diff --git a/.vscode/settings.json b/.vscode/settings.json
index 5737bf3d..95706042 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -256,6 +256,7 @@
   "shellformat.flag": "-ci -fn -i=2 -sr",
   "shellformat.useEditorConfig": true,
   "terminal.integrated.copyOnSelection": true,
+  "terminal.integrated.scrollback": 10000,
   "todo-tree.filtering.ignoreGitSubmodules": true,
   "todo-tree.filtering.includeHiddenFiles": false,
   "todo-tree.filtering.useBuiltInExcludes": "file and search excludes",
diff --git a/__tests__/interfaces/mock.ts b/__tests__/interfaces/mock.ts
index e41f522c..df54cdb0 100644
--- a/__tests__/interfaces/mock.ts
+++ b/__tests__/interfaces/mock.ts
@@ -1,6 +1,6 @@
 /**
- * @file Test Environment Interfaces - Spy
- * @module tests/interfaces/Spy
+ * @file Test Environment Interfaces - Mock
+ * @module tests/interfaces/Mock
  */
 
 import type { Fn } from '@flex-development/tutils'
@@ -11,9 +11,11 @@ import type * as vitest from 'vitest'
  *
  * @template F - Function being mocked
  *
+ * @extends {Fn<Parameters<F>,ReturnType<F>>}
  * @extends {vitest.Mock<Parameters<F>,ReturnType<F>>}
  */
 interface Mock<F extends Fn = Fn>
-  extends vitest.Mock<Parameters<F>, ReturnType<F>> {}
+  extends Fn<Parameters<F>, ReturnType<F>>,
+    vitest.Mock<Parameters<F>, ReturnType<F>> {}
 
 export type { Mock as default }
diff --git a/__tests__/interfaces/spy.ts b/__tests__/interfaces/spy.ts
index 5af9595a..658d2751 100644
--- a/__tests__/interfaces/spy.ts
+++ b/__tests__/interfaces/spy.ts
@@ -4,16 +4,18 @@
  */
 
 import type { Fn } from '@flex-development/tutils'
-import type { SpyInstance } from 'vitest'
+import type * as vitest from 'vitest'
 
 /**
- * {@linkcode SpyInstance} utility.
+ * {@linkcode vitest.SpyInstance} utility.
  *
  * @template F - Function being spied on
  *
- * @extends {SpyInstance<Parameters<F>,ReturnType<F>>}
+ * @extends {Fn<Parameters<F>,ReturnType<F>>}
+ * @extends {vitest.SpyInstance<Parameters<F>,ReturnType<F>>}
  */
 interface Spy<F extends Fn = Fn>
-  extends SpyInstance<Parameters<F>, ReturnType<F>> {}
+  extends Fn<Parameters<F>, ReturnType<F>>,
+    vitest.SpyInstance<Parameters<F>, ReturnType<F>> {}
 
 export type { Spy as default }
diff --git a/__tests__/reporters/notifier.ts b/__tests__/reporters/notifier.ts
index f5c074b5..0ddab858 100644
--- a/__tests__/reporters/notifier.ts
+++ b/__tests__/reporters/notifier.ts
@@ -3,7 +3,7 @@
  * @module tests/reporters/Notifier
  */
 
-import type { OneOrMany } from '@flex-development/tutils'
+import { cast, isArray, type OneOrMany } from '@flex-development/tutils'
 import notifier from 'node-notifier'
 import type NotificationCenter from 'node-notifier/notifiers/notificationcenter'
 import { performance } from 'node:perf_hooks'
@@ -20,22 +20,28 @@ import type { File, Reporter, Task, Test, Vitest } from 'vitest'
  */
 class Notifier implements Reporter {
   /**
+   * Test reporter context.
+   *
    * @public
-   * @member {Vitest} ctx - Test reporter context
+   * @member {Vitest} ctx
    */
-  public ctx: Vitest = {} as Vitest
+  public ctx!: Vitest
 
   /**
+   * Test run end time (in milliseconds).
+   *
    * @public
-   * @member {number} end - Test run end time (in milliseconds)
+   * @member {number} end
    */
-  public end: number = 0
+  public end!: number
 
   /**
+   * Test run start time (in milliseconds).
+   *
    * @public
-   * @member {number} start - Test run start time (in milliseconds)
+   * @member {number} start
    */
-  public start: number = 0
+  public start!: number
 
   /**
    * Sends a notification.
@@ -52,19 +58,39 @@ class Notifier implements Reporter {
     files: File[] = this.ctx.state.getFiles(),
     errors: unknown[] = this.ctx.state.getUnhandledErrors()
   ): Promise<void> {
-    /** @const {Test[]} tests - Tests run */
+    /**
+     * Tests that have been run.
+     *
+     * @const {Test[]} tests
+     */
     const tests: Test[] = this.tests(files)
 
-    /** @const {number} fails - Total number of failed tests */
+    /**
+     * Total number of failed tests.
+     *
+     * @const {number} fails
+     */
     const fails: number = tests.filter(t => t.result?.state === 'fail').length
 
-    /** @const {number} passes - Total number of passed tests */
+    /**
+     * Total number of passed tests.
+     *
+     * @const {number} passes
+     */
     const passes: number = tests.filter(t => t.result?.state === 'pass').length
 
-    /** @var {string} message - Notification message */
+    /**
+     * Notification message.
+     *
+     * @var {string} message
+     */
     let message: string = ''
 
-    /** @var {string} title - Notification title */
+    /**
+     * Notification title.
+     *
+     * @var {string} title
+     */
     let title: string = ''
 
     // get notification title and message based on number of failed tests
@@ -76,7 +102,11 @@ class Notifier implements Reporter {
 
       title = '\u274C Failed'
     } else {
-      /** @const {number} time - Time to run all tests (in milliseconds) */
+      /**
+       * Time to run all tests (in milliseconds).
+       *
+       * @const {number} time
+       */
       const time: number = this.end - this.start
 
       message = dedent`
@@ -128,7 +158,7 @@ class Notifier implements Reporter {
    */
   public onInit(context: Vitest): void {
     this.ctx = context
-    return void (this.start = performance.now())
+    return void ((this.start = performance.now()) && (this.end = 0))
   }
 
   /**
@@ -140,17 +170,13 @@ class Notifier implements Reporter {
    * @return {Test[]} `Test` object array
    */
   protected tests(tasks: OneOrMany<Task> = []): Test[] {
-    const { mode } = this.ctx
-
-    return (Array.isArray(tasks) ? tasks : [tasks]).flatMap(task => {
-      const { type } = task
-
-      return mode === 'typecheck' && type === 'suite' && task.tasks.length === 0
-        ? ([task] as unknown as [Test])
-        : type === 'test'
+    return (isArray<Task>(tasks) ? tasks : [tasks]).flatMap(task => {
+      return task.type === 'custom'
+        ? [cast(task)]
+        : task.type === 'test'
         ? [task]
         : 'tasks' in task
-        ? task.tasks.flatMap(t => (t.type === 'test' ? [t] : this.tests(t)))
+        ? task.tasks.flatMap(task => this.tests(task))
         : []
     })
   }
diff --git a/__tests__/setup/serializers/result-array.ts b/__tests__/setup/serializers/result-array.ts
index fa77c484..1e6eb2d0 100644
--- a/__tests__/setup/serializers/result-array.ts
+++ b/__tests__/setup/serializers/result-array.ts
@@ -4,9 +4,17 @@
  */
 
 import type { Result } from '#src/interfaces'
-import { isNIL, isObjectPlain, isString } from '@flex-development/tutils'
+import {
+  cast,
+  get,
+  isArray,
+  isNIL,
+  isObjectPlain,
+  isString,
+  omit,
+  pick
+} from '@flex-development/tutils'
 import pf from 'pretty-format'
-import { get, omit, pick } from 'radash'
 
 expect.addSnapshotSerializer({
   /**
@@ -16,7 +24,7 @@ expect.addSnapshotSerializer({
    * @return {string} `value` as printable string
    */
   print(value: unknown): string {
-    value = (value as Result[]).map(result => {
+    value = cast<Result[]>(value).map(result => {
       result.cwd = result.cwd.replace(/.*?(?=\/__.+)/, '${process.cwd()}')
 
       return {
@@ -37,16 +45,16 @@ expect.addSnapshotSerializer({
    * @return {value is Result[]} `true` if `value` is {@linkcode Result} array
    */
   test(value: unknown): value is Result[] {
-    return Array.isArray(value)
+    return isArray(value)
       ? value.every(item => {
           return (
             isString(get(item, 'cwd')) &&
-            Array.isArray(get(item, 'errors')) &&
+            isArray(get(item, 'errors')) &&
             (isObjectPlain(get(item, 'mangleCache')) ||
               isNIL(get(item, 'mangleCache'))) &&
             isString(get(item, 'outdir')) &&
-            Array.isArray(get(item, 'outputs')) &&
-            Array.isArray(get(item, 'warnings'))
+            isArray(get(item, 'outputs')) &&
+            isArray(get(item, 'warnings'))
           )
         })
       : false
diff --git a/__tests__/utils/create-testing-command.ts b/__tests__/utils/create-testing-command.ts
index 226c12ff..484f4a2f 100644
--- a/__tests__/utils/create-testing-command.ts
+++ b/__tests__/utils/create-testing-command.ts
@@ -5,6 +5,7 @@
 
 import AppModule from '#src/cli/app.module'
 import { CLI_NAME } from '#src/cli/constants'
+import type { Omit } from '@flex-development/tutils'
 import { Module } from '@nestjs/common'
 import type { TestingModule } from '@nestjs/testing'
 import { CommandRunnerModule } from 'nest-commander'
diff --git a/__tests__/utils/get-package-json.ts b/__tests__/utils/get-package-json.ts
index 44cf38de..f6ce7c60 100644
--- a/__tests__/utils/get-package-json.ts
+++ b/__tests__/utils/get-package-json.ts
@@ -5,6 +5,7 @@
 
 import type mlly from '@flex-development/mlly'
 import type pkg from '@flex-development/pkg-types'
+import { cast } from '@flex-development/tutils'
 
 /**
  * Retrieves a `package.json` object.
@@ -29,7 +30,7 @@ const getPackageJson = async (
    */
   const fs: typeof import('node:fs') = await vi.importActual('node:fs')
 
-  return JSON.parse(fs.readFileSync(id, 'utf8')) as pkg.PackageJson
+  return cast(JSON.parse(fs.readFileSync(id, 'utf8')))
 }
 
 export default getPackageJson
diff --git a/build.config.ts b/build.config.ts
index 6190b99a..2416780f 100644
--- a/build.config.ts
+++ b/build.config.ts
@@ -4,6 +4,7 @@
  */
 
 import { defineBuildConfig, type Config } from '#src'
+import pathe from '@flex-development/pathe'
 import pkg from './package.json' assert { type: 'json' }
 import tsconfig from './tsconfig.build.json' assert { type: 'json' }
 
@@ -15,7 +16,13 @@ import tsconfig from './tsconfig.build.json' assert { type: 'json' }
 const config: Config = defineBuildConfig({
   charset: 'utf8',
   entries: [
-    { ignore: ['cli/**'] },
+    { dts: 'only', ignore: ['cli/**'] },
+    { dts: false, pattern: ['(interfaces|types)/index.ts'] },
+    {
+      dts: false,
+      pattern: ['*.ts', 'config/*', 'internal/*', 'plugins/*', 'utils/*'],
+      sourcemap: true
+    },
     {
       bundle: true,
       external: [
@@ -30,11 +37,13 @@ const config: Config = defineBuildConfig({
       minify: true,
       name: 'cli',
       platform: 'node',
-      source: 'src/cli/index.ts'
+      source: 'src/cli/index.ts',
+      sourcemap: true,
+      sourcesContent: false
     }
   ],
-  sourcemap: true,
-  sourcesContent: false,
+  minifySyntax: true,
+  sourceRoot: 'file' + pathe.delimiter + pathe.sep.repeat(2),
   target: [
     pkg.engines.node.replace(/^\D+/, 'node'),
     tsconfig.compilerOptions.target
diff --git a/config/changelog.config.ts b/config/changelog.config.ts
index 3bb3a5dd..535483a2 100644
--- a/config/changelog.config.ts
+++ b/config/changelog.config.ts
@@ -17,7 +17,18 @@ import {
   type Commit
 } from '@flex-development/commitlint-config'
 import pathe from '@flex-development/pathe'
-import { CompareResult, isNIL } from '@flex-development/tutils'
+import {
+  CompareResult,
+  at,
+  constant,
+  includes,
+  isBoolean,
+  isNIL,
+  isString,
+  select,
+  trim,
+  type Optional
+} from '@flex-development/tutils'
 import { Inject, Module } from '@nestjs/common'
 import addStream from 'add-stream'
 import { Command, CommanderError } from 'commander'
@@ -338,13 +349,11 @@ class ChangelogCommand extends CommandRunner {
     const changelog: Readable = conventionalChangelog<Commit>(
       {
         append: false,
-        debug: debug ? consola.log.bind(consola) : undefined,
-        outputUnreleased:
-          typeof outputUnreleased === 'boolean'
-            ? outputUnreleased
-            : typeof outputUnreleased === 'string'
-            ? !!outputUnreleased.trim()
-            : false,
+        outputUnreleased: isBoolean(outputUnreleased)
+          ? outputUnreleased
+          : isString(outputUnreleased)
+          ? !!trim(outputUnreleased)
+          : false,
         pkg: { path: pathe.resolve('package.json') },
         preset: {
           header: '',
@@ -382,10 +391,10 @@ class ChangelogCommand extends CommandRunner {
           return void apply(null, {
             ...commit,
             committerDate: dateformat(commit.committerDate, 'yyyy-mm-dd', true),
-            mentions: commit.mentions.filter(m => m !== 'flexdevelopment'),
+            mentions: select(commit.mentions, m => m !== 'flexdevelopment'),
             // @ts-expect-error ts(2322)
             raw: commit,
-            references: commit.references.filter(ref => ref.action !== null),
+            references: select(commit.references, ref => ref.action !== null),
             version: commit.gitTags ? vgx.exec(commit.gitTags)?.[1] : undefined
           })
         },
@@ -480,35 +489,35 @@ class ChangelogCommand extends CommandRunner {
            *
            * @const {CommitEnhanced?} first_commit
            */
-          const first_commit: CommitEnhanced | undefined = commits.at(0)
+          const first_commit: Optional<CommitEnhanced> = at(commits, 0)
 
           /**
            * Last commit in release.
            *
            * @const {CommitEnhanced?} last_commit
            */
-          const last_commit: CommitEnhanced | undefined = commits.at(-1)
+          const last_commit: Optional<CommitEnhanced> = at(commits, -1)
 
           // set current and previous tags
           if (key && (!currentTag || !previousTag)) {
-            currentTag = key.version ?? undefined
+            currentTag = key.version
 
             // try setting previous tag based on current tag
-            if (gitSemverTags.includes(currentTag ?? '')) {
+            if (includes(gitSemverTags, currentTag)) {
               const { version = '' } = key
               previousTag = gitSemverTags[gitSemverTags.indexOf(version) + 1]
-              if (!previousTag) previousTag = last_commit?.hash ?? undefined
+              if (!previousTag) previousTag = last_commit?.hash
             }
           } else {
             currentTag = /^unreleased$/i.test(version ?? '')
               ? currentTag ??
-                (typeof outputUnreleased === 'string' && outputUnreleased
+                (isString(outputUnreleased) && outputUnreleased
                   ? outputUnreleased
-                  : first_commit?.hash ?? undefined)
+                  : first_commit?.hash)
               : !currentTag && version
               ? pkg.tagPrefix + version
               : currentTag ?? version
-            previousTag = previousTag ?? gitSemverTags[0]
+            previousTag = previousTag ?? at(gitSemverTags, 0)
           }
 
