diff --git a/.eslintrc.cjs b/.eslintrc.cjs
deleted file mode 100644
index de2207d9..00000000
--- a/.eslintrc.cjs
+++ /dev/null
@@ -1,42 +0,0 @@
-"use strict";
-
-module.exports = {
-    root: true,
-    extends: [
-        "eslint"
-    ],
-    parserOptions: {
-        ecmaVersion: 2020
-    },
-
-    /*
-     * it fixes eslint-plugin-jsdoc's reports: "Invalid JSDoc tag name "template" jsdoc/check-tag-names"
-     * refs: https://github.com/gajus/eslint-plugin-jsdoc#check-tag-names
-     */
-    settings: {
-        jsdoc: {
-            mode: "typescript"
-        }
-    },
-
-    overrides: [
-        {
-            files: ["tests/**/*"],
-            env: { mocha: true },
-            rules: {
-                "no-restricted-syntax": ["error", {
-                    selector: "CallExpression[callee.object.name='assert'][callee.property.name='doesNotThrow']",
-                    message: "`assert.doesNotThrow()` should be replaced with a comment next to the code."
-                }],
-
-                // Overcome https://github.com/mysticatea/eslint-plugin-node/issues/250
-                "node/no-unsupported-features/es-syntax": ["error", {
-                    ignores: [
-                        "modules",
-                        "dynamicImport"
-                    ]
-                }]
-            }
-        }
-    ]
-};
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
new file mode 100644
index 00000000..1a950cb4
--- /dev/null
+++ b/.github/CODEOWNERS
@@ -0,0 +1,2 @@
+.release-please-manifest.json @eslint/eslint-tsc
+.github/workflows/release-please.yml @eslint/eslint-tsc
\ No newline at end of file
diff --git a/.github/workflows/add-to-triage.yml b/.github/workflows/add-to-triage.yml
new file mode 100644
index 00000000..06dd5b63
--- /dev/null
+++ b/.github/workflows/add-to-triage.yml
@@ -0,0 +1,19 @@
+name: add-to-triage
+
+on:
+    issues:
+        types:
+            - opened
+            - reopened
+            - transferred
+
+    pull_request_target:
+        types:
+            - opened
+            - reopened
+
+jobs:
+    add-to-triage:
+        uses: eslint/workflows/.github/workflows/add-to-triage.yml@main
+        secrets:
+            project_bot_token: ${{ secrets.PROJECT_BOT_TOKEN }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4909f16e..06f78358 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -10,10 +10,10 @@ jobs:
     name: Verify Files
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
-    - uses: actions/setup-node@v3
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
       with:
-        node-version: '16.x'
+        node-version: "lts/*"
     - name: Install Packages
       run: npm install
     - name: Lint Files
@@ -24,19 +24,32 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        node: [21.x, 20.x, 19.x, 18.x, 17.x, 16.x, 14.x, 12.x, "12.22.0"]
+        node: [25.x, 24.x, 23.x, 22.x, 21.x, 20.x, 18.x, "18.18.0"]
         include:
         - os: windows-latest
-          node: "12.x"
+          node: "lts/*"
         - os: macOS-latest
-          node: "12.x"
+          node: "lts/*"
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v3
-    - uses: actions/setup-node@v3
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
       with:
         node-version: ${{ matrix.node }}
     - name: Install Packages
       run: npm install
     - name: Test
       run: npm test
+
+  test_types:
+    name: Test Types
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
+      with:
+        node-version: lts/*
+    - name: Install Packages
+      run: npm install
+    - name: Test
+      run: npm run test:types
diff --git a/.github/workflows/release-please.yml b/.github/workflows/release-please.yml
index c60c453b..cef408df 100644
--- a/.github/workflows/release-please.yml
+++ b/.github/workflows/release-please.yml
@@ -2,6 +2,7 @@ on:
   push:
     branches:
       - main
+
 name: release-please
 jobs:
   release-please:
@@ -11,37 +12,27 @@ jobs:
       pull-requests: write
       id-token: write
     steps:
-      - uses: google-github-actions/release-please-action@v3
+      - uses: googleapis/release-please-action@v4
         id: release
-        with:
-          release-type: node
-          package-name: '@eslint/eslintrc'
-          pull-request-title-pattern: 'chore: release ${version}'
-          changelog-types: >
-            [
-              { "type": "feat", "section": "Features", "hidden": false },
-              { "type": "fix", "section": "Bug Fixes", "hidden": false },
-              { "type": "docs", "section": "Documentation", "hidden": false },
-              { "type": "build", "section": "Build Related", "hidden": false },
-              { "type": "chore", "section": "Chores", "hidden": false },
-              { "type": "perf", "section": "Chores", "hidden": false },
-              { "type": "ci", "section": "Chores", "hidden": false },
-              { "type": "refactor", "section": "Chores", "hidden": false },
-              { "type": "test", "section": "Chores", "hidden": false }
-            ]
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         if: ${{ steps.release.outputs.release_created }}
-      - uses: actions/setup-node@v3
+      - uses: actions/setup-node@v4
         with:
           node-version: lts/*
           registry-url: https://registry.npmjs.org
         if: ${{ steps.release.outputs.release_created }}
-      - run: npm install
+
+        # npm 11.5.1 or later is required so update to latest to be sure
+      - name: Update npm
+        run: npm install -g npm@latest
         if: ${{ steps.release.outputs.release_created }}
-      - run: npm publish --provenance
-        env:
-          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+
+      - name: Publish to npm
+        run: |
+            npm install
+            npm publish --provenance
         if: ${{ steps.release.outputs.release_created }}
+
       - run: 'npx @humanwhocodes/tweet "eslint/eslintrc ${{ steps.release.outputs.tag_name }} has been released: ${{ steps.release.outputs.html_url }}"'
         if: ${{ steps.release.outputs.release_created }}
         env:
diff --git a/.github/workflows/stale.yml b/.github/workflows/stale.yml
new file mode 100644
index 00000000..fe232e62
--- /dev/null
+++ b/.github/workflows/stale.yml
@@ -0,0 +1,15 @@
+name: stale
+
+on:
+    schedule:
+        - cron: "31 22 * * *" # Runs every day at 10:31 PM UTC
+
+permissions:
+    issues: write
+    pull-requests: write
+
+jobs:
+    stale:
+        uses: eslint/workflows/.github/workflows/stale.yml@main
+        secrets:
+            token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/update-readme.yml b/.github/workflows/update-readme.yml
new file mode 100644
index 00000000..96d09866
--- /dev/null
+++ b/.github/workflows/update-readme.yml
@@ -0,0 +1,13 @@
+name: update-readme
+
+on:
+    schedule:
+        - cron: "0 8 * * *" # Runs every day at 08:00 AM UTC
+
+    workflow_dispatch:
+
+jobs:
+    update-readme:
+        uses: eslint/workflows/.github/workflows/update-readme.yml@main
+        secrets:
+            workflow_push_bot_token: ${{ secrets.WORKFLOW_PUSH_BOT_TOKEN }}
diff --git a/.gitignore b/.gitignore
index 5423bd14..38bb2a34 100644
--- a/.gitignore
+++ b/.gitignore
@@ -110,3 +110,10 @@ pnpm-lock.yaml
 
 # used in tests
 /tmp/
+
+# IDEs and editors
+/.vscode
+*.code-workspace
+
+# Automatically generated files by GitHub Actions workflow
+/.shared-workflows
diff --git a/.release-please-manifest.json b/.release-please-manifest.json
new file mode 100644
index 00000000..f5258250
--- /dev/null
+++ b/.release-please-manifest.json
@@ -0,0 +1,3 @@
+{
+    ".": "3.3.3"
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1f1f1b32..b6593e9a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,98 @@
 # Changelog
 
+## [3.3.3](https://github.com/eslint/eslintrc/compare/eslintrc-v3.3.2...eslintrc-v3.3.3) (2025-11-28)
+
+
+### Bug Fixes
+
+* release v3.3.3 because publishing v3.3.2 failed ([#211](https://github.com/eslint/eslintrc/issues/211)) ([8aa555a](https://github.com/eslint/eslintrc/commit/8aa555a3f5fcfb7d99249fb57e819a7b6f635496))
+
+## [3.3.2](https://github.com/eslint/eslintrc/compare/eslintrc-v3.3.1...eslintrc-v3.3.2) (2025-11-25)
+
+
+### Bug Fixes
+
+* Remove name property from all and recommended configs ([#200](https://github.com/eslint/eslintrc/issues/200)) ([344da49](https://github.com/eslint/eslintrc/commit/344da491898a2a3595943d4528ba78fe2f238217))
+
+## [3.3.1](https://github.com/eslint/eslintrc/compare/v3.3.0...v3.3.1) (2025-03-11)
+
+
+### Bug Fixes
+
+* correct `types` field in package.json ([#184](https://github.com/eslint/eslintrc/issues/184)) ([2f4cf3f](https://github.com/eslint/eslintrc/commit/2f4cf3fe36ee0df93c1c53f32c030c58db1816a2))
+
+## [3.3.0](https://github.com/eslint/eslintrc/compare/v3.2.0...v3.3.0) (2025-02-21)
+
+
+### Features
+
+* Add types to package ([#179](https://github.com/eslint/eslintrc/issues/179)) ([cb546be](https://github.com/eslint/eslintrc/commit/cb546be8ba53abcb4c64ed2fdd3a729dd1337f61))
+
+## [3.2.0](https://github.com/eslint/eslintrc/compare/v3.1.0...v3.2.0) (2024-11-14)
+
+
+### Features
+
+* merge rule.meta.defaultOptions before validation ([#166](https://github.com/eslint/eslintrc/issues/166)) ([d02f914](https://github.com/eslint/eslintrc/commit/d02f91452b81caff971f7895237cc4fb002e31da))
+
+## [3.1.0](https://github.com/eslint/eslintrc/compare/v3.0.2...v3.1.0) (2024-05-17)
+
+
+### Features
+
+* Expose loadConfigFile() function ([#160](https://github.com/eslint/eslintrc/issues/160)) ([59e890f](https://github.com/eslint/eslintrc/commit/59e890fcd9e03663ac185640d5bed5f1a85bd39b))
+
+
+### Chores
+
+* run tests in Node.js 22 ([#154](https://github.com/eslint/eslintrc/issues/154)) ([5e526f2](https://github.com/eslint/eslintrc/commit/5e526f2e2897b87d7a704391cec74702d4bed38c))
+* update dependency shelljs to ^0.8.5 ([#156](https://github.com/eslint/eslintrc/issues/156)) ([903b887](https://github.com/eslint/eslintrc/commit/903b8875581ee731fd1a9424f83f785359cfb22e))
+
+## [3.0.2](https://github.com/eslint/eslintrc/compare/v3.0.1...v3.0.2) (2024-02-12)
+
+
+### Chores
+
+* maintenance update of `globals` to `v14` ([#152](https://github.com/eslint/eslintrc/issues/152)) ([4151865](https://github.com/eslint/eslintrc/commit/4151865b09084369e89d591eb2e01b9617287982))
+
+## [3.0.1](https://github.com/eslint/eslintrc/compare/v3.0.0...v3.0.1) (2024-02-09)
+
+
+### Documentation
+
+* fix changelog for v3.0.0 ([#144](https://github.com/eslint/eslintrc/issues/144)) ([a613847](https://github.com/eslint/eslintrc/commit/a61384731aff386a8260a80d9710c912e4f62aaa))
+* More explicit about all and recommended configs ([#150](https://github.com/eslint/eslintrc/issues/150)) ([0fabc74](https://github.com/eslint/eslintrc/commit/0fabc7406e5a281a4e72be33de6e3bf8642aa746))
+
+
+### Chores
+
+* upgrade espree@10.0.1 ([#151](https://github.com/eslint/eslintrc/issues/151)) ([8c39944](https://github.com/eslint/eslintrc/commit/8c399441f47009344888e181c6aa2ecdc74ce8ea))
+
+## [3.0.0](https://github.com/eslint/eslintrc/compare/v2.1.4...v3.0.0) (2023-12-27)
+
+
+### ⚠ BREAKING CHANGES
+
+* Require Node.js `^18.18.0 || ^20.9.0 || >=21.1.0` ([#142](https://github.com/eslint/eslintrc/issues/142))
+* Set default `schema: []`, drop support for function-style rules ([#139](https://github.com/eslint/eslintrc/issues/139))
+
+### Features
+
+* Require Node.js `^18.18.0 || ^20.9.0 || >=21.1.0` ([#142](https://github.com/eslint/eslintrc/issues/142)) ([737eb25](https://github.com/eslint/eslintrc/commit/737eb25ac686550020b838ccf6efd5cd2aaa449e))
+* Set default `schema: []`, drop support for function-style rules ([#139](https://github.com/eslint/eslintrc/issues/139)) ([a6c240d](https://github.com/eslint/eslintrc/commit/a6c240de244b0e94ace4a518f2c67876a91f5882))
+
+
+### Chores
+
+* upgrade github actions ([#143](https://github.com/eslint/eslintrc/issues/143)) ([de34faf](https://github.com/eslint/eslintrc/commit/de34fafed28aaf1936845d51309f28484ed29e2f))
+
+## [2.1.4](https://github.com/eslint/eslintrc/compare/v2.1.3...v2.1.4) (2023-11-27)
+
+
+### Bug Fixes
+
+* Use original plugin from disk in FlatCompat ([#137](https://github.com/eslint/eslintrc/issues/137)) ([1c4cf6a](https://github.com/eslint/eslintrc/commit/1c4cf6a71378d480323bfdd404c9585bd0d21d65))
+
 ## [2.1.3](https://github.com/eslint/eslintrc/compare/v2.1.2...v2.1.3) (2023-11-01)
 
 
diff --git a/README.md b/README.md
index 7641c741..846cd120 100644
--- a/README.md
+++ b/README.md
@@ -8,12 +8,14 @@ This repository contains the legacy ESLintRC configuration file format for ESLin
 
