diff --git a/package.json b/package.json
index 672c720c..a14231ab 100644
--- a/package.json
+++ b/package.json
@@ -51,7 +51,7 @@
     "@types/p-map": "2.0.0",
     "@types/semver": "7.5.8",
     "eslint": "9.12.0",
-    "eslint-config-upleveled": "8.7.3",
+    "eslint-config-upleveled": "8.8.0",
     "p-map": "7.0.2",
     "prettier": "3.3.3",
     "size-limit": "11.1.6",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 25bda6eb..71c7a9c6 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -82,8 +82,8 @@ importers:
         specifier: 9.12.0
         version: 9.12.0(jiti@2.1.2)
       eslint-config-upleveled:
-        specifier: 8.7.3
-        version: 8.7.3(@babel/core@7.24.4)(@types/eslint@9.6.1)(@types/node@22.7.5)(@types/react-dom@18.2.25)(@types/react@18.2.79)(eslint-plugin-import@2.29.1(@typescript-eslint/parser@8.8.1(eslint@9.12.0(jiti@2.1.2))(typescript@5.6.3))(eslint@9.12.0(jiti@2.1.2)))(eslint@9.12.0(jiti@2.1.2))(globals@15.9.0)(typescript@5.6.3)
+        specifier: 8.8.0
+        version: 8.8.0(@babel/core@7.24.4)(@types/eslint@9.6.1)(@types/node@22.7.5)(@types/react-dom@18.2.25)(@types/react@18.2.79)(eslint-plugin-import@2.29.1(@typescript-eslint/parser@8.8.1(eslint@9.12.0(jiti@2.1.2))(typescript@5.6.3))(eslint@9.12.0(jiti@2.1.2)))(eslint@9.12.0(jiti@2.1.2))(globals@15.9.0)(typescript@5.6.3)
       p-map:
         specifier: 7.0.2
         version: 7.0.2
@@ -1502,15 +1502,15 @@ packages:
     peerDependencies:
       eslint: 9.12.0
 
-  eslint-config-upleveled@8.7.3:
-    resolution: {integrity: sha512-JnOFPjRTQiW/JW/QZZ7yxfUcT2R8zW+UOTVml3+5cEtnwFv4LUUeaOGquE90L4zOx+59+1vL37rt0VdZetmZBQ==}
+  eslint-config-upleveled@8.8.0:
+    resolution: {integrity: sha512-B5JWKaigin2yIrxKHXT6Rhl3bxWyI6d1tKku3yRSgwtUqPxfsnqDv/FyT5Nc+TbUu2kKFxQkbfv8+ISiwQsfXw==}
     engines: {node: '>=20.9.0'}
     hasBin: true
     peerDependencies:
       '@types/eslint': ^9.6.1
       '@types/node': '>=22.7.5'
       '@types/react': ^18.3.11
-      '@types/react-dom': ^18.3.0
+      '@types/react-dom': ^18.3.1
       eslint: 9.12.0
       globals: ^15.11.0
       typescript: 5.6.3
@@ -4926,7 +4926,7 @@ snapshots:
       eslint: 9.12.0(jiti@2.1.2)
       find-up-simple: 1.0.0
 
-  eslint-config-upleveled@8.7.3(@babel/core@7.24.4)(@types/eslint@9.6.1)(@types/node@22.7.5)(@types/react-dom@18.2.25)(@types/react@18.2.79)(eslint-plugin-import@2.29.1(@typescript-eslint/parser@8.8.1(eslint@9.12.0(jiti@2.1.2))(typescript@5.6.3))(eslint@9.12.0(jiti@2.1.2)))(eslint@9.12.0(jiti@2.1.2))(globals@15.9.0)(typescript@5.6.3):
+  eslint-config-upleveled@8.8.0(@babel/core@7.24.4)(@types/eslint@9.6.1)(@types/node@22.7.5)(@types/react-dom@18.2.25)(@types/react@18.2.79)(eslint-plugin-import@2.29.1(@typescript-eslint/parser@8.8.1(eslint@9.12.0(jiti@2.1.2))(typescript@5.6.3))(eslint@9.12.0(jiti@2.1.2)))(eslint@9.12.0(jiti@2.1.2))(globals@15.9.0)(typescript@5.6.3):
     dependencies:
       '@babel/eslint-parser': 7.25.8(@babel/core@7.24.4)(eslint@9.12.0(jiti@2.1.2))
       '@eslint/compat': 1.2.0(eslint@9.12.0(jiti@2.1.2))
diff --git a/src/checks/allChangesCommittedToGit.ts b/src/checks/allChangesCommittedToGit.ts
index c5f074e2..437b12b9 100644
--- a/src/checks/allChangesCommittedToGit.ts
+++ b/src/checks/allChangesCommittedToGit.ts
@@ -1,7 +1,7 @@
 import { promises as fs } from 'node:fs';
 import { execa } from 'execa';
-import { commandExample } from '../util/commandExample';
-import { isDrone } from '../util/drone';
+import { commandExample } from '../util/commandExample.ts';
+import { isDrone } from '../util/drone.ts';
 