           // set release date
@@ -615,7 +624,7 @@ class ChangelogCommand extends CommandRunner {
     cmd.addHelpCommand(false)
     cmd.allowExcessArguments(false)
     cmd.allowUnknownOption(false)
-    cmd.createHelp = () => this.help
+    cmd.createHelp = constant(this.help)
     cmd.combineFlagAndOptionalValue(false)
     cmd.enablePositionalOptions()
     cmd.helpOption(false)
diff --git a/loader.mjs b/loader.mjs
index d3ede91e..b450549f 100644
--- a/loader.mjs
+++ b/loader.mjs
@@ -68,7 +68,7 @@ export const load = async (url, context) => {
   /**
    * Module source code.
    *
-   * @type {esm.Source<Uint8Array | string> | undefined}
+   * @type {tutils.Optional<esm.Source<Uint8Array | string>>}
    * @var source
    */
   let source = await mlly.getSource(url, { format: context.format })
@@ -123,6 +123,7 @@ export const load = async (url, context) => {
 
   return { format: context.format, shortCircuit: true, source }
 }
+
 /**
  * Resolves the given module `specifier`, and its module format as a hint to the
  * {@linkcode load} hook.
diff --git a/package.json b/package.json
index 5e42b128..cee1ac53 100644
--- a/package.json
+++ b/package.json
@@ -29,8 +29,7 @@
   "type": "module",
   "files": [
     "CHANGELOG.md",
-    "dist",
-    "src"
+    "dist"
   ],
   "bin": "./dist/cli.mjs",
   "exports": {
@@ -44,7 +43,7 @@
   "module": "./dist/index.mjs",
   "types": "./dist/index.d.mts",
   "scripts": {
-    "build": "node --loader=./loader.mjs ./src/cli",
+    "build": "node --enable-source-maps --loader=./loader.mjs ./src/cli",
     "changelog": "node --loader=./loader.mjs ./config/changelog.config",
     "check:ci": "yarn dedupe --check && yarn check:format && yarn check:lint && yarn check:spelling && yarn typecheck && yarn test:cov && NODE_ENV=production yarn pack -o %s-%v.tgz && yarn clean:pack && yarn check:types:build && yarn pkg-size",
     "check:format": "prettier --check .",
@@ -89,16 +88,13 @@
     "@flex-development/pkg-types": "2.0.0",
     "@flex-development/toggle-pkg-type": "2.0.0",
     "@flex-development/tsconfig-utils": "1.1.2",
-    "@flex-development/tutils": "6.0.0-alpha.10",
+    "@flex-development/tutils": "6.0.0-alpha.18",
     "colorette": "2.0.20",
     "consola": "3.1.0",
     "cosmiconfig": "8.1.3",
-    "escape-string-regexp": "5.0.0",
     "exit-hook": "3.2.0",
     "fast-glob": "3.2.12",
-    "merge-anything": "5.1.6",
-    "pretty-bytes": "6.1.0",
-    "radash": "10.8.1"
+    "pretty-bytes": "6.1.0"
   },
   "devDependencies": {
     "@commitlint/cli": "17.6.3",
@@ -208,9 +204,7 @@
   },
   "resolutions": {
     "@ardatan/sync-fetch": "larsgw/sync-fetch#head=worker_threads",
-    "@flex-development/tutils": "6.0.0-alpha.10",
-    "nest-commander@npm:3.6.1": "patch:nest-commander@npm%3A3.6.1#patches/nest-commander+3.6.1.dev.patch",
-    "radash@npm:10.8.1": "patch:radash@npm%3A10.8.1#patches/radash+10.8.1.dev.patch"
+    "nest-commander@npm:3.6.1": "patch:nest-commander@npm%3A3.6.1#patches/nest-commander+3.6.1.dev.patch"
   },
   "engines": {
     "node": ">=16.20.0",
diff --git a/patches/radash+10.8.1.dev.patch b/patches/radash+10.8.1.dev.patch
deleted file mode 100644
index 3ffa779e..00000000
--- a/patches/radash+10.8.1.dev.patch
+++ /dev/null
@@ -1,7 +0,0 @@
-diff --git a/dist/esm/object.mjs b/dist/esm/object.mjs
-index v10.8.1..v10.8.1 100644
---- a/dist/esm/object.mjs
-+++ b/dist/esm/object.mjs
-@@ -114,1 +114,1 @@
--  if (!path || !value)
-+  if (!path || value === undefined)
diff --git a/src/cli/__tests__/app.module.functional.spec.ts b/src/cli/__tests__/app.module.functional.spec.ts
index 58a0e9d6..a13be7ef 100644
--- a/src/cli/__tests__/app.module.functional.spec.ts
+++ b/src/cli/__tests__/app.module.functional.spec.ts
@@ -6,12 +6,12 @@
 import { ERR_MODULE_NOT_FOUND, type NodeError } from '@flex-development/errnode'
 import * as mlly from '@flex-development/mlly'
 import pathe from '@flex-development/pathe'
+import { cast, template } from '@flex-development/tutils'
 import * as color from 'colorette'
 import { CommanderError } from 'commander'
 import consola from 'consola'
 import * as esbuild from 'esbuild'
 import { fileURLToPath } from 'node:url'
-import { template } from 'radash'
 import TestSubject from '../app.module'
 
 vi.mock('esbuild')
@@ -32,7 +32,7 @@ describe('functional:cli/AppModule', () => {
       TestSubject.errorHandler(error)
 
       // Expect
-      expect(process).to.have.property('exitCode').equal(error.exitCode)
+      expect(process).to.have.property('exitCode', error.exitCode)
       expect(consola.log).not.toHaveBeenCalled()
     })
 
@@ -41,7 +41,7 @@ describe('functional:cli/AppModule', () => {
       const code: string = 'commander.unknownOption'
       const message: string = "error: unknown option '--formatter'"
       const error: CommanderError = new CommanderError(1, code, message)
-      const log: string = template('{{0}} {{1}} {{2}}', {
+      const log: string = template('{0} {1} {2}', {
         0: color.red('✘'),
         1: color.bgRed('[ERROR]'),
         2: color.white(error.message)
@@ -65,7 +65,7 @@ describe('functional:cli/AppModule', () => {
         fileURLToPath(mlly.toURL('dist/make.mjs')),
         'module'
       )
-      const log: string = template('{{0}} {{1}} {{2}}', {
+      const log: string = template('{0} {1} {2}', {
         0: color.red('✘'),
         1: color.bgRed('[ERROR]'),
         2: color.white(error.message)
@@ -75,21 +75,23 @@ describe('functional:cli/AppModule', () => {
       TestSubject.serviceErrorHandler(error)
 
       // Expect
-      expect(process).to.have.property('exitCode').equal(1)
+      expect(process).to.have.property('exitCode', 1)
       expect(consola.log).toHaveBeenCalledOnce()
       expect(consola.log).toHaveBeenCalledWith(log)
     })
 
     it('should handle esbuild.BuildFailure', () => {
       // Act
-      TestSubject.serviceErrorHandler({
-        ...new Error('Cannot use "external" without "bundle"'),
-        errors: [],
-        warnings: []
-      } as esbuild.BuildFailure)
+      TestSubject.serviceErrorHandler(
+        cast<esbuild.BuildFailure>({
+          ...new Error('Cannot use "external" without "bundle"'),
+          errors: [],
+          warnings: []
+        })
+      )
 
       // Expect
-      expect(process).to.have.property('exitCode').equal(1)
+      expect(process).to.have.property('exitCode', 1)
       expect(consola.log).not.toHaveBeenCalled()
     })
   })
diff --git a/src/cli/app.module.ts b/src/cli/app.module.ts
index 751120f3..fdb17f96 100644
--- a/src/cli/app.module.ts
+++ b/src/cli/app.module.ts
@@ -3,12 +3,12 @@
  * @module mkbuild/cli/AppModule
  */
 
+import { cast, isArray, template } from '@flex-development/tutils'
 import { Module } from '@nestjs/common'
 import * as color from 'colorette'
 import type * as commander from 'commander'
 import consola from 'consola'
 import * as esbuild from 'esbuild'
-import { template } from 'radash'
 import { MkbuildCommand } from './commands'
 import { HelpService, UtilityService } from './providers'
 
@@ -35,7 +35,7 @@ class AppModule {
   public static errorHandler(error: commander.CommanderError): void {
     if (error.exitCode) {
       consola.log(
-        template('{{0}} {{1}} {{2}}', {
+        template('{{0} {1} {2}', {
           0: color.red('✘'),
           1: color.bgRed('[ERROR]'),
           2: color.white(error.message)
@@ -56,12 +56,12 @@ class AppModule {
    * @return {void} Nothing when complete
    */
   public static serviceErrorHandler(error: Error): void {
-    const { errors, warnings } = error as esbuild.BuildFailure
+    const { errors, warnings } = cast<esbuild.BuildFailure>(error)
 
     // format and log non-esbuild error
-    if (!Array.isArray(errors) && !Array.isArray(warnings)) {
+    if (!isArray(errors) && !isArray(warnings)) {
       consola.log(
-        template('{{0}} {{1}} {{2}}', {
+        template('{{0} {1} {2}', {
           0: color.red('✘'),
           1: color.bgRed('[ERROR]'),
           2: color.white(error.message)
diff --git a/src/cli/commands/__tests__/mkbuild.command.functional.spec.ts b/src/cli/commands/__tests__/mkbuild.command.functional.spec.ts
index 96ba690e..8417255d 100644
--- a/src/cli/commands/__tests__/mkbuild.command.functional.spec.ts
+++ b/src/cli/commands/__tests__/mkbuild.command.functional.spec.ts
@@ -10,11 +10,11 @@ import type { Jsx, LegalComments, OutputExtension, Sourcemap } from '#src/types'
 import type { Spy } from '#tests/interfaces'
 import createTestingCommand from '#tests/utils/create-testing-command'
 import * as mlly from '@flex-development/mlly'
+import { cast, descriptor } from '@flex-development/tutils'
 import type { TestingModule } from '@nestjs/testing'
 import consola from 'consola'
 import type * as esbuild from 'esbuild'
 import { CommandTestFactory } from 'nest-commander-testing'
-import { get } from 'radash'
 import TestSubject from '../mkbuild.command'
 
 vi.mock('#src/make')
@@ -431,7 +431,7 @@ describe('functional:cli/commands/MkbuildCommand', () => {
     let subject: TestSubject
 
     beforeEach(() => {
-      formatHelp = vi.spyOn(command.get(HelpService), 'formatHelp')
+      formatHelp = cast(vi.spyOn(command.get(HelpService), 'formatHelp'))
       subject = command.get(TestSubject)
     })
 
@@ -441,7 +441,7 @@ describe('functional:cli/commands/MkbuildCommand', () => {
 
       // Expect
       expect(formatHelp).toHaveBeenCalledOnce()
-      expect(formatHelp).toBeCalledWith(get(subject, 'command'))
+      expect(formatHelp).toBeCalledWith(descriptor(subject, 'command').value)
       expect(consola.log).toHaveBeenCalledOnce()
       expect(make).not.toHaveBeenCalled()
     })
@@ -452,7 +452,7 @@ describe('functional:cli/commands/MkbuildCommand', () => {
 
       // Expect
       expect(formatHelp).toHaveBeenCalledOnce()
-      expect(formatHelp).toBeCalledWith(get(subject, 'command'))
+      expect(formatHelp).toBeCalledWith(descriptor(subject, 'command').value)
       expect(consola.log).toHaveBeenCalledOnce()
       expect(make).not.toHaveBeenCalled()
     })
diff --git a/src/cli/commands/mkbuild.command.ts b/src/cli/commands/mkbuild.command.ts
index 8fd579f4..2d1435ac 100644
--- a/src/cli/commands/mkbuild.command.ts
+++ b/src/cli/commands/mkbuild.command.ts
@@ -17,7 +17,17 @@ import type {
 } from '#src/types'
 import { IGNORE_PATTERNS, loaders } from '#src/utils'
 import * as mlly from '@flex-development/mlly'
-import type * as pathe from '@flex-development/pathe'
+import * as pathe from '@flex-development/pathe'
+import {
+  DOT,
+  cast,
+  constant,
+  construct,
+  entries,
+  join,
+  keys,
+  set
+} from '@flex-development/tutils'
 import { Inject } from '@nestjs/common'
 import type * as commander from 'commander'
 import consola from 'consola'
@@ -28,7 +38,6 @@ import {
   OptionChoiceFor,
   RootCommand
 } from 'nest-commander'
-import { construct, set, shake } from 'radash'
 
 /**
  * `mkbuild` command model.
@@ -279,7 +288,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'charset'
   })
   protected parseCharset(val: string): esbuild.Charset {
-    return this.util.parseString<esbuild.Charset>(val)
+    return cast<esbuild.Charset>(val)
   }
 
   /**
@@ -399,7 +408,7 @@ class MkbuildCommand extends CommandRunner {
    * @return {string} Parsed option value
    */
   @Option({
-    defaultValue: '.',
+    defaultValue: DOT,
     description: 'Current working directory',
     flags: '--cwd <directory>',
     name: 'cwd'
@@ -488,7 +497,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'ext'
   })
   protected parseExt(val: string): OutputExtension {
-    return this.util.parseString<OutputExtension>(val)
+    return cast<OutputExtension>(val)
   }
 
   /**
@@ -550,7 +559,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'format'
   })
   protected parseFormat(val: string): esbuild.Format {
-    return this.util.parseString<esbuild.Format>(val)
+    return cast<esbuild.Format>(val)
   }
 
   /**
@@ -672,7 +681,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'jsx'
   })
   protected parseJsx(val: string): Jsx {
-    return this.util.parseString<Jsx>(val)
+    return cast<Jsx>(val)
   }
 
   /**
@@ -817,7 +826,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'legalComments'
   })
   protected parseLegalComments(val: string): LegalComments {
-    return this.util.parseString<LegalComments>(val)
+    return cast<LegalComments>(val)
   }
 
   /**
@@ -833,9 +842,11 @@ class MkbuildCommand extends CommandRunner {
   @Option({
     defaultValue: loaders(),
     defaultValueDescription: JSON.stringify(
-      Object.entries(loaders())
-        .map(([ext, loader]): string => `${ext}:${loader}`)
-        .join(',')
+      join(
+        entries(loaders()).map(([ext, loader]): string => {
+          return `${ext}${pathe.delimiter}${loader}`
+        })
+      )
     ),
     description: 'https://esbuild.github.io/api/#loader',
     flags: '--loader <list>',
@@ -863,7 +874,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'logLevel'
   })
   protected parseLogLevel(val: string): esbuild.LogLevel {
-    return this.util.parseString<esbuild.LogLevel>(val)
+    return cast<esbuild.LogLevel>(val)
   }
 
   /**
@@ -1216,7 +1227,7 @@ class MkbuildCommand extends CommandRunner {
     name: 'platform'
   })
   protected parsePlatform(val: string): esbuild.Platform {
-    return this.util.parseString<esbuild.Platform>(val)
+    return cast<esbuild.Platform>(val)
   }
 
   /**
@@ -1498,7 +1509,7 @@ class MkbuildCommand extends CommandRunner {
     try {
       return this.util.parseBoolean(val)
     } catch {
-      return this.util.parseString<Sourcemap>(val)
+      return cast<Sourcemap>(val)
     }
   }
 
@@ -1679,7 +1690,7 @@ class MkbuildCommand extends CommandRunner {
    */
   public async run(_: string[], flags: Flags = {}): Promise<void> {
     // remove defaults to prevent accidental config file option override
-    for (const key of Object.keys(flags)) {
+    for (const key of keys(flags)) {
       if (this.command.getOptionValueSource(key) !== 'default') continue
       Reflect.deleteProperty(flags, key)
     }
@@ -1691,7 +1702,7 @@ class MkbuildCommand extends CommandRunner {
     if (flags.version) return void consola.log(pkg.version)
 
     // run make
-    return void (await make(shake(set(construct(flags), 'write', true))))
+    return void (await make(set(construct(flags), 'write', true)))
   }
 
   /**
@@ -1708,7 +1719,7 @@ class MkbuildCommand extends CommandRunner {
     cmd.allowExcessArguments()
     cmd.allowUnknownOption(false)
     cmd.combineFlagAndOptionalValue(false)
-    cmd.createHelp = /* c8 ignore next */ () => this.help
+    cmd.createHelp = constant(this.help)
     cmd.enablePositionalOptions()
     cmd.helpOption(false)
     cmd.showHelpAfterError()
diff --git a/src/cli/index.ts b/src/cli/index.ts
index 12944b5a..bcd9aa9f 100644
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -5,6 +5,7 @@
  * @module mkbuild/cli
  */
 
+import type { Optional } from '@flex-development/tutils'
 import mri from 'mri'
 import { CommandFactory } from 'nest-commander'
 import AppModule from './app.module'
@@ -45,7 +46,7 @@ const {
   'serve.keyfile'?: string
   'serve.port'?: number
   'serve.servedir'?: string
-  serve?: boolean | undefined
+  serve?: Optional<boolean>
   watch?: boolean
 }>(process.argv.slice(2), {
   alias: { serve: 'S', watch: 'w' },
diff --git a/src/cli/providers/__tests__/help.service.spec.ts b/src/cli/providers/__tests__/help.service.spec.ts
index f191ad06..20f4839a 100644
--- a/src/cli/providers/__tests__/help.service.spec.ts
+++ b/src/cli/providers/__tests__/help.service.spec.ts
@@ -4,9 +4,9 @@
  */
 
 import { CLI_NAME } from '#src/cli/constants'
+import { cast, set } from '@flex-development/tutils'
 import * as commander from 'commander'
 import { Command } from 'commander'
-import { set } from 'radash'
 import TestSubject from '../help.service'
 
 describe('unit:cli/providers/HelpService', () => {
@@ -67,14 +67,14 @@ describe('unit:cli/providers/HelpService', () => {
       try {
         subject.optionTermByName(name, cmd)
       } catch (e: unknown) {
-        error = e as typeof error
+        error = cast(e)
       }
 
