Summary

When a tool is executing for a long period of time, for example uvx mlflow server,
running uv cache prune will remove its files while still running!

This is a screenshot from from htop:

However uv cache prune will remove it:

❯ ls /Users/radek/.cache/uv/archive-v0/yl7-ET-Ix2_OI5icDQcWe
CACHEDIR.TAG bin          lib          pyvenv.cfg   share
❯ uv cache prune
Pruning cache at: /Users/radek/.cache/uv
Removed 12436 files (465.6MiB)
❯ ls /Users/radek/.cache/uv/archive-v0/yl7-ET-Ix2_OI5icDQcWe
ls: /Users/radek/.cache/uv/archive-v0/yl7-ET-Ix2_OI5icDQcWe: No such file or directory

But the mflow server process is still running! This will cause any runtime imports to fail. If this happens during the process startup, it fails inevitably.

This is also contrary to the statement in docs:

uv cache prune removes all unused cache entries. For example, the cache directory may contain entries created in previous uv versions that are no longer necessary and can be safely removed. uv cache prune is safe to run periodically, to keep the cache directory clean.

https://docs.astral.sh/uv/concepts/cache/#clearing-the-cache

Naive fix idea

Add a new cache bucket which would use pid of the running process ~/.cache/uv/uvx-process-v1/{pid}/{symlink}
When pruning cache uv could check whether the process with pid still exists and if not - remove the directory.

Related feature request:

Also it would be nice to have a way to prune old versions of the tool only and keep the latest one (the one that would be used by uvx <tool> as per docs, we could have --keep-tools flag to uv cache prune or something like that:

uvx will use the latest available version of the requested tool on the first invocation. After that, uvx will use the cached version of the tool unless a different version is requested, the cache is pruned, or the cache is refreshed.

Context:

We're trying to create a platform which spawns processes using uvx:

https://github.com/i-am-bee/beeai/blob/85d970a5b7436f742bc85ed9ab6e324bf91bbeed/apps/beeai-server/src/beeai_server/domain/model.py#L203

However it leaves a lot of files on the filesystem potentially forever with no way to clean them because uv cache prune breaks the running processes.

Thanks for all the amazing work!

Platform

Darwin 24.3.0 arm64

Version

uv 0.6.2 (6d3614e 2025-02-19)

Python version

Python 3.11.11