diff --git a/src/Cms/Language.php b/src/Cms/Language.php
index e91026d7d7..2cfa204bd4 100644
--- a/src/Cms/Language.php
+++ b/src/Cms/Language.php
@@ -45,6 +45,7 @@ class Language implements Stringable
 	protected string $direction;
 	protected array $locale;
 	protected string $name;
+	protected bool $single;
 	protected array $slugs;
 	protected array $smartypants;
 	protected array $translations;
@@ -64,6 +65,7 @@ public function __construct(array $props)
 		$this->default      = ($props['default'] ?? false) === true;
 		$this->direction    = ($props['direction'] ?? null) === 'rtl' ? 'rtl' : 'ltr';
 		$this->name         = trim($props['name'] ?? $this->code);
+		$this->single       = $props['single'] ?? false;
 		$this->slugs        = $props['slugs'] ?? [];
 		$this->smartypants  = $props['smartypants'] ?? [];
 		$this->translations = $props['translations'] ?? [];
@@ -177,8 +179,8 @@ public static function create(array $props): static
 		if ($languages->count() === 0) {
 			foreach ($kirby->models() as $model) {
 				$model->storage()->convertLanguage(
-					'default',
-					$language->code()
+					Language::single(),
+					$language
 				);
 			}
 		}
@@ -225,7 +227,7 @@ public function delete(): bool
 
 		foreach ($kirby->models() as $model) {
 			if ($this->isLast() === true) {
-				$model->storage()->convertLanguage($code, 'default');
+				$model->storage()->convertLanguage($this, Language::single());
 			} else {
 				$model->storage()->deleteLanguage($code);
 			}
@@ -272,6 +274,11 @@ public function isDefault(): bool
 	 */
 	public function isDeletable(): bool
 	{
+		// a single-language object cannot be deleted
+		if ($this->isSingle() === true) {
+			return false;
+		}
+
 		// the default language can only be deleted if it's the last
 		if ($this->isDefault() === true && $this->isLast() === false) {
 			return false;
@@ -288,6 +295,15 @@ public function isLast(): bool
 		return App::instance()->languages()->count() === 1;
 	}
 
+	/**
+	 * Checks if this is the single language object
+	 * @internal
+	 */
+	public function isSingle(): bool
+	{
+		return $this->single;
+	}
+
 	/**
 	 * The id is required for collections
 	 * to work properly. The code is used as id
@@ -446,6 +462,20 @@ protected function siblingsCollection(): Languages
 		return App::instance()->languages();
 	}
 
+	/**
+	 * Create a placeholder language object in a
+	 * single-language installation
+	 */
+	public static function single(): static
+	{
+		return new static([
+			'code'    => 'en',
+			'default' => true,
+			'locale'  => App::instance()->option('locale', 'en_US.utf-8'),
+			'single'  => true
+		]);
+	}
+
 	/**
 	 * Returns the custom slug rules for this language
 	 */
diff --git a/src/Content/ContentStorage.php b/src/Content/ContentStorage.php
index b202cde56b..4dd680e796 100644
--- a/src/Content/ContentStorage.php
+++ b/src/Content/ContentStorage.php
@@ -3,6 +3,7 @@
 namespace Kirby\Content;
 
 use Generator;
+use Kirby\Cms\Language;
 use Kirby\Cms\ModelWithContent;
 use Kirby\Cms\Page;
 use Kirby\Exception\InvalidArgumentException;
@@ -73,9 +74,8 @@ public function all(): Generator
 	public function contentFile(
 		VersionId $versionId,
 		string $lang,
-		bool $force = false
 	): string {
-		$lang = $this->language($lang, $force);
+		$lang = $this->language($lang);
 		return $this->handler->contentFile($versionId, $lang);
 	}
 
@@ -83,11 +83,8 @@ public function contentFile(
 	 * Adapts all versions when converting languages
 	 * @internal
 	 */
-	public function convertLanguage(string $from, string $to): void
+	public function convertLanguage(Language $from, Language $to): void
 	{
-		$from = $this->language($from, true);
-		$to   = $this->language($to, true);
-
 		foreach ($this->dynamicVersions() as $versionId) {
 			$this->handler->move($versionId, $from, $versionId, $to);
 		}
@@ -116,9 +113,8 @@ public function create(
 	public function delete(
 		VersionId $versionId,
 		string|null $lang = null,
-		bool $force = false
 	): void {
-		$lang = $this->language($lang, $force);
+		$lang = $this->language($lang);
 		$this->handler->delete($versionId, $lang);
 	}
 
@@ -128,7 +124,7 @@ public function delete(
 	 */
 	public function deleteLanguage(string|null $lang): void
 	{
-		$lang = $this->language($lang, true);
+		$lang = $this->language($lang);
 
 		foreach ($this->dynamicVersions() as $version) {
 			$this->handler->delete($version, $lang);
@@ -218,7 +214,7 @@ public function touch(
 	 */
 	public function touchLanguage(string|null $lang): void
 	{
-		$lang = $this->language($lang, true);
+		$lang = $this->language($lang);
 
 		foreach ($this->dynamicVersions() as $version) {
 			if ($this->exists($version, $lang) === true) {
@@ -253,41 +249,34 @@ protected function ensureExistingVersion(
 		string $lang
 	): void {
 		if ($this->exists($versionId, $lang) !== true) {
-			throw new NotFoundException('Version "' . $versionId . ' (' . $lang . ')" does not already exist');
+
+			$message = match($this->model->kirby()->multilang()) {
+				true  => 'Version "' . $versionId . ' (' . $lang . ')" does not already exist',
+				false => 'Version "' . $versionId . '" does not already exist',
+			};
+
+			throw new NotFoundException($message);
 		}
 	}
 
 	/**
 	 * Converts a "user-facing" language code to a "raw" language code to be
 	 * used for storage
-	 *
-	 * @param bool $force If set to `true`, the language code is not validated
-	 * @return string Language code
 	 */
 	protected function language(
 		string|null $languageCode = null,
-		bool $force = false
-	): string {
-		// in force mode, use the provided language code even in single-lang for
-		// compatibility with the previous behavior in `$model->contentFile()`
-		if ($force === true) {
-			return $languageCode ?? 'default';
+	): Language {
+		// single language
+		if ($this->model->kirby()->multilang() === false) {
+			return Language::single();
 		}
 
-		// in multi-lang, …
-		if ($this->model->kirby()->multilang() === true) {
-			// look up the actual language object if possible
-			$language = $this->model->kirby()->language($languageCode);
-
-			// validate the language code
-			if ($language === null) {
-				throw new InvalidArgumentException('Invalid language: ' . $languageCode);
-			}
-
-			return $language->code();
+		// look up the actual language object if possible
+		if ($language = $this->model->kirby()->language($languageCode)) {
+			return $language;
 		}
 