       // Expect
       expect(error).to.be.instanceof(commander.CommanderError)
-      expect(error).to.have.property('code').equal('commander.unknownOption')
-      expect(error).to.have.property('exitCode').equal(1)
-      expect(error).to.have.property('message').equal(message)
+      expect(error).to.have.property('code', 'commander.unknownOption')
+      expect(error).to.have.property('exitCode', 1)
+      expect(error).to.have.property('message', message)
     })
   })
 })
diff --git a/src/cli/providers/__tests__/utility.service.spec.ts b/src/cli/providers/__tests__/utility.service.spec.ts
index 8b48849a..af1e42c9 100644
--- a/src/cli/providers/__tests__/utility.service.spec.ts
+++ b/src/cli/providers/__tests__/utility.service.spec.ts
@@ -56,14 +56,4 @@ describe('unit:cli/providers/UtilityService', () => {
       })
     })
   })
-
-  describe('#parseString', () => {
-    it('should return val', () => {
-      // Arrange
-      const string: string = 'esm'
-
-      // Act + Expect
-      expect(subject.parseString(string)).to.equal(string)
-    })
-  })
 })
diff --git a/src/cli/providers/help.service.ts b/src/cli/providers/help.service.ts
index e6e2a402..4f93a025 100644
--- a/src/cli/providers/help.service.ts
+++ b/src/cli/providers/help.service.ts
@@ -3,9 +3,17 @@
  * @module mkbuild/cli/providers/HelpService
  */
 
+import {
+  flat,
+  fork,
+  ifelse,
+  sort,
+  template,
+  trim,
+  type Optional
+} from '@flex-development/tutils'
 import { Injectable } from '@nestjs/common'
 import * as commander from 'commander'
-import { flat, fork, template } from 'radash'
 import { dedent } from 'ts-dedent'
 import wrap from 'word-wrap'
 
@@ -90,7 +98,9 @@ class HelpService extends commander.Help {
      */
     const options: commander.Option[] = flat(
       fork(
-        this.visibleOptions(cmd).sort((a, b) => a.long!.localeCompare(b.long!)),
+        sort(this.visibleOptions(cmd), (a, b) => {
+          return a.long!.localeCompare(b.long!)
+        }),
         option => option.name() !== 'help' && option.name() !== 'version'
       )
     )
@@ -100,7 +110,7 @@ class HelpService extends commander.Help {
       ${indentation}${this.wrap(this.commandDescription(cmd), linewidth, 0)}
 
       Usage
-      ${indentation}${template('$ {{0}}', { 0: this.commandUsage(cmd) })}
+      ${indentation}${template('$ {0}', { 0: this.commandUsage(cmd) })}
 
       Options
       ${options.reduce((acc: string, option: commander.Option): string => {
@@ -123,7 +133,7 @@ class HelpService extends commander.Help {
          *
          * @const {number} left
          */
-        const left: number = term.length + indent * (option.short ? 2 : 3)
+        const left: number = term.length + indent * ifelse(option.short, 2, 3)
 
         /**
          * String representation of {@linkcode option}.
@@ -132,7 +142,7 @@ class HelpService extends commander.Help {
          */
         const str: string =
           indentation +
-          ' '.repeat(indent * (option.short ? 0 : 2)) +
+          ' '.repeat(indent * ifelse(option.short, 0, 2)) +
           term +
           wrap(
             this.wrap(
@@ -142,9 +152,9 @@ class HelpService extends commander.Help {
             ),
             {
               cut: true,
-              indent: indentation.trim(),
-              newline: template('\n{{0}}', {
-                0: ' '.repeat(left - indent * (option.short ? 1 : 0))
+              indent: trim(indentation),
+              newline: template('\n{0}', {
+                0: ' '.repeat(left - indent * ifelse(option.short, 1, 0))
               }),
               width: linewidth - left
             }
@@ -180,9 +190,9 @@ class HelpService extends commander.Help {
     /**
      * Option in {@linkcode options} with the name {@linkcode name}, if any.
      *
-     * @const {commander.Option | undefined} option
+     * @const {Optional<commander.Option>} option
      */
-    const option: commander.Option | undefined = options.find(option => {
+    const option: Optional<commander.Option> = options.find(option => {
       return option.name() === name
     })
 
@@ -191,7 +201,7 @@ class HelpService extends commander.Help {
       throw new commander.CommanderError(
         1,
         'commander.unknownOption',
-        template("error: unknown option '{{name}}'", { name })
+        template("error: unknown option '{name}'", { name })
       )
     }
 
diff --git a/src/cli/providers/utility.service.ts b/src/cli/providers/utility.service.ts
index f823806d..658914ff 100644
--- a/src/cli/providers/utility.service.ts
+++ b/src/cli/providers/utility.service.ts
@@ -3,10 +3,16 @@
  * @module mkbuild/cli/providers/UtilityService
  */
 
-import type { JsonPrimitive } from '@flex-development/tutils'
+import {
+  cast,
+  objectify,
+  select,
+  split,
+  trim,
+  type JsonPrimitive
+} from '@flex-development/tutils'
 import { Injectable } from '@nestjs/common'
 import { CliUtilityService } from 'nest-commander'
-import { objectify } from 'radash'
 
 /**
  * CLI utilities provider.
@@ -32,8 +38,8 @@ class UtilityService extends CliUtilityService {
     delimiter: string = ','
   ): Set<T> {
     return val.includes(delimiter)
-      ? new Set<T>(val.split(delimiter).map(item => item.trim()) as T[])
-      : new Set<T>([val.trim()] as T[])
+      ? new Set<T>(cast(select(split(val, delimiter), null, trim)))
+      : new Set<T>(cast([trim(val)]))
   }
 
   /**
@@ -52,7 +58,7 @@ class UtilityService extends CliUtilityService {
   public parseObject<
     K extends string = string,
     V extends JsonPrimitive = string
-  >(val: string): Record<K, V> {
+  >(val: string): { [H in K]: V } {
     /**
      * Regular expression matching a key/value pair list.
      *
@@ -62,16 +68,18 @@ class UtilityService extends CliUtilityService {
       /(?:^|(?:(?<!^),))(?<pair>(?<key>[^,].+?):(?<value>(?:.+?(?=,(?=.+?:)))|(?:.+?(?=,?$))))/gs
 
     // convert key/pair list into object
-    return objectify<[string, string], K, V>(
-      [...val.matchAll(regex)].map(([, , key, value]) => [key!.trim(), value!]),
-      ([key]: [string, string]): K => this.parseString<K>(key),
-      ([, value]: [string, string]): V => {
-        try {
-          return JSON.parse(value) as V
-        } catch {
-          return value as V
+    return cast(
+      objectify(
+        select([...val.matchAll(regex)], null, ([, , k, v]) => [trim(k!), v!]),
+        ([key]): K => cast(key),
+        ([, value]): V => {
+          try {
+            return cast(JSON.parse(cast(value)))
+          } catch {
+            return cast(value)
+          }
         }
-      }
+      )
     )
   }
 
@@ -87,20 +95,6 @@ class UtilityService extends CliUtilityService {
     const [, pattern = '', flags] = /^\/(.+)\/(.+$)?/.exec(val) ?? []
     return new RegExp(pattern, flags)
   }
-
-  /**
-   * Helper for casting the given string value to a more complex string type.
-   *
-   * @public
-   *
-   * @template T - Complex string type
-   *
-   * @param {string} val - String to evaluate
-   * @return {T} `val` as `T`
-   */
-  public parseString<T extends string = string>(val: string): T {
-    return val as T
-  }
 }
 
 export default UtilityService
diff --git a/src/config/load.ts b/src/config/load.ts
index c124f2e3..3fd480f3 100644
--- a/src/config/load.ts
+++ b/src/config/load.ts
@@ -5,6 +5,7 @@
 
 import type { Config } from '#src/interfaces'
 import pathe from '@flex-development/pathe'
+import { DOT, cast, get } from '@flex-development/tutils'
 import { cosmiconfig } from 'cosmiconfig'
 import es from './loader-es'
 
@@ -18,10 +19,10 @@ import es from './loader-es'
  *
  * @async
  *
- * @param {string} [location='.'] - Directory to search
+ * @param {string} [location=DOT] - Directory to search
  * @return {Config} Build configuration options
  */
-const loadBuildConfig = async (location: string = '.'): Promise<Config> => {
+const loadBuildConfig = async (location: string = DOT): Promise<Config> => {
   /**
    * Module name.
    *
@@ -44,7 +45,7 @@ const loadBuildConfig = async (location: string = '.'): Promise<Config> => {
     stopDir: pathe.resolve(location)
   })
 
-  return ((await search(location))?.config as Config | null) ?? {}
+  return cast(get((await search(location)) ?? undefined, 'config', {}))
 }
 
 export default loadBuildConfig
diff --git a/src/config/loader-es.ts b/src/config/loader-es.ts
index 22bf84b7..17be8736 100644
--- a/src/config/loader-es.ts
+++ b/src/config/loader-es.ts
@@ -7,7 +7,7 @@ import type { Config } from '#src/interfaces'
 import * as mlly from '@flex-development/mlly'
 import * as pathe from '@flex-development/pathe'
 import * as tscu from '@flex-development/tsconfig-utils'
-import type { EmptyString } from '@flex-development/tutils'
+import { cast, get, type EmptyString } from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
 import { pathToFileURL, type URL } from 'node:url'
 
@@ -43,7 +43,7 @@ const esLoader = async (path: string, content: string): Promise<Config> => {
   // convert content to data url if content does not need to be transformed
   if (!/^\.(?:cts|mts|ts)$/.test(ext)) {
     content = mlly.toDataURL(await mlly.resolveModules(content, { parent }))
-    return ((await import(content)) as { default: Config }).default
+    return cast(get(await import(content), 'default'))
   }
 
   /**
@@ -65,14 +65,17 @@ const esLoader = async (path: string, content: string): Promise<Config> => {
   content = await mlly.resolveModules(content, { parent })
 
   // convert content to pure javascript
-  const { code } = await esbuild.transform(content, {
-    format: 'esm',
-    loader: ext.slice(/^\.[cm]/.test(ext) ? 2 : 1),
-    sourcefile: path,
-    tsconfigRaw: { compilerOptions: tscu.loadCompilerOptions(tsconfig) }
-  } as esbuild.TransformOptions)
+  const { code } = await esbuild.transform(
+    content,
+    cast<esbuild.TransformOptions>({
+      format: 'esm',
+      loader: ext.slice(/^\.[cm]/.test(ext) ? 2 : 1),
+      sourcefile: path,
+      tsconfigRaw: { compilerOptions: tscu.loadCompilerOptions(tsconfig) }
+    })
+  )
 
-  return ((await import(mlly.toDataURL(code))) as { default: Config }).default
+  return cast(get(await import(mlly.toDataURL(code)), 'default'))
 }
 
 export default esLoader
diff --git a/src/interfaces/__tests__/config.spec-d.ts b/src/interfaces/__tests__/config.spec-d.ts
index 0e50a011..c2f42c5d 100644
--- a/src/interfaces/__tests__/config.spec-d.ts
+++ b/src/interfaces/__tests__/config.spec-d.ts
@@ -4,6 +4,7 @@
  */
 
 import type { FileSystemAdapter } from '#src/types'
+import type { Omit, Optional } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import type TestSubject from '../config'
 import type Options from '../options'
@@ -17,36 +18,36 @@ describe('unit-d:interfaces/Config', () => {
   it('should match [configfile?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('configfile')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 
   it('should match [entries?: Partial<Omit<Task, "write">>[]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('entries')
-      .toEqualTypeOf<Partial<Omit<Task, 'write'>>[] | undefined>()
+      .toEqualTypeOf<Optional<Partial<Omit<Task, 'write'>>[]>>()
   })
 
   it('should match [fs?: FileSystemAdapter]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('fs')
-      .toEqualTypeOf<FileSystemAdapter | undefined>()
+      .toEqualTypeOf<Optional<FileSystemAdapter>>()
   })
 
   it('should match [serve?: esbuild.ServeOptions | boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('serve')
-      .toEqualTypeOf<esbuild.ServeOptions | boolean | undefined>()
+      .toEqualTypeOf<Optional<esbuild.ServeOptions | boolean>>()
   })
 
   it('should match [watch?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('watch')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 
   it('should match [write?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('write')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 })
diff --git a/src/interfaces/__tests__/flags.spec-d.ts b/src/interfaces/__tests__/flags.spec-d.ts
index 79c55015..21449e6f 100644
--- a/src/interfaces/__tests__/flags.spec-d.ts
+++ b/src/interfaces/__tests__/flags.spec-d.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/interfaces/tests/unit-d/Flags
  */
 
+import type { Omit, Optional } from '@flex-development/tutils'
 import type TestSubject from '../flags'
 import type Options from '../options'
 
@@ -14,18 +15,18 @@ describe('unit-d:interfaces/Flags', () => {
   it('should match [help?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('help')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 
   it('should match [version?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('version')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 
   it('should match [watch?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('watch')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 })
diff --git a/src/interfaces/__tests__/options.spec-d.ts b/src/interfaces/__tests__/options.spec-d.ts
index 6c138c83..c192ba17 100644
--- a/src/interfaces/__tests__/options.spec-d.ts
+++ b/src/interfaces/__tests__/options.spec-d.ts
@@ -9,7 +9,7 @@ import type {
   OutputExtension
 } from '#src/types'
 import type * as pathe from '@flex-development/pathe'
-import type { OneOrMany } from '@flex-development/tutils'
+import type { OneOrMany, Optional } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import type TestSubject from '../options'
 
@@ -21,96 +21,96 @@ describe('unit-d:interfaces/Options', () => {
   it('should match [banner?: { [K in GeneratedFileType]?: string }]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('banner')
-      .toEqualTypeOf<{ [K in GeneratedFileType]?: string } | undefined>()
+      .toEqualTypeOf<Optional<{ [K in GeneratedFileType]?: string }>>()
   })
 
   it('should match [clean?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('clean')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 
   it('should match [conditions?: Set<string> | string[]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('conditions')
-      .toEqualTypeOf<Set<string> | string[] | undefined>()
+      .toEqualTypeOf<Optional<Set<string> | string[]>>()
   })
 
   it('should match [createRequire?: boolean]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('createRequire')
-      .toEqualTypeOf<boolean | undefined>()
+      .toEqualTypeOf<Optional<boolean>>()
   })
 
   it('should match [cwd?: string]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('cwd')
-      .toEqualTypeOf<string | undefined>()
+      .toEqualTypeOf<Optional<string>>()
   })
 
   it('should match [dts?: boolean | "only"]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('dts')
-      .toEqualTypeOf<boolean | 'only' | undefined>()
+      .toEqualTypeOf<Optional<boolean | 'only'>>()
   })
 
   it('should match [ext?: OutputExtension]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('ext')
-      .toEqualTypeOf<OutputExtension | undefined>()
+      .toEqualTypeOf<Optional<OutputExtension>>()
   })
 
   it('should match [footer?: { [K in GeneratedFileType]?: string }]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('footer')
-      .toEqualTypeOf<{ [K in GeneratedFileType]?: string } | undefined>()
+      .toEqualTypeOf<Optional<{ [K in GeneratedFileType]?: string }>>()
   })
 
   it('should match [ignore?: Set<string> | string[]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('ignore')
-      .toEqualTypeOf<Set<string> | string[] | undefined>()
+      .toEqualTypeOf<Optional<Set<string> | string[]>>()
   })
 
   it('should match [loader?: Record<pathe.Ext, esbuild.Loader>]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('loader')
-      .toEqualTypeOf<Record<pathe.Ext, esbuild.Loader> | undefined>()
+      .toEqualTypeOf<Optional<Record<pathe.Ext, esbuild.Loader>>>()
   })
 
   it('should match [mainFields?: Set<string> | string[]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('mainFields')
-      .toEqualTypeOf<Set<string> | string[] | undefined>()
+      .toEqualTypeOf<Optional<Set<string> | string[]>>()
   })
 
   it('should match [name?: string]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('name')
-      .toEqualTypeOf<string | undefined>()
+      .toEqualTypeOf<Optional<string>>()
   })
 
   it('should match [outExtension?: Record<pathe.Ext, pathe.Ext>]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('outExtension')
-      .toEqualTypeOf<Record<pathe.Ext, pathe.Ext> | undefined>()
+      .toEqualTypeOf<Optional<Record<pathe.Ext, pathe.Ext>>>()
   })
 
   it('should match [pattern?: OneOrMany<string> | Set<string>]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('pattern')
-      .toEqualTypeOf<OneOrMany<string> | Set<string> | undefined>()
+      .toEqualTypeOf<Optional<OneOrMany<string> | Set<string>>>()
   })
 
   it('should match [resolveExtensions?: Set<string> | string[]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('resolveExtensions')
-      .toEqualTypeOf<Set<string> | string[] | undefined>()
+      .toEqualTypeOf<Optional<Set<string> | string[]>>()
   })
 
   it('should match [source?: string]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('source')
-      .toEqualTypeOf<string | undefined>()
+      .toEqualTypeOf<Optional<string>>()
   })
 })
diff --git a/src/interfaces/config.ts b/src/interfaces/config.ts
index fc15ae83..69349b82 100644
--- a/src/interfaces/config.ts
+++ b/src/interfaces/config.ts
@@ -4,6 +4,7 @@
  */
 
 import type { FileSystemAdapter } from '#src/types'
+import type { Omit } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import type Options from './options'
 import type Task from './task'
diff --git a/src/interfaces/flags.ts b/src/interfaces/flags.ts
index 0d4ee639..548c08a6 100644
--- a/src/interfaces/flags.ts
+++ b/src/interfaces/flags.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/interfaces/Flags
  */
 