 export const title = 'All changes committed to Git';
 
diff --git a/src/checks/linkOnGithubAbout.ts b/src/checks/linkOnGithubAbout.ts
index 71fa528d..8e81c75a 100644
--- a/src/checks/linkOnGithubAbout.ts
+++ b/src/checks/linkOnGithubAbout.ts
@@ -2,7 +2,7 @@ import { load } from 'cheerio';
 import type { Element } from 'domhandler';
 import { execa } from 'execa';
 import fetch from 'node-fetch';
-import { randomUserAgent } from '../util/randomUserAgent';
+import { randomUserAgent } from '../util/randomUserAgent.ts';
 
 export const title = 'GitHub repo has deployed project link under About';
 
diff --git a/src/checks/noDependencyProblems/noDependenciesWithoutTypes.ts b/src/checks/noDependencyProblems/noDependenciesWithoutTypes.ts
index 59003801..7c3c800c 100644
--- a/src/checks/noDependencyProblems/noDependenciesWithoutTypes.ts
+++ b/src/checks/noDependencyProblems/noDependenciesWithoutTypes.ts
@@ -1,8 +1,8 @@
 import { existsSync, promises as fs } from 'node:fs';
 import { algoliasearch } from 'algoliasearch';
 import pReduce from 'p-reduce';
-import { commandExample } from '../../util/commandExample';
-import { projectPackageJson } from '../../util/packageJson';
+import { commandExample } from '../../util/commandExample.ts';
+import { projectPackageJson } from '../../util/packageJson.ts';
 
 const client = algoliasearch(
   // Application ID and API key specific to UpLeveled
diff --git a/src/checks/noDependencyProblems/noUnusedDependencies.ts b/src/checks/noDependencyProblems/noUnusedDependencies.ts
index 233b543b..7e46bfed 100644
--- a/src/checks/noDependencyProblems/noUnusedDependencies.ts
+++ b/src/checks/noDependencyProblems/noUnusedDependencies.ts
@@ -1,6 +1,6 @@
 import { execa } from 'execa';
-import { commandExample } from '../../util/commandExample';
-import { preflightBinPath } from '../../util/preflightBinPath';
+import { commandExample } from '../../util/commandExample.ts';
+import { preflightBinPath } from '../../util/preflightBinPath.ts';
 
 export const title = 'No unused dependencies';
 
diff --git a/src/checks/noExtraneousFilesCommittedToGit.ts b/src/checks/noExtraneousFilesCommittedToGit.ts
index 1479acbb..a704b1e5 100644
--- a/src/checks/noExtraneousFilesCommittedToGit.ts
+++ b/src/checks/noExtraneousFilesCommittedToGit.ts
@@ -1,5 +1,5 @@
 import { execa } from 'execa';
-import { commandExample } from '../util/commandExample';
+import { commandExample } from '../util/commandExample.ts';
 
 export const title = 'No extraneous files committed to Git';
 
diff --git a/src/checks/noSecretsCommittedToGit.ts b/src/checks/noSecretsCommittedToGit.ts
index 425ec14c..7f0d640d 100644
--- a/src/checks/noSecretsCommittedToGit.ts
+++ b/src/checks/noSecretsCommittedToGit.ts
@@ -1,5 +1,5 @@
 import { execa } from 'execa';
-import { commandExample } from '../util/commandExample';
+import { commandExample } from '../util/commandExample.ts';
 
 export const title = 'No secrets committed to Git';
 
diff --git a/src/checks/nodeModulesIgnoredFromGit.ts b/src/checks/nodeModulesIgnoredFromGit.ts
index f345b225..98832c8a 100644
--- a/src/checks/nodeModulesIgnoredFromGit.ts
+++ b/src/checks/nodeModulesIgnoredFromGit.ts
@@ -1,7 +1,7 @@
 import { promises as fs } from 'node:fs';
 import { execa } from 'execa';
-import { commandExample } from '../util/commandExample';
-import { normalizeNewlines } from '../util/crossPlatform';
+import { commandExample } from '../util/commandExample.ts';
+import { normalizeNewlines } from '../util/crossPlatform.ts';
 
 export const title = 'node_modules/ folder ignored in Git';
 