-		// otherwise use hardcoded "default" code for single lang
-		return 'default';
+		// validate the language code
+		throw new InvalidArgumentException('Invalid language: ' . $languageCode);
 	}
 }
diff --git a/src/Content/ContentStorageHandler.php b/src/Content/ContentStorageHandler.php
index 43498add43..8b4de4d567 100644
--- a/src/Content/ContentStorageHandler.php
+++ b/src/Content/ContentStorageHandler.php
@@ -2,6 +2,7 @@
 
 namespace Kirby\Content;
 
+use Kirby\Cms\Language;
 use Kirby\Cms\ModelWithContent;
 
 /**
@@ -25,71 +26,57 @@ public function __construct(ModelWithContent $model);
 	/**
 	 * Creates a new version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @param array<string, string> $fields Content fields
 	 */
-	public function create(VersionId $versionId, string $lang, array $fields): void;
+	public function create(VersionId $versionId, Language $language, array $fields): void;
 
 	/**
 	 * Deletes an existing version in an idempotent way if it was already deleted
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function delete(VersionId $versionId, string $lang): void;
+	public function delete(VersionId $versionId, Language $language): void;
 
 	/**
 	 * Checks if a version exists
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function exists(VersionId $versionId, string $lang): bool;
+	public function exists(VersionId $versionId, Language $language): bool;
 
 	/**
 	 * Returns the modification timestamp of a version if it exists
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function modified(VersionId $versionId, string $lang): int|null;
+	public function modified(VersionId $versionId, Language $language): int|null;
 
 	/**
 	 * Moves content from one version-language combination to another
-	 *
-	 * @param string $fromLang Code `'default'` in a single-lang installation
-	 * @param string $toLang Code `'default'` in a single-lang installation
 	 */
 	public function move(
 		VersionId $fromVersionId,
-		string $fromLang,
+		Language $fromLanguage,
 		VersionId $toVersionId,
-		string $toLang
+		Language $toLanguage
 	): void;
 
 	/**
 	 * Returns the stored content fields
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @return array<string, string>
 	 *
 	 * @throws \Kirby\Exception\NotFoundException If the version does not exist
 	 */
-	public function read(VersionId $versionId, string $lang): array;
+	public function read(VersionId $versionId, Language $language): array;
 
 	/**
 	 * Updates the modification timestamp of an existing version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
-	 *
 	 * @throws \Kirby\Exception\NotFoundException If the version does not exist
 	 */
-	public function touch(VersionId $versionId, string $lang): void;
+	public function touch(VersionId $versionId, Language $language): void;
 
 	/**
 	 * Updates the content fields of an existing version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @param array<string, string> $fields Content fields
 	 *
 	 * @throws \Kirby\Exception\NotFoundException If the version does not exist
 	 */
-	public function update(VersionId $versionId, string $lang, array $fields): void;
+	public function update(VersionId $versionId, Language $language, array $fields): void;
 }
diff --git a/src/Content/ContentTranslation.php b/src/Content/ContentTranslation.php
index 49475e17f9..ee3eed2a76 100644
--- a/src/Content/ContentTranslation.php
+++ b/src/Content/ContentTranslation.php
@@ -87,8 +87,7 @@ public function contentFile(): string
 	{
 		return $this->contentFile = $this->parent->storage()->contentFile(
 			VersionId::default($this->parent),
-			$this->code,
-			true
+			$this->code
 		);
 	}
 
diff --git a/src/Content/PlainTextContentStorageHandler.php b/src/Content/PlainTextContentStorageHandler.php
index 432cc9c030..e01410a50e 100644
--- a/src/Content/PlainTextContentStorageHandler.php
+++ b/src/Content/PlainTextContentStorageHandler.php
@@ -3,6 +3,7 @@
 namespace Kirby\Content;
 
 use Kirby\Cms\File;
+use Kirby\Cms\Language;
 use Kirby\Cms\ModelWithContent;
 use Kirby\Cms\Page;
 use Kirby\Cms\Site;
@@ -53,17 +54,15 @@ protected function contentDirectory(VersionId $versionId): string
 	/**
 	 * Returns the absolute path to the content file
 	 * @internal To be made `protected` when the CMS core no longer relies on it
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function contentFile(VersionId $versionId, string $lang): string
+	public function contentFile(VersionId $versionId, Language $language): string
 	{
 		// get the filename without extension and language code
 		return match (true) {
-			$this->model instanceof File => $this->contentFileForFile($this->model, $versionId, $lang),
-			$this->model instanceof Page => $this->contentFileForPage($this->model, $versionId, $lang),
-			$this->model instanceof Site => $this->contentFileForSite($this->model, $versionId, $lang),
-			$this->model instanceof User => $this->contentFileForUser($this->model, $versionId, $lang),
+			$this->model instanceof File => $this->contentFileForFile($this->model, $versionId, $language),
+			$this->model instanceof Page => $this->contentFileForPage($this->model, $versionId, $language),
+			$this->model instanceof Site => $this->contentFileForSite($this->model, $versionId, $language),
+			$this->model instanceof User => $this->contentFileForUser($this->model, $versionId, $language),
 			// @codeCoverageIgnoreStart
 			default => throw new LogicException('Cannot determine content file for model type "' . $this->model::CLASS_ALIAS . '"')
 			// @codeCoverageIgnoreEnd
@@ -72,20 +71,16 @@ public function contentFile(VersionId $versionId, string $lang): string
 
 	/**
 	 * Returns the absolute path to the content file of a file model
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	protected function contentFileForFile(File $model, VersionId $versionId, string $lang): string
+	protected function contentFileForFile(File $model, VersionId $versionId, Language $language): string
 	{
-		return $this->contentDirectory($versionId) . '/' . $this->contentFilename($model->filename(), $lang);
+		return $this->contentDirectory($versionId) . '/' . $this->contentFilename($model->filename(), $language);
 	}
 
 	/**
 	 * Returns the absolute path to the content file of a page model
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	protected function contentFileForPage(Page $model, VersionId $versionId, string $lang): string
+	protected function contentFileForPage(Page $model, VersionId $versionId, Language $language): string
 	{
 		$directory = $this->contentDirectory($versionId);
 
@@ -99,42 +94,36 @@ protected function contentFileForPage(Page $model, VersionId $versionId, string
 			$directory = $this->model->root();
 		}
 
-		return $directory . '/' . $this->contentFilename($model->intendedTemplate()->name(), $lang);
+		return $directory . '/' . $this->contentFilename($model->intendedTemplate()->name(), $language);
 	}
 
 	/**
 	 * Returns the absolute path to the content file of a site model
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	protected function contentFileForSite(Site $model, VersionId $versionId, string $lang): string
+	protected function contentFileForSite(Site $model, VersionId $versionId, Language $language): string
 	{
-		return $this->contentDirectory($versionId) . '/' . $this->contentFilename('site', $lang);
+		return $this->contentDirectory($versionId) . '/' . $this->contentFilename('site', $language);
 	}
 