+import type { Omit } from '@flex-development/tutils'
 import type Options from './options'
 
 /**
diff --git a/src/internal/__snapshots__/defu-concat.snap b/src/internal/__snapshots__/defu-concat.snap
deleted file mode 100644
index 8729e251..00000000
--- a/src/internal/__snapshots__/defu-concat.snap
+++ /dev/null
@@ -1,39 +0,0 @@
-// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
-
-exports[`unit:internal/defuConcat > should return object with defaults assigned 1`] = `
-{
-  "bundle": false,
-  "clean": true,
-  "cwd": ".",
-  "entries": [],
-  "ext": ".mjs",
-  "format": "esm",
-  "fs": {
-    "lstat": [Function lstat],
-    "mkdir": [Function mkdir],
-    "readdir": [Function readdir],
-    "readdirSync": [Function readdirSync],
-    "rm": [Function rm],
-    "stat": [Function stat],
-    "unlink": [Function unlink],
-    "writeFile": [Function writeFile],
-  },
-  "ignore": [
-    "src/cli.ts",
-    "**/.DS_*",
-    "**/__mocks__",
-    "**/__snapshots__",
-    "**/__tests__",
-  ],
-  "outdir": "dist",
-  "pattern": "*.ts",
-  "source": ".",
-  "sourcemap": true,
-  "sourcesContent": false,
-  "target": [
-    "node16.20.0",
-    "es2022",
-  ],
-  "tsconfig": "tsconfig.build.json",
-}
-`;
diff --git a/src/internal/__snapshots__/defu.snap b/src/internal/__snapshots__/defu.snap
deleted file mode 100644
index 5bcbab2d..00000000
--- a/src/internal/__snapshots__/defu.snap
+++ /dev/null
@@ -1,38 +0,0 @@
-// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
-
-exports[`unit:internal/defu > should return object with defaults assigned 1`] = `
-{
-  "cwd": ".",
-  "entries": [
-    {
-      "ignore": [
-        "cli.ts",
-      ],
-    },
-    {
-      "bundle": true,
-      "minify": true,
-      "platform": "node",
-      "source": "src/cli.ts",
-    },
-  ],
-  "fs": {
-    "lstat": [Function lstat],
-    "mkdir": [Function mkdir],
-    "readdir": [Function readdir],
-    "readdirSync": [Function readdirSync],
-    "rm": [Function rm],
-    "stat": [Function stat],
-    "unlink": [Function unlink],
-    "writeFile": [Function writeFile],
-  },
-  "outdir": "dist",
-  "source": ".",
-  "sourcemap": true,
-  "sourcesContent": false,
-  "target": "node16.20.0",
-  "tsconfig": "tsconfig.build.json",
-  "watch": false,
-  "write": false,
-}
-`;
diff --git a/src/internal/__tests__/create-context.integration.spec.ts b/src/internal/__tests__/create-context.integration.spec.ts
index 87b36129..687bfa8e 100644
--- a/src/internal/__tests__/create-context.integration.spec.ts
+++ b/src/internal/__tests__/create-context.integration.spec.ts
@@ -10,6 +10,7 @@ import getPackageJson from '#tests/utils/get-package-json'
 import * as mlly from '@flex-development/mlly'
 import * as pathe from '@flex-development/pathe'
 import type { PackageJson } from '@flex-development/pkg-types'
+import { DOT } from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
 import testSubject from '../create-context'
 
@@ -102,7 +103,7 @@ describe('integration:internal/createContext', () => {
           mainFields,
           metafile: true,
           outExtension: { '.js': '.cjs' },
-          outbase: '.',
+          outbase: DOT,
           outdir,
           platform,
           plugins: [
@@ -119,7 +120,7 @@ describe('integration:internal/createContext', () => {
       it('should create context for cjs transpilation', async () => {
         // Arrange
         const pattern: string = 'buddy.js'
-        const source: string = '.'
+        const source: string = DOT
 
         // Act
         await testSubject({ ...task, pattern, source }, pkg)
@@ -336,7 +337,7 @@ describe('integration:internal/createContext', () => {
           mainFields,
           metafile: true,
           outExtension: { '.js': '.js' },
-          outbase: '.',
+          outbase: DOT,
           outdir,
           platform,
           plugins: [
@@ -353,7 +354,7 @@ describe('integration:internal/createContext', () => {
       it('should create context for iife transpilation', async () => {
         // Arrange
         const pattern: string[] = ['find-uniq.cts']
-        const source: string = '.'
+        const source: string = DOT
 
         // Act
         await testSubject({ ...task, pattern, source })
diff --git a/src/internal/__tests__/create-context.spec.ts b/src/internal/__tests__/create-context.spec.ts
index f1659fc7..8774c6fe 100644
--- a/src/internal/__tests__/create-context.spec.ts
+++ b/src/internal/__tests__/create-context.spec.ts
@@ -5,7 +5,7 @@
 
 import pkg from '#pkg' assert { type: 'json' }
 import type { Task } from '#src'
-import type { PackageJson } from '@flex-development/pkg-types'
+import { cast } from '@flex-development/tutils'
 import testSubject from '../create-context'
 
 vi.mock('#src/utils/fs')
@@ -22,7 +22,7 @@ describe('unit:internal/createContext', () => {
     }
 
     // Act
-    const result = await testSubject(task, pkg as PackageJson)
+    const result = await testSubject(task, cast(pkg))
 
     // Expect
     expect(result).to.have.property('cancel').be.instanceof(Function)
diff --git a/src/internal/__tests__/defu-concat.spec.ts b/src/internal/__tests__/defu-concat.spec.ts
deleted file mode 100644
index 387aaabf..00000000
--- a/src/internal/__tests__/defu-concat.spec.ts
+++ /dev/null
@@ -1,45 +0,0 @@
-/**
- * @file Unit Tests - defuConcat
- * @module mkbuild/internal/tests/unit/defuConcat
- */
-
-import type { Config } from '#src/interfaces'
-import fs from '#src/utils/fs'
-import testSubject from '../defu-concat'
-
-describe('unit:internal/defuConcat', () => {
-  it('should return object with defaults assigned', () => {
-    // Arrange
-    const object: Config = {
-      ignore: ['src/cli.ts'],
-      pattern: '*.ts',
-      source: '.',
-      sourcemap: true,
-      sourcesContent: false,
-      target: ['node16.20.0'],
-      tsconfig: 'tsconfig.build.json'
-    }
-    const defaults: Config = {
-      bundle: false,
-      clean: true,
-      cwd: '.',
-      entries: [],
-      ext: '.mjs',
-      format: 'esm',
-      fs,
-      ignore: new Set<string>([
-        '**/.DS_*',
-        '**/__mocks__',
-        '**/__snapshots__',
-        '**/__tests__'
-      ]),
-      outdir: 'dist',
-      pattern: '**',
-      source: 'src',
-      target: ['es2022']
-    }
-
-    // Act + Expect
-    expect(testSubject(object, defaults)).toMatchSnapshot()
-  })
-})
diff --git a/src/internal/__tests__/defu.spec.ts b/src/internal/__tests__/defu.spec.ts
deleted file mode 100644
index ab1e1aed..00000000
--- a/src/internal/__tests__/defu.spec.ts
+++ /dev/null
@@ -1,37 +0,0 @@
-/**
- * @file Unit Tests - defu
- * @module mkbuild/internal/tests/unit/defu
- */
-
-import type { Config } from '#src/interfaces'
-import fs from '#src/utils/fs'
-import testSubject from '../defu'
-
-describe('unit:internal/defu', () => {
-  it('should return object with defaults assigned', () => {
-    // Arrange
-    const object: Config = {
-      entries: [
-        { ignore: ['cli.ts'] },
-        { bundle: true, minify: true, platform: 'node', source: 'src/cli.ts' }
-      ],
-      source: '.',
-      sourcemap: true,
-      sourcesContent: false,
-      target: 'node16.20.0',
-      tsconfig: 'tsconfig.build.json'
-    }
-    const defaults: Config = {
-      cwd: '.',
-      entries: [],
-      fs,
-      outdir: 'dist',
-      sourcemap: false,
-      watch: false,
-      write: false
-    }
-
-    // Act + Expect
-    expect(testSubject(object, defaults)).toMatchSnapshot()
-  })
-})
diff --git a/src/internal/create-context.ts b/src/internal/create-context.ts
index cf8b8621..ae8081db 100644
--- a/src/internal/create-context.ts
+++ b/src/internal/create-context.ts
@@ -13,11 +13,20 @@ import { EXT_DTS_REGEX } from '@flex-development/ext-regex'
 import * as mlly from '@flex-development/mlly'
 import * as pathe from '@flex-development/pathe'
 import type { PackageJson } from '@flex-development/pkg-types'
-import { isString, isUndefined } from '@flex-development/tutils'
+import {
+  DOT,
+  cast,
+  get,
+  isString,
+  isUndefined,
+  keys,
+  omit,
+  regexp,
+  shake,
+  sift
+} from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
-import regexp from 'escape-string-regexp'
 import fg from 'fast-glob'
-import { get, omit, shake, sift } from 'radash'
 import gitignore from './gitignore'
 
 /**
@@ -50,7 +59,7 @@ async function createContext(
     clean = true,
     color = true,
     conditions = ['import', 'default'],
-    cwd = '.',
+    cwd = DOT,
     drop,
     dts = await (async () => {
       try {
@@ -62,7 +71,7 @@ async function createContext(
         return false
       }
     })(),
-    external = bundle ? Object.keys(get(pkg, 'peerDependencies', {})!) : [],
+    external = bundle ? keys(get(pkg, 'peerDependencies', {})) : [],
     footer = {},
     format = 'esm',
     ignore = IGNORE_PATTERNS,
@@ -74,7 +83,7 @@ async function createContext(
     name = '[name]',
     outExtension = {},
     outdir = 'dist',
-    pattern = '**',
+    pattern = mlly.PATTERN_CHARACTER.repeat(2),
     pure,
     platform = 'neutral',
     plugins = [],
@@ -157,13 +166,13 @@ async function createContext(
       color,
       conditions: [...new Set(conditions)],
       drop: [...new Set(drop)],
-      entryNames: `[dir]/${name}`,
+      entryNames: `[dir]${pathe.sep}${name}`,
       entryPoints: files
         .map((file: string): SourceFile => {
           return {
-            ext: pathe.extname(file) as pathe.Ext,
+            ext: cast(pathe.extname(file)),
             file:
-              bundle && outbase !== '.'
+              bundle && outbase !== DOT
                 ? // outbase support for bundles (esbuild only uses outbase for
                   // multiple entries); https://esbuild.github.io/api/#outbase
                   file
@@ -177,12 +186,7 @@ async function createContext(
           return pathe.join(bundle ? outbase : source, sourcefile.file)
         }),
       external: bundle
-        ? [
-            ...new Set([
-              ...Object.keys(get(pkg, 'peerDependencies', {})!),
-              ...external
-            ])
-          ]
+        ? [...new Set([...keys(get(pkg, 'peerDependencies', {})), ...external])]
         : [],
       footer,
       format,
@@ -191,7 +195,7 @@ async function createContext(
       logLimit,
       logOverride,
       mainFields: [...new Set(mainFields)],
-      metafile: true,
+      metafile: true as const,
       outExtension: { ...outExtension, '.js': pathe.formatExt(ext) },
       outbase,
       outdir,
@@ -207,18 +211,16 @@ async function createContext(
         ...plugins,
         mkp.filter(dts === 'only' ? EXT_DTS_REGEX : undefined),
         write && mkp.write(fs)
-      ]) as esbuild.Plugin[],
+      ]),
       pure: [...new Set(pure)],
-      resolveExtensions: [...new Set(resolveExtensions)].map(ext => {
-        return pathe.formatExt(ext)
-      }),
+      resolveExtensions: [...new Set(resolveExtensions)].map(pathe.formatExt),
       target: isUndefined(target)
         ? undefined
         : isString(target)
         ? target
         : [...new Set(target)],
       tsconfig,
-      write: false
+      write: false as const
     })
   )
 }
diff --git a/src/internal/defu-concat.ts b/src/internal/defu-concat.ts
deleted file mode 100644
index 21e2e557..00000000
--- a/src/internal/defu-concat.ts
+++ /dev/null
@@ -1,54 +0,0 @@
-/**
- * @file Internal - defuConcat
- * @module mkbuild/internal/defuConcat
- */
-
-import {
-  isUndefined,
-  type ExactOptionalPropertyTypes,
-  type ObjectPlain
-} from '@flex-development/tutils'
-import { mergeAndCompare as merge, type Merge } from 'merge-anything'
-
-/**
- * Assigns default properties to the given `object`.
- *
- * Leftmost arguments have more priority when assigning defaults.
- *
- * Supports {@linkcode Set} and array concatenation.
- *
- * @internal
- *
- * @template T - Destination object type
- * @template D - Source object type(s)
- *
- * @param {T} object - Destination object
- * @param {D} defaults - Object(s) used to assign default properties
- * @return {ExactOptionalPropertyTypes<Merge<T, D> & T>} `object` with defaults
- */
-function defuConcat<T extends ObjectPlain, D extends ObjectPlain[]>(
-  object: T,
-  ...defaults: D
-): ExactOptionalPropertyTypes<Merge<T, D> & T> {
-  return merge<T, D>(
-    /**
-     * Determines how to assign a property.
-     *
-     * @param {unknown} v1 - Original value from {@linkcode object}
-     * @param {unknown} v2 - Incoming value from object in {@linkcode defaults}
-     * @return {unknown} Property value for {@linkcode object}
-     */
-    (v1: unknown, v2: unknown): unknown => {
-      return (Array.isArray(v1) || v1 instanceof Set) &&
-        (Array.isArray(v2) || v2 instanceof Set)
-        ? [...new Set([...v1, ...v2])]
-        : isUndefined(v1)
-        ? v2
-        : v1
-    },
-    object,
-    ...defaults
-  )
-}
-
-export default defuConcat
diff --git a/src/internal/defu.ts b/src/internal/defu.ts
deleted file mode 100644
index e561de17..00000000
--- a/src/internal/defu.ts
+++ /dev/null
@@ -1,45 +0,0 @@
-/**
- * @file Internal - defu
- * @module mkbuild/internal/defu
- */
-
-import {
-  isUndefined,
-  type ExactOptionalPropertyTypes,
-  type ObjectPlain
-} from '@flex-development/tutils'
-import { mergeAndCompare as merge, type Merge } from 'merge-anything'
-
-/**
- * Assigns default properties to the given `object`.
- *
- * Leftmost arguments have more priority when assigning defaults.
- *
- * @internal
- *
- * @template T - Destination object type
- * @template D - Source object type(s)
- *
- * @param {T} object - Destination object
- * @param {D} defaults - Object(s) used to assign default properties
- * @return {ExactOptionalPropertyTypes<Merge<T, D> & T>} `object` with defaults
- */
-function defu<T extends ObjectPlain, D extends ObjectPlain[]>(
-  object: T,
-  ...defaults: D
-): ExactOptionalPropertyTypes<Merge<T, D> & T> {
-  return merge<T, D>(
-    /**
-     * Determines how to assign a property.
-     *
-     * @param {unknown} v1 - Original value from {@linkcode object}
-     * @param {unknown} v2 - Incoming value from object in {@linkcode defaults}
-     * @return {unknown} Property value for {@linkcode object}
-     */
-    (v1: unknown, v2: unknown): unknown => (isUndefined(v1) ? v2 : v1),
-    object,
-    ...defaults
-  )
-}
-
-export default defu
diff --git a/src/internal/gitignore.ts b/src/internal/gitignore.ts
index df747505..8346ca2b 100644
--- a/src/internal/gitignore.ts
+++ b/src/internal/gitignore.ts
@@ -5,6 +5,7 @@
 
 import * as mlly from '@flex-development/mlly'
 import * as pathe from '@flex-development/pathe'
+import { cast, isEmptyString, trim } from '@flex-development/tutils'
 
 /**
  * Returns a set of ignore patterns found in a `.gitignore` file.
@@ -37,13 +38,13 @@ const gitignore = async (absWorkingDir: string): Promise<Set<string>> => {
      *
      * @const {string} gitignore
      */
-    const content: string = (await mlly.getSource(path)) as string
+    const content: string = cast(await mlly.getSource(path))
 