diff --git a/src/checks/preflightIsLatestVersion.ts b/src/checks/preflightIsLatestVersion.ts
index bd23d782..8d15971e 100644
--- a/src/checks/preflightIsLatestVersion.ts
+++ b/src/checks/preflightIsLatestVersion.ts
@@ -1,8 +1,8 @@
 import os from 'node:os';
 import { execa } from 'execa';
 import semver from 'semver';
-import { commandExample } from '../util/commandExample';
-import { preflightPackageJson } from '../util/packageJson';
+import { commandExample } from '../util/commandExample.ts';
+import { preflightPackageJson } from '../util/packageJson.ts';
 
 export const title = 'Preflight is latest version';
 
diff --git a/src/checks/prettier.ts b/src/checks/prettier.ts
index 473eabf6..f46c0c48 100644
--- a/src/checks/prettier.ts
+++ b/src/checks/prettier.ts
@@ -1,5 +1,5 @@
 import { execa } from 'execa';
-import { normalizeNewlines } from '../util/crossPlatform';
+import { normalizeNewlines } from '../util/crossPlatform.ts';
 
 export const title = 'Prettier';
 
diff --git a/src/checks/projectFolderNameMatchesCorrectFormat.ts b/src/checks/projectFolderNameMatchesCorrectFormat.ts
index ff4525a3..bb49fc4e 100644
--- a/src/checks/projectFolderNameMatchesCorrectFormat.ts
+++ b/src/checks/projectFolderNameMatchesCorrectFormat.ts
@@ -1,5 +1,5 @@
 import path from 'node:path';
-import { commandExample } from '../util/commandExample';
+import { commandExample } from '../util/commandExample.ts';
 
 export const title = 'Project folder name matches correct format';
 
diff --git a/src/checks/stylelint.ts b/src/checks/stylelint.ts
index 1f186bb9..31378d54 100644
--- a/src/checks/stylelint.ts
+++ b/src/checks/stylelint.ts
@@ -1,6 +1,6 @@
 import { sep } from 'node:path';
 import { execa } from 'execa';
-import { LintResult } from 'stylelint';
+import type { LintResult } from 'stylelint';
 
 export const supportedStylelintFileExtensions = [
   'css',
diff --git a/src/checks/stylelintConfigIsValid.ts b/src/checks/stylelintConfigIsValid.ts
index 633b28f7..de04cdcd 100644
--- a/src/checks/stylelintConfigIsValid.ts
+++ b/src/checks/stylelintConfigIsValid.ts
@@ -3,7 +3,7 @@ import { createRequire } from 'node:module';
 import { execa } from 'execa';
 import readdirp from 'readdirp';
 import semver from 'semver';
-import { supportedStylelintFileExtensions } from './stylelint';
+import { supportedStylelintFileExtensions } from './stylelint.ts';
 
 const require = createRequire(`${process.cwd()}/`);
 
diff --git a/src/checks/useSinglePackageManager.ts b/src/checks/useSinglePackageManager.ts
index 59b16353..b27b393b 100644
--- a/src/checks/useSinglePackageManager.ts
+++ b/src/checks/useSinglePackageManager.ts
@@ -1,5 +1,5 @@
 import { execa } from 'execa';
-import { commandExample } from '../util/commandExample';
+import { commandExample } from '../util/commandExample.ts';
 
 export const title = 'Use single package manager';
 
diff --git a/src/index.ts b/src/index.ts
index 6e2bb7dc..2378fc94 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,29 +1,29 @@
 import {
   Listr,
-  ListrContext,
-  ListrDefaultRenderer,
-  ListrTask,
+  type ListrContext,
+  type ListrDefaultRenderer,
+  type ListrTask,
   ListrTaskWrapper,
 } from 'listr2';
-import * as allChangesCommittedToGit from './checks/allChangesCommittedToGit.js';
-import * as eslint from './checks/eslint.js';
-import * as eslintConfigIsValid from './checks/eslintConfigIsValid.js';
-import * as linkOnGithubAbout from './checks/linkOnGithubAbout.js';
-import * as nodeModulesIgnoredFromGit from './checks/nodeModulesIgnoredFromGit.js';
-import * as noDependenciesWithoutTypes from './checks/noDependencyProblems/noDependenciesWithoutTypes.js';
-import * as noUnusedAndMissingDependencies from './checks/noDependencyProblems/noUnusedDependencies.js';
-import * as noExtraneousFilesCommittedToGit from './checks/noExtraneousFilesCommittedToGit.js';
-import * as noSecretsCommittedToGit from './checks/noSecretsCommittedToGit.js';
-import * as preflightIsLatestVersion from './checks/preflightIsLatestVersion.js';
-import * as prettier from './checks/prettier.js';
-import * as projectFolderNameMatchesCorrectFormat from './checks/projectFolderNameMatchesCorrectFormat.js';
-import * as stylelint from './checks/stylelint.js';
-import * as stylelintConfigIsValid from './checks/stylelintConfigIsValid.js';
-import * as useSinglePackageManager from './checks/useSinglePackageManager.js';
+import * as allChangesCommittedToGit from './checks/allChangesCommittedToGit.ts';
+import * as eslint from './checks/eslint.ts';
+import * as eslintConfigIsValid from './checks/eslintConfigIsValid.ts';
+import * as linkOnGithubAbout from './checks/linkOnGithubAbout.ts';
+import * as nodeModulesIgnoredFromGit from './checks/nodeModulesIgnoredFromGit.ts';
+import * as noDependenciesWithoutTypes from './checks/noDependencyProblems/noDependenciesWithoutTypes.ts';
+import * as noUnusedAndMissingDependencies from './checks/noDependencyProblems/noUnusedDependencies.ts';
+import * as noExtraneousFilesCommittedToGit from './checks/noExtraneousFilesCommittedToGit.ts';
+import * as noSecretsCommittedToGit from './checks/noSecretsCommittedToGit.ts';
+import * as preflightIsLatestVersion from './checks/preflightIsLatestVersion.ts';
+import * as prettier from './checks/prettier.ts';
+import * as projectFolderNameMatchesCorrectFormat from './checks/projectFolderNameMatchesCorrectFormat.ts';
+import * as stylelint from './checks/stylelint.ts';
+import * as stylelintConfigIsValid from './checks/stylelintConfigIsValid.ts';
+import * as useSinglePackageManager from './checks/useSinglePackageManager.ts';
 import {
   preflightPackageJson,
   projectPackageJson,
-} from './util/packageJson.js';
+} from './util/packageJson.ts';
 
