[v4-alpha] @tailwindcss/vite throws "Cannot convert undefined or null to object" loop when using Bun

[Kat404]

What version of Tailwind CSS are you using?

v4.0.0

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

Vite 7.3.0

What version of Node.js are you using?

Node.js 25.2.1, using Bun 1.3.5 (baseline version) for the whole proyect

What browser are you using?

Firefox 146.0.1

What operating system are you using?

Arch Linux x86_64

Reproduction URL

https://github.com/Kat404/CSS-Aprendizaje

Describe your issue

Hello! I'm trying to test Tailwind CSS v4 (alpha/beta) using Bun and Vite on a machine with an older CPU (Intel Celeron J4115, Gemini Lake).

The dev server starts correctly, but I get a huge ERROR screen.

Also, immediately after loading, terminal is flooded with errors from the @tailwindcss/vite plugin.

Reproduction Steps:

1. OS: Arch Linux x86_64
2. Runtime: Bun v1.3.5 (Baseline version, installed via script due to no AVX2 support on CPU).
3. Scaffold a new project: bun create vite (Vanilla JS).
4. Install v4 deps: bun add -D tailwindcss@next @tailwindcss/vite@next vite.
5. Configure vite.config.js with the tailwindcss plugin.
6. Add @import "tailwindcss"; to CSS.
7. Run bunx vite dev.

[wongjn]

Diagnosis

You seem to have mixmatched Tailwind package versions. This is because earlier versions of Tailwind v4 weren't strict enough with their dependency versioning:

$ bun pm ls --all | grep tailwindcss
├── @tailwindcss/node@4.1.18
│   └── tailwindcss@4.1.18
├── @tailwindcss/oxide@4.1.18
├── @tailwindcss/oxide-android-arm64@4.1.18
├── @tailwindcss/oxide-darwin-arm64@4.1.18
├── @tailwindcss/oxide-darwin-x64@4.1.18
├── @tailwindcss/oxide-freebsd-x64@4.1.18
├── @tailwindcss/oxide-linux-arm-gnueabihf@4.1.18
├── @tailwindcss/oxide-linux-arm64-gnu@4.1.18
├── @tailwindcss/oxide-linux-arm64-musl@4.1.18
├── @tailwindcss/oxide-linux-x64-gnu@4.1.18
├── @tailwindcss/oxide-linux-x64-musl@4.1.18
├── @tailwindcss/oxide-wasm32-wasi@4.1.18
├── @tailwindcss/oxide-win32-arm64-msvc@4.1.18
├── @tailwindcss/oxide-win32-x64-msvc@4.1.18
├── @tailwindcss/vite@4.0.0
├── tailwindcss@4.0.0

Notice how your explicitly-installed packages are 4.0.0 but the others are 4.1.18.

Fix

We can explicitly update the packages to ensure everything is using the same version:

$ bun update tailwindcss @tailwindcss/vite

$ bun pm ls --all | grep tailwindcss
├── @tailwindcss/node@4.1.18
├── @tailwindcss/oxide@4.1.18
├── @tailwindcss/oxide-android-arm64@4.1.18
├── @tailwindcss/oxide-darwin-arm64@4.1.18
├── @tailwindcss/oxide-darwin-x64@4.1.18
├── @tailwindcss/oxide-freebsd-x64@4.1.18
├── @tailwindcss/oxide-linux-arm-gnueabihf@4.1.18
├── @tailwindcss/oxide-linux-arm64-gnu@4.1.18
├── @tailwindcss/oxide-linux-arm64-musl@4.1.18
├── @tailwindcss/oxide-linux-x64-gnu@4.1.18
├── @tailwindcss/oxide-linux-x64-musl@4.1.18
├── @tailwindcss/oxide-wasm32-wasi@4.1.18
├── @tailwindcss/oxide-win32-arm64-msvc@4.1.18
├── @tailwindcss/oxide-win32-x64-msvc@4.1.18
├── @tailwindcss/vite@4.1.18
├── tailwindcss@4.1.18

The error should now be gone.

[Kat404]

Firstly, thank you so much, you're awesome dude :D
Secondly, the @next tag is the producer of this bug, the result of executing bun add -d tailwindcss @tailwindcss/vite vite is going to be:

bun add v1.3.5 (1e86cebd)

installed tailwindcss@4.1.18
installed @tailwindcss/vite@4.1.18
installed vite@7.3.0 with binaries:
 - vite

34 packages installed [3.87s]

So, without @next tag, TailwindCSS itself and TailwindCSS => Vite are going to be the exact version of the rest of the dependencies, skipping the effort of doing bun update tailwindcss @tailwindcss/vite