 You can install the package as follows:
 
-```
-npm install @eslint/eslintrc --save-dev
-
+```shell
+npm install @eslint/eslintrc -D
 # or
-
 yarn add @eslint/eslintrc -D
+# or
+pnpm install @eslint/eslintrc -D
+# or
+bun install @eslint/eslintrc -D
 ```
 
 ## Usage (ESM)
@@ -33,14 +35,14 @@ const __dirname = path.dirname(__filename);
 const compat = new FlatCompat({
     baseDirectory: __dirname,                  // optional; default: process.cwd()
     resolvePluginsRelativeTo: __dirname,       // optional
-    recommendedConfig: js.configs.recommended, // optional
-    allConfig: js.configs.all,                 // optional
+    recommendedConfig: js.configs.recommended, // optional unless you're using "eslint:recommended"
+    allConfig: js.configs.all,                 // optional unless you're using "eslint:all"
 });
 
 export default [
 
     // mimic ESLintRC-style extends
-    ...compat.extends("standard", "example"),
+    ...compat.extends("standard", "example", "plugin:react/recommended"),
 
     // mimic environments
     ...compat.env({
@@ -49,11 +51,11 @@ export default [
     }),
 
     // mimic plugins
-    ...compat.plugins("airbnb", "react"),
+    ...compat.plugins("jsx-a11y", "react"),
 
     // translate an entire config
     ...compat.config({
-        plugins: ["airbnb", "react"],
+        plugins: ["jsx-a11y", "react"],
         extends: "standard",
         env: {
             es2020: true,
@@ -77,14 +79,14 @@ const js = require("@eslint/js");
 const compat = new FlatCompat({
     baseDirectory: __dirname,                  // optional; default: process.cwd()
     resolvePluginsRelativeTo: __dirname,       // optional
-    recommendedConfig: js.configs.recommended, // optional
-    allConfig: js.configs.all,                 // optional
+    recommendedConfig: js.configs.recommended, // optional unless using "eslint:recommended"
+    allConfig: js.configs.all,                 // optional unless using "eslint:all"
 });
 
 module.exports = [
 
     // mimic ESLintRC-style extends
-    ...compat.extends("standard", "example"),
+    ...compat.extends("standard", "example", "plugin:react/recommended"),
 
     // mimic environments
     ...compat.env({
@@ -93,11 +95,11 @@ module.exports = [
     }),
 
     // mimic plugins
-    ...compat.plugins("airbnb", "react"),
+    ...compat.plugins("jsx-a11y", "react"),
 
     // translate an entire config
     ...compat.config({
-        plugins: ["airbnb", "react"],
+        plugins: ["jsx-a11y", "react"],
         extends: "standard",
         env: {
             es2020: true,
@@ -110,6 +112,34 @@ module.exports = [
 ];
 ```
 
+## Troubleshooting
+
+**TypeError: Missing parameter 'recommendedConfig' in FlatCompat constructor**
+
+The `recommendedConfig` option is required when any config uses `eslint:recommended`, including any config in an `extends` clause. To fix this, follow the example above using `@eslint/js` to provide the `eslint:recommended` config.
+
+**TypeError: Missing parameter 'allConfig' in FlatCompat constructor**
+
+The `allConfig` option is required when any config uses `eslint:all`, including any config in an `extends` clause. To fix this, follow the example above using `@eslint/js` to provide the `eslint:all` config.
+
 ## License
 
 MIT License
+
+<!-- NOTE: This section is autogenerated. Do not manually edit.-->
+<!--sponsorsstart-->
+
+## Sponsors
+
+The following companies, organizations, and individuals support ESLint's ongoing maintenance and development. [Become a Sponsor](https://eslint.org/donate)
+to get your logo on our READMEs and [website](https://eslint.org/sponsors).
+
+<h3>Platinum Sponsors</h3>
+<p><a href="https://automattic.com"><img src="https://images.opencollective.com/automattic/d0ef3e1/logo.png" alt="Automattic" height="128"></a> <a href="https://www.airbnb.com/"><img src="https://images.opencollective.com/airbnb/d327d66/logo.png" alt="Airbnb" height="128"></a></p><h3>Gold Sponsors</h3>
+<p><a href="https://qlty.sh/"><img src="https://images.opencollective.com/qltysh/33d157d/logo.png" alt="Qlty Software" height="96"></a> <a href="https://shopify.engineering/"><img src="https://avatars.githubusercontent.com/u/8085" alt="Shopify" height="96"></a></p><h3>Silver Sponsors</h3>
+<p><a href="https://vite.dev/"><img src="https://images.opencollective.com/vite/e6d15e1/logo.png" alt="Vite" height="64"></a> <a href="https://liftoff.io/"><img src="https://images.opencollective.com/liftoff/2d6c3b6/logo.png" alt="Liftoff" height="64"></a> <a href="https://americanexpress.io"><img src="https://avatars.githubusercontent.com/u/3853301" alt="American Express" height="64"></a> <a href="https://stackblitz.com"><img src="https://avatars.githubusercontent.com/u/28635252" alt="StackBlitz" height="64"></a></p><h3>Bronze Sponsors</h3>
+<p><a href="https://cybozu.co.jp/"><img src="https://images.opencollective.com/cybozu/933e46d/logo.png" alt="Cybozu" height="32"></a> <a href="https://syntax.fm"><img src="https://github.com/syntaxfm.png" alt="Syntax" height="32"></a> <a href="https://www.n-ix.com/"><img src="https://images.opencollective.com/n-ix-ltd/575a7a5/logo.png" alt="N-iX Ltd" height="32"></a> <a href="https://icons8.com/"><img src="https://images.opencollective.com/icons8/7fa1641/logo.png" alt="Icons8" height="32"></a> <a href="https://discord.com"><img src="https://images.opencollective.com/discordapp/f9645d9/logo.png" alt="Discord" height="32"></a> <a href="https://www.gitbook.com"><img src="https://avatars.githubusercontent.com/u/7111340" alt="GitBook" height="32"></a> <a href="https://nx.dev"><img src="https://avatars.githubusercontent.com/u/23692104" alt="Nx" height="32"></a> <a href="https://opensource.mercedes-benz.com/"><img src="https://avatars.githubusercontent.com/u/34240465" alt="Mercedes-Benz Group" height="32"></a> <a href="https://herocoders.com"><img src="https://avatars.githubusercontent.com/u/37549774" alt="HeroCoders" height="32"></a> <a href="https://www.lambdatest.com"><img src="https://avatars.githubusercontent.com/u/171592363" alt="LambdaTest" height="32"></a></p>
+<h3>Technology Sponsors</h3>
+Technology sponsors allow us to use their products and services for free as part of a contribution to the open source ecosystem and our work.
+<p><a href="https://netlify.com"><img src="https://raw.githubusercontent.com/eslint/eslint.org/main/src/assets/images/techsponsors/netlify-icon.svg" alt="Netlify" height="32"></a> <a href="https://algolia.com"><img src="https://raw.githubusercontent.com/eslint/eslint.org/main/src/assets/images/techsponsors/algolia-icon.svg" alt="Algolia" height="32"></a> <a href="https://1password.com"><img src="https://raw.githubusercontent.com/eslint/eslint.org/main/src/assets/images/techsponsors/1password-icon.svg" alt="1Password" height="32"></a></p>
+<!--sponsorsend-->
diff --git a/conf/environments.js b/conf/environments.js
index 50d1b1d1..e296fae7 100644
--- a/conf/environments.js
+++ b/conf/environments.js
@@ -23,7 +23,7 @@ function getDiff(current, prev) {
     const retv = {};
 
     for (const [key, value] of Object.entries(current)) {
-        if (!Object.hasOwnProperty.call(prev, key)) {
+        if (!Object.hasOwn(prev, key)) {
             retv[key] = value;
         }
     }
diff --git a/eslint.config.js b/eslint.config.js
new file mode 100644
index 00000000..0981a822
--- /dev/null
+++ b/eslint.config.js
@@ -0,0 +1,52 @@
+/**
+ * @fileoverview ESLint configuration file
+ * @author Nicholas C. Zakas
+ */
+
+//-----------------------------------------------------------------------------
+// Imports
+//-----------------------------------------------------------------------------
+
+import eslintConfigESLint from "eslint-config-eslint";
+import eslintConfigESLintFormatting from "eslint-config-eslint/formatting";
+
+//-----------------------------------------------------------------------------
+// Config
+//-----------------------------------------------------------------------------
+
+export default [
+
+    {
+        ignores: [
+            "tests/fixtures",
+            "coverage",
+            "docs",
+            "jsdoc",
+            "dist"
+        ]
+    },
+
+    ...eslintConfigESLint,
+    eslintConfigESLintFormatting,
+    {
+        files: ["tests/**/*"],
+        languageOptions: {
+            globals: {
+                describe: "readonly",
+                xdescribe: "readonly",
+                it: "readonly",
+                xit: "readonly",
+                beforeEach: "readonly",
+                afterEach: "readonly",
+                before: "readonly",
+                after: "readonly"
+            }
+        },
+        rules: {
+            "no-restricted-syntax": ["error", {
+                selector: "CallExpression[callee.object.name='assert'][callee.property.name='doesNotThrow']",
+                message: "`assert.doesNotThrow()` should be replaced with a comment next to the code."
+            }]
+        }
+    }
+];
diff --git a/lib/cascading-config-array-factory.js b/lib/cascading-config-array-factory.js
index 597352e4..71549107 100644
--- a/lib/cascading-config-array-factory.js
+++ b/lib/cascading-config-array-factory.js
@@ -23,8 +23,8 @@
 //------------------------------------------------------------------------------
 
 import debugOrig from "debug";
-import os from "os";
-import path from "path";
+import os from "node:os";
+import path from "node:path";
 
 import { ConfigArrayFactory } from "./config-array-factory.js";
 import {
@@ -193,7 +193,7 @@ function createCLIConfigArray({
  */
 class ConfigurationNotFoundError extends Error {
 
-    // eslint-disable-next-line jsdoc/require-description
+
     /**
      * @param {string} directoryPath The directory path.
      */
@@ -345,6 +345,7 @@ class CascadingConfigArrayFactory {
      * @param {string} directoryPath The path to a leaf directory.
      * @param {boolean} configsExistInSubdirs `true` if configurations exist in subdirectories.
      * @returns {ConfigArray} The loaded config.
+     * @throws {Error} If a config file is invalid.
      * @private
      */
     _loadConfigInAncestors(directoryPath, configsExistInSubdirs = false) {
@@ -446,6 +447,7 @@ class CascadingConfigArrayFactory {
      * @param {string} directoryPath The path to the leaf directory to find config files.
      * @param {boolean} ignoreNotFoundError If `true` then it doesn't throw `ConfigurationNotFoundError`.
      * @returns {ConfigArray} The loaded config.
+     * @throws {Error} If a config file is invalid.
      * @private
      */
     _finalizeConfigArray(configArray, directoryPath, ignoreNotFoundError) {
@@ -482,7 +484,7 @@ class CascadingConfigArrayFactory {
                     !directoryPath.startsWith(homePath)
                 ) {
                     const lastElement =
-                        personalConfigArray[personalConfigArray.length - 1];
+                        personalConfigArray.at(-1);
 
                     emitDeprecationWarning(
                         lastElement.filePath,
diff --git a/lib/config-array-factory.js b/lib/config-array-factory.js
index 23cb3529..4f55ae2e 100644
--- a/lib/config-array-factory.js
+++ b/lib/config-array-factory.js
@@ -39,10 +39,10 @@
 //------------------------------------------------------------------------------
 
 import debugOrig from "debug";
-import fs from "fs";
+import fs from "node:fs";
 import importFresh from "import-fresh";
-import { createRequire } from "module";
-import path from "path";
+import { createRequire } from "node:module";
+import path from "node:path";
 import stripComments from "strip-json-comments";
 
 import {
@@ -254,7 +254,7 @@ function loadPackageJSONConfigFile(filePath) {
     try {
         const packageData = loadJSONConfigFile(filePath);
 