 	/**
 	 * Returns the absolute path to the content file of a user model
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	protected function contentFileForUser(User $model, VersionId $versionId, string $lang): string
+	protected function contentFileForUser(User $model, VersionId $versionId, Language $language): string
 	{
-		return $this->contentDirectory($versionId) . '/' . $this->contentFilename('user', $lang);
+		return $this->contentDirectory($versionId) . '/' . $this->contentFilename('user', $language);
 	}
 
 	/**
 	 * Creates a filename with extension and optional language code
 	 * in a multi-language installation
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	protected function contentFilename(string $name, string $lang): string
+	protected function contentFilename(string $name, Language $language): string
 	{
 		$kirby     = $this->model->kirby();
 		$extension = $kirby->contentExtension();
 
-		if ($lang !== 'default') {
-			return $name . '.' . $lang . '.' . $extension;
+		if ($language->isSingle() === false) {
+			return $name . '.' . $language->code() . '.' . $extension;
 		}
 
 		return $name . '.' . $extension;
@@ -148,36 +137,33 @@ public function contentFiles(VersionId $versionId): array
 	{
 		if ($this->model->kirby()->multilang() === true) {
 			return $this->model->kirby()->languages()->values(
-				fn ($lang) => $this->contentFile($versionId, $lang)
+				fn ($language) => $this->contentFile($versionId, $language)
 			);
 		}
 
 		return [
-			$this->contentFile($versionId, 'default')
+			$this->contentFile($versionId, Language::single())
 		];
 	}
 
 	/**
 	 * Creates a new version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @param array<string, string> $fields Content fields
 	 *
 	 * @throws \Kirby\Exception\Exception If the file cannot be written
 	 */
-	public function create(VersionId $versionId, string $lang, array $fields): void
+	public function create(VersionId $versionId, Language $language, array $fields): void
 	{
-		$this->write($versionId, $lang, $fields);
+		$this->write($versionId, $language, $fields);
 	}
 
 	/**
 	 * Deletes an existing version in an idempotent way if it was already deleted
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function delete(VersionId $versionId, string $lang): void
+	public function delete(VersionId $versionId, Language $language): void
 	{
-		$contentFile = $this->contentFile($versionId, $lang);
+		$contentFile = $this->contentFile($versionId, $language);
 		$success = F::unlink($contentFile);
 
 		// @codeCoverageIgnoreStart
@@ -204,23 +190,19 @@ public function delete(VersionId $versionId, string $lang): void
 
 	/**
 	 * Checks if a version exists
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function exists(VersionId $versionId, string $lang): bool
+	public function exists(VersionId $versionId, Language $language): bool
 	{
-		return is_file($this->contentFile($versionId, $lang)) === true;
+		return is_file($this->contentFile($versionId, $language)) === true;
 	}
 
 	/**
 	 * Returns the modification timestamp of a version
 	 * if it exists
-	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 */
-	public function modified(VersionId $versionId, string $lang): int|null
+	public function modified(VersionId $versionId, Language $language): int|null
 	{
-		$modified = F::modified($this->contentFile($versionId, $lang));
+		$modified = F::modified($this->contentFile($versionId, $language));
 
 		if (is_int($modified) === true) {
 			return $modified;
@@ -231,43 +213,37 @@ public function modified(VersionId $versionId, string $lang): int|null
 
 	/**
 	 * Moves content from one version-language combination to another
-	 *
-	 * @param string $fromLang Code `'default'` in a single-lang installation
-	 * @param string $toLang Code `'default'` in a single-lang installation
 	 */
 	public function move(
 		VersionId $fromVersionId,
-		string $fromLang,
+		Language $fromLanguage,
 		VersionId $toVersionId,
-		string $toLang
+		Language $toLanguage
 	): void {
 		F::move(
-			$this->contentFile($fromVersionId, $fromLang),
-			$this->contentFile($toVersionId, $toLang)
+			$this->contentFile($fromVersionId, $fromLanguage),
+			$this->contentFile($toVersionId, $toLanguage)
 		);
 	}
 
 	/**
 	 * Returns the stored content fields
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @return array<string, string>
 	 */
-	public function read(VersionId $versionId, string $lang): array
+	public function read(VersionId $versionId, Language $language): array
 	{
-		return Data::read($this->contentFile($versionId, $lang));
+		return Data::read($this->contentFile($versionId, $language));
 	}
 
 	/**
 	 * Updates the modification timestamp of an existing version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
-	 *
 	 * @throws \Kirby\Exception\Exception If the file cannot be touched
 	 */
-	public function touch(VersionId $versionId, string $lang): void
+	public function touch(VersionId $versionId, Language $language): void
 	{
-		$success = touch($this->contentFile($versionId, $lang));
+		$success = touch($this->contentFile($versionId, $language));
 
 		// @codeCoverageIgnoreStart
 		if ($success !== true) {
@@ -279,27 +255,25 @@ public function touch(VersionId $versionId, string $lang): void
 	/**
 	 * Updates the content fields of an existing version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @param array<string, string> $fields Content fields
 	 *
 	 * @throws \Kirby\Exception\Exception If the file cannot be written
 	 */
-	public function update(VersionId $versionId, string $lang, array $fields): void
+	public function update(VersionId $versionId, Language $language, array $fields): void
 	{
-		$this->write($versionId, $lang, $fields);
+		$this->write($versionId, $language, $fields);
 	}
 
 	/**
 	 * Writes the content fields of an existing version
 	 *
-	 * @param string $lang Code `'default'` in a single-lang installation
 	 * @param array<string, string> $fields Content fields
 	 *
 	 * @throws \Kirby\Exception\Exception If the content cannot be written
 	 */
-	protected function write(VersionId $versionId, string $lang, array $fields): void
+	protected function write(VersionId $versionId, Language $language, array $fields): void
 	{
-		$success = Data::write($this->contentFile($versionId, $lang), $fields);
+		$success = Data::write($this->contentFile($versionId, $language), $fields);
 
