ESLint 9 flat config: WXT auto-import globals not respected when using @antfu/eslint-config (no-undef + Config Layering Failures)

Describe the bug

Summary

When integrating WXT’s generated ESLint auto-import globals (imports.eslintrc.enabled: 9) with @antfu/eslint-config under ESLint 9 flat config mode, the global identifiers provided by WXT are not recognized by ESLint (resulting in no-undef errors for browser, defineBackground, defineContentScript). Attempts to compose / layer the generated flat-config with @antfu/eslint-config either have no effect or produce structural errors (e.g. TypeError: antfuConfigs is not iterable, ConfigError: Unexpected key "0"). The only stable workaround is to reintroduce explicit imports — which defeats the purpose of WXT auto-imports.

What I expected

A documented, stable pattern to compose WXT-generated ESLint flat-config (languageOptions.globals) with @antfu/eslint-config so that WXT globals are recognized without adding explicit imports.

What actually happens

• Removing explicit imports produces ESLint no-undef errors for WXT globals, while TypeScript build OK.
• Attempts to merge/compose configs either do not add globals or break flat config validation / composition with @antfu/eslint-config.

Reproduction

Minimal reproduction layout

The issue can be reproduced using these minimal files:

wxt.config.ts

import tailwindcss from '@tailwindcss/vite';
import { defineConfig } from 'wxt';

export default defineConfig({
  modules: ['@wxt-dev/module-vue'],
  imports: {
    eslintrc: {
      enabled: 9,
    },
  },
});

src/background.ts

// Removing these imports causes ESLint no-undef errors
import { browser } from 'wxt/browser';
import { defineBackground } from 'wxt/utils/define-background';

export default defineBackground({
  /* ... */
});

eslint-auto-imports.mjs (generated by WXT)

const globals = {
  browser: true,
  defineBackground: true,
  defineContentScript: true
};

export default {
  name: 'wxt/auto-imports',
  languageOptions: {
    globals,
    sourceType: 'module'
  }
};

eslint.config.js

import antfu from '@antfu/eslint-config';
import oxlint from 'eslint-plugin-oxlint';

export default antfu({
  ignores: ['dist/**', 'node_modules/**'],
  vue: { a11y: true },
  typescript: { tsconfigPath: 'tsconfig.json' },
  rules: {
    'antfu/no-top-level-await': 'off',
    'no-console': 'off'
  }
},
...oxlint.buildFromOxlintConfigFile('./.oxlintrc.json'));

Steps to reproduce

No response

System Info

System:
    OS: macOS 26.0.1
    CPU: (12) arm64 Apple M2 Pro
    Memory: 71.42 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 25.0.0 
    npm: 11.6.2 
    bun: 1.3.1 
  Browsers:
    Brave Browser: 141.1.83.120
    Chrome: 141.0.7390.108
    Edge: 140.0.3485.94
    Firefox Developer Edition: 145.0
    Safari: 26.0.1
  npmPackages:
    wxt: 0.20.11 => 0.20.11

Used Package Manager

bun

Validations

• 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.
• 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.

Start with the reproduced wxt.config.ts, generated eslint-auto-imports.mjs, eslint.config.js, and src/background.ts. Trace how the generated flat config is composed with @antfu/eslint-config and oxlint, then verify the WXT globals no longer trigger no-undef without explicit imports. Done means a documented, stable composition pattern that passes ESLint flat-config validation.