-        if (!Object.hasOwnProperty.call(packageData, "eslintConfig")) {
+        if (!Object.hasOwn(packageData, "eslintConfig")) {
             throw Object.assign(
                 new Error("package.json file doesn't have 'eslintConfig' field."),
                 { code: "ESLINT_CONFIG_FIELD_NOT_FOUND" }
@@ -273,6 +273,7 @@ function loadPackageJSONConfigFile(filePath) {
  * Loads a `.eslintignore` from a file.
  * @param {string} filePath The filename to load.
  * @returns {string[]} The ignore patterns from the file.
+ * @throws {Error} If the file cannot be read.
  * @private
  */
 function loadESLintIgnoreFile(filePath) {
@@ -345,7 +346,7 @@ function loadConfigFile(filePath) {
 function writeDebugLogForLoading(request, relativeTo, filePath) {
     /* istanbul ignore next */
     if (debug.enabled) {
-        let nameAndVersion = null;
+        let nameAndVersion = null; // eslint-disable-line no-useless-assignment -- known bug in the rule
 
         try {
             const packageJsonPath = ModuleResolver.resolve(
@@ -510,6 +511,7 @@ class ConfigArrayFactory {
      * @param {Object} [options] The options.
      * @param {string} [options.basePath] The base path to resolve relative paths in `overrides[].files`, `overrides[].excludedFiles`, and `ignorePatterns`.
      * @param {string} [options.name] The config name.
+     * @throws {Error} If the config file is invalid.
      * @returns {ConfigArray} Loaded config. An empty `ConfigArray` if any config doesn't exist.
      */
     loadInDirectory(directoryPath, { basePath, name } = {}) {
@@ -595,6 +597,7 @@ class ConfigArrayFactory {
     /**
      * Load `.eslintignore` file in the current working directory.
      * @returns {ConfigArray} Loaded config. An empty `ConfigArray` if any config doesn't exist.
+     * @throws {Error} If the ignore file is invalid.
      */
     loadDefaultESLintIgnore() {
         const slots = internalSlotsMap.get(this);
@@ -607,7 +610,7 @@ class ConfigArrayFactory {
         if (fs.existsSync(packageJsonPath)) {
             const data = loadJSONConfigFile(packageJsonPath);
 
-            if (Object.hasOwnProperty.call(data, "eslintIgnore")) {
+            if (Object.hasOwn(data, "eslintIgnore")) {
                 if (!Array.isArray(data.eslintIgnore)) {
                     throw new Error("Package.json eslintIgnore property requires an array of paths");
                 }
@@ -796,6 +799,7 @@ class ConfigArrayFactory {
      * @param {string} extendName The name of a base config.
      * @param {ConfigArrayFactoryLoadingContext} ctx The loading context.
      * @returns {IterableIterator<ConfigArrayElement>} The normalized config.
+     * @throws {Error} If the extended config file can't be loaded.
      * @private
      */
     _loadExtends(extendName, ctx) {
@@ -819,6 +823,7 @@ class ConfigArrayFactory {
      * @param {string} extendName The name of a base config.
      * @param {ConfigArrayFactoryLoadingContext} ctx The loading context.
      * @returns {IterableIterator<ConfigArrayElement>} The normalized config.
+     * @throws {Error} If the extended config file can't be loaded.
      * @private
      */
     _loadExtendedBuiltInConfig(extendName, ctx) {
@@ -868,6 +873,7 @@ class ConfigArrayFactory {
      * @param {string} extendName The name of a base config.
      * @param {ConfigArrayFactoryLoadingContext} ctx The loading context.
      * @returns {IterableIterator<ConfigArrayElement>} The normalized config.
+     * @throws {Error} If the extended config file can't be loaded.
      * @private
      */
     _loadExtendedPluginConfig(extendName, ctx) {
@@ -905,6 +911,7 @@ class ConfigArrayFactory {
      * @param {string} extendName The name of a base config.
      * @param {ConfigArrayFactoryLoadingContext} ctx The loading context.
      * @returns {IterableIterator<ConfigArrayElement>} The normalized config.
+     * @throws {Error} If the extended config file can't be loaded.
      * @private
      */
     _loadExtendedShareableConfig(extendName, ctx) {
@@ -1106,6 +1113,7 @@ class ConfigArrayFactory {
         if (plugin) {
             return new ConfigDependency({
                 definition: normalizePlugin(plugin),
+                original: plugin,
                 filePath: "", // It's unknown where the plugin came from.
                 id,
                 importerName: ctx.name,
@@ -1142,6 +1150,7 @@ class ConfigArrayFactory {
 
                 return new ConfigDependency({
                     definition: normalizePlugin(pluginDefinition),
+                    original: pluginDefinition,
                     filePath,
                     id,
                     importerName: ctx.name,
@@ -1219,4 +1228,8 @@ class ConfigArrayFactory {
     }
 }
 
-export { ConfigArrayFactory, createContext };
+export {
+    ConfigArrayFactory,
+    createContext,
+    loadConfigFile
+};
diff --git a/lib/config-array/config-array.js b/lib/config-array/config-array.js
index 133f5a24..8b3ec28c 100644
--- a/lib/config-array/config-array.js
+++ b/lib/config-array/config-array.js
@@ -178,6 +178,7 @@ class PluginConflictError extends Error {
  * @param {Record<string, DependentPlugin>} target The destination to merge
  * @param {Record<string, DependentPlugin>|undefined} source The source to merge.
  * @returns {void}
+ * @throws {PluginConflictError} When a plugin was conflicted.
  */
 function mergePlugins(target, source) {
     if (!isNonNullObject(source)) {
@@ -258,6 +259,7 @@ function mergeRuleConfigs(target, source) {
  * @param {ConfigArray} instance The config elements.
  * @param {number[]} indices The indices to use.
  * @returns {ExtractedConfig} The extracted config.
+ * @throws {Error} When a plugin is conflicted.
  */
 function createConfig(instance, indices) {
     const config = new ExtractedConfig();
@@ -319,31 +321,18 @@ function createConfig(instance, indices) {
  * @param {string} pluginId The plugin ID for prefix.
  * @param {Record<string,T>} defs The definitions to collect.
  * @param {Map<string, U>} map The map to output.
- * @param {function(T): U} [normalize] The normalize function for each value.
  * @returns {void}
  */
-function collect(pluginId, defs, map, normalize) {
+function collect(pluginId, defs, map) {
     if (defs) {
         const prefix = pluginId && `${pluginId}/`;
 
         for (const [key, value] of Object.entries(defs)) {
-            map.set(
-                `${prefix}${key}`,
-                normalize ? normalize(value) : value
-            );
+            map.set(`${prefix}${key}`, value);
         }
     }
 }
 
-/**
- * Normalize a rule definition.
- * @param {Function|Rule} rule The rule definition to normalize.
- * @returns {Rule} The normalized rule definition.
- */
-function normalizePluginRule(rule) {
-    return typeof rule === "function" ? { create: rule } : rule;
-}
-
 /**
  * Delete the mutation methods from a given map.
  * @param {Map<any, any>} map The map object to delete.
@@ -385,7 +374,7 @@ function initPluginMemberMaps(elements, slots) {
 
             collect(pluginId, plugin.environments, slots.envMap);
             collect(pluginId, plugin.processors, slots.processorMap);
-            collect(pluginId, plugin.rules, slots.ruleMap, normalizePluginRule);
+            collect(pluginId, plugin.rules, slots.ruleMap);
         }
     }
 
diff --git a/lib/config-array/config-dependency.js b/lib/config-array/config-dependency.js
index 2883c3a2..80968950 100644
--- a/lib/config-array/config-dependency.js
+++ b/lib/config-array/config-dependency.js
@@ -15,7 +15,7 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import util from "util";
+import util from "node:util";
 
 /**
  * The class is to store parsers or plugins.
@@ -28,6 +28,7 @@ class ConfigDependency {
      * Initialize this instance.
      * @param {Object} data The dependency data.
      * @param {T} [data.definition] The dependency if the loading succeeded.
+     * @param {T} [data.original] The original, non-normalized dependency if the loading succeeded.
      * @param {Error} [data.error] The error object if the loading failed.
      * @param {string} [data.filePath] The actual path to the dependency if the loading succeeded.
      * @param {string} data.id The ID of this dependency.
@@ -36,6 +37,7 @@ class ConfigDependency {
      */
     constructor({
         definition = null,
+        original = null,
         error = null,
         filePath = null,
         id,
@@ -49,6 +51,12 @@ class ConfigDependency {
          */
         this.definition = definition;
 
+        /**
+         * The original dependency as loaded directly from disk if the loading succeeded.
+         * @type {T|null}
+         */
+        this.original = original;
+
         /**
          * The error object if the loading failed.
          * @type {Error|null}
@@ -80,8 +88,8 @@ class ConfigDependency {
         this.importerPath = importerPath;
     }
 
-    // eslint-disable-next-line jsdoc/require-description
     /**
+     * Converts this instance to a JSON compatible object.
      * @returns {Object} a JSON compatible object.
      */
     toJSON() {
@@ -95,13 +103,14 @@ class ConfigDependency {
         return obj;
     }
 
-    // eslint-disable-next-line jsdoc/require-description
     /**
+     * Custom inspect method for Node.js `console.log()`.
      * @returns {Object} an object to display by `console.log()`.
      */
     [util.inspect.custom]() {
         const {
-            definition: _ignore, // eslint-disable-line no-unused-vars
+            definition: _ignore1, // eslint-disable-line no-unused-vars -- needed to make `obj` correct
+            original: _ignore2, // eslint-disable-line no-unused-vars -- needed to make `obj` correct
             ...obj
         } = this;
 
diff --git a/lib/config-array/extracted-config.js b/lib/config-array/extracted-config.js
index e93b0b67..65206f27 100644
--- a/lib/config-array/extracted-config.js
+++ b/lib/config-array/extracted-config.js
@@ -120,10 +120,10 @@ class ExtractedConfig {
      */
     toCompatibleObjectAsConfigFileContent() {
         const {
-            /* eslint-disable no-unused-vars */
+            /* eslint-disable no-unused-vars -- needed to make `config` correct */
             configNameOfNoInlineConfig: _ignore1,
             processor: _ignore2,
-            /* eslint-enable no-unused-vars */
+            /* eslint-enable no-unused-vars -- needed to make `config` correct */
             ignores,
             ...config
         } = this;
diff --git a/lib/config-array/ignore-pattern.js b/lib/config-array/ignore-pattern.js
index 3022ba9f..edb52872 100644
--- a/lib/config-array/ignore-pattern.js
+++ b/lib/config-array/ignore-pattern.js
@@ -32,8 +32,8 @@
 // Requirements
 //------------------------------------------------------------------------------
 
-import assert from "assert";
-import path from "path";
+import assert from "node:assert";
+import path from "node:path";
 import ignore from "ignore";
 import debugOrig from "debug";
 
@@ -117,6 +117,9 @@ const DotPatterns = Object.freeze([".*", "!.eslintrc.*", "!../"]);
 // Public
 //------------------------------------------------------------------------------
 
+/**
+ * Represents a set of glob patterns to ignore against a base path.
+ */
 class IgnorePattern {
 
     /**
@@ -153,9 +156,7 @@ class IgnorePattern {
         debug("Create with: %o", ignorePatterns);
 
         const basePath = getCommonAncestorPath(ignorePatterns.map(p => p.basePath));
-        const patterns = [].concat(
-            ...ignorePatterns.map(p => p.getPatternsRelativeTo(basePath))
-        );
+        const patterns = ignorePatterns.flatMap(p => p.getPatternsRelativeTo(basePath));
         const ig = ignore({ allowRelativePaths: true }).add([...DotPatterns, ...patterns]);
         const dotIg = ignore({ allowRelativePaths: true }).add(patterns);
 
diff --git a/lib/config-array/override-tester.js b/lib/config-array/override-tester.js
index 460aafcf..3a445b1a 100644
--- a/lib/config-array/override-tester.js
+++ b/lib/config-array/override-tester.js
@@ -17,9 +17,9 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import assert from "assert";
-import path from "path";
-import util from "util";
+import assert from "node:assert";
+import path from "node:path";
+import util from "node:util";
 import minimatch from "minimatch";
 
 const { Minimatch } = minimatch;
@@ -94,6 +94,7 @@ class OverrideTester {
      * @param {string|string[]} excludedFiles The glob patterns for excluded files.
      * @param {string} basePath The path to the base directory to test paths.
      * @returns {OverrideTester|null} The created instance or `null`.
+     * @throws {Error} When invalid patterns are given.
      */
     static create(files, excludedFiles, basePath) {
         const includePatterns = normalizePatterns(files);
@@ -183,6 +184,7 @@ class OverrideTester {
      * Test if a given path is matched or not.
      * @param {string} filePath The absolute path to the target file.
      * @returns {boolean} `true` if the path was matched.
+     * @throws {Error} When invalid `filePath` is given.
      */
     test(filePath) {
         if (typeof filePath !== "string" || !path.isAbsolute(filePath)) {
@@ -196,8 +198,8 @@ class OverrideTester {
         ));
     }
 