 		// @codeCoverageIgnoreStart
 		if ($success !== true) {
diff --git a/tests/Cms/Languages/LanguageConversionTest.php b/tests/Cms/Languages/LanguageConversionTest.php
new file mode 100644
index 0000000000..1fbbea7534
--- /dev/null
+++ b/tests/Cms/Languages/LanguageConversionTest.php
@@ -0,0 +1,131 @@
+<?php
+
+namespace Kirby\Cms;
+
+use Kirby\Data\Data;
+
+/**
+ * @coversDefaultClass \Kirby\Cms\Language
+ */
+class LanguageConversionTest extends TestCase
+{
+	public const TMP = KIRBY_TMP_DIR . '/Cms.LanguageConversion';
+
+	protected $app;
+
+	public function setUp(): void
+	{
+		Dir::make(static::TMP);
+	}
+
+	public function tearDown(): void
+	{
+		Dir::remove(static::TMP);
+	}
+
+	public function testConvertFromSingleLanguageToMultiLanguage(): void
+	{
+		$app = new App([
+			'roots' => [
+				'index' => static::TMP
+			],
+		]);
+
+		// create the page model
+		Data::write($app->root('content') . '/test/test.txt', [
+			'title' => 'Title'
+		]);
+
+		$this->assertCount(0, $app->languages());
+		$this->assertFalse($app->multilang());
+
+		// get the page model
+		$page = $app->page('test');
+
+		// and check if the content is loadable
+		$this->assertSame('Title', $page->content()->title()->value());
+
+		// create a new Language to switch to multi-language mode
+		Language::create([
+			'code' => 'en',
+		]);
+
+		// make sure that Kirby actually switched to multi-language mode
+		$this->assertCount(1, $app->languages());
+		$this->assertTrue($app->multilang());
+
+		// the content file should now have been moved to .en
+		$this->assertFileExists($page->root() . '/test.en.txt');
+		$this->assertFileDoesNotExist($page->root() . '/test.txt');
+
+		// the content should still be loadable for the page
+		$this->assertSame('Title', $page->content()->title()->value());
+		$this->assertSame('Title', $page->content('en')->title()->value());
+
+		$this->assertSame('Title', Data::read($page->root() . '/test.en.txt')['title']);
+	}
+
+	public function testConvertFromMultiLanguageToSingleLanguage(): void
+	{
+		$app = new App([
+			'roots' => [
+				'index' => static::TMP
+			],
+		]);
+
+		// create two languages
+		Data::write($app->root('languages') . '/en.php', [
+			'code'    => 'en',
+			'default' => true
+		]);
+
+		Data::write($app->root('languages') . '/de.php', [
+			'code' => 'de',
+		]);
+
+		// create some models
+		Data::write($app->root('content') . '/test/test.en.txt', [
+			'title' => 'English Title'
+		]);
+
+		Data::write($app->root('content') . '/test/test.de.txt', [
+			'title' => 'German Title'
+		]);
+
+		$this->assertCount(2, $app->languages());
+		$this->assertTrue($app->multilang());
+
+		// get the page model
+		$page = $app->page('test');
+
+		$this->assertSame('English Title', $page->content('en')->title()->value());
+		$this->assertSame('German Title', $page->content('de')->title()->value());
+
+		// delete the first language to check file removal.
+		$app->language('de')->delete();
+
+		// the .de file should now be gone
+		$this->assertFileDoesNotExist($page->root() . '/test.de.txt');
+
+		// the .en file should still be there
+		$this->assertFileExists($page->root() . '/test.en.txt');
+
+		// delete the last language to switch to single-language mode
+		$app->language('en')->delete();
+
+		// the .en file should now be gone
+		$this->assertFileDoesNotExist($page->root() . '/test.en.txt');
+
+		// … and should be replaced by the content file without language code
+		$this->assertFileExists($page->root() . '/test.txt');
+
+		// meanwhile, Kirby should have been switched to single language mode
+		$this->assertCount(0, $app->languages());
+		$this->assertFalse($app->multilang());
+
+		// the page should still load the english content
+		$this->assertSame('English Title', $page->content()->title()->value());
+		$this->assertSame('English Title', Data::read($page->root() . '/test.txt')['title']);
+	}
+
+}
diff --git a/tests/Cms/Languages/LanguageTest.php b/tests/Cms/Languages/LanguageTest.php
index 75d800c110..a71d326258 100644
--- a/tests/Cms/Languages/LanguageTest.php
+++ b/tests/Cms/Languages/LanguageTest.php
@@ -280,6 +280,27 @@ public function testIsDefault()
 		$this->assertFalse($language->isDefault());
 	}
 
+	/**
+	 * @covers ::isSingle
+	 */
+	public function testIsSingle()
+	{
+		// default
+		$language = new Language([
+			'code' => 'en'
+		]);
+
+		$this->assertFalse($language->isSingle());
+
+		// true
+		$language = new Language([
+			'code'   => 'en',
+			'single' => true
+		]);
+
+		$this->assertTrue($language->isSingle());
+	}
+
 	/**
 	 * @covers ::locale
 	 */
@@ -565,6 +586,17 @@ public function testSave()
 		$this->assertSame('test', $data['custom']);
 	}
 
+	/**
+	 * @covers ::single
+	 */
+	public function testSingle()
+	{
+		$language = Language::single();
+
+		$this->assertSame('en', $language->code());
+		$this->assertSame('en', $language->name());
+	}
+
 	/**
 	 * @covers ::toArray
 	 * @covers ::__debugInfo
diff --git a/tests/Content/ContentStorageTest.php b/tests/Content/ContentStorageTest.php
index 086c0a3ec0..c6a1b9e2af 100644
--- a/tests/Content/ContentStorageTest.php
+++ b/tests/Content/ContentStorageTest.php
@@ -77,9 +77,9 @@ public function testCreateChangesSingleLang()
 	public function testReadDoesNotExist()
 	{
 		$this->expectException(NotFoundException::class);
-		$this->expectExceptionMessage('Version "published (default)" does not already exist');
+		$this->expectExceptionMessage('Version "published" does not already exist');
 
-		$this->storage->read(VersionId::published(), 'default');
+		$this->storage->read(VersionId::published());
 	}
 
 	/**
@@ -89,9 +89,9 @@ public function testReadDoesNotExist()
 	public function testTouchDoesNotExist()
 	{
 		$this->expectException(NotFoundException::class);
-		$this->expectExceptionMessage('Version "published (default)" does not already exist');
+		$this->expectExceptionMessage('Version "published" does not already exist');
 
-		$this->storage->touch(VersionId::published(), 'default');
+		$this->storage->touch(VersionId::published());
 	}
 
 	/**
@@ -101,7 +101,7 @@ public function testTouchDoesNotExist()
 	public function testUpdateDoesNotExist()
 	{
 		$this->expectException(NotFoundException::class);
-		$this->expectExceptionMessage('Version "published (default)" does not already exist');
+		$this->expectExceptionMessage('Version "published" does not already exist');
 
 		$fields = [
 			'title' => 'Foo',
@@ -113,9 +113,8 @@ public function testUpdateDoesNotExist()
 
 	/**
 	 * @covers ::language
-	 * @dataProvider languageProvider
 	 */
-	public function testLanguageMultiLang(string|null $languageCode, bool $force, array $expectedCodes)
+	public function testLanguageMultiLang()
 	{
 		$app = new App([
 			'languages' => [
@@ -129,8 +128,17 @@ public function testLanguageMultiLang(string|null $languageCode, bool $force, ar
 			]
 		]);
 
