Classes not generated after upgrading npm packages when CSS classes are inside TYPO3 Fluid template tags

What version of Tailwind CSS are you using?

Like suggested in this issue (#16801 (comment)), I've installed the "insiders" versions.

Currently installed versions:

• "@tailwindcss/vite": "^0.0.0-insiders.7005ad7"
• "tailwindcss": "^0.0.0-insiders.7005ad7"

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

• Vite 6.1.0

What version of Node.js are you using?

• Node version: v22.14.0

What browser are you using?

• Latest Google Chrome

What operating system are you using?

• Linux Fedora

Reproduction URL

I cannot provide a reproduction URL.

Describe your issue

I'm using the new Tailwindcss v4 with Vite in a PHP project (TYPO3 CMS). TYPO3 uses it's own templating engine to generate HTML for the frontend, which is called Fluid.

Here's an example Fluid template snippet:

<!-- Fluid template language -->
<f:variable name="bgStyle">
  <f:switch expression="{data.layout}">
    <f:case value="0">from-blue-900 to-cyan-200</f:case>
    <f:case value="1">from-cyan-600 to-teal-200</f:case>
    <f:defaultCase>from-blue-300 to-cyan-100</f:defaultCase>
  </f:switch>
</f:variable>

<!-- Normal HTML code with Fluid variable "bgStyle" in the "class" attribute -->
<div class="bg-gradient-to-br from-20% {bgStyle}">...</div>

Up until today this worked just fine. Today I updated my NPM packages (npm update). The packages were updated from version 4.0.6 to version 4.0.12. Now CSS classes that are not written inside normal HTML code (last line in the example), are not picked up and therefore are not added to the final CSS file.

Then I've read about the insiders versions and tried to install those. But still the CSS classes inside the Fluid template part are not recognized.

I did some quick testing: I tried every version between 4.0.6 and 4.0.12:

With the following versions, the CSS classes inside the Fluid template tags are picked up correctly:

• 4.0.6, 4.0.7, 4.0.8, 4.0.9

With the following versions, the CSS classes are not recognized and therefore ignored:

• 4.0.10, 4.0.11, 4.0.12

As mentioned in my opening post, with the "insiders" version it still doesn't work like before.

I hope this helps to narrow down the possible source of the issue.

[RobinMalfait]

This has been fixed by #17094 and will be available in the next release.

@RobinMalfait Thank your for fixing this issue so quickly 👍