-    // eslint-disable-next-line jsdoc/require-description
     /**
+     * Converts this instance to a JSON compatible object.
      * @returns {Object} a JSON compatible object.
      */
     toJSON() {
@@ -213,8 +215,8 @@ class OverrideTester {
         };
     }
 
-    // eslint-disable-next-line jsdoc/require-description
     /**
+     * Custom inspect method for Node.js `console.log()`.
      * @returns {Object} an object to display by `console.log()`.
      */
     [util.inspect.custom]() {
diff --git a/lib/flat-compat.js b/lib/flat-compat.js
index e0d7ab66..c5c4e1c2 100644
--- a/lib/flat-compat.js
+++ b/lib/flat-compat.js
@@ -8,7 +8,7 @@
 //-----------------------------------------------------------------------------
 
 import createDebug from "debug";
-import path from "path";
+import path from "node:path";
 
 import environments from "../conf/environments.js";
 import { ConfigArrayFactory } from "./config-array-factory.js";
@@ -37,6 +37,7 @@ const cafactory = Symbol("cafactory");
  * @param {ReadOnlyMap<string,Processor>} options.pluginProcessors A map of plugin processor
  *      names to objects.
  * @returns {Object} A flag-config-style config object.
+ * @throws {Error} If a plugin or environment cannot be resolved.
  */
 function translateESLintRC(eslintrcConfig, {
     resolveConfigRelativeTo,
@@ -132,7 +133,7 @@ function translateESLintRC(eslintrcConfig, {
             debug(`Translating plugin: ${pluginName}`);
             debug(`Resolving plugin '${pluginName} relative to ${resolvePluginsRelativeTo}`);
 
-            const { definition: plugin, error } = eslintrcConfig.plugins[pluginName];
+            const { original: plugin, error } = eslintrcConfig.plugins[pluginName];
 
             if (error) {
                 throw error;
@@ -219,21 +220,31 @@ class FlatCompat {
         this[cafactory] = new ConfigArrayFactory({
             cwd: baseDirectory,
             resolvePluginsRelativeTo,
-            getEslintAllConfig: () => {
+            getEslintAllConfig() {
 
                 if (!allConfig) {
                     throw new TypeError("Missing parameter 'allConfig' in FlatCompat constructor.");
                 }
 
-                return allConfig;
+                // remove name property if it exists
+                const config = { ...allConfig };
+
+                delete config.name;
+
+                return config;
             },
-            getEslintRecommendedConfig: () => {
+            getEslintRecommendedConfig() {
 
                 if (!recommendedConfig) {
                     throw new TypeError("Missing parameter 'recommendedConfig' in FlatCompat constructor.");
                 }
 
-                return recommendedConfig;
+                // remove name property if it exists
+                const config = { ...recommendedConfig };
+
+                delete config.name;
+
+                return config;
             }
         });
     }
diff --git a/lib/index.js b/lib/index.js
index 9e3d13f5..a37e5746 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -8,7 +8,8 @@
 
 import {
     ConfigArrayFactory,
-    createContext as createConfigArrayFactoryContext
+    createContext as createConfigArrayFactoryContext,
+    loadConfigFile
 } from "./config-array-factory.js";
 
 import { CascadingConfigArrayFactory } from "./cascading-config-array-factory.js";
@@ -39,6 +40,7 @@ const Legacy = {
     OverrideTester,
     getUsedExtractedConfigs,
     environments,
+    loadConfigFile,
 
     // shared
     ConfigOps,
diff --git a/lib/shared/ajv.js b/lib/shared/ajv.js
index b79ad36c..7e53d12a 100644
--- a/lib/shared/ajv.js
+++ b/lib/shared/ajv.js
@@ -184,7 +184,7 @@ export default (additionalOptions = {}) => {
     });
 
     ajv.addMetaSchema(metaSchema);
-    // eslint-disable-next-line no-underscore-dangle
+    // eslint-disable-next-line no-underscore-dangle -- part of the API
     ajv._opts.defaultMeta = metaSchema.id;
 
     return ajv;
diff --git a/lib/shared/config-ops.js b/lib/shared/config-ops.js
index d203be0e..465d9b86 100644
--- a/lib/shared/config-ops.js
+++ b/lib/shared/config-ops.js
@@ -13,7 +13,7 @@ const RULE_SEVERITY_STRINGS = ["off", "warn", "error"],
         map[value] = index;
         return map;
     }, {}),
-    VALID_SEVERITIES = [0, 1, 2, "off", "warn", "error"];
+    VALID_SEVERITIES = new Set([0, 1, 2, "off", "warn", "error"]);
 
 //------------------------------------------------------------------------------
 // Public Interface
@@ -83,7 +83,7 @@ function isValidSeverity(ruleConfig) {
     if (typeof severity === "string") {
         severity = severity.toLowerCase();
     }
-    return VALID_SEVERITIES.indexOf(severity) !== -1;
+    return VALID_SEVERITIES.has(severity);
 }
 
 /**
diff --git a/lib/shared/config-validator.js b/lib/shared/config-validator.js
index 32174a56..6857e7a0 100644
--- a/lib/shared/config-validator.js
+++ b/lib/shared/config-validator.js
@@ -3,16 +3,23 @@
  * @author Brandon Mills
  */
 
-/* eslint class-methods-use-this: "off" */
+/* eslint class-methods-use-this: "off" -- not needed in this file */
+
+//------------------------------------------------------------------------------
+// Typedefs
+//------------------------------------------------------------------------------
+
+/** @typedef {import("../shared/types").Rule} Rule */
 
 //------------------------------------------------------------------------------
 // Requirements
 //------------------------------------------------------------------------------
 
-import util from "util";
+import util from "node:util";
 import * as ConfigOps from "./config-ops.js";
 import { emitDeprecationWarning } from "./deprecation-warnings.js";
 import ajvOrig from "./ajv.js";
+import { deepMergeArrays } from "./deep-merge-arrays.js";
 import configSchema from "../../conf/config-schema.js";
 import BuiltInEnvironments from "../../conf/environments.js";
 
@@ -33,10 +40,20 @@ const severityMap = {
 
 const validated = new WeakSet();
 
+// JSON schema that disallows passing any options
+const noOptionsSchema = Object.freeze({
+    type: "array",
+    minItems: 0,
+    maxItems: 0
+});
+
 //-----------------------------------------------------------------------------
 // Exports
 //-----------------------------------------------------------------------------
 
+/**
+ * Validator for configuration objects.
+ */
 export default class ConfigValidator {
     constructor({ builtInRules = new Map() } = {}) {
         this.builtInRules = builtInRules;
@@ -44,17 +61,36 @@ export default class ConfigValidator {
 
     /**
      * Gets a complete options schema for a rule.
-     * @param {{create: Function, schema: (Array|null)}} rule A new-style rule object
-     * @returns {Object} JSON Schema for the rule's options.
+     * @param {Rule} rule A rule object
+     * @throws {TypeError} If `meta.schema` is specified but is not an array, object or `false`.
+     * @returns {Object|null} JSON Schema for the rule's options.
+     *      `null` if rule wasn't passed or its `meta.schema` is `false`.
      */
     getRuleOptionsSchema(rule) {
         if (!rule) {
             return null;
         }
 
-        const schema = rule.schema || rule.meta && rule.meta.schema;
+        if (!rule.meta) {
+            return { ...noOptionsSchema }; // default if `meta.schema` is not specified
+        }
+
+        const schema = rule.meta.schema;
+
+        if (typeof schema === "undefined") {
+            return { ...noOptionsSchema }; // default if `meta.schema` is not specified
+        }
 
-        // Given a tuple of schemas, insert warning level at the beginning
+        // `schema:false` is an allowed explicit opt-out of options validation for the rule
+        if (schema === false) {
+            return null;
+        }
+
+        if (typeof schema !== "object" || schema === null) {
+            throw new TypeError("Rule's `meta.schema` must be an array or object");
+        }
+
+        // ESLint-specific array form needs to be converted into a valid JSON Schema definition
         if (Array.isArray(schema)) {
             if (schema.length) {
                 return {
@@ -64,22 +100,20 @@ export default class ConfigValidator {
                     maxItems: schema.length
                 };
             }
-            return {
-                type: "array",
-                minItems: 0,
-                maxItems: 0
-            };
 
+            // `schema:[]` is an explicit way to specify that the rule does not accept any options
+            return { ...noOptionsSchema };
         }
 
-        // Given a full schema, leave it alone
-        return schema || null;
+        // `schema:<object>` is assumed to be a valid JSON Schema definition
+        return schema;
     }
 
     /**
      * Validates a rule's severity and returns the severity value. Throws an error if the severity is invalid.
      * @param {options} options The given options for the rule.
      * @returns {number|string} The rule's severity value
+     * @throws {Error} If the severity is invalid.
      */
     validateRuleSeverity(options) {
         const severity = Array.isArray(options) ? options[0] : options;
@@ -98,20 +132,32 @@ export default class ConfigValidator {
      * @param {{create: Function}} rule The rule to validate
      * @param {Array} localOptions The options for the rule, excluding severity
      * @returns {void}
+     * @throws {Error} If the options are invalid.
      */
     validateRuleSchema(rule, localOptions) {
         if (!ruleValidators.has(rule)) {
-            const schema = this.getRuleOptionsSchema(rule);
+            try {
+                const schema = this.getRuleOptionsSchema(rule);
+
+                if (schema) {
+                    ruleValidators.set(rule, ajv.compile(schema));
+                }
+            } catch (err) {
+                const errorWithCode = new Error(err.message, { cause: err });
+
+                errorWithCode.code = "ESLINT_INVALID_RULE_OPTIONS_SCHEMA";
 
-            if (schema) {
-                ruleValidators.set(rule, ajv.compile(schema));
+                throw errorWithCode;
             }
         }
 
         const validateRule = ruleValidators.get(rule);
 
         if (validateRule) {
-            validateRule(localOptions);
+            const mergedOptions = deepMergeArrays(rule.meta?.defaultOptions, localOptions);
+
+            validateRule(mergedOptions);
+
             if (validateRule.errors) {
                 throw new Error(validateRule.errors.map(
                     error => `\tValue ${JSON.stringify(error.data)} ${error.message}.\n`
@@ -128,6 +174,7 @@ export default class ConfigValidator {
      * @param {string|null} source The name of the configuration source to report in any errors. If null or undefined,
      * no source is prepended to the message.
      * @returns {void}
+     * @throws {Error} If the options are invalid.
      */
     validateRuleOptions(rule, ruleId, options, source = null) {
         try {
@@ -137,13 +184,21 @@ export default class ConfigValidator {
                 this.validateRuleSchema(rule, Array.isArray(options) ? options.slice(1) : []);
             }
         } catch (err) {
-            const enhancedMessage = `Configuration for rule "${ruleId}" is invalid:\n${err.message}`;
+            let enhancedMessage = err.code === "ESLINT_INVALID_RULE_OPTIONS_SCHEMA"
+                ? `Error while processing options validation schema of rule '${ruleId}': ${err.message}`
+                : `Configuration for rule "${ruleId}" is invalid:\n${err.message}`;
 
             if (typeof source === "string") {
-                throw new Error(`${source}:\n\t${enhancedMessage}`);
-            } else {
-                throw new Error(enhancedMessage);
+                enhancedMessage = `${source}:\n\t${enhancedMessage}`;
+            }
+
+            const enhancedError = new Error(enhancedMessage, { cause: err });
+
+            if (err.code) {
+                enhancedError.code = err.code;
             }
+
+            throw enhancedError;
         }
     }
 
@@ -151,8 +206,9 @@ export default class ConfigValidator {
      * Validates an environment object
      * @param {Object} environment The environment config object to validate.
      * @param {string} source The name of the configuration source to report in any errors.
-     * @param {function(envId:string): Object} [getAdditionalEnv] A map from strings to loaded environments.
+     * @param {(envId:string) => Object} [getAdditionalEnv] A map from strings to loaded environments.
      * @returns {void}
+     * @throws {Error} If the environment is invalid.
      */
     validateEnvironment(
         environment,
@@ -180,7 +236,7 @@ export default class ConfigValidator {
      * Validates a rules config object
      * @param {Object} rulesConfig The rules config object to validate.
      * @param {string} source The name of the configuration source to report in any errors.
-     * @param {function(ruleId:string): Object} getAdditionalRule A map from strings to loaded rules
+     * @param {(ruleId:string) => Object} getAdditionalRule A map from strings to loaded rules
      * @returns {void}
      */
     validateRules(
@@ -224,8 +280,9 @@ export default class ConfigValidator {
      * Validate `processor` configuration.
      * @param {string|undefined} processorName The processor name.
      * @param {string} source The name of config file.
-     * @param {function(id:string): Processor} getProcessor The getter of defined processors.
+     * @param {(id:string) => Processor} getProcessor The getter of defined processors.
      * @returns {void}
+     * @throws {Error} If the processor is invalid.
      */
     validateProcessor(processorName, source, getProcessor) {
         if (processorName && !getProcessor(processorName)) {
@@ -264,6 +321,7 @@ export default class ConfigValidator {
      * @param {Object} config The config object to validate.
      * @param {string} source The name of the configuration source to report in any errors.
      * @returns {void}
+     * @throws {Error} If the config is invalid.
      */
     validateConfigSchema(config, source = null) {
         validateSchema = validateSchema || ajv.compile(configSchema);
@@ -272,7 +330,7 @@ export default class ConfigValidator {
             throw new Error(`ESLint configuration in ${source} is invalid:\n${this.formatErrors(validateSchema.errors)}`);
         }
 
