v4 alpha 0.28 breaks plugin (tailwindcss-animate) & weird behavior with new p3 color opacity

[ajayvignesh01]

What version of Tailwind CSS are you using?

v4.0.0-alpha.28

What build tool (or framework if it abstracts the build tool) are you using?

postcss 8.4.47, Next.js 15.0.0-rc.1

What version of Node.js are you using?

v20.16.0

What browser are you using?

Chrome

What operating system are you using?

For example: macOS

Reproduction URL

https://github.com/ajayvignesh01/tailwind-v4.0.0-alpha.28-plugins

Describe your issue

The tailwindcss-animate plugin was working since plugin support landed a few weeks ago. But when I upgrade to alpha 0.28, it stops working. No errors are thrown, but animations that rendered with alpha 0.21 - 0.27 are now not rendering.

Another bug is from the introduction of p3 colors. If you hover over the primary button which has bg-primary hover:bg-primary/90, the hover color shows a hue of green for some reason.

Preview with alpha 0.27 - https://tailwind-v4-0-0-alpha-28-plugins-gjaplla02.vercel.app/
Preview with alpha 0.28 - https://tailwind-v4-0-0-alpha-28-plugins-4pzuz8jxf.vercel.app/

[thecrypticace]

Dropping some notes for me to look at tomorrow:

Regarding the colors:

• This is only an issue in Chrome, FF and Safari are fine
• The trigger requires an oklch/okblab color with a none component. Replacing it with a 0 fixes the issue.
• Changing the color space of the color-mix also fixes the issue (but should not be necessary)

button {
  /* broken */
  background-color: color-mix(in srgb, oklch(0.985 0 none) 95%, transparent);

  /* works */
  background-color: color-mix(in srgb, oklch(0.985 0 0) 95%, transparent);
  background-color: color-mix(in oklch, oklch(0.985 0 none) 95%, transparent);
  background-color: color-mix(in oklab, oklch(0.985 0 none) 95%, transparent);
}

I think what's happening is that it gets converted into color(srgb …) internally, carries over the none component, and replaces the none at the end with 0 — instead of doing it before the conversion. Based on the following observations:

button {
  /* this is yellow */
  background-color: color-mix(in srgb, color(srgb 1.0 1.0 none) 95%, transparent);

  /* as is this */
  background-color: color-mix(in srgb, color(srgb 1.0 1.0 0) 95%, transparent);
  
  /* window.getComputedStyle($0)["background-color"] produces a color(srgb …) value */
  background-color: color-mix(in srgb, oklch(0.985 0 none) 95%, transparent);
}