# Tailwind CSS v4.1.6 — Release & Upgrade Intelligence
- **Product:** Tailwind CSS (https://tailwindcss.com)
- **Version:** v4.1.6
- **Released:** May 09, 2025
- **Impact Score:** 5/10
- **Breaking Changes:** Not verified
- **Canonical Analysis:** https://changelogs.us/tailwind/updates/v4.1.6/

## Executive Summary (TL;DR)
Tailwind CSS v4.1.6. Source highlight: Upgrade: Automatically convert arbitrary values to named values when possible (e.g. `h-[1lh]` to `h-lh`) (#17831, #17854)

## New Features
- Upgrade: Automatically convert arbitrary values to named values when possible (e.g. `h-[1lh]` to `h-lh`) (#17831, #17854)
- Upgrade: Update dependencies in parallel for improved performance (#17898)
- Add support for generating source maps in development (#17775)

## Bug Fixes
- Add detailed logging about `@source` directives, discovered files and scanned files when using `DEBUG=*` (#17906, #17952)
- Ensure negative arbitrary `scale` values generate negative values (#17831)
- Fix HAML extraction with embedded Ruby (#17846)
- Don't scan files for utilities when using `@reference` (#17836)
- Fix incorrectly replacing `_` with ` ` in arbitrary modifier shorthand `bg-red-500/(--my_opacity)` (#17889)
- Don't scan `.log` files for classes by default (#17906)

## Upgrade Command
```bash
npm install --save-exact tailwindcss@4.1.6
```