     // add ignore patterns from .gitignore
     for (const line of content.split(/\r?\n/)) {
-      if (!line.trim()) continue
+      if (isEmptyString(trim(line))) continue
       if (line.startsWith('#') || line.startsWith('!')) continue
-      ignore.add(line.trim())
+      ignore.add(trim(line))
     }
   } catch {
     // do nothing if .gitignore file was not found
diff --git a/src/internal/index.ts b/src/internal/index.ts
index 7ac609d8..02fd10de 100644
--- a/src/internal/index.ts
+++ b/src/internal/index.ts
@@ -4,6 +4,4 @@
  */
 
 export { default as createContext } from './create-context'
-export { default as defu } from './defu'
-export { default as defuConcat } from './defu-concat'
 export { default as gitignore } from './gitignore'
diff --git a/src/make.ts b/src/make.ts
index 240a1bae..04965cef 100644
--- a/src/make.ts
+++ b/src/make.ts
@@ -7,17 +7,23 @@ import { ERR_MODULE_NOT_FOUND, type NodeError } from '@flex-development/errnode'
 import * as mlly from '@flex-development/mlly'
 import pathe from '@flex-development/pathe'
 import type { PackageJson } from '@flex-development/pkg-types'
-import type { Nullable } from '@flex-development/tutils'
+import {
+  DOT,
+  cast,
+  defaults,
+  get,
+  regexp,
+  type Nullable
+} from '@flex-development/tutils'
 import * as color from 'colorette'
 import consola from 'consola'
 import type * as esbuild from 'esbuild'
-import regexp from 'escape-string-regexp'
 import { asyncExitHook as exitHook } from 'exit-hook'
 import { fileURLToPath } from 'node:url'
 import pb from 'pretty-bytes'
 import loadBuildConfig from './config/load'
 import type { Config, Context, Result, Task } from './interfaces'
-import { createContext, defu, defuConcat } from './internal'
+import * as internal from './internal'
 import type { OutputMetadata } from './types'
 import { analyzeOutputs, fs as fsa } from './utils'
 
@@ -46,19 +52,19 @@ import { analyzeOutputs, fs as fsa } from './utils'
  */
 async function make({
   configfile = true,
-  cwd = '.',
+  cwd = DOT,
   ...config
 }: Config = {}): Promise<Result[]> {
-  const { entries, fs, serve, watch, write, ...options } = defu(
+  const { entries, fs, serve, watch, write, ...options } = defaults(
     config,
     configfile ? await loadBuildConfig(cwd) : {},
     {
       cwd,
-      entries: [{}] as Partial<Task>[],
+      entries: cast<Partial<Task>[]>([{}]),
       fs: fsa,
-      logLevel: 'info',
+      logLevel: cast<esbuild.LogLevel>('info'),
       outdir: 'dist',
-      serve: false as esbuild.ServeOptions | boolean,
+      serve: cast<esbuild.ServeOptions | boolean>(false),
       watch: false,
       write: false
     }
@@ -115,7 +121,7 @@ async function make({
       ...rest
     } = entry
 
-    return defuConcat(
+    return defaults(
       {
         bundle,
         cwd,
@@ -147,7 +153,7 @@ async function make({
   if (!watch && serve === false) {
     for (const task of tasks) {
       // create build context
-      context = await createContext(task, pkg, fs)
+      context = await internal.createContext(task, pkg, fs)
 
       /**
        * esbuild build result.
@@ -181,7 +187,7 @@ async function make({
            *
            * @const {OutputMetadata} metadata
            */
-          const metadata: OutputMetadata = result.metafile.outputs[outfile]!
+          const metadata: OutputMetadata = get(result.metafile.outputs, outfile)
 
           return {
             bytes: metadata.bytes,
@@ -227,7 +233,7 @@ async function make({
 
   // enable serve or watch mode
   if (serve !== false || watch) {
-    const [task] = tasks as [Task]
+    const [task] = cast<[Task]>(tasks)
 
     // force clean output directory
     task.clean = true
@@ -236,14 +242,14 @@ async function make({
     task.write = true
 
     // create build context
-    context = await createContext(task, pkg, fs)
+    context = await internal.createContext(task, pkg, fs)
 
     // watch files
     watch && (await context.watch())
 
     // serve files
     if (serve !== false) {
-      await context.serve({ ...(serve as esbuild.ServeOptions) })
+      await context.serve({ ...cast<esbuild.ServeOptions>(serve) })
     }
 
     // dispose build context on process exit
diff --git a/src/plugins/clean/__tests__/options.spec-d.ts b/src/plugins/clean/__tests__/options.spec-d.ts
index 480e5c40..b76e27b9 100644
--- a/src/plugins/clean/__tests__/options.spec-d.ts
+++ b/src/plugins/clean/__tests__/options.spec-d.ts
@@ -4,24 +4,25 @@
  */
 
 import type { FileSystemAdapter } from '#src/types'
+import type { Optional } from '@flex-development/tutils'
 import type TestSubject from '../options'
 
 describe('unit-d:plugins/clean/CleanPluginOptions', () => {
   it('should match [mkdir?: FileSystemAdapter["mkdir"]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('mkdir')
-      .toEqualTypeOf<FileSystemAdapter['mkdir'] | undefined>()
+      .toEqualTypeOf<Optional<FileSystemAdapter['mkdir']>>()
   })
 
   it('should match [rm?: FileSystemAdapter["rm"]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('rm')
-      .toEqualTypeOf<FileSystemAdapter['rm'] | undefined>()
+      .toEqualTypeOf<Optional<FileSystemAdapter['rm']>>()
   })
 
   it('should match [unlink?: FileSystemAdapter["unlink"]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('unlink')
-      .toEqualTypeOf<FileSystemAdapter['unlink'] | undefined>()
+      .toEqualTypeOf<Optional<FileSystemAdapter['unlink']>>()
   })
 })
diff --git a/src/plugins/create-require/__tests__/plugin.spec.ts b/src/plugins/create-require/__tests__/plugin.spec.ts
index 074edaf3..d8582e6b 100644
--- a/src/plugins/create-require/__tests__/plugin.spec.ts
+++ b/src/plugins/create-require/__tests__/plugin.spec.ts
@@ -4,6 +4,7 @@
  */
 
 import createPluginAPI from '#tests/utils/create-plugin-api'
+import { cast } from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -46,7 +47,7 @@ describe('unit:plugins/create-require', () => {
 
   it('should throw if esbuild is writing output files', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
@@ -56,31 +57,27 @@ describe('unit:plugins/create-require', () => {
         })
       )
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!).to.have.property('message').equal('write must be disabled')
+    expect(error).to.have.property('message', 'write must be disabled')
   })
 
   it('should throw if metafile is disabled', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(
-        createPluginAPI({
-          initialOptions: { bundle: true, format: 'esm' }
-        })
+        createPluginAPI({ initialOptions: { bundle: true, format: 'esm' } })
       )
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!).to.have.property('message').equal('metafile required')
+    expect(error).to.have.property('message', 'metafile required')
   })
 })
diff --git a/src/plugins/create-require/plugin.ts b/src/plugins/create-require/plugin.ts
index 986b92ba..c5c76316 100644
--- a/src/plugins/create-require/plugin.ts
+++ b/src/plugins/create-require/plugin.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/plugins/create-require/plugin
  */
 
+import { constant, define, join, regexp } from '@flex-development/tutils'
 import {
   transform,
   type BuildOptions,
@@ -11,9 +12,15 @@ import {
   type Plugin,
   type PluginBuild
 } from 'esbuild'
-import regexp from 'escape-string-regexp'
 import util from 'node:util'
 
+/**
+ * Plugin-specific build options.
+ *
+ * @internal
+ */
+type SpecificOptions = { metafile: true; write: false }
+
 /**
  * Returns a plugin that defines the `require` function in ESM bundles.
  *
@@ -91,10 +98,13 @@ const plugin = (): Plugin => {
      *
      * @const {string} snippet
      */
-    const snippet: string = [
-      "import { createRequire as __createRequire } from 'node:module'",
-      'const require = __createRequire(import.meta.url)'
-    ].join('\n')
+    const snippet: string = join(
+      [
+        "import { createRequire as __createRequire } from 'node:module'",
+        'const require = __createRequire(import.meta.url)'
+      ],
+      '\n'
+    )
 
     // transform snippet to re-add banner and minify
     let { code } = await transform(snippet, {
@@ -108,7 +118,7 @@ const plugin = (): Plugin => {
     // remove new line from end of code snippet if output should be minified
     if (minify || minifyWhitespace) code = code.replace(/\n$/, '')
 
-    return void onEnd((result: BuildResult): void => {
+    return void onEnd((result: BuildResult<SpecificOptions>): void => {
       /**
        * Regex used to deduce if an output file includes the `__require` shim.
        *
@@ -117,7 +127,7 @@ const plugin = (): Plugin => {
       const filter: RegExp = /Dynamic require of ".*" is not supported/m
 
       // insert require function definitions
-      result.outputFiles = result.outputFiles!.map((output: OutputFile) => {
+      result.outputFiles = result.outputFiles.map((output: OutputFile) => {
         // do nothing if output file does not contain shim
         if (!filter.test(output.text)) return output
 
@@ -129,20 +139,16 @@ const plugin = (): Plugin => {
          *
          * @var {string} text
          */
-        let text: string = output.text
-
-        // remove hashbang and re-add hashbang to code snippet
-        text = text.replace(hashbang, '')
-        code = `${hashbang}${code}`
+        let text: string = output.text.replace(hashbang, '')
 
         // remove banner
         if (banner) text = text.replace(new RegExp(regexp(banner) + '\n?'), '')
 
-        // insert require function definition
-        text = `${code}${text}`
+        // redefine output text to insert require function definition
+        define(output, 'text', { get: constant(hashbang + code + text) })
 
         // reset output file contents
-        output.contents = new util.TextEncoder().encode(text)
+        output.contents = new util.TextEncoder().encode(output.text)
 
         /**
          * Relative path to output file.
@@ -163,9 +169,9 @@ const plugin = (): Plugin => {
         const bytes: number = Buffer.byteLength(output.contents)
 
         // reset output file size
-        result.metafile!.outputs[outfile]!.bytes = bytes
+        result.metafile.outputs[outfile]!.bytes = bytes
 
-        return { ...output, text }
+        return output
       })
     })
   }
diff --git a/src/plugins/decorators/plugin.ts b/src/plugins/decorators/plugin.ts
index 654206ed..260cc101 100644
--- a/src/plugins/decorators/plugin.ts
+++ b/src/plugins/decorators/plugin.ts
@@ -8,7 +8,7 @@ import { EXT_DTS_REGEX, EXT_TS_REGEX } from '@flex-development/ext-regex'
 import * as mlly from '@flex-development/mlly'
 import pathe from '@flex-development/pathe'
 import * as tscu from '@flex-development/tsconfig-utils'
-import type { Nullable } from '@flex-development/tutils'
+import { DOT, cast, type Nullable } from '@flex-development/tutils'
 import type {
   BuildOptions,
   OnLoadArgs,
@@ -53,7 +53,7 @@ const plugin = (options?: tscu.LoadTsconfigOptions): Plugin => {
     initialOptions,
     onLoad
   }: PluginBuild): Promise<void> => {
-    const { absWorkingDir = '.', tsconfig = 'tsconfig.json' } = initialOptions
+    const { absWorkingDir = DOT, tsconfig = 'tsconfig.json' } = initialOptions
 
     /**
      * User compiler options.
@@ -89,16 +89,16 @@ const plugin = (options?: tscu.LoadTsconfigOptions): Plugin => {
      */
     const opts: OnLoadOptions = { filter: /.*/ }
 
-    // transpile typescript modules containing decorators
+    // transpile modules containing decorators
     onLoad(opts, async (args: OnLoadArgs): Promise<Nullable<OnLoadResult>> => {
       /**
        * Callback result.
        *
-       * @var {Nullable<OnLoadResult>} result
+       * @var {?OnLoadResult} result
        */
       let result: Nullable<OnLoadResult> = null
 
-      // transpile typescript modules, but skip typescript declaration modules
+      // transpile modules, but skip typescript declaration modules
       if (EXT_TS_REGEX.test(args.path) && !EXT_DTS_REGEX.test(args.path)) {
         /**
          * URL of module to load.
@@ -112,9 +112,9 @@ const plugin = (options?: tscu.LoadTsconfigOptions): Plugin => {
          *
          * @const {string} source
          */
-        const source: string = (await mlly.getSource(url)) as string
+        const source: string = cast(await mlly.getSource(url))
 
-        // do nothing if module does not use decorators
+        // do nothing if module does contain decorators
         if (!DECORATOR_REGEX.test(source)) return null
 
         // transpile module to emit decorator metadata
diff --git a/src/plugins/dts/__tests__/plugin.spec.ts b/src/plugins/dts/__tests__/plugin.spec.ts
index 58b291bf..e56b211b 100644
--- a/src/plugins/dts/__tests__/plugin.spec.ts
+++ b/src/plugins/dts/__tests__/plugin.spec.ts
@@ -4,6 +4,7 @@
  */
 
 import createPluginAPI from '#tests/utils/create-plugin-api'
+import { cast } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -30,33 +31,31 @@ describe('unit:plugins/dts', () => {
 
   it('should throw if esbuild is writing output files', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI({ initialOptions: { write: true } }))
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!).to.have.property('message').equal('write must be disabled')
+    expect(error).to.have.property('message', 'write must be disabled')
   })
 
   it('should throw if metafile is disabled', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI())
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!.message).to.equal('metafile required')
+    expect(error).to.have.property('message', 'metafile required')
   })
 })
diff --git a/src/plugins/dts/plugin.ts b/src/plugins/dts/plugin.ts
index 26809b0c..b17629da 100644
--- a/src/plugins/dts/plugin.ts
+++ b/src/plugins/dts/plugin.ts
@@ -3,8 +3,6 @@
  * @module mkbuild/plugins/dts
  */
 
-import defu from '#src/internal/defu'
-import type { OutputMetadata } from '#src/types'
 import {
   EXT_DTS_REGEX,
   EXT_JS_REGEX,
@@ -12,6 +10,17 @@ import {
 } from '@flex-development/ext-regex'
 import pathe from '@flex-development/pathe'
 import * as tscu from '@flex-development/tsconfig-utils'
+import {
+  DOT,
+  cast,
+  constant,
+  defaults,
+  define,
+  get,
+  includes,
+  keys,
+  shake
+} from '@flex-development/tutils'
 import type {
   BuildOptions,
   BuildResult,
@@ -27,6 +36,13 @@ import type {
   WriteFileCallback
 } from 'typescript'
 
+/**
+ * Plugin-specific build options.
+ *
+ * @internal
+ */
+type SpecificOptions = { metafile: true; write: false }
+
 /**
  * Returns a TypeScript declaration plugin.
  *
@@ -64,7 +80,7 @@ const plugin = (): Plugin => {
       metafile,
       outExtension: { '.js': ext = '.js' } = {},
       outbase = '',
-      outdir = '.',
+      outdir = DOT,
       preserveSymlinks = false,
       tsconfig = 'tsconfig.json',
       write
@@ -110,7 +126,7 @@ const plugin = (): Plugin => {
       return void sourcefiles.push(pathe.resolve(args.resolveDir, args.path))
     })
 
-    return void onEnd((result: BuildResult): void => {
+    return void onEnd((result: BuildResult<SpecificOptions>): void => {
       /**
        * TypeScript compiler options.
        *
@@ -143,37 +159,40 @@ const plugin = (): Plugin => {
       delete compilerOptions.noEmitOnError
 
       // merge compiler options with defaults
-      compilerOptions = defu(compilerOptions, {
-        allowJs: true,
-        allowUmdGlobalAccess: format === 'iife',
-        allowUnreachableCode: false,
-        baseUrl: absWorkingDir,
-        checkJs: false,
-        declaration: true,
-        declarationMap: false,
-        emitDeclarationOnly: true,
-        esModuleInterop: true,
-        forceConsistentCasingInFileNames: true,
-        isolatedModules: true,
-        module: ts.ModuleKind.ESNext,
-        moduleResolution: tscu.normalizeModuleResolution(
-          tscu.ModuleResolutionKind.NodeJs
-        ),
-        noEmit: false,
-        noEmitOnError: false,
-        noErrorTruncation: true,
-        noImplicitAny: true,
-        noImplicitOverride: true,
-        noImplicitReturns: true,
-        outDir: pathe.resolve(absWorkingDir, outdir),
-        preserveConstEnums: true,
-        preserveSymlinks,
-        pretty: color,
-        resolveJsonModule: true,
-        rootDir: pathe.resolve(absWorkingDir, outbase),
-        skipLibCheck: true,
-        target: ts.ScriptTarget.ESNext
-      })
+      compilerOptions = defaults(
+        compilerOptions,
+        shake({
+          allowJs: true,
+          allowUmdGlobalAccess: format === 'iife',
+          allowUnreachableCode: false,
+          baseUrl: absWorkingDir,
+          checkJs: false,
+          declaration: true,
+          declarationMap: false,
+          emitDeclarationOnly: true,
+          esModuleInterop: true,
+          forceConsistentCasingInFileNames: true,
+          isolatedModules: true,
+          module: ts.ModuleKind.ESNext,
+          moduleResolution: tscu.normalizeModuleResolution(
+            tscu.ModuleResolutionKind.NodeJs
+          ),
+          noEmit: false,
+          noEmitOnError: false,
+          noErrorTruncation: true,
+          noImplicitAny: true,
+          noImplicitOverride: true,
+          noImplicitReturns: true,
+          outDir: pathe.resolve(absWorkingDir, outdir),
+          preserveConstEnums: true,
+          preserveSymlinks,
+          pretty: color,
+          resolveJsonModule: true,
+          rootDir: pathe.resolve(absWorkingDir, outbase),
+          skipLibCheck: true,
+          target: ts.ScriptTarget.ESNext
+        })
+      )
 
