uv 0.12.3

uv 0.12.3 shipped on August 7, 2026. Maintenance release. One Python addition, three preview refinements, four performance wins.

Python Support

• CPython 3.13.15 added to managed downloads (#20997)

Preview Features

• uv cache size gains --output-format — choose automatic, human-readable, or raw-byte output (#20992)
• uv workspace metadata --quiet now preserves JSON output while suppressing diagnostics (#20991)
• uv workspace metadata JSON output is streamed — memory use drops sharply on large workspaces (#20990)

Performance

• Linux startup latency reduced — workspace cache initializes before the extra thread spawns (#20989)
• Compiled workspace exclusion patterns are reused during workspace discovery (#20988)
• Conflict-heavy resolutions speed up — materialized range complements avoided (#20982)
• Python interpreter discovery on Linux skips slow procfs reads (#20987)

Documentation

• GitHub Actions publishing example adds PEP 740 attestations (#20986)
• Publishing example restricted to Python version tags (#20973)
• uv init --bare example corrected — --python-pin is now --pin-python (#20876)

Upgrade with uv self update. No breaking changes in this release.