On the bundled sample: 35 findings (18 errors, 14 warnings, 3 info) in 1 file from 19 rules.

Who it’s for
Front-end developers and teams with a Tailwind CSS v3 codebase who are about to bump tailwindcss to v4.

What breaks, and when
Tailwind v4 dropped the @tailwind directives and removed the -opacity- utilities. In v4, outline-none hides the focus ring in forced-colors mode, and custom utilities inside @layer utilities silently stop working.

What you get
• SKILL.md, an offline Node scanner and the 19-rule table
• file:line, severity and what changes in v4

See it first
The real output of the bundled example is on getreadystack.com/skills/tailwind-v4-upgrade-check/ — free, no sign-up, so you see what it finds before you pay.

Install in 30 seconds
Unzip into ~/.claude/skills/, then ask Claude Code: “We want to move this project from Tailwind v3 to v4. What will break or look different? Don’t edit anything yet.”. Needs Node 16+.

What it does not do
It does not run Tailwind or migrate tailwind.config.js.

FAQ
Q: How is this different from asking Claude without the skill?
A: The skill carries a dated rule table and a scanner that reads every file, so Claude quotes the exact date and line instead of guessing from memory.
Q: How do I get the files?
A: In your Whop library after paying: the lesson “tailwind-v4-upgrade-check.zip”.