       /**
        * TypeScript compiler host.
@@ -185,9 +204,9 @@ const plugin = (): Plugin => {
       /**
        * Virtual file system for declaration files.
        *
-       * @const {Map<string, string>} vfs
+       * @const {Record<string, string>} vfs
        */
-      const vfs: Map<string, string> = new Map()
+      const vfs: Record<string, string> = {}
 
       // first letter before "js" or "ts" in output file extension
       const [, cm = ''] = /\.(c|m)?[jt]sx?$/.exec(ext)!
@@ -203,10 +222,8 @@ const plugin = (): Plugin => {
         filename: string,
         contents: string
       ): void => {
-        return void vfs.set(
-          filename.replace(EXT_DTS_REGEX, `.d.${cm}ts`),
-          contents
-        )
+        filename = filename.replace(EXT_DTS_REGEX, `.d.${cm}ts`)
+        return void (vfs[filename] = contents)
       }
 
       // override write file function
@@ -220,56 +237,33 @@ const plugin = (): Plugin => {
       ).emit()
 
       // remap output files to insert declaration file outputs
-      return void (result.outputFiles = result.outputFiles!.flatMap(output => {
+      return void (result.outputFiles = result.outputFiles.flatMap(output => {
         /**
          * Absolute path to declaration file for {@linkcode output}.
          *
          * @const {string} dtspath
          */
-        const dtspath: string = EXT_JS_REGEX.test(output.path)
+        const path: string = EXT_JS_REGEX.test(output.path)
           ? output.path.replace(EXT_JS_REGEX, '.d.$1ts')
           : EXT_TS_REGEX.test(output.path) && !EXT_DTS_REGEX.test(output.path)
           ? output.path.replace(EXT_TS_REGEX, '.d.$2ts')
           : ''
 
         // do nothing if missing declaration file
-        if (!vfs.has(dtspath)) return [output]
-
-        /**
-         * Relative path to output file.
-         *
-         * **Note**: Relative to {@linkcode absWorkingDir}.
-         *
-         * @const {string} outfile
-         */
-        const outfile: string = output.path
-          .replace(absWorkingDir, '')
-          .replace(/^\//, '')
-
-        /**
-         * {@linkcode output} metadata.
-         *
-         * @const {OutputMetadata} metadata
-         */
-        const metadata: OutputMetadata = result.metafile!.outputs[outfile]!
-
-        /**
-         * Declaration output file content.
-         *
-         * @const {string} dtstext
-         */
-        const dtstext: string = vfs.get(dtspath)!
+        if (!includes(keys(vfs), path)) return [output]
 
         /**
          * Declaration file output.
          *
          * @const {OutputFile} dts
          */
-        const dts: OutputFile = {
-          contents: new util.TextEncoder().encode(dtstext),
-          path: dtspath,
-          text: dtstext
-        }
+        const dts: OutputFile = cast({
+          contents: new util.TextEncoder().encode(vfs[path]),
+          path
+        })
+
+        // redefine output text
+        define(dts, 'text', { get: constant(vfs[path]) })
 
         /**
          * Relative path to declaration output file.
@@ -278,13 +272,16 @@ const plugin = (): Plugin => {
          *
          * @const {string} dtsoutfile
          */
-        const dtsoutfile: string = dtspath
+        const outfile: string = path
           .replace(absWorkingDir, '')
           .replace(/^\//, '')
 
         // update metafile
-        result.metafile!.outputs[dtsoutfile] = {
-          ...metadata,
+        result.metafile.outputs[outfile] = {
+          ...get(
+            result.metafile.outputs,
+            output.path.replace(absWorkingDir, '').replace(/^\//, '')
+          ),
           bytes: Buffer.byteLength(dts.contents)
         }
 
diff --git a/src/plugins/filter/__tests__/plugin.integration.spec.ts b/src/plugins/filter/__tests__/plugin.integration.spec.ts
index 77236374..42580a87 100644
--- a/src/plugins/filter/__tests__/plugin.integration.spec.ts
+++ b/src/plugins/filter/__tests__/plugin.integration.spec.ts
@@ -5,6 +5,7 @@
 
 import ESBUILD_OPTIONS from '#fixtures/options-esbuild'
 import pathe from '@flex-development/pathe'
+import { keys } from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -29,7 +30,7 @@ describe('integration:plugins/filter', () => {
       })
 
       // Expect
-      expect(Object.keys(metafile.outputs)).to.each.match(filter)
+      expect(keys(metafile.outputs)).to.each.match(filter)
       expect(outputFiles).to.each.have.property('path').match(filter)
     })
   })
diff --git a/src/plugins/filter/__tests__/plugin.spec.ts b/src/plugins/filter/__tests__/plugin.spec.ts
index 9ae57919..fa59e426 100644
--- a/src/plugins/filter/__tests__/plugin.spec.ts
+++ b/src/plugins/filter/__tests__/plugin.spec.ts
@@ -4,6 +4,7 @@
  */
 
 import createPluginAPI from '#tests/utils/create-plugin-api'
+import { cast } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -24,12 +25,11 @@ describe('unit:plugins/filter', () => {
         createPluginAPI({ initialOptions: { metafile: true, write: true } })
       )
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error).to.not.be.undefined
-    expect(error.message).to.equal('write must be disabled')
+    expect(error).to.have.property('message', 'write must be disabled')
   })
 
   it('should throw if metafile is disabled', async () => {
@@ -40,11 +40,10 @@ describe('unit:plugins/filter', () => {
     try {
       await subject.setup(createPluginAPI())
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error).to.not.be.undefined
-    expect(error.message).to.equal('metafile required')
+    expect(error).to.have.property('message', 'metafile required')
   })
 })
diff --git a/src/plugins/filter/plugin.ts b/src/plugins/filter/plugin.ts
index 2316ed88..45987826 100644
--- a/src/plugins/filter/plugin.ts
+++ b/src/plugins/filter/plugin.ts
@@ -4,18 +4,20 @@
  */
 
 import type { OutputMetadata } from '#src/types'
-import type {
-  BuildOptions,
-  BuildResult,
-  OutputFile,
-  Plugin,
-  PluginBuild
-} from 'esbuild'
+import { entries, select } from '@flex-development/tutils'
+import type { BuildOptions, BuildResult, Plugin, PluginBuild } from 'esbuild'
 
 /**
- * Returns an {@linkcode OutputFile.path} filter plugin.
+ * Plugin-specific build options.
  *
- * @param {RegExp} [filter=/.+/] - {@linkcode OutputFile.path} filter
+ * @internal
+ */
+type SpecificOptions = { metafile: true; write: false }
+
+/**
+ * Returns an output file filter plugin.
+ *
+ * @param {RegExp} [filter=/.+/] - Output file path filter
  * @return {Plugin} Output file path filter plugin
  */
 const plugin = (filter: RegExp = /.+/): Plugin => {
@@ -38,38 +40,30 @@ const plugin = (filter: RegExp = /.+/): Plugin => {
     // esbuild write must be disabled to filter result.outputFiles
     if (initialOptions.write) throw new Error('write must be disabled')
 
-    // filter output files
-    return void onEnd(
-      (result: BuildResult<{ metafile: true; write: false }>): void => {
-        /**
-         * Output file metadata.
-         *
-         * @const {Record<string, OutputMetadata>} outputs
-         */
-        const outputs: Record<string, OutputMetadata> = {}
+    // filter output files and metadata
+    return void onEnd((result: BuildResult<SpecificOptions>): void => {
+      /**
+       * Output file metadata.
+       *
+       * @const {Record<string, OutputMetadata>} outputs
+       */
+      const outputs: Record<string, OutputMetadata> = {}
 
-        // filter output files
-        result.outputFiles = result.outputFiles.filter((output: OutputFile) => {
-          return filter.test(output.path)
-        })
+      // filter output files
+      result.outputFiles = select(result.outputFiles, o => filter.test(o.path))
 
-        // filter output file metadata
-        for (const output of Object.entries(result.metafile.outputs)) {
-          const [outfile, metadata] = output
-          if (result.outputFiles.some(o => o.path.endsWith(outfile))) {
-            outputs[outfile] = metadata
-          }
+      // filter output file metadata
+      for (const [outfile, metadata] of entries(result.metafile.outputs)) {
+        if (result.outputFiles.some(o => o.path.endsWith(outfile))) {
+          outputs[outfile] = metadata
         }
+      }
 
-        // reset metafile
-        result.metafile = {
-          inputs: result.metafile.inputs,
-          outputs
-        }
+      // reset metafile
+      result.metafile.outputs = outputs
 
-        return void result
-      }
-    )
+      return void result
+    })
   }
 
   return { name: 'filter', setup }
diff --git a/src/plugins/fully-specified/__tests__/plugin.integration.spec.ts b/src/plugins/fully-specified/__tests__/plugin.integration.spec.ts
index 4767d719..84e3b7b2 100644
--- a/src/plugins/fully-specified/__tests__/plugin.integration.spec.ts
+++ b/src/plugins/fully-specified/__tests__/plugin.integration.spec.ts
@@ -4,12 +4,12 @@
  */
 
 import ESBUILD_OPTIONS from '#fixtures/options-esbuild'
-import type { Mock } from '#tests/interfaces'
 import {
   ERR_PACKAGE_IMPORT_NOT_DEFINED,
   type NodeError
 } from '@flex-development/errnode'
 import * as mlly from '@flex-development/mlly'
+import { cast } from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -50,21 +50,21 @@ describe('integration:plugins/fully-specified', () => {
 
       // Act
       try {
-        ;(mlly.fillModules as unknown as Mock).mockRejectedValueOnce(error)
+        vi.mocked(mlly.fillModules).mockRejectedValueOnce(error)
         await esbuild.build(options)
       } catch (e: unknown) {
-        errors = (e as esbuild.BuildFailure).errors
+        errors = cast<esbuild.BuildFailure>(e).errors
       }
 
       // Expect
       expect(errors).to.be.an('array').of.length(1)
-      expect(errors[0]).to.have.property('id').equal(error.code)
-      expect(errors[0]).to.have.property('location').be.null
+      expect(errors[0]).to.have.property('id', error.code)
+      expect(errors[0]).to.have.property('location', null)
       expect(errors[0]).to.have.property('notes').be.an('array').of.length(1)
-      expect(errors[0]).to.have.property('pluginName').equal('fully-specified')
-      expect(errors[0]).to.have.property('text').equal(error.message)
-      expect(errors[0]!.notes[0]).to.have.property('location').be.null
-      expect(errors[0]!.notes[0]).to.have.property('text').equal(error.stack)
+      expect(errors[0]).to.have.property('pluginName', 'fully-specified')
+      expect(errors[0]).to.have.property('text', error.message)
+      expect(errors[0]!.notes[0]).to.have.property('location', null)
+      expect(errors[0]!.notes[0]).to.have.property('text', error.stack)
     })
   })
 })
diff --git a/src/plugins/fully-specified/__tests__/plugin.spec.ts b/src/plugins/fully-specified/__tests__/plugin.spec.ts
index 36abedf6..2eed0e74 100644
--- a/src/plugins/fully-specified/__tests__/plugin.spec.ts
+++ b/src/plugins/fully-specified/__tests__/plugin.spec.ts
@@ -4,6 +4,7 @@
  */
 
 import createPluginAPI from '#tests/utils/create-plugin-api'
+import { cast } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -30,33 +31,31 @@ describe('unit:plugins/fully-specified', () => {
 
   it('should throw if esbuild is writing output files', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI({ initialOptions: { write: true } }))
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!).to.have.property('message').equal('write must be disabled')
+    expect(error).to.have.property('message', 'write must be disabled')
   })
 
   it('should throw if metafile is disabled', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI())
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!.message).to.equal('metafile required')
+    expect(error).to.have.property('message', 'metafile required')
   })
 })
diff --git a/src/plugins/fully-specified/plugin.ts b/src/plugins/fully-specified/plugin.ts
index 921136d7..e7ab03a1 100644
--- a/src/plugins/fully-specified/plugin.ts
+++ b/src/plugins/fully-specified/plugin.ts
@@ -7,6 +7,7 @@ import type { OutputMetadata } from '#src/types'
 import type { NodeError } from '@flex-development/errnode'
 import * as mlly from '@flex-development/mlly'
 import * as pathe from '@flex-development/pathe'
+import { at, cast, constant, define, get, keys } from '@flex-development/tutils'
 import type {
   BuildOptions,
   BuildResult,
@@ -17,6 +18,13 @@ import type {
 } from 'esbuild'
 import util from 'node:util'
 
+/**
+ * Plugin-specific build options.
+ *
+ * @internal
+ */
+type SpecificOptions = { metafile: true; write: false }
+
 /**
  * Plugin name.
  *
@@ -86,88 +94,90 @@ const plugin = (): Plugin => {
     // metafile required to get output metadata
     if (!metafile) throw new Error('metafile required')
 
-    return void onEnd(async (result: BuildResult): Promise<OnEndResult> => {
-      /**
-       * Output file objects.
-       *
-       * @const {OutputFile[]} outputFiles
-       */
-      const outputFiles: OutputFile[] = []
-
-      for (const output of result.outputFiles!) {
-        /**
-         * Relative path to output file.
-         *
-         * **Note**: Relative to {@linkcode absWorkingDir}.
-         *
-         * @const {string} outfile
-         */
-        const outfile: string = output.path
-          .replace(absWorkingDir, '')
-          .replace(/^\//, '')
-
+    return void onEnd(
+      async (result: BuildResult<SpecificOptions>): Promise<OnEndResult> => {
         /**
-         * {@linkcode output} metadata.
+         * Output file objects.
          *
-         * @const {OutputMetadata} metadata
+         * @const {OutputFile[]} outputFiles
          */
-        const metadata: OutputMetadata = result.metafile!.outputs[outfile]!
+        const outputFiles: OutputFile[] = []
 
-        // because this plugin doesn't handle bundles, the entry point can be
-        // reset to the first (and only!) key in metadata.inputs
-        if (!metadata.entryPoint) {
-          const [entryPoint = ''] = Object.keys(metadata.inputs)
-          metadata.entryPoint = entryPoint
-        }
-
-        // skip output files without entry points
-        if (!metadata.entryPoint) {
-          outputFiles.push(output)
-          continue
-        }
+        for (const output of result.outputFiles) {
+          /**
+           * {@linkcode output} metadata.
+           *
+           * @const {OutputMetadata} metadata
+           */
+          const metadata: OutputMetadata = get(
+            result.metafile.outputs,
+            output.path.replace(absWorkingDir, '').replace(/^\//, '')
+          )
 
-        try {
           /**
-           * {@linkcode output.text} with fully specified modules.
+           * Relative path to source file.
            *
-           * @const {string} text
+           * @const {string} entryPoint
            */
-          const text: string = await mlly.fillModules(output.text, {
-            conditions: new Set(conditions),
-            ext,
-            extensions: new Set(resolveExtensions),
-            parent: mlly.toURL(pathe.join(absWorkingDir, metadata.entryPoint)),
-            preserveSymlinks
-          })
-
-          // add output file with fully specified modules
-          outputFiles.push({
-            ...output,
-            contents: new util.TextEncoder().encode(text),
-            text
-          })
-        } catch (e: unknown) {
-          const { code, message, stack = '' } = e as NodeError
-
-          return {
-            errors: [
-              {
-                id: code,
-                location: null,
-                notes: [{ location: null, text: stack }],
-                pluginName: PLUGIN_NAME,
-                text: message
-              }
-            ]
+          const entryPoint: string = get(
+            metadata,
+            'entryPoint',
+            // because this plugin doesn't handle bundles, the entry point can
+            // fallback to the first (and only!) key in metadata.inputs
+            at(keys(metadata.inputs), 0, '')
+          )
+
+          // skip output files without entry points
+          if (!entryPoint) {
+            outputFiles.push(output)
+            continue
+          }
+
+          // reset entry point
+          metadata.entryPoint = entryPoint
+
+          try {
+            // redefine output text
+            define(output, 'text', {
+              get: constant(
+                await mlly.fillModules(output.text, {
+                  conditions: new Set(conditions),
+                  ext,
+                  extensions: new Set(resolveExtensions),
+                  parent: mlly.toURL(pathe.join(absWorkingDir, entryPoint)),
+                  preserveSymlinks
+                })
+              )
+            })
+
+            // reset output contents
+            output.contents = new util.TextEncoder().encode(output.text)
+
+            // add output file with fully specified modules
+            outputFiles.push(output)
+          } catch (e: unknown) {
+            const { code, message, stack = '' } = cast<NodeError>(e)
+
+            return {
+              errors: [
+                {
+                  id: code,
+                  location: null,
+                  notes: [{ location: null, text: stack }],
+                  pluginName: PLUGIN_NAME,
+                  text: message
+                }
+              ]
+            }
           }
         }
-      }
 
