If you are installing pgAdmin through FlyEnv on Windows and the installation fails while building pywinpty, you may see an error similar to:
error: the configured Python interpreter version (3.14)
is newer than PyO3's maximum supported version (3.13)
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You may also see:
ERROR: Failed building wheel for pywinpty
Failed to build installable wheels for some pyproject.toml
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based projects
The important part of the error is not actually pip itself. In this case, pywinpty is being built from source and uses PyO3/Rust. The version of PyO3 involved in the build does not support Python 3.14, so the build fails.
The Fix
The simplest workaround is to make sure FlyEnv uses Python 3.13 for the pgAdmin installation instead of Python 3.14.
1. Select Python 3.13 in FlyEnv
In FlyEnv, open the Python section and make sure a Python 3.13 installation is available and selected.
For example:
Python 3.13.x
Do not use Python 3.14 for this installation while the affected dependency still has this compatibility limitation.
2. Remove the failed pgAdmin virtual environment
If FlyEnv already created a pgAdmin virtual environment using Python 3.14, simply changing the global Python version may not be enough because the existing venv still points to the old interpreter.
From the pgAdmin directory:
cd "C:\Program Files\FlyEnv-Data\server\postgresql\pgadmin4"
Remove the existing virtual environment:
rmdir /s /q venv
Then reinstall pgAdmin through FlyEnv so that the virtual environment is recreated using Python 3.13.
3. Verify the interpreter
After installation:
venv\Scripts\python.exe --version
You should see something similar to:
Python 3.13.x
You can also verify that pgAdmin was installed correctly:
venv\Scripts\python.exe -m pip show pgadmin4
4. Launch pgAdmin
The executable should be available at:
venv\Scripts\pgadmin4.exe
You can launch it with:
venv\Scripts\pgadmin4.exe
FlyEnv should then open pgAdmin in your browser, usually at:
What about Python 3.14?
This workaround does not mean Python 3.14 itself is broken.
The problem is the dependency chain used during the pgAdmin installation. In particular, the pywinpty build in the affected setup uses a version of PyO3 that does not yet recognize Python 3.14.
This may no longer be necessary in a future FlyEnv/pgAdmin release if the affected dependencies are updated to support Python 3.14.
So if you encounter this error, try Python 3.13 first rather than fighting the Rust/build-toolchain errors.