven't been able to reproduce this - but I'm not sure if that's because my Fedora test machine is Fedora 42, or because I'm unfamiliar with Toolbox.
On Fedora 42, if I create a toolbox container,
pip install briefcase, and then runbriefcase dev, the python3.13 binary exists in the expected.briefcase/helloworld/dev.cpython-313-aarch64-linux-gnu/bin/python, and an app starts as expected.Three things to check:
python3 -m venv testvenvinside the toolbox container, doestestbenv/bin/pythonexist? Is it a symlink to python3, which is a symlink to /usr/bin/python3? Anything else notable about the binary?briefcase dev -r -vv, you'll get a full trace of the commands that are executed by Briefcase to create and populate the venv. If you manually reproduce those commands (with a location other than the.briefcase/dev....folder, can you reproduce the error (or the absence of the python3 binary?.briefcasefolder, then runbriefcase dev, and provide the log file that is generated on failure?