 const projectDependencies = projectPackageJson.dependencies || {};
 
diff --git a/tsconfig.json b/tsconfig.json
index a33910ab..bdfab1b8 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -3,7 +3,6 @@
   "files": [],
   "references": [
     { "path": "./docker/tsconfig.json" },
-    { "path": "./tsconfig.nonsrc.json" },
-    { "path": "./tsconfig.src.json" }
+    { "path": "./tsconfig.root.json" }
   ]
 }
diff --git a/tsconfig.nonsrc.json b/tsconfig.root.json
similarity index 62%
rename from tsconfig.nonsrc.json
rename to tsconfig.root.json
index 094e0cce..aa6f4c3f 100644
--- a/tsconfig.nonsrc.json
+++ b/tsconfig.root.json
@@ -4,9 +4,9 @@
   "extends": "eslint-config-upleveled/tsconfig.base.json",
   "compilerOptions": {
     "composite": true,
-    "module": "Node16",
-    "moduleResolution": "Node16",
-    "target": "ES2020",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "allowImportingTsExtensions": true,
     "checkJs": true
   },
   "include": [
@@ -17,12 +17,5 @@
     "**/*.cjs",
     "**/*.mjs"
   ],
-  "exclude": [
-    "node_modules",
-    "__tests__/fixtures",
-    "bin",
-    "dist",
-    "docker",
-    "src"
-  ]
+  "exclude": ["node_modules", "__tests__/fixtures", "docker"]
 }
diff --git a/tsconfig.src.json b/tsconfig.src.json
deleted file mode 100644
index 5a2efa56..00000000
--- a/tsconfig.src.json
+++ /dev/null
@@ -1,36 +0,0 @@
-{
-  "include": ["src"],
-  "exclude": ["dist"],
-  "compilerOptions": {
-    "module": "esnext",
-    "lib": ["dom", "esnext"],
-    "target": "es2020",
-    "importHelpers": true,
-    // output .d.ts declaration files for consumers
-    "declaration": true,
-    // output .js.map sourcemap files for consumers
-    "sourceMap": true,
-    // match output dir to input dir. e.g. dist/index instead of dist/src/index
-    "rootDir": "./src",
-    // stricter type-checking for stronger correctness. Recommended by TS
-    "strict": true,
-    // linter checks for common issues
-    "noImplicitReturns": true,
-    "noUncheckedIndexedAccess": true,
-    "noFallthroughCasesInSwitch": true,
-    // use Node's module resolution algorithm, instead of the legacy TS one
-    "moduleResolution": "bundler",
-    // transpile JSX to React.createElement
-    "jsx": "react",
-    // interop between ESM and CJS modules. Recommended by TS
-    "esModuleInterop": true,
-    // significant perf increase by skipping checking .d.ts files, particularly those in node_modules. Recommended by TS
-    "skipLibCheck": true,
-    // error out if import and file system have a casing mismatch. Recommended by TS
-    "forceConsistentCasingInFileNames": true,
-    // `tsdx build` ignores this option, but it is commonly used when type-checking separately with `tsc`
-    "noEmit": true,
-    "resolveJsonModule": true,
-    "checkJs": true
-  }
-}