I Finally Got pgAdmin 4 Working in FlyEnv on Windows — Here’s What Actually Went Wrong

Installing pgAdmin 4 via FlyEnv on Windows can present challenges, particularly when encountering errors during the build of pywinpty. This issue arises due to the Python version incompatibility between the build system and the desired Python installation. The error message indicates that the configured Python interpreter version (3.14) exceeds PyO3's maximum supported version (3.13).

The root cause lies in the fact that the pywinpty component, built from source during the installation process, relies on an older version of PyO3, which does not yet support Python 3.14. To rectify the issue, the recommended workaround is to ensure FlyEnv utilizes Python 3.13 for the pgAdmin installation, rather than the newer Python 3.14.

To implement this solution, first, select Python 3.13 within the FlyEnv environment. Navigate to the Python settings and confirm that a Python 3.13.x installation is available and selected. Avoid using Python 3.14 for this particular installation while the affected dependency continues to have this compatibility limitation.

Next, if FlyEnv has already created a pgAdmin virtual environment utilizing Python 3.14, it is essential to remove this existing environment. From the pgAdmin directory, execute the command "rmdir /s /q venv" to delete the outdated virtual environment. Subsequently, reinstall pgAdmin through FlyEnv, ensuring that the virtual environment is recreated using the correct Python 3.13 interpreter.

After the successful installation, verify the Python version within the virtual environment by executing "venv\Scripts\python.exe --version". The output should display Python 3.13.x, confirming the proper setup. Additionally, validate the installation by running "venv\Scripts\python.exe -m pip show pgadmin4" to ensure pgAdmin was installed correctly.

Finally, locate the pgAdmin executable at "venv\Scripts\pgadmin4.exe". Launch the application by executing "venv\Scripts\pgadmin4.exe". Upon launching, FlyEnv should automatically open pgAdmin in your default web browser, typically at "http://127.0.0.1:5050".

It is important to note that this workaround does not imply Python 3.14 itself is defective. Rather, the issue stems from the dependency chain during the pgAdmin installation process. Specifically, the pywinpty build within the affected setup relies on a PyO3 version that does not yet accommodate Python 3.14. Future updates to FlyEnv or pgAdmin may resolve this compatibility issue if the affected dependencies are updated to support Python 3.14.

For now, utilizing Python 3.13 as the Python version for the pgAdmin installation through FlyEnv is the recommended solution.