unit test failure in isolated venv

Recent changes in #575 to include support for Python 3.14 is successfully running vi CI, but it is failing in an isolated virtual environment.

```bash
uv sync --all-extras --python 3.14
uv run python -m pytest --cov=fab tests/unit_tests
```

stack trace:
[fab-unit_test.log](https://github.com/user-attachments/files/29332270/fab-unit_test.log)

Reproduce the failure with `uv sync --all-extras --python 3.14` followed by `uv run python -m pytest --cov=fab tests/unit_tests`. Start by reviewing the attached `fab-unit_test.log` and the Python 3.14 support changes in #575. Done means the unit tests pass in the isolated virtual environment.

Written by the indexing model from the issue text.