-		$language = $this->language($this->storage, $languageCode, $force);
-		$this->assertSame($expectedCodes[0], $language);
+		$language = $this->language($this->storage, 'en');
+		$this->assertSame('en', $language->code());
+
+		$language = $this->language($this->storage, 'de');
+		$this->assertSame('de', $language->code());
+
+		$language = $this->language($this->storage, 'default');
+		$this->assertSame('en', $language->code());
+
+		$language = $this->language($this->storage);
+		$this->assertSame('en', $language->code());
 	}
 
 	/**
@@ -158,12 +166,14 @@ public function testLanguageMultiLangInvalid()
 
 	/**
 	 * @covers ::language
-	 * @dataProvider languageProvider
 	 */
-	public function testLanguageSingleLang(string|null $languageCode, bool $force, array $expectedCodes)
+	public function testLanguageSingleLang()
 	{
-		$language = $this->language($this->storage, $languageCode, $force);
-		$this->assertSame($expectedCodes[1], $language);
+		$language = $this->language($this->storage, 'en');
+		$this->assertSame('en', $language->code());
+
+		$language = $this->language($this->storage, 'de');
+		$this->assertSame('en', $language->code());
 	}
 
 	/**
@@ -172,7 +182,7 @@ public function testLanguageSingleLang(string|null $languageCode, bool $force, a
 	public function testLanguageSingleLangInvalid()
 	{
 		$language = $this->language($this->storage, 'fr', false);
-		$this->assertSame('default', $language);
+		$this->assertSame('en', $language->code());
 	}
 
 	public static function languageProvider(): array
diff --git a/tests/Content/ContentTranslationTest.php b/tests/Content/ContentTranslationTest.php
index 9419347450..6e0dbc8af3 100644
--- a/tests/Content/ContentTranslationTest.php
+++ b/tests/Content/ContentTranslationTest.php
@@ -109,9 +109,18 @@ public function testContentMerged()
 	public function testContentFile()
 	{
 		$app = new App([
+			'languages' => [
+				[
+					'code'    => 'en',
+					'default' => true
+				],
+				[
+					'code' => 'de'
+				]
+			],
 			'roots' => [
 				'content' => '/content',
-			]
+			],
 		]);
 
 		$page = new Page([
diff --git a/tests/Content/PlainTextContentStorageHandlerTest.php b/tests/Content/PlainTextContentStorageHandlerTest.php
index a2b52747a9..3fc4aff8c7 100644
--- a/tests/Content/PlainTextContentStorageHandlerTest.php
+++ b/tests/Content/PlainTextContentStorageHandlerTest.php
@@ -4,6 +4,7 @@
 
 use Kirby\Cms\App;
 use Kirby\Cms\File;
+use Kirby\Cms\Language;
 use Kirby\Cms\Page;
 use Kirby\Cms\User;
 use Kirby\Data\Data;
@@ -19,21 +20,66 @@ class PlainTextContentStorageHandlerTest extends TestCase
 {
 	public const TMP = KIRBY_TMP_DIR . '/Content.PlainTextContentStorage';
 
+	protected $app;
 	protected $model;
 	protected $storage;
 
 	public function setUp(): void
 	{
 		Dir::make(static::TMP);
+	}
 
-		$this->model = new Page([
-			'kirby'    => new App(),
-			'root'     => static::TMP,
-			'slug'     => 'a-page',
-			'template' => 'article'
+	public function setUpMultiLanguage(): void
+	{
+		$this->app = new App([
+			'languages' => [
+				[
+					'code'    => 'en',
+					'default' => true
+				],
+				[
+					'code' => 'de'
+				]
+			],
+			'roots' => [
+				'index' => static::TMP
+			],
+			'site' => [
+				'children' => [
+					[
+						'slug'     => 'a-page',
+						'template' => 'article',
+					]
+				]
+			]
 		]);
 
+		$this->model   = $this->app->page('a-page');
 		$this->storage = new PlainTextContentStorageHandler($this->model);
+
+		Dir::make($this->model->root());
+	}
+
+	public function setUpSingleLanguage(): void
+	{
+		$this->app = new App([
+			'roots' => [
+				'index' => static::TMP
+			],
+			'site' => [
+				'children' => [
+					[
+						'slug'     => 'a-page',
+						'template' => 'article'
+					]
+				]
+			]
+		]);
+
+		$this->model   = $this->app->page('a-page');
+		$this->storage = new PlainTextContentStorageHandler($this->model);
+
+		Dir::make($this->model->root());
 	}
 
 	public function tearDown(): void
@@ -47,13 +93,15 @@ public function tearDown(): void
 	 */
 	public function testCreateChangesMultiLang()
 	{
+		$this->setUpMultiLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		$this->storage->create(VersionId::changes(), 'en', $fields);
-		$this->assertSame($fields, Data::read(static::TMP . '/_changes/article.en.txt'));
+		$this->storage->create(VersionId::changes(), $this->app->language('en'), $fields);
+		$this->assertSame($fields, Data::read($this->model->root() . '/_changes/article.en.txt'));
 	}
 
 	/**
@@ -61,13 +109,15 @@ public function testCreateChangesMultiLang()
 	 */
 	public function testCreateChangesSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		$this->storage->create(VersionId::changes(), 'default', $fields);
-		$this->assertSame($fields, Data::read(static::TMP . '/_changes/article.txt'));
+		$this->storage->create(VersionId::changes(), Language::single(), $fields);
+		$this->assertSame($fields, Data::read($this->model->root() . '/_changes/article.txt'));
 	}
 
 	/**
@@ -75,13 +125,15 @@ public function testCreateChangesSingleLang()
 	 */
 	public function testCreatePublishedMultiLang()
 	{
+		$this->setUpMultiLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		$this->storage->create(VersionId::published(), 'en', $fields);
-		$this->assertSame($fields, Data::read(static::TMP . '/article.en.txt'));
+		$this->storage->create(VersionId::published(), $this->app->language('en'), $fields);
+		$this->assertSame($fields, Data::read($this->model->root() . '/article.en.txt'));
 	}
 
 	/**
@@ -89,13 +141,15 @@ public function testCreatePublishedMultiLang()
 	 */
 	public function testCreatePublishedSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		$this->storage->create(VersionId::published(), 'default', $fields);
-		$this->assertSame($fields, Data::read(static::TMP . '/article.txt'));
+		$this->storage->create(VersionId::published(), Language::single(), $fields);
+		$this->assertSame($fields, Data::read($this->model->root() . '/article.txt'));
 	}
 
 	/**
@@ -103,9 +157,11 @@ public function testCreatePublishedSingleLang()
 	 */
 	public function testDeleteNonExisting()
 	{
+		$this->setUpSingleLanguage();
+
 		// test idempotency
-		$this->storage->delete(VersionId::published(), 'default');
-		$this->assertDirectoryDoesNotExist(static::TMP);
+		$this->storage->delete(VersionId::published(), Language::single());
+		$this->assertDirectoryDoesNotExist($this->model->root());
 	}
 
