Ruff 0.16.5

Ruff 0.16.5 was released on August 27, 2026 as the latest patch in the 0.16 line. This release refines the new default-rules setup, introduces category selectors, and resolves several targeted bugs across popular rule plugins. No breaking changes are included.

Overview

Ruff 0.16.5 lands roughly one week after 0.16.4 and continues the steady, weekly cadence the Astral team has maintained through 2026. The release is low-risk by design: it tightens preview behavior, expands how rules can be selected, and fixes a handful of false positives reported by the community.

Preview Features

• Rules without codes are now allowed, giving plugin authors more flexibility when defining experimental diagnostics.
• Category selectors have been introduced, letting you enable or configure rules at a higher level instead of listing individual rule codes.
• The default preview rules and categories were refreshed to align with the direction of future stable releases.

Bug Fixes

• flake8-async: detect blocking generic HTTP requests (ASYNC210).
• flake8-datetimez: allow timezone-safe strptime chains (DTZ007).
• flake8-simplify: respect side effects in lambda defaults (SIM401).

Server Improvements

The Ruff language server received a documentation correction for the ClientOptions doc comment. The release also adds documentation covering rule acceptance guidelines and the new category selectors.

How to Update

Upgrading is straightforward. Run pip install -U ruff or uv tool upgrade ruff, or pull the latest release through your package manager of choice. If you rely on preview-mode rules, review the updated preview defaults before enabling the new category selectors.