Performance regression since version above 6.0.2

[DarkSorrow]

Related plugins

• plugin-react

• plugin-react-swc

• plugin-rsc

Describe the bug

Hello,

I have a huge private project for a company where i use the plugin-react, i upgraded it to the 6.0.3 and 6.0.4 but both those version made the build go from 3 minutes to 2h54 minutes.
I had to downgrade to 6.0.2 for it to build again in two minutes. The project is relatively big with mui v9, icons react-flow and huggingface/trasnformers but i have to pin the plugin to its version 6.0.2 for it to work well

I can show you the vite config file which is very simple

import { defineConfig } from 'vite';
import react, { reactCompilerPreset } from '@vitejs/plugin-react';
import babel from '@rolldown/plugin-babel';
import svgr from 'vite-plugin-svgr';

const host = process.env.NOVA_BACKEND_URL || 'http://localhost:8000';

/**
 * E2E + @cypress/code-coverage: instrument via [babel-plugin-istanbul](https://github.com/istanbuljs/babel-plugin-istanbul)
 * in the same Babel pass as the React compiler (matches production transforms).
 */
const e2eCoverage = process.env.CYPRESS_COVERAGE === 'true';

// https://vitejs.dev/config/
export default defineConfig({
  server: {
    host: '0.0.0.0',
    open: false,
    port: 3000,
    watch: {
      usePolling: true,
      interval: 1000,
      ignoreInitial: true,
    },
    proxy: {
      '/api': {
        target: host,
        changeOrigin: true,
      },
      '/public': {
        target: host,
        changeOrigin: true,
      },
      '/oidc': {
        target: host,
        changeOrigin: true,
      },
    },
  },

  build: {
    outDir: 'build',
    target: 'es2020',
  },
  optimizeDeps: {
    include: [
      '@emotion/react',
      '@emotion/styled',
      '@mui/material',
      '@mui/material/InitColorSchemeScript',
      '@mui/icons-material',
      '@huggingface/transformers',
    ],
  },
  worker: {
    format: 'es',
  },
  plugins: [
    react(),
    babel({
      presets: [reactCompilerPreset({ target: '19' })],
      plugins: e2eCoverage
        ? [
          [
            'babel-plugin-istanbul',
            {
              cwd: process.cwd(),
              nycrcPath: '.nycrc.json',
            },
          ],
        ]
        : [],
    }),
    svgr({ svgrOptions: { icon: true } }),
  ],
});

And for additional info here are the tests i made before finding this

• vite: 8.1.5 (also reproduced on 8.0.16 and 8.1.1 — not vite-version-dependent)
• rolldown: 1.1.5 (also reproduced with rolldown pinned to 1.1.3/1.2.0 — not rolldown-version-dependent on its own)
• @vitejs/plugin-react: 6.0.2 (works) vs 6.0.3/6.0.4 (hangs)
• Build command: vite build (production), triggered via tsc && vite build

Edit

Well this is what the LLM said as well

Root cause identified: The hang is not from the @rolldown/pluginutils bump as your issue draft suggests — it's from a new defaultCodeFilter regex that plugin-react 6.0.3 introduced in reactCompilerPreset (the changelog omits this code change). The regex's third alternation [^\s:=(){}[],;]\s(?:(|[:=]\s*(?:function|()) catastrophically backtracks (O(n²)) on any module containing a multi-megabyte single-line sourceMappingURL base64 data URI — exactly what onnxruntime-web's unbundled .mjs files ship (4M-char lines in ort.all.mjs, 1.8M in ort.mjs, etc.), pulled into your graph by @huggingface/transformers. The old 6.0.2 regex (/\b[A-Z]|\buse/) has no quantifier and finishes in <1ms on the same input.

Reproduction

https://bolt.new/p/69393844

Steps to reproduce

No response

System Info

- OS: Windows 11
- Node: v24

- Linux (github action)

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.