-        if (Object.hasOwnProperty.call(config, "ecmaFeatures")) {
+        if (Object.hasOwn(config, "ecmaFeatures")) {
             emitDeprecationWarning(source, "ESLINT_LEGACY_ECMAFEATURES");
         }
     }
@@ -281,8 +339,8 @@ export default class ConfigValidator {
      * Validates an entire config object.
      * @param {Object} config The config object to validate.
      * @param {string} source The name of the configuration source to report in any errors.
-     * @param {function(ruleId:string): Object} [getAdditionalRule] A map from strings to loaded rules.
-     * @param {function(envId:string): Object} [getAdditionalEnv] A map from strings to loaded envs.
+     * @param {(ruleId:string) => Object} [getAdditionalRule] A map from strings to loaded rules.
+     * @param {(envId:string) => Object} [getAdditionalEnv] A map from strings to loaded envs.
      * @returns {void}
      */
     validate(config, source, getAdditionalRule, getAdditionalEnv) {
diff --git a/lib/shared/deep-merge-arrays.js b/lib/shared/deep-merge-arrays.js
new file mode 100644
index 00000000..0c7ec349
--- /dev/null
+++ b/lib/shared/deep-merge-arrays.js
@@ -0,0 +1,58 @@
+/**
+ * @fileoverview Applies default rule options
+ * @author JoshuaKGoldberg
+ */
+
+/**
+ * Check if the variable contains an object strictly rejecting arrays
+ * @param {unknown} value an object
+ * @returns {boolean} Whether value is an object
+ */
+function isObjectNotArray(value) {
+    return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+/**
+ * Deeply merges second on top of first, creating a new {} object if needed.
+ * @param {T} first Base, default value.
+ * @param {U} second User-specified value.
+ * @returns {T | U | (T & U)} Merged equivalent of second on top of first.
+ */
+function deepMergeObjects(first, second) {
+    if (second === void 0) {
+        return first;
+    }
+
+    if (!isObjectNotArray(first) || !isObjectNotArray(second)) {
+        return second;
+    }
+
+    const result = { ...first, ...second };
+
+    for (const key of Object.keys(second)) {
+        if (Object.prototype.propertyIsEnumerable.call(first, key)) {
+            result[key] = deepMergeObjects(first[key], second[key]);
+        }
+    }
+
+    return result;
+}
+
+/**
+ * Deeply merges second on top of first, creating a new [] array if needed.
+ * @param {T[] | undefined} first Base, default values.
+ * @param {U[] | undefined} second User-specified values.
+ * @returns {(T | U | (T & U))[]} Merged equivalent of second on top of first.
+ */
+function deepMergeArrays(first, second) {
+    if (!first || !second) {
+        return second || first || [];
+    }
+
+    return [
+        ...first.map((value, i) => deepMergeObjects(value, second[i])),
+        ...second.slice(first.length)
+    ];
+}
+
+export { deepMergeArrays };
diff --git a/lib/shared/deprecation-warnings.js b/lib/shared/deprecation-warnings.js
index 91907b13..39cfe2c6 100644
--- a/lib/shared/deprecation-warnings.js
+++ b/lib/shared/deprecation-warnings.js
@@ -7,7 +7,7 @@
 // Requirements
 //------------------------------------------------------------------------------
 
-import path from "path";
+import path from "node:path";
 
 //------------------------------------------------------------------------------
 // Private
diff --git a/lib/shared/relative-module-resolver.js b/lib/shared/relative-module-resolver.js
index 1df0ca80..81415b42 100644
--- a/lib/shared/relative-module-resolver.js
+++ b/lib/shared/relative-module-resolver.js
@@ -3,7 +3,7 @@
  * @author Teddy Katz
  */
 
-import Module from "module";
+import Module from "node:module";
 
 /*
  * `Module.createRequire` is added in v12.2.0. It supports URL as well.
@@ -17,6 +17,7 @@ const createRequire = Module.createRequire;
  * @param {string} relativeToPath An absolute path indicating the module that `moduleName` should be resolved relative to. This must be
  * a file rather than a directory, but the file need not actually exist.
  * @returns {string} The absolute path that would result from calling `require.resolve(moduleName)` in a file located at `relativeToPath`
+ * @throws {Error} When the module cannot be resolved.
  */
 function resolve(moduleName, relativeToPath) {
     try {
diff --git a/lib/types/index.d.ts b/lib/types/index.d.ts
new file mode 100644
index 00000000..258d3a5f
--- /dev/null
+++ b/lib/types/index.d.ts
@@ -0,0 +1,76 @@
+/**
+ * @fileoverview This file contains the core types for ESLint. It was initially extracted
+ * from the `@types/eslint__eslintrc` package.
+ */
+
+/*
+ * MIT License
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE
+ */
+
+import type { Linter } from "eslint";
+
+/**
+ * A compatibility class for working with configs.
+ */
+export class FlatCompat {
+    constructor({
+        baseDirectory,
+        resolvePluginsRelativeTo,
+        recommendedConfig,
+        allConfig,
+    }?: {
+        /**
+         * default: process.cwd()
+         */
+        baseDirectory?: string;
+        resolvePluginsRelativeTo?: string;
+        recommendedConfig?: Linter.LegacyConfig;
+        allConfig?: Linter.LegacyConfig;
+    });
+
+    /**
+     * Translates an ESLintRC-style config into a flag-config-style config.
+     * @param eslintrcConfig The ESLintRC-style config object.
+     * @returns A flag-config-style config object.
+     */
+    config(eslintrcConfig: Linter.LegacyConfig): Linter.Config[];
+
+    /**
+     * Translates the `env` section of an ESLintRC-style config.
+     * @param envConfig The `env` section of an ESLintRC config.
+     * @returns An array of flag-config objects representing the environments.
+     */
+    env(envConfig: { [name: string]: boolean }): Linter.Config[];
+
+    /**
+     * Translates the `extends` section of an ESLintRC-style config.
+     * @param configsToExtend The names of the configs to load.
+     * @returns An array of flag-config objects representing the config.
+     */
+    extends(...configsToExtend: string[]): Linter.Config[];
+
+    /**
+     * Translates the `plugins` section of an ESLintRC-style config.
+     * @param plugins The names of the plugins to load.
+     * @returns An array of flag-config objects representing the plugins.
+     */
+    plugins(...plugins: string[]): Linter.Config[];
+}
diff --git a/package.json b/package.json
index 6f148ac7..030d3fc7 100644
--- a/package.json
+++ b/package.json
@@ -1,13 +1,15 @@
 {
   "name": "@eslint/eslintrc",
-  "version": "2.1.3",
+  "version": "3.3.3",
   "description": "The legacy ESLintRC config file format for ESLint",
   "type": "module",
   "main": "./dist/eslintrc.cjs",
+  "types": "./dist/eslintrc.d.cts",
   "exports": {
     ".": {
       "import": "./lib/index.js",
-      "require": "./dist/eslintrc.cjs"
+      "require": "./dist/eslintrc.cjs",
+      "types": "./lib/types/index.d.ts"
     },
     "./package.json": "./package.json",
     "./universal": {
@@ -26,16 +28,12 @@
     "access": "public"
   },
   "scripts": {
-    "build": "rollup -c",
+    "build": "rollup -c && node -e \"fs.copyFileSync('./lib/types/index.d.ts', './dist/eslintrc.d.cts')\"",
     "lint": "eslint . --report-unused-disable-directives",
     "lint:fix": "npm run lint -- --fix",
     "prepare": "npm run build",
-    "release:generate:latest": "eslint-generate-release",
-    "release:generate:alpha": "eslint-generate-prerelease alpha",
-    "release:generate:beta": "eslint-generate-prerelease beta",
-    "release:generate:rc": "eslint-generate-prerelease rc",
-    "release:publish": "eslint-publish-release",
-    "test": "mocha -R progress -c 'tests/lib/*.cjs' && c8 mocha -R progress -c 'tests/lib/**/*.js'"
+    "test": "mocha -R progress -c 'tests/lib/*.cjs' && c8 mocha -R progress -c 'tests/lib/**/*.js'",
+    "test:types": "tsc -p tests/lib/types/tsconfig.json"
   },
   "repository": "eslint/eslintrc",
   "funding": "https://opencollective.com/eslint",
@@ -53,30 +51,28 @@
   "devDependencies": {
     "c8": "^7.7.3",
     "chai": "^4.3.4",
-    "eslint": "^7.31.0",
-    "eslint-config-eslint": "^7.0.0",
-    "eslint-plugin-jsdoc": "^35.4.1",
-    "eslint-plugin-node": "^11.1.0",
-    "eslint-release": "^3.2.0",
+    "eslint": "^9.20.1",
+    "eslint-config-eslint": "^11.0.0",
     "fs-teardown": "^0.1.3",
     "mocha": "^9.0.3",
     "rollup": "^2.70.1",
-    "shelljs": "^0.8.4",
+    "shelljs": "^0.8.5",
     "sinon": "^11.1.2",
-    "temp-dir": "^2.0.0"
+    "temp-dir": "^2.0.0",
+    "typescript": "^5.7.3"
   },
   "dependencies": {
     "ajv": "^6.12.4",
     "debug": "^4.3.2",
-    "espree": "^9.6.0",
-    "globals": "^13.19.0",
+    "espree": "^10.0.1",
+    "globals": "^14.0.0",
     "ignore": "^5.2.0",
     "import-fresh": "^3.2.1",
-    "js-yaml": "^4.1.0",
+    "js-yaml": "^4.1.1",
     "minimatch": "^3.1.2",
     "strip-json-comments": "^3.1.1"
   },
   "engines": {
-    "node": "^12.22.0 || ^14.17.0 || >=16.0.0"
+    "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
   }
 }
diff --git a/release-please-config.json b/release-please-config.json
new file mode 100644
index 00000000..7fb338a4
--- /dev/null
+++ b/release-please-config.json
@@ -0,0 +1,9 @@
+{
+    "bootstrap-sha": "556e80029f01d07758ab1f5801bc9421bca4b072",
+    "packages": {
+        ".": {
+            "release-type": "node",
+            "pull-request-title-pattern": "chore: release ${version} 🚀"
+        }
+    }
+}
diff --git a/rollup.config.js b/rollup.config.js
index c8f1a330..6e151eff 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -1,3 +1,21 @@
+/** List of modules not included in the bundle. */
+const external = [
+    "node:assert",
+    "node:fs",
+    "node:module",
+    "node:os",
+    "node:path",
+    "node:url",
+    "node:util",
+    "ajv",
+    "debug",
+    "globals",
+    "ignore",
+    "import-fresh",
+    "minimatch",
+    "strip-json-comments"
+];
+
 /**
  * Custom Rollup plugin for `import.meta.url` transformation to commonjs.
  * The default transformation ('file:' + __filename) does not check characters in __filename,
@@ -20,11 +38,7 @@ function importMetaURLPlugin() {
 export default [
     {
         input: "./lib/index.js",
-        external: [
-            "module", "util", "os", "path", "debug", "fs", "import-fresh",
-            "strip-json-comments", "assert", "ignore", "minimatch", "url", "ajv",
-            "globals"
-        ],
+        external,
         treeshake: false,
         output: {
             format: "cjs",
@@ -36,11 +50,7 @@ export default [
     },
     {
         input: "./lib/index-universal.js",
-        external: [
-            "module", "util", "os", "path", "debug", "fs", "import-fresh",
-            "strip-json-comments", "assert", "ignore", "minimatch", "url", "ajv",
-            "globals"
-        ],
+        external,
         treeshake: false,
         output: {
             format: "cjs",
diff --git a/tests/fixtures/rules/custom-rule.cjs b/tests/fixtures/rules/custom-rule.cjs
index 6d8b662b..a7cc1340 100644
--- a/tests/fixtures/rules/custom-rule.cjs
+++ b/tests/fixtures/rules/custom-rule.cjs
@@ -1,15 +1,17 @@
-module.exports = function(context) {
+"use strict";
 
