`nitro/vite` will break down unocss in `tanstack start RC`

[zouhangwithsweet]

Environment

• nitro: 3.0.0-20250925-181710-5191890e
• nodejs: v24.5.0

Reproduction

https://github.com/fisand/f3-app/tree/main/apps/web-tanstack

Describe the bug

If I use nitro/vite to build a tanstack start(RC) APP, it looks like will remove vite:css-post plugin, then the CSS will not generator succefully.

[plugin unocss:global:build:generate] [unocss] failed to find vite:css-post plugin. It might be an internal bug of UnoCSS

Other issue is nitro/vite will not match a 404 route to noFoundComponent in a tanstack start(RC) APP, it will always loading util the APP crash.

node:internal/deps/undici/undici:13484
      Error.captureStackTrace(err);
            ^

TypeError: fetch failed
    at node:internal/deps/undici/undici:13484:13

  [cause]: HeadersTimeoutError: Headers Timeout Error
      at FastTimer.onParserTimeout [as _onTimeout] (/node_modules/.pnpm/[email protected]/node_modules/undici/lib/dispatcher/client-h1.js:757:28)
      at Timeout.onTick [as _onTimeout] (/Users/SYY/Desktop/work/f3-app/node_modules/.pnpm/[email protected]/node_modules/undici/lib/util/timers.js:162:13)
      at listOnTimeout (node:internal/timers:594:17)
      at process.processTimers (node:internal/timers:529:7) {
    code: 'UND_ERR_HEADERS_TIMEOUT'
  }

Additional context

No response

Logs

[pi0]

Can you please share a minimal reproduction with nitro plugin only + unocss? (no tanstack start)

[zouhangwithsweet]

Sorry I cannot make a reproduction successfully. But I think it has a relation with these codes:

https://github.com/unocss/unocss/blob/main/packages-integrations/vite/src/modes/global/build.ts#L127

async configResolved(config) {
        const distDirs = [
          resolve(config.root, config.build.outDir),
        ]

        // for Vite lib more with rollupOptions.output, #2231
        if (config.build.rollupOptions.output) {
          const outputOptions = config.build.rollupOptions.output
          const outputDirs = Array.isArray(outputOptions)
            ? outputOptions.map(option => option.dir).filter(Boolean) as string[]
            : outputOptions.dir
              ? [outputOptions.dir]
              : []

          outputDirs.forEach((dir) => {
            distDirs.push(dir)

            if (!isAbsolute(dir))
              distDirs.push(resolve(config.root, dir))
          })
        }

        const cssPostPlugin = config.plugins.find(i => i.name === 'vite:css-post') as Plugin | undefined
        const cssPlugin = config.plugins.find(i => i.name === 'vite:css') as Plugin | undefined

        if (cssPostPlugin)
          distDirs.forEach(dir => cssPostPlugins.set(dir, cssPostPlugin))

        if (cssPlugin)
          distDirs.forEach(dir => cssPlugins.set(dir, cssPlugin))

        await ready
      },

nitro/vite use a custom viteserver to build file, but the unocss just read the user's vite.config. So when it scan the file, it will not find the right path.

https://github.com/nitrojs/nitro/blob/main/src/build/vite/build.ts#L10

const builder = await createBuilder({
    base: nitro.options.rootDir,
    plugins: [nitroPlugin({ _nitro: nitro })],
  });

[zouhangwithsweet]

So to fix it issue the easy way is that we can let unocss/vite know nitro output path. Just add the build.outdir filed. But I will not effect the nitro.

[zouhangwithsweet]

But I think it's a problem about nitro working with all other vite plugins. When we use nitro/vite, the development servert & the builder is not using a same config. What do you think about that ? @pi0

[pi0]

Maybe we default userConfig.build.outDir when not set by users?

[zouhangwithsweet]

We can explicitly point out the differences in configuration between nitro/vite and other Vite plugins in the document to help users understand. Currently, considering that this will not affect the core functions of nitro, it is recommended that no changes be made for the time being.

[zouhangwithsweet]

I also notice that nitro/vite have differrent behavoir with vite or rolldown/vite

[gxres042]

I also notice that nitro/vite have differrent behavoir with vite or rolldown/vite

nitro/vite hadn't supported rolldown-vite yet

[zouhangwithsweet]

[email protected] will break dev server down with tanstack start.

node:internal/url:826
      href = bindingUrl.parse(input, base, true);
                        ^

TypeError: Invalid URL
    at new URL (node:internal/url:826:25)

[pi0]

I have added a fix to [email protected] to this issue. You can update lockfile to get fix.

(keeping issue open, we should fix some more places in nitro to avoid similar issues in the future)

[zouhangwithsweet]

nitro build will copy node_modules into server folder, but the packages's lost many files. Like drizzle-orm, it losts index.js balabla.

--- update --- I can fix it with the options noExternals: true, but nitro default value is false

[pi0]

@zouhangwithsweet only used files will be traced. Did you get a runtime error for drizzle usage? (if yes it is a bug with nf3 integration)

[zouhangwithsweet]

@zouhangwithsweet only used files will be traced. Did you get a runtime error for drizzle usage? (if yes it is a bug with nf3 integration)

Yes, there is a runtime error.cannot resolve drizzel-orm/index.js. Look likes a upstream bug.

[zouhangwithsweet]

I had updated https://github.com/fisand/f3-app/tree/main/apps/web-tanstack, you can reproduce it easily.