 	/**
@@ -113,14 +169,16 @@ public function testDeleteNonExisting()
 	 */
 	public function testDeleteChangesMultiLang()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/article.en.txt');
-		touch(static::TMP . '/_changes/article.en.txt');
+		$this->setUpMultiLanguage();
+
+		Dir::make($this->model->root() . '/_changes');
+		touch($this->model->root() . '/article.en.txt');
+		touch($this->model->root() . '/_changes/article.en.txt');
 
-		$this->storage->delete(VersionId::changes(), 'en');
-		$this->assertFileDoesNotExist(static::TMP . '/_changes/article.en.txt');
-		$this->assertDirectoryDoesNotExist(static::TMP . '/_changes');
-		$this->assertDirectoryExists(static::TMP);
+		$this->storage->delete(VersionId::changes(), $this->app->language('en'));
+		$this->assertFileDoesNotExist($this->model->root() . '/_changes/article.en.txt');
+		$this->assertDirectoryDoesNotExist($this->model->root() . '/_changes');
+		$this->assertDirectoryExists($this->model->root());
 	}
 
 	/**
@@ -128,13 +186,15 @@ public function testDeleteChangesMultiLang()
 	 */
 	public function testDeleteChangesSingleLang()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/article.txt');
-		touch(static::TMP . '/_changes/article.txt');
+		$this->setUpSingleLanguage();
+
+		Dir::make($this->model->root() . '/_changes');
+		touch($this->model->root() . '/article.txt');
+		touch($this->model->root() . '/_changes/article.txt');
 
-		$this->storage->delete(VersionId::changes(), 'default');
-		$this->assertFileDoesNotExist(static::TMP . '/_changes/article.txt');
-		$this->assertDirectoryDoesNotExist(static::TMP . '/_changes');
+		$this->storage->delete(VersionId::changes(), Language::single());
+		$this->assertFileDoesNotExist($this->model->root() . '/_changes/article.txt');
+		$this->assertDirectoryDoesNotExist($this->model->root() . '/_changes');
 	}
 
 	/**
@@ -142,13 +202,15 @@ public function testDeleteChangesSingleLang()
 	 */
 	public function testDeletePublishedMultiLang()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/article.en.txt');
-		touch(static::TMP . '/_changes/article.en.txt');
+		$this->setUpMultiLanguage();
+
+		Dir::make($this->model->root() . '/_changes');
+		touch($this->model->root() . '/_changes/article.en.txt');
+		touch($this->model->root() . '/article.en.txt');
 
-		$this->storage->delete(VersionId::published(), 'en');
-		$this->assertFileDoesNotExist(static::TMP . '/article.en.txt');
-		$this->assertDirectoryExists(static::TMP);
+		$this->storage->delete(VersionId::published(), $this->app->language('en'));
+		$this->assertFileDoesNotExist($this->model->root() . '/article.en.txt');
+		$this->assertDirectoryExists($this->model->root());
 	}
 
 	/**
@@ -156,64 +218,86 @@ public function testDeletePublishedMultiLang()
 	 */
 	public function testDeletePublishedSingleLang()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/article.txt');
-		touch(static::TMP . '/_changes/article.txt');
+		$this->setUpSingleLanguage();
 
-		$this->storage->delete(VersionId::published(), 'default');
-		$this->assertFileDoesNotExist(static::TMP . '/article.txt');
-		$this->assertDirectoryExists(static::TMP);
+		Dir::make($this->model->root() . '/_changes');
+		touch($this->model->root() . '/_changes/article.txt');
+		touch($this->model->root() . '/article.txt');
+
+		$this->storage->delete(VersionId::published(), Language::single());
+		$this->assertFileDoesNotExist($this->model->root() . '/article.txt');
+		$this->assertDirectoryExists($this->model->root());
 	}
 
 	/**
 	 * @covers ::exists
-	 * @dataProvider existsProvider
 	 */
-	public function testExistsNoneExisting(VersionId $id, string $language)
+	public function testExistsNoneExistingMultiLanguage()
 	{
-		$this->assertFalse($this->storage->exists($id, $language));
+		$this->setUpMultiLanguage();
+
+		$this->assertFalse($this->storage->exists(VersionId::changes(), $this->app->language('en')));
+		$this->assertFalse($this->storage->exists(VersionId::changes(), $this->app->language('de')));
 	}
 
-	public static function existsProvider(): array
+	/**
+	 * @covers ::exists
+	 */
+	public function testExistsNoneExistingSingleLanguage()
 	{
-		return [
-			[VersionId::changes(), 'default', [false, false]],
-			[VersionId::changes(), 'en', [true, true]],
-			[VersionId::published(), 'default', [true, true]],
-			[VersionId::published(), 'en', [false, false]]
-		];
+		$this->setUpSingleLanguage();
+
+		$this->assertFalse($this->storage->exists(VersionId::changes(), Language::single()));
 	}
 
 	/**
 	 * @covers ::modified
-	 * @dataProvider modifiedProvider
 	 */
-	public function testModifiedNoneExisting(VersionId $id, string $language)
+	public function testModifiedNoneExistingMultiLanguage()
 	{
-		$this->assertNull($this->storage->modified($id, $language));
+		$this->setUpMultiLanguage();
+
+		$this->assertNull($this->storage->modified(VersionId::changes(), $this->app->language('en')));
+		$this->assertNull($this->storage->modified(VersionId::published(), $this->app->language('en')));
 	}
 
 	/**
 	 * @covers ::modified
-	 * @dataProvider modifiedProvider
 	 */
-	public function testModifiedSomeExisting(VersionId $id, string $language, int|null $expected)
+	public function testModifiedNoneExistingSingleLanguage()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/article.txt', 1234567890);
-		touch(static::TMP . '/_changes/article.en.txt', 1234567890);
+		$this->setUpSingleLanguage();
 
-		$this->assertSame($expected, $this->storage->modified($id, $language));
+		$this->assertNull($this->storage->modified(VersionId::changes(), Language::single()));
+		$this->assertNull($this->storage->modified(VersionId::published(), Language::single()));
 	}
 
-	public static function modifiedProvider(): array
+	/**
+	 * @covers ::modified
+	 */
+	public function testModifiedSomeExistingMultiLanguage()
 	{
-		return [
-			[VersionId::changes(), 'default', null],
-			[VersionId::changes(), 'en', 1234567890],
-			[VersionId::published(), 'default', 1234567890],
-			[VersionId::published(), 'en', null]
-		];
+		$this->setUpMultiLanguage();
+
+		Dir::make($this->model->root() . '/_changes');
+		touch($this->model->root() . '/_changes/article.en.txt', $modified = 1234567890);
+
+		$this->assertSame($modified, $this->storage->modified(VersionId::changes(), $this->app->language('en')));
+		$this->assertNull($this->storage->modified(VersionId::published(), $this->app->language('en')));
+	}
+
+	/**
+	 * @covers ::modified
+	 */
+	public function testModifiedSomeExistingSingleLanguage()
+	{
+		$this->setUpSingleLanguage();
+
+		Dir::make(static::TMP . '/content/a-page/_changes');
+		touch(static::TMP . '/content/a-page/_changes/article.txt', $modified = 1234567890);
+
+		$this->assertSame($modified, $this->storage->modified(VersionId::changes(), Language::single()));
+		$this->assertNull($this->storage->modified(VersionId::published(), Language::single()));
 	}
 