-    "use strict";
+module.exports = {
+    meta: {
+        schema: []
+    },
 
-    return {
-        "Identifier": function(node) {
-            if (node.name === "foo") {
-                context.report(node, "Identifier cannot be named 'foo'.");
+    create(context) {
+        return {
+            "Identifier": function(node) {
+                if (node.name === "foo") {
+                    context.report(node, "Identifier cannot be named 'foo'.");
+                }
             }
-        }
-    };
-
+        };
+    }
 };
-
-module.exports.schema = [];
diff --git a/tests/fixtures/rules/dir1/no-strings.cjs b/tests/fixtures/rules/dir1/no-strings.cjs
index 1f566ac0..4997bbbe 100644
--- a/tests/fixtures/rules/dir1/no-strings.cjs
+++ b/tests/fixtures/rules/dir1/no-strings.cjs
@@ -1,14 +1,15 @@
 "use strict";
 
-module.exports = function(context) {
+module.exports = {
+    create(context) {
+        return {
 
-    return {
+            "Literal": function(node) {
+                if (typeof node.value === 'string') {
+                    context.report(node, "String!");
+                }
 
-        "Literal": function(node) {
-            if (typeof node.value === 'string') {
-                context.report(node, "String!");
             }
-
-        }
-    };
+        };
+    }
 };
diff --git a/tests/fixtures/rules/dir2/no-literals.cjs b/tests/fixtures/rules/dir2/no-literals.cjs
index fdaa2d08..d872718a 100644
--- a/tests/fixtures/rules/dir2/no-literals.cjs
+++ b/tests/fixtures/rules/dir2/no-literals.cjs
@@ -1,11 +1,12 @@
 "use strict";
 
-module.exports = function(context) {
+module.exports = {
+    create (context) {
+        return {
 
-    return {
-
-        "Literal": function(node) {
-            context.report(node, "Literal!");
-        }
-    };
+            "Literal": function(node) {
+                context.report(node, "Literal!");
+            }
+        };
+    }
 };
diff --git a/tests/fixtures/rules/make-syntax-error-rule.cjs b/tests/fixtures/rules/make-syntax-error-rule.cjs
index 528b4b0f..3d34d9d1 100644
--- a/tests/fixtures/rules/make-syntax-error-rule.cjs
+++ b/tests/fixtures/rules/make-syntax-error-rule.cjs
@@ -1,14 +1,18 @@
-module.exports = function(context) {
-    return {
-        Program: function(node) {
-            context.report({
-                node: node,
-                message: "ERROR",
-                fix: function(fixer) {
-                    return fixer.insertTextAfter(node, "this is a syntax error.");
-                }
-            });
-        }
-    };
+module.exports = {
+    meta: {
+        schema: []
+    },
+    create(context) {
+        return {
+            Program: function(node) {
+                context.report({
+                    node: node,
+                    message: "ERROR",
+                    fix: function(fixer) {
+                        return fixer.insertTextAfter(node, "this is a syntax error.");
+                    }
+                });
+            }
+        };
+    }
 };
-module.exports.schema = [];
diff --git a/tests/fixtures/rules/wrong/custom-rule.cjs b/tests/fixtures/rules/wrong/custom-rule.cjs
index 9a64230c..b3923e4d 100644
--- a/tests/fixtures/rules/wrong/custom-rule.cjs
+++ b/tests/fixtures/rules/wrong/custom-rule.cjs
@@ -1,5 +1,7 @@
-module.exports = function() {
+"use strict";
 
-    "use strict";
-    return (null).something;
+module.exports = {
+    create() {
+        return (null).something;
+    }
 };
diff --git a/tests/lib/cascading-config-array-factory.js b/tests/lib/cascading-config-array-factory.js
index 7250f9a8..7567e423 100644
--- a/tests/lib/cascading-config-array-factory.js
+++ b/tests/lib/cascading-config-array-factory.js
@@ -8,14 +8,14 @@
 //-----------------------------------------------------------------------------
 
 import { assert } from "chai";
-import fs from "fs";
-import { createRequire } from "module";
-import os from "os";
-import path from "path";
+import fs from "node:fs";
+import { createRequire } from "node:module";
+import os from "node:os";
+import path from "node:path";
 import sh from "shelljs";
 import sinon from "sinon";
 import systemTempDir from "temp-dir";
-import { fileURLToPath } from "url";
+import { fileURLToPath } from "node:url";
 
 import { Legacy } from "../../lib/index.js";
 import { createCustomTeardown } from "../_utils/index.js";
@@ -557,7 +557,8 @@ describe("CascadingConfigArrayFactory", () => {
                 // key is path, value is file content (string)
                 const flattened = {};
 
-                /** Recursively joins path segments and populates `flattened` object
+                /**
+                 * Recursively joins path segments and populates `flattened` object
                  * @param {Object} object key is path segment, value is file content (string) or another object of the same kind
                  * @param {string} prefix parent directory
                  * @returns {void}
@@ -654,7 +655,7 @@ describe("CascadingConfigArrayFactory", () => {
                      * exceeds the default test timeout, so raise it just for this hook.
                      * Mocha uses `this` to set timeouts on an individual hook level.
                      */
-                    this.timeout(60 * 1000); // eslint-disable-line no-invalid-this
+                    this.timeout(60 * 1000); // eslint-disable-line no-invalid-this -- needed for test
 
                     fixtureDir = `${systemTempDir}/eslint/fixtures`;
                     sh.mkdir("-p", fixtureDir);
@@ -696,7 +697,7 @@ describe("CascadingConfigArrayFactory", () => {
                 });
 
                 // TODO: Tests should not rely on project files!!!
-                it("should return the project config when called in current working directory", () => {
+                it.skip("should return the project config when called in current working directory", () => {
                     const factory = new CascadingConfigArrayFactory({
                         eslintAllPath,
                         eslintRecommendedPath
@@ -1882,7 +1883,7 @@ describe("CascadingConfigArrayFactory", () => {
                      * exceeds the default test timeout, so raise it just for this hook.
                      * Mocha uses `this` to set timeouts on an individual hook level.
                      */
-                    this.timeout(60 * 1000); // eslint-disable-line no-invalid-this
+                    this.timeout(60 * 1000); // eslint-disable-line no-invalid-this -- needed for test
 
                     fixtureDir = `${systemTempDir}/eslint/fixtures`;
                     sh.mkdir("-p", fixtureDir);
@@ -1924,7 +1925,7 @@ describe("CascadingConfigArrayFactory", () => {
                 });
 
                 // TODO: Tests should not rely on project files!!!
-                it("should return the project config when called in current working directory", () => {
+                it.skip("should return the project config when called in current working directory", () => {
                     const factory = new CascadingConfigArrayFactory({
                         getEslintAllConfig,
                         getEslintRecommendedConfig
diff --git a/tests/lib/commonjs.cjs b/tests/lib/commonjs.cjs
index a6840cde..3d17a017 100644
--- a/tests/lib/commonjs.cjs
+++ b/tests/lib/commonjs.cjs
@@ -9,10 +9,10 @@
 // Requirements
 //------------------------------------------------------------------------------
 
-const assert = require("assert");
+const assert = require("node:assert");
 const eslintrc = require("../../dist/eslintrc.cjs");
 const universal = require("../../dist/eslintrc-universal.cjs");
-const path = require("path");
+const path = require("node:path");
 const sh = require("shelljs");
 
 //------------------------------------------------------------------------------
diff --git a/tests/lib/config-array-factory.js b/tests/lib/config-array-factory.js
index 6b991381..4951770e 100644
--- a/tests/lib/config-array-factory.js
+++ b/tests/lib/config-array-factory.js
@@ -8,12 +8,12 @@
 //-----------------------------------------------------------------------------
 
 import { assert } from "chai";
-import fs from "fs";
-import { createRequire } from "module";
-import path from "path";
+import fs from "node:fs";
+import { createRequire } from "node:module";
+import path from "node:path";
 import sinon from "sinon";
 import systemTempDir from "temp-dir";
-import { fileURLToPath } from "url";
+import { fileURLToPath } from "node:url";
 
 import { Legacy } from "../../lib/index.js";
 import { createCustomTeardown } from "../_utils/index.js";
@@ -173,7 +173,7 @@ describe("ConfigArrayFactory", () => {
         it("should return a config array that contains the yielded elements from '_normalizeConfigData(configData, ctx)'.", () => {
             const elements = [{}, {}];
 
-            factory._normalizeConfigData = () => elements; // eslint-disable-line no-underscore-dangle
+            factory._normalizeConfigData = () => elements; // eslint-disable-line no-underscore-dangle -- needed for test
 
             const configArray = factory.create({});
 
@@ -237,7 +237,7 @@ describe("ConfigArrayFactory", () => {
         });
 
         for (const filePath of Object.keys(basicFiles)) {
-            it(`should load '${filePath}' then return a config array what contains that file content.`, () => { // eslint-disable-line no-loop-func
+            it(`should load '${filePath}' then return a config array what contains that file content.`, () => { // eslint-disable-line no-loop-func -- needed for test
                 const configArray = factory.loadFile(filePath);
 
                 assert.strictEqual(configArray.length, 1);
@@ -267,7 +267,7 @@ describe("ConfigArrayFactory", () => {
         it("should return a config array that contains the yielded elements from '_normalizeConfigData(configData, ctx)'.", () => {
             const elements = [{}, {}];
 
-            factory._normalizeConfigData = () => elements; // eslint-disable-line no-underscore-dangle
+            factory._normalizeConfigData = () => elements; // eslint-disable-line no-underscore-dangle -- needed for test
 
             const configArray = factory.loadFile("js/.eslintrc.js");
 
@@ -335,7 +335,7 @@ describe("ConfigArrayFactory", () => {
         for (const filePath of Object.keys(basicFiles)) {
             const directoryPath = filePath.split("/")[0];
 
-            it(`should load '${directoryPath}' then return a config array what contains the config file of that directory.`, () => { // eslint-disable-line no-loop-func
+            it(`should load '${directoryPath}' then return a config array what contains the config file of that directory.`, () => { // eslint-disable-line no-loop-func -- needed for test
                 const configArray = factory.loadInDirectory(directoryPath);
 
                 assert.strictEqual(configArray.length, 1);
@@ -365,7 +365,7 @@ describe("ConfigArrayFactory", () => {
         it("should return a config array that contains the yielded elements from '_normalizeConfigData(configData, ctx)'.", () => {
             const elements = [{}, {}];
 
-            factory._normalizeConfigData = () => elements; // eslint-disable-line no-underscore-dangle
+            factory._normalizeConfigData = () => elements; // eslint-disable-line no-underscore-dangle -- needed for test
 
             const configArray = factory.loadInDirectory("js");
 
@@ -395,7 +395,7 @@ describe("ConfigArrayFactory", () => {
         function create(configData, { filePath, name } = {}) {
             const ctx = createContext({ cwd: tempDir }, void 0, name, filePath, void 0);
 
-            return new ConfigArray(...factory._normalizeConfigData(configData, ctx)); // eslint-disable-line no-underscore-dangle
+            return new ConfigArray(...factory._normalizeConfigData(configData, ctx)); // eslint-disable-line no-underscore-dangle -- needed for test
         }
 
         describe("misc", () => {
@@ -631,6 +631,10 @@ describe("ConfigArrayFactory", () => {
                 it("should have the path to the package at 'plugins[id].filePath' property.", () => {
                     assert.strictEqual(element.plugins.xxx.filePath, path.join(getPath(), "node_modules/custom-eslint-plugin-xxx/index.js"));
                 });
+
+                it("should have the original definition equal to the origina plugin object", () => {
+                    assert.strictEqual(element.plugins.xxx.original, require(path.join(getPath(), "node_modules/custom-eslint-plugin-xxx/index.js")));
+                });
             });
 
             describe("if 'extends' property was 'foo', the returned value", () => {
diff --git a/tests/lib/config-array/config-array.js b/tests/lib/config-array/config-array.js
index d0808ee8..2883671e 100644
--- a/tests/lib/config-array/config-array.js
+++ b/tests/lib/config-array/config-array.js
@@ -3,8 +3,8 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import path from "path";
-import { fileURLToPath } from "url";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
 import { assert } from "chai";
 import { ConfigArray, OverrideTester, getUsedExtractedConfigs } from "../../../lib/config-array/index.js";
 
@@ -37,7 +37,7 @@ describe("ConfigArray", () => {
                 });
 
                 for (let i = 0; i < elements.length; ++i) {
-                    it(`should have ${JSON.stringify(elements[i])} at configArray[${i}].`, () => { // eslint-disable-line no-loop-func
+                    it(`should have ${JSON.stringify(elements[i])} at configArray[${i}].`, () => { // eslint-disable-line no-loop-func -- needed for test
                         assert.strictEqual(configArray[i], elements[i]);
                     });
                 }
@@ -702,7 +702,7 @@ describe("ConfigArray", () => {
             { filePaths: [filename, `${filename}.ts`] },
             { filePaths: [filename, `${filename}.ts`, path.join(dirname, "foo.js")] }
         ]) {
-            describe(`after it called 'extractConfig(filePath)' ${filePaths.length} time(s) with ${JSON.stringify(filePaths, null, 4)}, the returned array`, () => { // eslint-disable-line no-loop-func
+            describe(`after it called 'extractConfig(filePath)' ${filePaths.length} time(s) with ${JSON.stringify(filePaths, null, 4)}, the returned array`, () => { // eslint-disable-line no-loop-func -- needed for test
                 let configs;
                 let usedConfigs;
 
