Build Failure After Upgrading from Tailwind CSS 4.0.8 to 4.0.12

[softwarecurator]

What version of Tailwind CSS are you using?
Upgrading from v4.0.8 to v4.0.12 causes the issue
@tailwindcss/vite: Upgrading from 4.0.8 to 4.0.12

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

• SvelteKit (Svelte 5)
• Vite
• Bits UI integration

What version of Node.js are you using?
v20.18.1

What browser are you using?
N/A - Build failure issue

What operating system are you using?
Mac OS

Description
Build failure occurs when upgrading from Tailwind CSS 4.0.8 to 4.0.12. Project uses custom theme configuration with CSS variables, custom fonts, and glass morphism effects.

Relevant configuration:

@import 'tailwindcss';

@theme {
  --font-family-display: 'JetBrains Mono', sans-serif;
  --color-primary: #15de6d;
  --color-dark: #18181c;
  --color-bg: #111115;
}

Steps to reproduce:

1. Start with working project on Tailwind 4.0.8
2. Upgrade to 4.0.12
3. Project fails to build

bash11:31:01 AM [vite-plugin-svelte] src/routes/marketplace/+page.svelte:145:9 Self-closing HTML tags for non-void elements are ambiguous — use<div ...>rather than<div ... />https://svelte.dev/e/element_invalid_self_closing_tag 143: <div class="h-4 bg-[#252525] rounded w-3/4 mb-1" /> 144: <div class="h-3 bg-[#252525] rounded w-1/2 mb-2" /> 145: <div class="h-4 bg-[#252525] rounded w-1/4" /> ^ 146: </div> 147: </div> transforming (58) src/routes/support/+page.svelte^C%

^ Freezes after this step and doesnt continue build until timeout

[RobinMalfait]

Can you provide a minimal reproduction repo? These errors seem unlikely to Tailwind CSS because we don't modify your HTML in any way shape or form 🤔