-      // reset output files
-      result.outputFiles = outputFiles
+        // reset output files
+        result.outputFiles = outputFiles
 
-      return {}
-    })
+        return {}
+      }
+    )
   }
 
   return { name: PLUGIN_NAME, setup }
diff --git a/src/plugins/tsconfig-paths/__tests__/plugin.integration.spec.ts b/src/plugins/tsconfig-paths/__tests__/plugin.integration.spec.ts
index 920786c5..01a6a790 100644
--- a/src/plugins/tsconfig-paths/__tests__/plugin.integration.spec.ts
+++ b/src/plugins/tsconfig-paths/__tests__/plugin.integration.spec.ts
@@ -4,7 +4,6 @@
  */
 
 import ESBUILD_OPTIONS from '#fixtures/options-esbuild'
-import type { Mock } from '#tests/interfaces'
 import {
   ERR_INVALID_MODULE_SPECIFIER,
   type NodeError
@@ -12,6 +11,7 @@ import {
 import * as mlly from '@flex-development/mlly'
 import pathe from '@flex-development/pathe'
 import * as tscu from '@flex-development/tsconfig-utils'
+import { cast } from '@flex-development/tutils'
 import * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -53,21 +53,21 @@ describe('integration:plugins/tsconfig-paths', () => {
 
       // Act
       try {
-        ;(tscu.resolvePaths as unknown as Mock).mockRejectedValueOnce(error)
+        vi.mocked(tscu.resolvePaths).mockRejectedValueOnce(error)
         await esbuild.build(options)
       } catch (e: unknown) {
-        errors = (e as esbuild.BuildFailure).errors
+        errors = cast<esbuild.BuildFailure>(e).errors
       }
 
       // Expect
       expect(errors).to.be.an('array').of.length(1)
-      expect(errors[0]).to.have.property('id').equal(error.code)
-      expect(errors[0]).to.have.property('location').be.null
+      expect(errors[0]).to.have.property('id', error.code)
+      expect(errors[0]).to.have.property('location', null)
       expect(errors[0]).to.have.property('notes').be.an('array').of.length(1)
       expect(errors[0]).to.have.property('pluginName').equal('tsconfig-paths')
-      expect(errors[0]).to.have.property('text').equal(error.message)
-      expect(errors[0]!.notes[0]).to.have.property('location').be.null
-      expect(errors[0]!.notes[0]).to.have.property('text').equal(error.stack)
+      expect(errors[0]).to.have.property('text', error.message)
+      expect(errors[0]!.notes[0]).to.have.property('location', null)
+      expect(errors[0]!.notes[0]).to.have.property('text', error.stack)
     })
   })
 })
diff --git a/src/plugins/tsconfig-paths/__tests__/plugin.spec.ts b/src/plugins/tsconfig-paths/__tests__/plugin.spec.ts
index a7e9ec69..96cda20b 100644
--- a/src/plugins/tsconfig-paths/__tests__/plugin.spec.ts
+++ b/src/plugins/tsconfig-paths/__tests__/plugin.spec.ts
@@ -4,6 +4,7 @@
  */
 
 import createPluginAPI from '#tests/utils/create-plugin-api'
+import { cast } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -30,33 +31,31 @@ describe('unit:plugins/tsconfig-paths', () => {
 
   it('should throw if esbuild is writing output files', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI({ initialOptions: { write: true } }))
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!).to.have.property('message').equal('write must be disabled')
+    expect(error).to.have.property('message', 'write must be disabled')
   })
 
   it('should throw if metafile is disabled', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI())
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!.message).to.equal('metafile required')
+    expect(error).to.have.property('message', 'metafile required')
   })
 })
diff --git a/src/plugins/tsconfig-paths/plugin.ts b/src/plugins/tsconfig-paths/plugin.ts
index 3e213d58..8a18826d 100644
--- a/src/plugins/tsconfig-paths/plugin.ts
+++ b/src/plugins/tsconfig-paths/plugin.ts
@@ -7,6 +7,7 @@ import type { OutputMetadata } from '#src/types'
 import type { NodeError } from '@flex-development/errnode'
 import pathe from '@flex-development/pathe'
 import * as tscu from '@flex-development/tsconfig-utils'
+import { at, cast, constant, define, get, keys } from '@flex-development/tutils'
 import type {
   BuildOptions,
   BuildResult,
@@ -17,6 +18,13 @@ import type {
 } from 'esbuild'
 import util from 'node:util'
 
+/**
+ * Plugin-specific build options.
+ *
+ * @internal
+ */
+type SpecificOptions = { metafile: true; write: false }
+
 /**
  * Plugin name.
  *
@@ -66,93 +74,95 @@ const plugin = ({ file, read }: tscu.LoadTsconfigOptions = {}): Plugin => {
     // metafile required to get output metadata
     if (!metafile) throw new Error('metafile required')
 
-    return void onEnd(async (result: BuildResult): Promise<OnEndResult> => {
-      /**
-       * Output file objects.
-       *
-       * @const {OutputFile[]} outputFiles
-       */
-      const outputFiles: OutputFile[] = []
-
-      // resolve path aliases in output content
-      for (const output of result.outputFiles!) {
-        /**
-         * Relative path to output file.
-         *
-         * **Note**: Relative to {@linkcode absWorkingDir}.
-         *
-         * @const {string} outfile
-         */
-        const outfile: string = output.path
-          .replace(absWorkingDir, '')
-          .replace(/^\//, '')
-
+    return void onEnd(
+      async (result: BuildResult<SpecificOptions>): Promise<OnEndResult> => {
         /**
-         * {@linkcode output} metadata.
+         * Output file objects.
          *
-         * @const {OutputMetadata} metadata
+         * @const {OutputFile[]} outputFiles
          */
-        const metadata: OutputMetadata = result.metafile!.outputs[outfile]!
+        const outputFiles: OutputFile[] = []
 
-        // because this plugin doesn't handle bundles, the entry point can be
-        // reset to the first (and only!) key in metadata.inputs
-        if (!metadata.entryPoint) {
-          const [entryPoint = ''] = Object.keys(metadata.inputs)
-          metadata.entryPoint = entryPoint
-        }
-
-        // skip output files without entry points
-        if (!metadata.entryPoint) {
-          outputFiles.push(output)
-          continue
-        }
+        // resolve path aliases in output content
+        for (const output of result.outputFiles) {
+          /**
+           * {@linkcode output} metadata.
+           *
+           * @const {OutputMetadata} metadata
+           */
+          const metadata: OutputMetadata = get(
+            result.metafile.outputs,
+            output.path.replace(absWorkingDir, '').replace(/^\//, '')
+          )
 
-        try {
           /**
-           * {@linkcode output.text} with path aliases replaced.
+           * Relative path to source file.
            *
-           * @const {string} text
+           * @const {string} entryPoint
            */
-          const text: string = await tscu.resolvePaths(output.text, {
-            baseUrl: absWorkingDir,
-            conditions: new Set(conditions),
-            ext: '',
-            extensions: new Set(resolveExtensions),
-            file,
-            parent: pathe.resolve(absWorkingDir, metadata.entryPoint),
-            preserveSymlinks,
-            read,
-            tsconfig: pathe.resolve(absWorkingDir, tsconfig)
-          })
-
-          // add output file with path aliases replaced
-          outputFiles.push({
-            ...output,
-            contents: new util.TextEncoder().encode(text),
-            text
-          })
-        } catch (e: unknown) {
-          const { code, message, stack = '' } = e as NodeError
-
-          return {
-            errors: [
-              {
-                id: code,
-                location: null,
-                notes: [{ location: null, text: stack }],
-                pluginName: PLUGIN_NAME,
-                text: message
-              }
-            ]
+          const entryPoint: string = get(
+            metadata,
+            'entryPoint',
+            // because this plugin doesn't handle bundles, the entry point can
+            // fallback to the first (and only!) key in metadata.inputs
+            at(keys(metadata.inputs), 0, '')
+          )
+
+          // skip output files without entry points
+          if (!entryPoint) {
+            outputFiles.push(output)
+            continue
+          }
+
+          // reset entry point
+          metadata.entryPoint = entryPoint
+
+          try {
+            // replace path aliases
+            define(output, 'text', {
+              get: constant(
+                await tscu.resolvePaths(output.text, {
+                  baseUrl: absWorkingDir,
+                  conditions: new Set(conditions),
+                  ext: '',
+                  extensions: new Set(resolveExtensions),
+                  file,
+                  parent: pathe.resolve(absWorkingDir, entryPoint),
+                  preserveSymlinks,
+                  read,
+                  tsconfig: pathe.resolve(absWorkingDir, tsconfig)
+                })
+              )
+            })
+
+            // reset output contents
+            output.contents = new util.TextEncoder().encode(output.text)
+
+            // add output file with path aliases replaced
+            outputFiles.push(output)
+          } catch (e: unknown) {
+            const { code, message, stack = '' } = cast<NodeError>(e)
+
+            return {
+              errors: [
+                {
+                  id: code,
+                  location: null,
+                  notes: [{ location: null, text: stack }],
+                  pluginName: PLUGIN_NAME,
+                  text: message
+                }
+              ]
+            }
           }
         }
-      }
 
-      // reset output files
-      result.outputFiles = outputFiles
+        // reset output files
+        result.outputFiles = outputFiles
 
-      return {}
-    })
+        return {}
+      }
+    )
   }
 
   return { name: PLUGIN_NAME, setup }
diff --git a/src/plugins/write/__tests__/options.spec-d.ts b/src/plugins/write/__tests__/options.spec-d.ts
index d8bb5081..444c5a6d 100644
--- a/src/plugins/write/__tests__/options.spec-d.ts
+++ b/src/plugins/write/__tests__/options.spec-d.ts
@@ -4,24 +4,25 @@
  */
 
 import type { FileSystemAdapter } from '#src/types'
+import type { Optional } from '@flex-development/tutils'
 import type TestSubject from '../options'
 
 describe('unit-d:plugins/write/WritePluginOptions', () => {
-  it('should match [filter?: RegExp]', () => {
+  it('should match [filter?: Optional<RegExp>]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('filter')
-      .toEqualTypeOf<RegExp | undefined>()
+      .toEqualTypeOf<Optional<RegExp>>()
   })
 
   it('should match [mkdir?: FileSystemAdapter["mkdir"]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('mkdir')
-      .toEqualTypeOf<FileSystemAdapter['mkdir'] | undefined>()
+      .toEqualTypeOf<Optional<FileSystemAdapter['mkdir']>>()
   })
 
   it('should match [writeFile?: FileSystemAdapter["writeFile"]]', () => {
     expectTypeOf<TestSubject>()
       .toHaveProperty('writeFile')
-      .toEqualTypeOf<FileSystemAdapter['writeFile'] | undefined>()
+      .toEqualTypeOf<Optional<FileSystemAdapter['writeFile']>>()
   })
 })
diff --git a/src/plugins/write/__tests__/plugin.spec.ts b/src/plugins/write/__tests__/plugin.spec.ts
index d19efbf4..505c3201 100644
--- a/src/plugins/write/__tests__/plugin.spec.ts
+++ b/src/plugins/write/__tests__/plugin.spec.ts
@@ -4,6 +4,7 @@
  */
 
 import createPluginAPI from '#tests/utils/create-plugin-api'
+import { cast } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 import testSubject from '../plugin'
 
@@ -16,17 +17,16 @@ describe('unit:plugins/write', () => {
 
   it('should throw if esbuild is writing output files', async () => {
     // Arrange
-    let error: Error
+    let error!: Error
 
     // Act
     try {
       await subject.setup(createPluginAPI({ initialOptions: { write: true } }))
     } catch (e: unknown) {
-      error = e as typeof error
+      error = cast(e)
     }
 
     // Expect
-    expect(error!).to.not.be.undefined
-    expect(error!.message).to.equal('write must be disabled')
+    expect(error).to.have.property('message', 'write must be disabled')
   })
 })
diff --git a/src/plugins/write/options.ts b/src/plugins/write/options.ts
index 69530304..a8bb7352 100644
--- a/src/plugins/write/options.ts
+++ b/src/plugins/write/options.ts
@@ -4,6 +4,7 @@
  */
 
 import type { FileSystemAdapter } from '#src/types'
+import type { Optional } from '@flex-development/tutils'
 
 /**
  * Output file writing options.
@@ -14,7 +15,7 @@ interface WritePluginOptions {
    *
    * @default /.+/
    */
-  filter?: RegExp | undefined
+  filter?: Optional<RegExp>
 
   /**
    * Creates a directory.
diff --git a/src/types/__tests__/generated-file-type.spec-d.ts b/src/types/__tests__/generated-file-type.spec-d.ts
index 809e84c8..e80f81c2 100644
--- a/src/types/__tests__/generated-file-type.spec-d.ts
+++ b/src/types/__tests__/generated-file-type.spec-d.ts
@@ -7,10 +7,10 @@ import type TestSubject from '../generated-file-type'
 
 describe('unit-d:types/GeneratedFileType', () => {
   it('should extract "css"', () => {
-    expectTypeOf<TestSubject>().extract<'css'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'css'>().not.toBeNever()
   })
 
   it('should extract "js"', () => {
-    expectTypeOf<TestSubject>().extract<'js'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'js'>().not.toBeNever()
   })
 })
diff --git a/src/types/__tests__/jsx.spec-d.ts b/src/types/__tests__/jsx.spec-d.ts
index f77e9a80..6a3cd6ba 100644
--- a/src/types/__tests__/jsx.spec-d.ts
+++ b/src/types/__tests__/jsx.spec-d.ts
@@ -7,14 +7,14 @@ import type TestSubject from '../jsx'
 
 describe('unit-d:types/Jsx', () => {
   it('should extract "automatic"', () => {
-    expectTypeOf<TestSubject>().extract<'automatic'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'automatic'>().not.toBeNever()
   })
 
   it('should extract "preserve"', () => {
-    expectTypeOf<TestSubject>().extract<'preserve'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'preserve'>().not.toBeNever()
   })
 
   it('should extract "transform"', () => {
-    expectTypeOf<TestSubject>().extract<'transform'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'transform'>().not.toBeNever()
   })
 })
diff --git a/src/types/__tests__/legal-comments.spec-d.ts b/src/types/__tests__/legal-comments.spec-d.ts
index 23a2ff44..50f735b9 100644
--- a/src/types/__tests__/legal-comments.spec-d.ts
+++ b/src/types/__tests__/legal-comments.spec-d.ts
@@ -7,22 +7,22 @@ import type TestSubject from '../legal-comments'
 
 describe('unit-d:types/LegalComments', () => {
   it('should extract "eof"', () => {
-    expectTypeOf<TestSubject>().extract<'eof'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'eof'>().not.toBeNever()
   })
 
   it('should extract "external"', () => {
-    expectTypeOf<TestSubject>().extract<'external'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'external'>().not.toBeNever()
   })
 
   it('should extract "inline"', () => {
-    expectTypeOf<TestSubject>().extract<'inline'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'inline'>().not.toBeNever()
   })
 
   it('should extract "linked"', () => {
-    expectTypeOf<TestSubject>().extract<'linked'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'linked'>().not.toBeNever()
   })
 
   it('should extract "none"', () => {
-    expectTypeOf<TestSubject>().extract<'none'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'none'>().not.toBeNever()
   })
 })
diff --git a/src/types/__tests__/output-extension.spec-d.ts b/src/types/__tests__/output-extension.spec-d.ts
index d43fef40..7c0db56c 100644
--- a/src/types/__tests__/output-extension.spec-d.ts
+++ b/src/types/__tests__/output-extension.spec-d.ts
@@ -7,52 +7,52 @@ import type TestSubject from '../output-extension'
 
 describe('unit-d:types/OutputExtension', () => {
   it('should extract ".cjs"', () => {
-    expectTypeOf<TestSubject>().extract<'.cjs'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'.cjs'>().not.toBeNever()
   })
 
   it('should extract ".js"', () => {
-    expectTypeOf<TestSubject>().extract<'.js'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'.js'>().not.toBeNever()
   })
 
   it('should extract ".mjs"', () => {
-    expectTypeOf<TestSubject>().extract<'.mjs'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'.mjs'>().not.toBeNever()
   })
 
   it('should extract "cjs"', () => {
-    expectTypeOf<TestSubject>().extract<'cjs'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'cjs'>().not.toBeNever()
   })
 
   it('should extract "js"', () => {
-    expectTypeOf<TestSubject>().extract<'js'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'js'>().not.toBeNever()
   })
 
   it('should extract "mjs"', () => {
-    expectTypeOf<TestSubject>().extract<'mjs'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'mjs'>().not.toBeNever()
   })
 
   describe('min', () => {
     it('should extract ".min.cjs"', () => {
-      expectTypeOf<TestSubject>().extract<'.min.cjs'>().toBeString()
+      expectTypeOf<TestSubject>().extract<'.min.cjs'>().not.toBeNever()
     })
 
     it('should extract ".min.js"', () => {
-      expectTypeOf<TestSubject>().extract<'.min.js'>().toBeString()
+      expectTypeOf<TestSubject>().extract<'.min.js'>().not.toBeNever()
     })
 
     it('should extract ".min.mjs"', () => {
-      expectTypeOf<TestSubject>().extract<'.min.mjs'>().toBeString()
+      expectTypeOf<TestSubject>().extract<'.min.mjs'>().not.toBeNever()
     })
 
     it('should extract "min.cjs"', () => {
-      expectTypeOf<TestSubject>().extract<'min.cjs'>().toBeString()
+      expectTypeOf<TestSubject>().extract<'min.cjs'>().not.toBeNever()
     })
 
     it('should extract "min.js"', () => {
-      expectTypeOf<TestSubject>().extract<'min.js'>().toBeString()
+      expectTypeOf<TestSubject>().extract<'min.js'>().not.toBeNever()
     })
 
     it('should extract "min.mjs"', () => {
-      expectTypeOf<TestSubject>().extract<'min.mjs'>().toBeString()
+      expectTypeOf<TestSubject>().extract<'min.mjs'>().not.toBeNever()
     })
   })
 })
diff --git a/src/types/__tests__/sourcemap.spec-d.ts b/src/types/__tests__/sourcemap.spec-d.ts
index 14c81a94..f1fa7a81 100644
--- a/src/types/__tests__/sourcemap.spec-d.ts
+++ b/src/types/__tests__/sourcemap.spec-d.ts
@@ -7,18 +7,18 @@ import type TestSubject from '../sourcemap'
 
 describe('unit-d:types/Sourcemap', () => {
   it('should extract "both"', () => {
-    expectTypeOf<TestSubject>().extract<'both'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'both'>().not.toBeNever()
   })
 
   it('should extract "external"', () => {
-    expectTypeOf<TestSubject>().extract<'external'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'external'>().not.toBeNever()
   })
 
   it('should extract "inline"', () => {
-    expectTypeOf<TestSubject>().extract<'inline'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'inline'>().not.toBeNever()
   })
 
   it('should extract "linked"', () => {
-    expectTypeOf<TestSubject>().extract<'linked'>().toBeString()
+    expectTypeOf<TestSubject>().extract<'linked'>().not.toBeNever()
   })
 })
diff --git a/src/types/jsx.ts b/src/types/jsx.ts
index f62c107a..d702efdf 100644
--- a/src/types/jsx.ts
+++ b/src/types/jsx.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/types/Jsx
  */
 
