Memory leak in 4.0.18 causing OOM when running multiple tests

[natew]

Describe the bug

vitest 4.0.18 has a memory leak when running multiple tests in sequence, causing OOM (Out of Memory) errors. Downgrading to 4.0.4 resolves the issue.

Reproduction

The tamagui monorepo has a reproduction of this issue:

• Commit with fix (pinning to 4.0.4): tamagui/tamagui@9a8381a175
• Commit before fix (4.0.18): tamagui/tamagui@3ac968be38

Steps to reproduce:

1. Clone https://github.com/tamagui/tamagui at commit 3ac968be38 (using vitest ^4.0.18)
2. Run bun install && bun run build:js
3. Run cd code/compiler/static-tests && bun run test:babel:web
4. Observe OOM error after running 27 tests

With vitest 4.0.4 (commit 9a8381a175), the same tests pass in ~1 second without any memory issues.

System Info

Node.js v24.3.0
macOS Darwin 25.2.0
vitest 4.0.18 (broken)
vitest 4.0.4 (working)

Used Package Manager

bun

Expected behavior

Tests should run without OOM errors regardless of the number of tests being run.

Actual behavior

After running ~20+ tests, the process runs out of memory and crashes with:

FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory

Additional context

• This only occurs when running multiple tests in the same session
• Individual tests pass fine
• Memory accumulates across tests, suggesting workers/processes aren't being cleaned up properly
• Adding --max-old-space-size=8192 or --no-file-parallelism doesn't help
• The issue appeared after upgrading from 4.0.4 to 4.0.18

Validations

• Check that there isn't already an issue that reports the same bug
• The provided reproduction is minimal and self-contained

[AriPerkkio]

A minimal reproduction would be really helpful. The first thing Vitest maintainers need to do here is reduce the reproduction to a smaller one.

I'm seeing this same OOM crash even without Vitest in your project. Just by running node example.ts that has the same code inlined.

import * as babel from '@babel/core'
import type { ExtractToClassNamesProps } from '@tamagui/static'
import * as temp from '@tamagui/static'

const { createExtractor, extractToClassNames } = temp.default

export async function extractForNative(code: string) {
  const out = await babel.transformAsync(code, {
    configFile: './babel-config-test.cjs',
    filename: 'test.tsx',
  })

  return out
}

// cache extractor to avoid OOM in CI from repeated config loading
let cachedExtractor: ReturnType<typeof createExtractor> | null = null

function getExtractor() {
  if (!cachedExtractor) {
    cachedExtractor = createExtractor()
  }
  return cachedExtractor
}

export async function extractForWeb(
  source: string,
  opts?: Partial<ExtractToClassNamesProps>
) {
  return await extractToClassNames({
    extractor: getExtractor(),
    shouldPrintDebug: source.startsWith('// debug'),
    source,
    sourcePath: `/test.tsx`,
    ...opts,
    options: {
      platform: 'web',
      components: ['tamagui', '@tamagui/core', '@tamagui/test-design-system'],
      config: './tests/lib/tamagui.config.cjs',
      ...opts?.options,
    },
  })
}

// This is what's called in test case and causes OOM

const output = await extractForWeb(
  `
    import { View } from '@tamagui/core'
    export function Test(props) {
      return (
        <View
        p="$2"                              // base padding
        pb={floating ? 18 : 15}             // should override bottom
        mr={floating2 ? 2 : 1}              // unrelated ternary
        borderTopRightRadius={10}           // base tr radius
        borderRadius={floating ? 5 : 2}     // should override the tr radius always
        {...floating2 && {
          borderTopLeftRadius: 7
          }}
          />
          )
          }
          `,
  {
    options: {
      platform: 'web',
      components: ['@tamagui/core'],
    },
  }
)

ari ~/Git/tamagui/code/compiler/static-tests ((HEAD detached at 9a8381a175)) $ node example.ts 

(node:66443) [MODULE_TYPELESS_PACKAGE_JSON] Warning: Module type of file:///Users/ari/Git/tamagui/code/compiler/static-tests/example.ts is not specified and it doesn't parse as CommonJS.
Reparsing as ES module because module syntax was detected. This incurs a performance overhead.
To eliminate this warning, add "type": "module" to /Users/ari/Git/tamagui/code/compiler/static-tests/package.json.
(Use `node --trace-warnings ...` to show where the warning was created)

  ➡ [tamagui] built config, components, prompt (42ms)