 	/**
@@ -221,15 +305,17 @@ public static function modifiedProvider(): array
 	 */
 	public function testReadChangesMultiLang()
 	{
+		$this->setUpMultiLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		Dir::make(static::TMP . '/_changes');
-		Data::write(static::TMP . '/_changes/article.en.txt', $fields);
+		Dir::make($this->model->root() . '/_changes');
+		Data::write($this->model->root() . '/_changes/article.en.txt', $fields);
 
-		$this->assertSame($fields, $this->storage->read(VersionId::changes(), 'en'));
+		$this->assertSame($fields, $this->storage->read(VersionId::changes(), $this->app->language('en')));
 	}
 
 	/**
@@ -237,15 +323,17 @@ public function testReadChangesMultiLang()
 	 */
 	public function testReadChangesSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		Dir::make(static::TMP . '/_changes');
-		Data::write(static::TMP . '/_changes/article.txt', $fields);
+		Dir::make($this->model->root() . '/_changes');
+		Data::write($this->model->root() . '/_changes/article.txt', $fields);
 
-		$this->assertSame($fields, $this->storage->read(VersionId::changes(), 'default'));
+		$this->assertSame($fields, $this->storage->read(VersionId::changes(), Language::single()));
 	}
 
 	/**
@@ -253,14 +341,16 @@ public function testReadChangesSingleLang()
 	 */
 	public function testReadPublishedMultiLang()
 	{
+		$this->setUpMultiLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		Data::write(static::TMP . '/article.en.txt', $fields);
+		Data::write($this->model->root() . '/article.en.txt', $fields);
 
-		$this->assertSame($fields, $this->storage->read(VersionId::published(), 'en'));
+		$this->assertSame($fields, $this->storage->read(VersionId::published(), $this->app->language('en')));
 	}
 
 	/**
@@ -268,14 +358,16 @@ public function testReadPublishedMultiLang()
 	 */
 	public function testReadPublishedSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
 		];
 
-		Data::write(static::TMP . '/article.txt', $fields);
+		Data::write($this->model->root() . '/article.txt', $fields);
 
-		$this->assertSame($fields, $this->storage->read(VersionId::published(), 'default'));
+		$this->assertSame($fields, $this->storage->read(VersionId::published(), Language::single()));
 	}
 
 	/**
@@ -283,16 +375,20 @@ public function testReadPublishedSingleLang()
 	 */
 	public function testTouchChangesMultiLang()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/_changes/article.en.txt', 123456);
-		$this->assertSame(123456, filemtime(static::TMP . '/_changes/article.en.txt'));
+		$this->setUpMultiLanguage();
+
+		$root = $this->model->root() . '/_changes';
+
+		Dir::make($root);
+		touch($root . '/article.en.txt', 123456);
+		$this->assertSame(123456, filemtime($root . '/article.en.txt'));
 
 		$minTime = time();
 
-		$this->storage->touch(VersionId::changes(), 'en');
+		$this->storage->touch(VersionId::changes(), $this->app->language('en'));
 
 		clearstatcache();
-		$this->assertGreaterThanOrEqual($minTime, filemtime(static::TMP . '/_changes/article.en.txt'));
+		$this->assertGreaterThanOrEqual($minTime, filemtime($root . '/article.en.txt'));
 	}
 
 	/**
@@ -300,16 +396,20 @@ public function testTouchChangesMultiLang()
 	 */
 	public function testTouchChangesSingleLang()
 	{
-		Dir::make(static::TMP . '/_changes');
-		touch(static::TMP . '/_changes/article.txt', 123456);
-		$this->assertSame(123456, filemtime(static::TMP . '/_changes/article.txt'));
+		$this->setUpSingleLanguage();
+
+		$root = $this->model->root() . '/_changes';
+
+		Dir::make($root);
+		touch($root . '/article.txt', 123456);
+		$this->assertSame(123456, filemtime($root . '/article.txt'));
 
 		$minTime = time();
 
-		$this->storage->touch(VersionId::changes(), 'default');
+		$this->storage->touch(VersionId::changes(), Language::single());
 
 		clearstatcache();
-		$this->assertGreaterThanOrEqual($minTime, filemtime(static::TMP . '/_changes/article.txt'));
+		$this->assertGreaterThanOrEqual($minTime, filemtime($root . '/article.txt'));
 	}
 
 	/**
@@ -317,15 +417,19 @@ public function testTouchChangesSingleLang()
 	 */
 	public function testTouchPublishedMultiLang()
 	{
-		touch(static::TMP . '/article.en.txt', 123456);
-		$this->assertSame(123456, filemtime(static::TMP . '/article.en.txt'));
+		$this->setUpMultiLanguage();
+
+		$root = $this->model->root() . '/article.en.txt';
+
+		touch($root, 123456);
+		$this->assertSame(123456, filemtime($root));
 
 		$minTime = time();
 
-		$this->storage->touch(VersionId::published(), 'en');
+		$this->storage->touch(VersionId::published(), $this->app->language('en'));
 
 		clearstatcache();
-		$this->assertGreaterThanOrEqual($minTime, filemtime(static::TMP . '/article.en.txt'));
+		$this->assertGreaterThanOrEqual($minTime, filemtime($root));
 	}
 
 	/**
@@ -333,15 +437,19 @@ public function testTouchPublishedMultiLang()
 	 */
 	public function testTouchPublishedSingleLang()
 	{
-		touch(static::TMP . '/article.txt', 123456);
-		$this->assertSame(123456, filemtime(static::TMP . '/article.txt'));
+		$this->setUpSingleLanguage();
+
+		$root = $this->model->root() . '/article.txt';
+
+		touch($root, 123456);
+		$this->assertSame(123456, filemtime($root));
 
 		$minTime = time();
 
-		$this->storage->touch(VersionId::published(), 'default');
+		$this->storage->touch(VersionId::published(), Language::single());
 
 		clearstatcache();
-		$this->assertGreaterThanOrEqual($minTime, filemtime(static::TMP . '/article.txt'));
+		$this->assertGreaterThanOrEqual($minTime, filemtime($root));
 	}
 