@@ -716,7 +716,7 @@ describe("ConfigArray", () => {
                 });
 
                 for (let i = 0; i < filePaths.length; ++i) {
-                    it(`should contain 'configs[${i}]'.`, () => { // eslint-disable-line no-loop-func
+                    it(`should contain 'configs[${i}]'.`, () => { // eslint-disable-line no-loop-func -- needed for test
                         assert(usedConfigs.includes(configs[i]));
                     });
                 }
diff --git a/tests/lib/config-array/config-dependency.js b/tests/lib/config-array/config-dependency.js
index 3087b8ca..ddb04b88 100644
--- a/tests/lib/config-array/config-dependency.js
+++ b/tests/lib/config-array/config-dependency.js
@@ -3,9 +3,9 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import assert from "assert";
-import { Console } from "console";
-import { Writable } from "stream";
+import assert from "node:assert";
+import { Console } from "node:console";
+import { Writable } from "node:stream";
 import { ConfigDependency } from "../../../lib/config-array/config-dependency.js";
 
 describe("ConfigDependency", () => {
@@ -80,7 +80,7 @@ describe("ConfigDependency", () => {
         let output = "";
         const localConsole = new Console(
             new class extends Writable {
-                write(chunk) { // eslint-disable-line class-methods-use-this
+                write(chunk) { // eslint-disable-line class-methods-use-this -- needed for test
                     output += chunk;
                 }
             }()
diff --git a/tests/lib/config-array/extracted-config.js b/tests/lib/config-array/extracted-config.js
index cf2a8c71..52d8c4a9 100644
--- a/tests/lib/config-array/extracted-config.js
+++ b/tests/lib/config-array/extracted-config.js
@@ -3,7 +3,7 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import assert from "assert";
+import assert from "node:assert";
 import { ExtractedConfig } from "../../../lib/config-array/extracted-config.js";
 
 describe("'ExtractedConfig' class", () => {
diff --git a/tests/lib/config-array/ignore-pattern.js b/tests/lib/config-array/ignore-pattern.js
index 9be97452..10030199 100644
--- a/tests/lib/config-array/ignore-pattern.js
+++ b/tests/lib/config-array/ignore-pattern.js
@@ -3,8 +3,8 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import assert from "assert";
-import path from "path";
+import assert from "node:assert";
+import path from "node:path";
 import sinon from "sinon";
 import { IgnorePattern } from "../../../lib/config-array/ignore-pattern.js";
 
diff --git a/tests/lib/config-array/override-tester.js b/tests/lib/config-array/override-tester.js
index ba54cfe5..a9837800 100644
--- a/tests/lib/config-array/override-tester.js
+++ b/tests/lib/config-array/override-tester.js
@@ -3,10 +3,10 @@
  * @author Toru Nagashima <https://github.com/mysticatea>
  */
 
-import assert from "assert";
-import { Console } from "console";
-import path from "path";
-import { Writable } from "stream";
+import assert from "node:assert";
+import { Console } from "node:console";
+import path from "node:path";
+import { Writable } from "node:stream";
 import { OverrideTester } from "../../../lib/config-array/override-tester.js";
 
 describe("OverrideTester", () => {
diff --git a/tests/lib/flat-compat.js b/tests/lib/flat-compat.js
index 2afb38a0..a46ebb62 100644
--- a/tests/lib/flat-compat.js
+++ b/tests/lib/flat-compat.js
@@ -7,13 +7,15 @@
 // Requirements
 //-----------------------------------------------------------------------------
 
-import path from "path";
-import { fileURLToPath, pathToFileURL } from "url";
+import path from "node:path";
+import { fileURLToPath, pathToFileURL } from "node:url";
 import { assert } from "chai";
 import { FlatCompat } from "../../lib/index.js";
 import environments from "../../conf/environments.js";
+import { createRequire } from "node:module";
 
 const dirname = path.dirname(fileURLToPath(import.meta.url));
+const require = createRequire(import.meta.url);
 
 //-----------------------------------------------------------------------------
 // Helpers
@@ -21,22 +23,6 @@ const dirname = path.dirname(fileURLToPath(import.meta.url));
 
 const FIXTURES_BASE_PATH = path.resolve(dirname, "../fixtures/flat-compat/");
 
-/**
- * Normalizes a plugin object to have all available keys. This matches what
- * ConfigArrayFactory does.
- * @param {Object} plugin The plugin object to normalize.
- * @returns {Object} The normalized plugin object.
- */
-function normalizePlugin(plugin) {
-    return {
-        configs: {},
-        rules: {},
-        environments: {},
-        processors: {},
-        ...plugin
-    };
-}
-
 /**
  * Returns the full directory path for a fixture directory.
  * @param {string} dirName The directory name to resolve.
@@ -56,9 +42,9 @@ describe("FlatCompat", () => {
 
         let compat;
         const baseDirectory = getFixturePath("config");
-        const pluginFixture1 = normalizePlugin((await import(pathToFileURL(path.join(baseDirectory, "node_modules/eslint-plugin-fixture1.js")))).default);
-        const pluginFixture2 = normalizePlugin((await import(pathToFileURL(path.join(baseDirectory, "node_modules/eslint-plugin-fixture2.js")))).default);
-        const pluginFixture3 = normalizePlugin((await import(pathToFileURL(path.join(baseDirectory, "node_modules/eslint-plugin-fixture3.js")))).default);
+        const pluginFixture1 = (await import(pathToFileURL(path.join(baseDirectory, "node_modules/eslint-plugin-fixture1.js")))).default;
+        const pluginFixture2 = (await import(pathToFileURL(path.join(baseDirectory, "node_modules/eslint-plugin-fixture2.js")))).default;
+        const pluginFixture3 = (await import(pathToFileURL(path.join(baseDirectory, "node_modules/eslint-plugin-fixture3.js")))).default;
 
         beforeEach(() => {
             compat = new FlatCompat({
@@ -1041,6 +1027,28 @@ describe("FlatCompat", () => {
             }, /Missing parameter 'recommendedConfig'/gu);
         });
 
+        it("should remove name property from eslint:all and eslint:recommended configs", () => {
+            const compatWithNames = new FlatCompat({
+                baseDirectory: getFixturePath("config"),
+                recommendedConfig: {
+                    name: "eslint:recommended",
+                    settings: { "eslint:recommended": true }
+                },
+                allConfig: {
+                    name: "eslint:all",
+                    settings: { "eslint:all": true }
+                }
+            });
+
+            const allResult = compatWithNames.extends("eslint:all");
+            const recommendedResult = compatWithNames.extends("eslint:recommended");
+
+            assert.strictEqual(allResult.length, 1);
+            assert.isTrue(allResult[0].settings["eslint:all"]);
+
+            assert.strictEqual(recommendedResult.length, 1);
+            assert.isTrue(recommendedResult[0].settings["eslint:recommended"]);
+        });
     });
 
     describe("plugins()", () => {
@@ -1059,13 +1067,7 @@ describe("FlatCompat", () => {
             assert.strictEqual(result.length, 1);
             assert.deepStrictEqual(result[0], {
                 plugins: {
-                    fixture1: {
-                        configs: {},
-                        rules: {},
-                        environments: {},
-                        processors: {},
-                        ...(await import(pathToFileURL(path.join(compat.baseDirectory, "node_modules/eslint-plugin-fixture1.js")))).default
-                    }
+                    fixture1: (await import(pathToFileURL(path.join(compat.baseDirectory, "node_modules/eslint-plugin-fixture1.js")))).default
                 }
             });
         });
@@ -1087,13 +1089,7 @@ describe("FlatCompat", () => {
             });
             assert.deepStrictEqual(result[1], {
                 plugins: {
-                    fixture2: {
-                        configs: {},
-                        rules: {},
-                        environments: {},
-                        processors: {},
-                        ...plugin
-                    }
+                    fixture2: plugin
                 }
             });
         });
@@ -1109,24 +1105,19 @@ describe("FlatCompat", () => {
             });
             assert.deepStrictEqual(result[1], {
                 plugins: {
-                    fixture1: {
-                        configs: {},
-                        rules: {},
-                        environments: {},
-                        processors: {},
-                        ...(await import(pathToFileURL(path.join(compat.baseDirectory, "node_modules/eslint-plugin-fixture1.js")))).default
-                    },
-                    fixture2: {
-                        configs: {},
-                        rules: {},
-                        environments: {},
-                        processors: {},
-                        ...plugin
-                    }
+                    fixture1: (await import(pathToFileURL(path.join(compat.baseDirectory, "node_modules/eslint-plugin-fixture1.js")))).default,
+                    fixture2: plugin
                 }
             });
         });
 
+        it("should use the same plugin instance as require()", async () => {
+            const result = compat.config({ plugins: ["fixture2"] });
+            const plugin = require(path.join(compat.baseDirectory, "node_modules/eslint-plugin-fixture2.js"));
+
+            assert.strictEqual(result[1].plugins.fixture2, plugin);
+        });
+
     });
 
 });
diff --git a/tests/lib/shared/config-ops.js b/tests/lib/shared/config-ops.js
index 574918e3..cb1a92c4 100644
--- a/tests/lib/shared/config-ops.js
+++ b/tests/lib/shared/config-ops.js
@@ -9,7 +9,7 @@
 
 import { assert } from "chai";
 
-import util from "util";
+import util from "node:util";
 
 import * as ConfigOps from "../../../lib/shared/config-ops.js";
 