<--- Last few GCs --->

[66443:0x7cc80c000]    18946 ms: Mark-Compact 4060.8 (4136.9) -> 4056.7 (4140.9) MB, pooled: 0 MB, 635.71 / 0.00 ms  (average mu = 0.283, current mu = 0.214) allocation failure; scavenge might not succeed
[66443:0x7cc80c000]    20214 ms: Mark-Compact 4065.3 (4143.9) -> 4061.5 (4161.6) MB, pooled: 0 MB, 1150.75 / 0.00 ms  (average mu = 0.179, current mu = 0.092) allocation failure; GC in old space requested


<--- JS stacktrace --->

FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
----- Native stack trace -----

 1: 0x102de7040 node::OOMErrorHandler(char const*, v8::OOMDetails const&) [/Users/ari/.nvm/versions/node/v22.22.0/bin/node]
 2: 0x102fc379c v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, v8::OOMDetails const&) [/Users/ari/.nvm/versions/node/v22.22.0/bin/node]
 3: 0x1031d2f30 v8::internal::Heap::stack() [/Users/ari/.nvm/versions/node/v22.22.0/bin/node]
29: 0x10e56a584 
30: 0x10e56837c 

...

69: 0x102ce6518 node::SpinEventLoopInternal(node::Environment*) [/Users/ari/.nvm/versions/node/v22.22.0/bin/node]
70: 0x102e3193c node::NodeMainInstance::Run() [/Users/ari/.nvm/versions/node/v22.22.0/bin/node]
71: 0x102da1d50 node::Start(int, char**) [/Users/ari/.nvm/versions/node/v22.22.0/bin/node]
72: 0x18a0c1d54 start [/usr/lib/dyld]
Abort trap: 6

I don't think this is a bug in Vitest @natew.

[github-actions]

Hello @natew. Please provide a minimal reproduction using a GitHub repository or StackBlitz (you can also use examples). Issues marked with needs reproduction will be closed if they have no activity within 3 days.

[AriPerkkio]

Marking as needs reproduction as the out-of-memory error can only be triggered with code that causes same error without Vitest.

[pijuzmagnificuz]

Same issue, simple tests with custom class InputStream, no visible reason for crashing in code. Tests are passing, but OOM occurs in exit process when cleaning worker.

• Stack: Vitest 4.0.18 + n|Solid (node fork)

[AriPerkkio]

@pijuzmagnificuz please open a new issue for that, or post the reproduction here. Setting up a reproduction with simple test like that shouldn't take more than couple of minutes. 🙌

[pijuzmagnificuz]

Hi @AriPerkkio ! Just found the problem was on my code (auto-cleanup of connections made the job, now if dev forgot to close, mem will be free). Vitest seems pretty fine, tested with valgrind when test was still failing, and got zero memory leaks :)

[Viktor-Ivliev]

Similarly, when upgrading from 4.0.17 to 4.0.18, a memory leak began to appear. The problem was solved by adding afterEach(() => { vi.clearAllTimers(); }).

I should mention that this only happens for ChromiumHeadless mode on ci. But locally, I also noticed a significant increase in memory usage.

Although I have eliminated some of the memory leaks, I will continue to use version 17 for now, as it is more stable. Apart from my own project, I cannot reproduce this elsewhere. So this is more of an informative message about where something has been changed, which sometimes leads to memory leaks.

Data that I can provide in accordance with company policy:

{
  "name": "frontend",
  "version": "0.0.0",
  "packageManager": "pnpm@10.32.1",
  "browserslist": "> 5%, last 3 Chrome versions, last 3 Firefox version, last 2 Edge major versions, last 2 Safari major versions, last 2 iOS major versions, Firefox ESR",
  "scripts": {
    "watch": "pnpm store prune && ng build --watch --output-hashing=all",
    "start": "ng serve",
    "build": "ng build --configuration production",
    "test": "ng test --browsers=chromium",
    "test-ci": "ng test --browsers=ChromiumHeadless --coverage --watch=false",
    "lint": "ng lint",
    "bundle-report": "ng build --configuration production --stats-json && webpack-bundle-analyzer ../public/frontend/stats.json"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "21.2.2",
    "@angular/cdk": "21.2.1",
    "@angular/common": "21.2.2",
    "@angular/compiler": "21.2.2",
    "@angular/core": "21.2.2",
    "@angular/forms": "21.2.2",
    "@angular/platform-browser": "21.2.2",
    "@angular/platform-browser-dynamic": "21.2.2",
    "@angular/router": "21.2.2",
    "@ctrl/ngx-emoji-mart": "9.3.0",
    "@fontsource/inter": "5.2.8",
    "@fontsource/poppins": "5.2.7",
    "@fortawesome/fontawesome-free": "7.2.0",
    "@ng-select/ng-select": "21.5.2",
    "@ngstack/code-editor": "9.0.0",
    "@ngx-translate/core": "17.0.0",
    "@popperjs/core": "2.11.8",
    "@primeuix/themes": "2.0.3",
    "@rails/actioncable": "8.1.200",
    "@rails/activestorage": "8.1.200",
    "@types/crypto-js": "4.2.2",
    "@types/jquery": "3.5.34",
    "@types/sanitize-html": "2.16.1",
    "@typescript-plus/fast-memoize-decorator": "0.2.1",
    "angular-mentions": "1.5.0",
    "autolinker": "4.1.5",
    "bootstrap": "5.3.8",
    "chart.js": "4.5.1",
    "chartjs-plugin-datalabels": "2.2.0",
    "crypto-js": "4.2.0",
    "dayjs": "1.11.19",
    "deepmerge-ts": "7.1.5",
    "jquery": "3.7.1",
    "jspdf": "4.2.0",
    "jspdf-autotable": "5.0.7",
    "marked": "17.0.4",
    "monaco-editor": "0.52.2",
    "ngx-color": "10.1.0",
    "ngx-cookie-service": "21.1.0",
    "ngx-translate-multi-http-loader": "20.0.0",
    "object-to-formdata": "4.5.1",
    "primeicons": "7.0.0",
    "primeng": "21.1.3",
    "rxjs": "7.8.2",
    "sanitize-html": "2.17.1",
    "tslib": "2.8.1",
    "typescript": "5.9.3",
    "vite": "7.3.1",
    "zone.js": "0.16.1"
  },
  "devDependencies": {
    "@angular-devkit/core": "21.2.2",
    "@angular-devkit/schematics": "21.2.2",
    "@angular-eslint/builder": "21.3.0",
    "@angular-eslint/eslint-plugin": "21.3.0",
    "@angular-eslint/eslint-plugin-template": "21.3.0",
    "@angular-eslint/schematics": "21.3.0",
    "@angular-eslint/template-parser": "21.3.0",
    "@angular/build": "21.2.2",
    "@angular/cli": "21.2.2",
    "@angular/compiler-cli": "21.2.2",
    "@types/node": "25.4.0",
    "@typescript-eslint/eslint-plugin": "8.57.0",
    "@typescript-eslint/parser": "8.57.0",
    "@typescript-eslint/utils": "8.57.0",
    "@vitest/browser-playwright": "4.0.18",
    "@vitest/coverage-v8": "4.0.18",
    "eslint": "9.39.4",
    "eslint-plugin-import": "2.32.0",
    "eslint-plugin-jsdoc": "62.7.1",
    "eslint-plugin-prefer-arrow": "1.2.3",
    "eslint-plugin-unused-imports": "4.4.1",
    "postcss-preset-env": "11.2.0",
    "vitest": "4.0.18",
    "webpack-bundle-analyzer": "5.2.0"
  }
}

vitest.config.ts

import { defineConfig } from 'vitest/config';
import path from 'path';

export default defineConfig({
  resolve: {
    alias: { 
      fs: path.resolve('./src/vitest-mocks/fs.ts'),
      path: path.resolve('./src/vitest-mocks/path.ts'),
      qs: path.resolve('./src/vitest-mocks/qs.ts'),
      url: path.resolve('./src/vitest-mocks/url.ts'),
      '/frontend/browser/assets': path.resolve('./src/assets'),
      '/frontend/browser/media': path.resolve('./node_modules/@fortawesome/fontawesome-free/webfonts'),
    },
  },
  test: {
    setupFiles: ['./src/vitest.setup.ts'],
    fileParallelism: true,
    pool: 'threads'
  }
});

vitest.setup.ts

import { afterEach, beforeEach, vi } from 'vitest';
import { TestBed } from '@angular/core/testing';


(globalThis as any).process = { env: {}, cwd: () => '/', };

beforeEach(() => {
  vi.useFakeTimers();
});

afterEach(() => {
  vi.restoreAllMocks();
  vi.clearAllTimers();
  vi.useRealTimers();
  TestBed.resetTestingModule();
});

---

note: looks like ti angular problem =( it works correctly with 21.1.6 but with 21.2.2 we have problems. So this is not a problem.