Keep your dependencies updated!
Tailwind 4 can be configured in the CSS file (no need of tailwind.config.js)
However you need to first update tailwind.config.js in a very specific way to run the upgrade command smoothly.
I highly recommend you to read the official release notes & upgrade guide to be familiar with the latest syntax.
Official upgrade guide: [member-only link]
Gem tailwindcss-rails: [member-only link]
Episode source code: [member-only link]
0:00 About Tailwind 4 on Rails
1:21 Old Tailwind setup
3:13 Run upgrade tool
5:50 Borrow best practices from new app
7:24 Prepare Yarn/NPM upgrade package
9:20 Run upgrade command
10:24 Tailwind Watch not working
11:35 Fix aspect ratio
12:15 Fix dialogs
13:00 Fix opacity