diff --git a/tests/lib/shared/config-validator.js b/tests/lib/shared/config-validator.js
new file mode 100644
index 00000000..dd2bdcea
--- /dev/null
+++ b/tests/lib/shared/config-validator.js
@@ -0,0 +1,286 @@
+/**
+ * @fileoverview Tests for ConfigValidator class
+ */
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+import { assert } from "chai";
+import nodeAssert from "node:assert";
+
+import ConfigValidator from "../../../lib/shared/config-validator.js";
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const mockRule = {
+    meta: {
+        schema: [{
+            enum: ["first", "second"]
+        }]
+    },
+    create(context) {
+        return {
+            Program(node) {
+                context.report(node, "Expected a validation error.");
+            }
+        };
+    }
+};
+
+const mockObjectRule = {
+    meta: {
+        schema: {
+            enum: ["first", "second"]
+        }
+    },
+    create(context) {
+        return {
+            Program(node) {
+                context.report(node, "Expected a validation error.");
+            }
+        };
+    }
+};
+
+const mockInvalidSchemaTypeRule = {
+    meta: {
+        schema: true
+    },
+    create(context) {
+        return {
+            Program(node) {
+                context.report(node, "Expected a validation error.");
+            }
+        };
+    }
+};
+
+const mockInvalidJSONSchemaRule = {
+    meta: {
+        schema: {
+            minItems: []
+        }
+    },
+    create(context) {
+        return {
+            Program(node) {
+                context.report(node, "Expected a validation error.");
+            }
+        };
+    }
+};
+
+const mockMaxPropertiesSchema = {
+    meta: {
+        defaultOptions: [{
+            foo: 42
+        }],
+        schema: [{
+            type: "object",
+            maxProperties: 2
+        }]
+    },
+    create() {
+        return {};
+    }
+};
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("ConfigValidator", () => {
+    let validator;
+
+    beforeEach(() => {
+        validator = new ConfigValidator();
+    });
+
+    describe("getRuleOptionsSchema", () => {
+
+        const noOptionsSchema = {
+            type: "array",
+            minItems: 0,
+            maxItems: 0
+        };
+
+        it("should return null for a missing rule", () => {
+            assert.strictEqual(validator.getRuleOptionsSchema(void 0), null);
+            assert.strictEqual(validator.getRuleOptionsSchema(null), null);
+        });
+
+        it("should not modify object schema", () => {
+            assert.deepStrictEqual(validator.getRuleOptionsSchema(mockObjectRule), {
+                enum: ["first", "second"]
+            });
+        });
+
+        it("should return schema that doesn't accept options if rule doesn't have `meta`", () => {
+            const rule = {};
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(result, noOptionsSchema);
+        });
+
+        it("should return schema that doesn't accept options if rule doesn't have `meta.schema`", () => {
+            const rule = { meta: {} };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(result, noOptionsSchema);
+        });
+
+        it("should return schema that doesn't accept options if `meta.schema` is `undefined`", () => {
+            const rule = { meta: { schema: void 0 } };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(result, noOptionsSchema);
+        });
+
+        it("should return schema that doesn't accept options if `meta.schema` is `[]`", () => {
+            const rule = { meta: { schema: [] } };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(result, noOptionsSchema);
+        });
+
+        it("should return JSON Schema definition object if `meta.schema` is in the array form", () => {
+            const firstOption = { enum: ["always", "never"] };
+            const rule = { meta: { schema: [firstOption] } };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(
+                result,
+                {
+                    type: "array",
+                    items: [firstOption],
+                    minItems: 0,
+                    maxItems: 1
+                }
+            );
+        });
+
+        it("should return `meta.schema` as is if `meta.schema` is an object", () => {
+            const schema = {
+                type: "array",
+                items: [{
+                    enum: ["always", "never"]
+                }]
+            };
+            const rule = { meta: { schema } };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(result, schema);
+        });
+
+        it("should return `null` if `meta.schema` is `false`", () => {
+            const rule = { meta: { schema: false } };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.strictEqual(result, null);
+        });
+
+        [null, true, 0, 1, "", "always", () => {}].forEach(schema => {
+            it(`should throw an error if \`meta.schema\` is ${typeof schema} ${schema}`, () => {
+                const rule = { meta: { schema } };
+
+                assert.throws(() => {
+                    validator.getRuleOptionsSchema(rule);
+                }, "Rule's `meta.schema` must be an array or object");
+            });
+        });
+
+        it("should ignore top-level `schema` property", () => {
+            const rule = { schema: { enum: ["always", "never"] } };
+            const result = validator.getRuleOptionsSchema(rule);
+
+            assert.deepStrictEqual(result, noOptionsSchema);
+        });
+
+    });
+
+    describe("validateRuleOptions", () => {
+
+        it("should throw for incorrect warning level number", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockRule, "mock-rule", 3, "tests");
+
+            assert.throws(fn, "tests:\n\tConfiguration for rule \"mock-rule\" is invalid:\n\tSeverity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '3').\n");
+        });
+
+        it("should throw for incorrect warning level string", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockRule, "mock-rule", "booya", "tests");
+
+            assert.throws(fn, "tests:\n\tConfiguration for rule \"mock-rule\" is invalid:\n\tSeverity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '\"booya\"').\n");
+        });
+
+        it("should throw for invalid-type warning level", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockRule, "mock-rule", [["error"]], "tests");
+
+            assert.throws(fn, "tests:\n\tConfiguration for rule \"mock-rule\" is invalid:\n\tSeverity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '[ \"error\" ]').\n");
+        });
+
+        it("should only check warning level for nonexistent rules", () => {
+            const fn1 = validator.validateRuleOptions.bind(validator, void 0, "non-existent-rule", [3, "foobar"], "tests");
+
+            assert.throws(fn1, "tests:\n\tConfiguration for rule \"non-existent-rule\" is invalid:\n\tSeverity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '3').\n");
+
+            const fn2 = validator.validateRuleOptions.bind(validator, null, "non-existent-rule", [3, "foobar"], "tests");
+
+            assert.throws(fn2, "tests:\n\tConfiguration for rule \"non-existent-rule\" is invalid:\n\tSeverity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '3').\n");
+        });
+
+        it("should throw for incorrect configuration values", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockRule, "mock-rule", [2, "frist"], "tests");
+
+            assert.throws(fn, "tests:\n\tConfiguration for rule \"mock-rule\" is invalid:\n\tValue \"frist\" should be equal to one of the allowed values.\n");
+        });
+
+        it("should throw for too many configuration values", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockRule, "mock-rule", [2, "first", "second"], "tests");
+
+            assert.throws(fn, "tests:\n\tConfiguration for rule \"mock-rule\" is invalid:\n\tValue [\"first\",\"second\"] should NOT have more than 1 items.\n");
+        });
+
+        it("should throw with error code ESLINT_INVALID_RULE_OPTIONS_SCHEMA for rule with an invalid schema type", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockInvalidSchemaTypeRule, "invalid-schema-rule", [2], "tests");
+
+            nodeAssert.throws(
+                fn,
+                {
+                    code: "ESLINT_INVALID_RULE_OPTIONS_SCHEMA",
+                    message: "tests:\n\tError while processing options validation schema of rule 'invalid-schema-rule': Rule's `meta.schema` must be an array or object"
+                }
+            );
+        });
+
+        it("should throw with error code ESLINT_INVALID_RULE_OPTIONS_SCHEMA for rule with an invalid JSON schema", () => {
+            const fn = validator.validateRuleOptions.bind(validator, mockInvalidJSONSchemaRule, "invalid-schema-rule", [2], "tests");
+
+            nodeAssert.throws(
+                fn,
+                {
+                    code: "ESLINT_INVALID_RULE_OPTIONS_SCHEMA",
+                    message: "tests:\n\tError while processing options validation schema of rule 'invalid-schema-rule': minItems must be number"
+                }
+            );
+        });
+
+    });
+
+    describe("validateRuleSchema", () => {
+
+        it("should throw when rule options are invalid after defaults are applied", () => {
+            const fn = validator.validateRuleSchema.bind(validator, mockMaxPropertiesSchema, [{ bar: 6, baz: 7 }]);
+
+            nodeAssert.throws(
+                fn,
+                {
+                    message: '\tValue {"foo":42,"bar":6,"baz":7} should NOT have more than 2 properties.\n'
+                }
+            );
+        });
+
+    });
+});
diff --git a/tests/lib/shared/deep-merge-arrays.js b/tests/lib/shared/deep-merge-arrays.js
new file mode 100644
index 00000000..55cc272a
--- /dev/null
+++ b/tests/lib/shared/deep-merge-arrays.js
@@ -0,0 +1,134 @@
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+import assert from "node:assert";
+
+import { deepMergeArrays } from "../../../lib/shared/deep-merge-arrays.js";
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+/**
+ * Turns a value into its string equivalent for a test name.
+ * @param {unknown} value Value to be stringified.
+ * @returns {string} String equivalent of the value.
+ */
+function toTestCaseName(value) {
+    return typeof value === "object" ? JSON.stringify(value) : `${value}`;
+}
+
+describe("deepMerge", () => {
+    for (const [first, second, result] of [
+        [void 0, void 0, []],
+        [[], void 0, []],
+        [["abc"], void 0, ["abc"]],
+        [void 0, ["abc"], ["abc"]],
+        [[], ["abc"], ["abc"]],
+        [[void 0], ["abc"], ["abc"]],
+        [[void 0, void 0], ["abc"], ["abc", void 0]],
+        [[void 0, void 0], ["abc", "def"], ["abc", "def"]],
+        [[void 0, null], ["abc"], ["abc", null]],
+        [[void 0, null], ["abc", "def"], ["abc", "def"]],
+        [[null], ["abc"], ["abc"]],
+        [[123], [void 0], [123]],
+        [[123], [null], [null]],
+        [[123], [{ a: 0 }], [{ a: 0 }]],
+        [["abc"], [void 0], ["abc"]],
+        [["abc"], [null], [null]],
+        [["abc"], ["def"], ["def"]],
+        [["abc"], [{ a: 0 }], [{ a: 0 }]],
+        [[["abc"]], [null], [null]],
+        [[["abc"]], ["def"], ["def"]],
+        [[["abc"]], [{ a: 0 }], [{ a: 0 }]],
+        [[{ abc: true }], ["def"], ["def"]],
+        [[{ abc: true }], [["def"]], [["def"]]],
+        [[null], [{ abc: true }], [{ abc: true }]],
+        [[{ a: void 0 }], [{ a: 0 }], [{ a: 0 }]],
+        [[{ a: null }], [{ a: 0 }], [{ a: 0 }]],
+        [[{ a: null }], [{ a: { b: 0 } }], [{ a: { b: 0 } }]],
+        [[{ a: 0 }], [{ a: 1 }], [{ a: 1 }]],
+        [[{ a: 0 }], [{ a: null }], [{ a: null }]],
+        [[{ a: 0 }], [{ a: void 0 }], [{ a: 0 }]],
+        [[{ a: 0 }], ["abc"], ["abc"]],
+        [[{ a: 0 }], [123], [123]],
+        [[[{ a: 0 }]], [123], [123]],
+        [
+            [{ a: ["b"] }],
+            [{ a: ["c"] }],
+            [{ a: ["c"] }]
+        ],
+        [
+            [{ a: [{ b: "c" }] }],
+            [{ a: [{ d: "e" }] }],
+            [{ a: [{ d: "e" }] }]
+        ],
+        [
+            [{ a: { b: "c" }, d: true }],
+            [{ a: { e: "f" } }],
+            [{ a: { b: "c", e: "f" }, d: true }]
+        ],
+        [
+            [{ a: { b: "c" } }],
+            [{ a: { e: "f" }, d: true }],
+            [{ a: { b: "c", e: "f" }, d: true }]
+        ],
+        [
+            [{ a: { b: "c" } }, { d: true }],
+            [{ a: { e: "f" } }, { f: 123 }],
+            [{ a: { b: "c", e: "f" } }, { d: true, f: 123 }]
+        ],
+        [
+            [{ hasOwnProperty: true }],
+            [{}],
+            [{ hasOwnProperty: true }]
+        ],
+        [
+            [{ hasOwnProperty: false }],
+            [{}],
+            [{ hasOwnProperty: false }]
+        ],
+        [
+            [{ hasOwnProperty: null }],
+            [{}],
+            [{ hasOwnProperty: null }]
+        ],
+        [
+            [{ hasOwnProperty: void 0 }],
+            [{}],
+            [{ hasOwnProperty: void 0 }]
+        ],
+        [
+            [{}],
+            [{ hasOwnProperty: null }],
+            [{ hasOwnProperty: null }]
+        ],
+        [
+            [{}],
+            [{ hasOwnProperty: void 0 }],
+            [{ hasOwnProperty: void 0 }]
+        ],
+        [
+            [{
+                allow: [],
+                ignoreDestructuring: false,
+                ignoreGlobals: false,
+                ignoreImports: false,
+                properties: "always"
+            }],
+            [],
+            [{
+                allow: [],
+                ignoreDestructuring: false,
+                ignoreGlobals: false,
+                ignoreImports: false,
+                properties: "always"
+            }]
+        ]
+    ]) {
+        it(`${toTestCaseName(first)}, ${toTestCaseName(second)}`, () => {
+            assert.deepStrictEqual(deepMergeArrays(first, second), result);
+        });
+    }
+});
diff --git a/tests/lib/shared/relative-module-resolver.js b/tests/lib/shared/relative-module-resolver.js
index 92eaa6ed..33c18361 100644
--- a/tests/lib/shared/relative-module-resolver.js
+++ b/tests/lib/shared/relative-module-resolver.js
@@ -3,7 +3,7 @@
  */
 
 import { assert } from "chai";
-import path from "path";
+import path from "node:path";
 
 import { Legacy } from "../../../lib/index.js";
 
diff --git a/tests/lib/types/tsconfig.json b/tests/lib/types/tsconfig.json
new file mode 100644
index 00000000..03a89990
--- /dev/null
+++ b/tests/lib/types/tsconfig.json
@@ -0,0 +1,17 @@
+{
+    "compilerOptions": {
+        "module": "node16",
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true,
+        "exactOptionalPropertyTypes": true
+    },
+    "files": [
+        "../../../lib/types/index.d.ts",
+        "types.test.mts"
+    ]
+}
diff --git a/tests/lib/types/types.test.mts b/tests/lib/types/types.test.mts
new file mode 100644
index 00000000..375a1798
--- /dev/null
+++ b/tests/lib/types/types.test.mts
@@ -0,0 +1,62 @@
+/**
+ * @fileoverview This file contains tests for types. It was initially extracted
+ * from the `@types/eslint__eslintrc` package.
+ */
+
+/*
+ * MIT License
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE
+ */
+
+
+import { FlatCompat } from "../../../lib/types/index.js";
+import { Linter } from "eslint";
+
+const __dirname = "/path/to/project";
+
+const compat = new FlatCompat({
+    baseDirectory: __dirname,
+    resolvePluginsRelativeTo: __dirname,
+});
+
+const config: Linter.Config[] = [
+    ...compat.extends("standard", "example"),
+
+    ...compat.env({
+        es2020: true,
+        node: true,
+    }),
+
+    ...compat.plugins("airbnb", "react"),
+
+    ...compat.config({
+        plugins: ["airbnb", "react"],
+        extends: "standard",
+        env: {
+            es2020: true,
+            node: true,
+        },
+        rules: {
+            semi: "error",
+        },
+    }),
+];
+
+export default config;
diff --git a/universal.js b/universal.js
index 4e1846ee..2257383e 100644
--- a/universal.js
+++ b/universal.js
@@ -1,3 +1,5 @@
+/* global module, require -- required for CJS file */
+
 // Jest (and probably some other runtimes with custom implementations of
 // `require`) doesn't support `exports` in `package.json`, so this file is here
 // to help them load this module. Note that it is also `.js` and not `.cjs` for
@@ -5,5 +7,4 @@
 // since Jest doesn't respect `module` outside of ESM mode it still works in
 // this case (and the `require` in _this_ file does specify the extension).
 
-// eslint-disable-next-line no-undef
 module.exports = require("./dist/eslintrc-universal.cjs");