[Tailwind v4] Fully Dynamic Class Names from Server-Side Data Not Applied at Runtime

[krishnamk-2604]

We are dynamically injecting utility class names from the server side. For example, the server returns:

{
  "className": "my-4 sm:my-5 md:my-8 lg:my-10"
}

This is applied in the component like so:

<div className={cn(
  "space-y-8 md:space-y-12 lg:space-y-14",
  webPages?.className
)}>
  ...
</div>

Observed Behavior
The combined class string renders correctly in the DOM:

class="space-y-8 md:space-y-12 lg:space-y-14 my-4 sm:my-5 md:my-8 lg:my-10"

However, styles from the dynamically injected classes (my-4, sm:my-5, etc.) are not applied. The base and statically coded classes work correctly. The values are unpredictable, user-configured, and cannot be feasibly safelisted. and is not practical due to unpredictable nature of the data (e.g., hundreds of possible permutations).

[rozsazoltan]

Related: #18137 (comment)