uv 0.12.15

Astral shipped uv 0.12.15 on September 15, 2026. If you jumped straight to 0.12.14, this patch cleans up a regression that quietly rejected some perfectly valid installation commands. Worth reading before you blame your Dockerfile.

The regression that bit real workflows

The 0.12.14 release introduced stricter argument validation that went too far. Commands like uv pip install --system inside python:* Docker images, and uv pip install --target . for project-local installs, were being refused even though they had always worked. For anyone running uv inside containers or shipping --system flags in CI, that meant suddenly green pipelines going red.

What actually changed

• Rejects now accepted: valid installation commands using --system in base images and --target for local installs are recognized again.
• Scope contained: this is a focused bug-fix patch, not a feature release. No new surface area to adopt, no config drift.

The honest take

Patches that only undo a previous patch are never exciting, but they matter when they restore something you rely on. The real lesson is to pin uv in CI rather than tracking latest, because a one-tick tooling regression like this one is exactly the kind of thing a @latest pin will hand you without warning. Upgrade when you next touch Python tooling, not because 0.12.15 is new, but so you stop being pinned on a broken 0.12.14.