+import type { Fallback } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 
 /**
@@ -10,6 +11,6 @@ import type * as esbuild from 'esbuild'
  *
  * @see https://esbuild.github.io/api/#jsx
  */
-type Jsx = NonNullable<esbuild.BuildOptions['jsx']>
+type Jsx = Fallback<esbuild.BuildOptions['jsx'], never>
 
 export type { Jsx as default }
diff --git a/src/types/legal-comments.ts b/src/types/legal-comments.ts
index aed62420..bbc840fa 100644
--- a/src/types/legal-comments.ts
+++ b/src/types/legal-comments.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/types/LegalComments
  */
 
+import type { Fallback } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 
 /**
@@ -10,6 +11,6 @@ import type * as esbuild from 'esbuild'
  *
  * @see https://esbuild.github.io/api/#legal-comments
  */
-type LegalComments = NonNullable<esbuild.BuildOptions['legalComments']>
+type LegalComments = Fallback<esbuild.BuildOptions['legalComments'], never>
 
 export type { LegalComments as default }
diff --git a/src/types/options-esbuild.ts b/src/types/options-esbuild.ts
index e6302cef..d523ef3c 100644
--- a/src/types/options-esbuild.ts
+++ b/src/types/options-esbuild.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/types/EsbuildOptions
  */
 
+import type { Omit } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 
 /**
diff --git a/src/types/output-extension.ts b/src/types/output-extension.ts
index 0cc4e5ef..cc73e24e 100644
--- a/src/types/output-extension.ts
+++ b/src/types/output-extension.ts
@@ -3,12 +3,12 @@
  * @module mkbuild/types/OutputExtension
  */
 
-import type { EmptyString } from '@flex-development/tutils'
+import type { Dot, EmptyString } from '@flex-development/tutils'
 
 /**
  * Output file extensions.
  */
-type OutputExtension = `${EmptyString | '.'}${EmptyString | 'min.'}${
+type OutputExtension = `${Dot | EmptyString}${EmptyString | `min${Dot}`}${
   | 'cjs'
   | 'js'
   | 'mjs'}`
diff --git a/src/types/sourcemap.ts b/src/types/sourcemap.ts
index ea405825..c561eb4e 100644
--- a/src/types/sourcemap.ts
+++ b/src/types/sourcemap.ts
@@ -3,6 +3,7 @@
  * @module mkbuild/types/Sourcemap
  */
 
+import type { Fallback, Optional } from '@flex-development/tutils'
 import type * as esbuild from 'esbuild'
 
 /**
@@ -10,9 +11,10 @@ import type * as esbuild from 'esbuild'
  *
  * @see https://esbuild.github.io/api/#sourcemap
  */
-type Sourcemap = Exclude<
-  NonNullable<esbuild.BuildOptions['sourcemap']>,
-  boolean
+type Sourcemap = Fallback<
+  esbuild.BuildOptions['sourcemap'],
+  never,
+  Optional<boolean>
 >
 
 export type { Sourcemap as default }
diff --git a/src/utils/__mocks__/fs.ts b/src/utils/__mocks__/fs.ts
index e1b89a53..b3cd66c7 100644
--- a/src/utils/__mocks__/fs.ts
+++ b/src/utils/__mocks__/fs.ts
@@ -4,11 +4,7 @@
  */
 
 import volume from '#fixtures/volume'
-import type {
-  IMkdirOptions,
-  IRmOptions,
-  IWriteFileOptions
-} from 'memfs/lib/volume'
+import { cast, type Optional } from '@flex-development/tutils'
 import fsc, {
   type MakeDirectoryOptions,
   type Mode,
@@ -27,15 +23,15 @@ import fsp from 'node:fs/promises'
  *
  * @param {PathLike} directory - Directory to create
  * @param {MakeDirectoryOptions | Mode} [options] - Directory creation options
- * @return {Promise<string | undefined>} First directory path created if
+ * @return {Promise<Optional<string>>} First directory path created if
  * `options.recursive` is `true` or `undefined` if `false`
  */
 const mkdir = vi.fn(
   async (
     directory: PathLike,
     options: MakeDirectoryOptions | Mode
-  ): Promise<string | undefined> => {
-    return volume.mkdirSync(directory, options as IMkdirOptions)
+  ): Promise<Optional<string>> => {
+    return volume.mkdirSync(directory, cast(options))
   }
 )
 
@@ -47,11 +43,11 @@ const mkdir = vi.fn(
  * @async
  *
  * @param {PathLike} id - Module id to evaluate
- * @param {RmOptions} [options] - Removal options
+ * @param {RmOptions?} [options] - Removal options
  * @return {Promise<void>} Nothing when complete
  */
 const rm = vi.fn(async (id: PathLike, options?: RmOptions): Promise<void> => {
-  return void volume.rmSync(id, options as IRmOptions)
+  return void volume.rmSync(id, cast(options))
 })
 
 /**
@@ -63,7 +59,7 @@ const rm = vi.fn(async (id: PathLike, options?: RmOptions): Promise<void> => {
  *
  * @param {PathLike} file - Filename or handle
  * @param {Uint8Array | string} data - File content
- * @param {WriteFileOptions} [options] - Write file options
+ * @param {WriteFileOptions?} [options] - Write file options
  * @return {Promise<void>} Nothing when complete
  */
 const writeFile = vi.fn(
@@ -72,7 +68,7 @@ const writeFile = vi.fn(
     data: Uint8Array | string,
     options?: WriteFileOptions
   ): Promise<void> => {
-    return void volume.writeFileSync(file, data, options as IWriteFileOptions)
+    return void volume.writeFileSync(file, data, cast(options))
   }
 )
 
diff --git a/src/utils/__tests__/define-build-config.spec-d.ts b/src/utils/__tests__/define-build-config.spec-d.ts
index 48145e65..bf0d3bd2 100644
--- a/src/utils/__tests__/define-build-config.spec-d.ts
+++ b/src/utils/__tests__/define-build-config.spec-d.ts
@@ -4,15 +4,16 @@
  */
 
 import type { Config } from '#src/interfaces'
+import type { Optional } from '@flex-development/tutils'
 import type testSubject from '../define-build-config'
 
 describe('unit-d:utils/defineBuildConfig', () => {
-  it('should be callable with [Config | undefined]', () => {
+  it('should be callable with [Optional<Config>]', () => {
     // Arrange
-    type Expected = [config?: Config | undefined]
+    type Expect = [config?: Optional<Config>]
 
     // Expect
-    expectTypeOf<typeof testSubject>().parameters.toEqualTypeOf<Expected>()
+    expectTypeOf<typeof testSubject>().parameters.toEqualTypeOf<Expect>()
   })
 
   it('should return Config', () => {
diff --git a/src/utils/analyze-outputs.ts b/src/utils/analyze-outputs.ts
index 122862d5..0a31ead3 100644
--- a/src/utils/analyze-outputs.ts
+++ b/src/utils/analyze-outputs.ts
@@ -4,9 +4,9 @@
  */
 
 import type { OutputMetadata } from '#src/types'
+import { entries, join, template } from '@flex-development/tutils'
 import * as color from 'colorette'
 import pb from 'pretty-bytes'
-import { template } from 'radash'
 
 /**
  * Generates a build analysis for the given `outputs`.
@@ -39,17 +39,17 @@ const analyzeOutputs = (
    *
    * @const {number} size
    */
-  const size: number = Object.entries(outputs).reduce((acc, output) => {
+  const size: number = entries(outputs).reduce((acc, output) => {
     const [outfile, metadata] = output
     strings.push(color.gray(`${indent}└─ ${outfile} (${pb(metadata.bytes)})`))
     return acc + metadata.bytes
   }, 0)
 
   return {
-    analysis: template(`${indent}{{0}} (total size: {{1}})\n{{2}}`, {
+    analysis: template(`${indent}{0} (total size: {1})\n{2}`, {
       0: color.bold(outdir),
       1: color.cyan(pb(size)),
-      2: strings.join('\n')
+      2: join(strings, '\n')
     }),
     bytes: size
   }
diff --git a/vitest.config.ts b/vitest.config.ts
index 10b3f4aa..faee5ccb 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -5,9 +5,8 @@
  */
 
 import pathe from '@flex-development/pathe'
-import { NodeEnv } from '@flex-development/tutils'
+import { NodeEnv, template } from '@flex-development/tutils'
 import ci from 'is-ci'
-import { template } from 'radash'
 import tsconfigpaths from 'vite-tsconfig-paths'
 import GithubActionsReporter from 'vitest-github-actions-reporter'
 import {
@@ -141,7 +140,7 @@ const config: UserConfigExport = defineConfig((): UserConfig => {
         checker: 'tsc',
         ignoreSourceErrors: false,
         include: ['**/__tests__/*.spec-d.ts'],
-        tsconfig: template('{{0}}/tsconfig.typecheck.json', {
+        tsconfig: template('{0}/tsconfig.typecheck.json', {
           0: pathe.resolve(TYPESCRIPT_V5 ? '' : '__tests__/ts/v4')
         })
       },
diff --git a/yarn.lock b/yarn.lock
index 88c3b929..50e8d7f8 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1151,7 +1151,7 @@ __metadata:
     "@flex-development/pkg-types": "npm:2.0.0"
     "@flex-development/toggle-pkg-type": "npm:2.0.0"
     "@flex-development/tsconfig-utils": "npm:1.1.2"
-    "@flex-development/tutils": "npm:6.0.0-alpha.10"
+    "@flex-development/tutils": "npm:6.0.0-alpha.18"
     "@graphql-eslint/eslint-plugin": "npm:3.18.0"
     "@nestjs/common": "npm:9.4.1"
     "@nestjs/core": "npm:9.4.0"
@@ -1196,7 +1196,6 @@ __metadata:
     cspell: "npm:6.31.1"
     dateformat: "npm:5.0.3"
     esbuild: "npm:0.17.19"
-    escape-string-regexp: "npm:5.0.0"
     eslint: "npm:8.39.0"
     eslint-config-prettier: "npm:8.8.0"
     eslint-plugin-chai-expect: "npm:3.0.0"
@@ -1220,7 +1219,6 @@ __metadata:
     jsonc-eslint-parser: "npm:2.3.0"
     lint-staged: "npm:13.2.2"
     memfs: "npm:3.5.1"
-    merge-anything: "npm:5.1.6"
     mri: "npm:1.2.0"
     nest-commander: "npm:3.6.1"
     nest-commander-testing: "npm:3.1.0"
@@ -1230,7 +1228,6 @@ __metadata:
     prettier-plugin-sh: "npm:0.12.8"
     pretty-bytes: "npm:6.1.0"
     pretty-format: "npm:29.5.0"
-    radash: "npm:10.8.1"
     reflect-metadata: "npm:0.1.13"
     rxjs: "npm:8.0.0-alpha.9"
     semver: "npm:7.5.2"
@@ -1367,6 +1364,26 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@flex-development/tutils@npm:6.0.0-alpha.18":
+  version: 6.0.0-alpha.18
+  resolution: "@flex-development/tutils@npm:6.0.0-alpha.18::__archiveUrl=https%3A%2F%2Fnpm.pkg.github.com%2Fdownload%2F%40flex-development%2Ftutils%2F6.0.0-alpha.18%2Fa8693102aab522ad1ecafda09438e513014dca6c"
+  dependencies:
+    dequal: "npm:2.0.3"
+  peerDependencies:
+    typescript: ">=5.0.4"
+  checksum: c506828a3a86998e36d8808b7313ca0c14922f5f49008c600706eec9b06678919b56f96004919b056e59392255f63002d5fe2ea98504212f44e16f6e43d7b141
+  languageName: node
+  linkType: hard
+
+"@flex-development/tutils@npm:6.0.0-alpha.7":
+  version: 6.0.0-alpha.7
+  resolution: "@flex-development/tutils@npm:6.0.0-alpha.7::__archiveUrl=https%3A%2F%2Fnpm.pkg.github.com%2Fdownload%2F%40flex-development%2Ftutils%2F6.0.0-alpha.7%2F786916dcfd30bf076b5ac74cb31ca4031f74e1f0"
+  peerDependencies:
+    typescript: ">=4.7"
+  checksum: 626d2df21cd31cfe0445c94e0946b7ca77a3c95ca93c92b20c512820bad32e7fe34c4c59f870eddcdc449decc0c364614df4fc1c3f4fef1b76592d5ec53c59d3
+  languageName: node
+  linkType: hard
+
 "@gar/promisify@npm:^1.1.3":
   version: 1.1.3
   resolution: "@gar/promisify@npm:1.1.3"
@@ -4307,6 +4324,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"dequal@npm:2.0.3":
+  version: 2.0.3
+  resolution: "dequal@npm:2.0.3"
+  checksum: 7a633ec0ba78bc08ba217b762b15157d2ec99edb50a82124df2c341255b1943217215872888981cc6a6ee02406ab1b09783f5b51b7db8d8f8f1284092f379aad
+  languageName: node
+  linkType: hard
+
 "detect-indent@npm:^6.0.0":
   version: 6.1.0
   resolution: "detect-indent@npm:6.1.0"
@@ -6752,15 +6776,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"merge-anything@npm:5.1.6":
-  version: 5.1.6
-  resolution: "merge-anything@npm:5.1.6"
-  dependencies:
-    is-what: "npm:^4.1.8"
-  checksum: 3ccff2beef56b55200993400972056ba383f837369f22f359ec87c38106d1b27e135ffb3d736cbf423465d40c9292989178e254bd7f0d5d81a41172e18ea421e
-  languageName: node
-  linkType: hard
-
 "merge-stream@npm:^2.0.0":
   version: 2.0.0
   resolution: "merge-stream@npm:2.0.0"
@@ -7912,20 +7927,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"radash@npm:10.8.1":
-  version: 10.8.1
-  resolution: "radash@npm:10.8.1"
-  checksum: 43c1a0a67ed5e960841f68d4dd9d19a6879e5e13b9b8d6d817c309c65fa834ad51577243d2dfd9bbb8c40d2e7959e594f202c85abe6568aee93cfe88ee5400f2
-  languageName: node
-  linkType: hard
-
-"radash@patch:radash@npm%3A10.8.1#patches/radash+10.8.1.dev.patch::locator=%40flex-development%2Fmkbuild%40workspace%3A.":
-  version: 10.8.1
-  resolution: "radash@patch:radash@npm%3A10.8.1#patches/radash+10.8.1.dev.patch::version=10.8.1&hash=29b41c&locator=%40flex-development%2Fmkbuild%40workspace%3A."
-  checksum: dca43393e14f057da74df3976927030f21e3eb78aeff5db24f324623818d587ccd7975feeca6b701628f2874446dc7b74e7ea36b33fe2152d6c4b6edf1f1af6d
-  languageName: node
-  linkType: hard
-
 "range-parser@npm:1.2.0":
   version: 1.2.0
   resolution: "range-parser@npm:1.2.0"