Ruff v0.16.0: default rules increased from 59 to 413

Astral shipped Ruff v0.16.0 on July 23rd, 2026, raising the number of default rules from 59 to 413. The previous default was set in v0.1.0. The total rule count grew from 708 to 968. Many new rules catch syntax errors and runtime issues that were previously not enabled. Author Simon Willison tested on his projects Datasette, sqlite-utils, and LLM, finding hundreds of minor issues. For sqlite-utils, running 'uvx ruff@latest check . --fix --unsafe-fixes' fixed 1538 out of 1618 errors. Examples of remaining issues include DTZ005 (datetime.now without tz), BLE001 (catching blind Exception), and B018 (useless attribute access). Willison used Codex (GPT-5.6 Sol high) for LLM and sqlite-utils, and Claude Code (with Opus 5) for Datasette.