Simon Willison Finds a Cache-Friendly uvx Recipe for GitHub Actions: Pin UV_EXCLUDE_NEWER Into the Cache Key

Simon Willison·medium signal

Willison shares a workflow trick that finally makes `uvx tool-name` cacheable in GitHub Actions: set `UV_EXCLUDE_NEWER: "2026-07-12"` as an env var and fold that date into the cache key. Because the exclude-newer date makes uv's dependency resolution deterministic, tool versions stay stable across runs and PyPI downloads stop repeating; bumping the date is how you deliberately invalidate the cache. A small, directly-applicable CI optimization for anyone running Python tooling in Actions.