Summary

Running uv sync --active will delete and recreate the activated virtualenv when the following environment is used:

UV_PYTHON_INSTALL_DIR=.python-installs    # MUST be a relative path
UV_PYTHON_PREFERENCE=only-managed
UV_PYTHON_DOWNLOADS=automatic

This happens regardless of whether the active virtualenv already uses a uv managed python.

As the --active flag is designed for syncing to a virtualenv "outside of the project or script" I would never expect the sync command to delete it.

Example (from within a uv project directory)

export UV_PYTHON_INSTALL_DIR=.python-installs
export UV_PYTHON_PREFERENCE=only-managed
export UV_PYTHON_DOWNLOADS=automatic
uv venv foobar
source foobar/bin/activate
uv sync --active   # stdout tells you that uv "Removed virtual environment at: foobar"

Platform

Linux 6.8.0-85-generic x86_64 GNU/Linux

Version

uv 0.9.7

Python version

No response