 	/**
@@ -349,6 +457,8 @@ public function testTouchPublishedSingleLang()
 	 */
 	public function testUpdateChangesMultiLang()
 	{
+		$this->setUpMultiLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
@@ -357,7 +467,7 @@ public function testUpdateChangesMultiLang()
 		Dir::make(static::TMP . '/_changes');
 		Data::write(static::TMP . '/_changes/article.en.txt', $fields);
 
-		$this->storage->update(VersionId::changes(), 'en', $fields);
+		$this->storage->update(VersionId::changes(), $this->app->language('en'), $fields);
 		$this->assertSame($fields, Data::read(static::TMP . '/_changes/article.en.txt'));
 	}
 
@@ -366,6 +476,8 @@ public function testUpdateChangesMultiLang()
 	 */
 	public function testUpdateChangesSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
@@ -374,7 +486,7 @@ public function testUpdateChangesSingleLang()
 		Dir::make(static::TMP . '/_changes');
 		Data::write(static::TMP . '/_changes/article.txt', $fields);
 
-		$this->storage->update(VersionId::changes(), 'default', $fields);
+		$this->storage->update(VersionId::changes(), Language::single(), $fields);
 		$this->assertSame($fields, Data::read(static::TMP . '/_changes/article.txt'));
 	}
 
@@ -383,6 +495,8 @@ public function testUpdateChangesSingleLang()
 	 */
 	public function testUpdatePublishedMultiLang()
 	{
+		$this->setUpMultiLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
@@ -390,7 +504,7 @@ public function testUpdatePublishedMultiLang()
 
 		Data::write(static::TMP . '/article.en.txt', $fields);
 
-		$this->storage->update(VersionId::published(), 'en', $fields);
+		$this->storage->update(VersionId::published(), $this->app->language('en'), $fields);
 		$this->assertSame($fields, Data::read(static::TMP . '/article.en.txt'));
 	}
 
@@ -399,6 +513,8 @@ public function testUpdatePublishedMultiLang()
 	 */
 	public function testUpdatePublishedSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$fields = [
 			'title' => 'Foo',
 			'text'  => 'Bar'
@@ -406,23 +522,19 @@ public function testUpdatePublishedSingleLang()
 
 		Data::write(static::TMP . '/article.txt', $fields);
 
-		$this->storage->update(VersionId::published(), 'default', $fields);
+		$this->storage->update(VersionId::published(), Language::single(), $fields);
 		$this->assertSame($fields, Data::read(static::TMP . '/article.txt'));
 	}
 
 	/**
 	 * @covers ::contentFile
-	 * @dataProvider contentFileProvider
+	 * @dataProvider contentFileProviderMultiLang
 	 */
-	public function testContentFile(string $type, VersionId $id, string $language, string $expected)
+	public function testContentFileMultiLang(string $type, VersionId $id, string $language, string $expected)
 	{
-		$app = new App([
-			'roots' => [
-				'index' => static::TMP
-			]
-		]);
+		$this->setUpMultiLanguage();
 
-		$site = $app->site();
+		$site = $this->app->site();
 
 		$model = match ($type) {
 			'file' => new File([
@@ -430,80 +542,107 @@ public function testContentFile(string $type, VersionId $id, string $language, s
 				'filename' => 'image.jpg'
 			]),
 			'page' => new Page([
-				'kirby'    => $app,
+				'kirby'    => $this->app,
 				'slug'     => 'a-page',
 				'template' => 'article'
 			]),
 			'site' => $site,
 			'user' => new User([
-				'kirby' => $app,
+				'kirby' => $this->app,
 				'id'    => 'abcdefgh'
 			])
 		};
 
 		$storage = new PlainTextContentStorageHandler($model);
-		$this->assertSame(static::TMP . '/' . $expected, $storage->contentFile($id, $language));
+		$this->assertSame(static::TMP . '/' . $expected, $storage->contentFile($id, $this->app->language($language)));
 	}
 
-	public static function contentFileProvider(): array
+	public static function contentFileProviderMultiLang(): array
 	{
 		return [
-			['file', VersionId::changes(), 'default', 'content/_changes/image.jpg.txt'],
 			['file', VersionId::changes(), 'en', 'content/_changes/image.jpg.en.txt'],
-			['file', VersionId::published(), 'default', 'content/image.jpg.txt'],
 			['file', VersionId::published(), 'en', 'content/image.jpg.en.txt'],
-			['page', VersionId::changes(), 'default', 'content/a-page/_changes/article.txt'],
 			['page', VersionId::changes(), 'en', 'content/a-page/_changes/article.en.txt'],
-			['page', VersionId::published(), 'default', 'content/a-page/article.txt'],
 			['page', VersionId::published(), 'en', 'content/a-page/article.en.txt'],
-			['site', VersionId::changes(), 'default', 'content/_changes/site.txt'],
 			['site', VersionId::changes(), 'en', 'content/_changes/site.en.txt'],
-			['site', VersionId::published(), 'default', 'content/site.txt'],
 			['site', VersionId::published(), 'en', 'content/site.en.txt'],
-			['user', VersionId::changes(), 'default', 'site/accounts/abcdefgh/_changes/user.txt'],
 			['user', VersionId::changes(), 'en', 'site/accounts/abcdefgh/_changes/user.en.txt'],
-			['user', VersionId::published(), 'default', 'site/accounts/abcdefgh/user.txt'],
 			['user', VersionId::published(), 'en', 'site/accounts/abcdefgh/user.en.txt'],
 		];
 	}
 
 	/**
 	 * @covers ::contentFile
-	 * @dataProvider contentFileDraftProvider
+	 * @dataProvider contentFileProviderSingleLang
 	 */
-	public function testContentFileDraft(string $language, string $expected)
+	public function testContentFileSingleLang(string $type, VersionId $id, string $expected)
 	{
-		$app = new App([
-			'roots' => [
-				'index' => static::TMP
-			]
-		]);
+		$this->setUpSingleLanguage();
+
+		$site = $this->app->site();
+
+		$model = match ($type) {
+			'file' => new File([
+				'parent'   => $site,
+				'filename' => 'image.jpg'
+			]),
+			'page' => new Page([
+				'kirby'    => $this->app,
+				'slug'     => 'a-page',
+				'template' => 'article'
+			]),
+			'site' => $site,
+			'user' => new User([
+				'kirby' => $this->app,
+				'id'    => 'abcdefgh'
+			])
+		};
+
+		$storage = new PlainTextContentStorageHandler($model);
+		$this->assertSame(static::TMP . '/' . $expected, $storage->contentFile($id, Language::single()));
+	}
+
+	public static function contentFileProviderSingleLang(): array
+	{
+		return [
+			['file', VersionId::changes(), 'content/_changes/image.jpg.txt'],
+			['file', VersionId::published(), 'content/image.jpg.txt'],
+			['page', VersionId::changes(), 'content/a-page/_changes/article.txt'],
+			['page', VersionId::published(), 'content/a-page/article.txt'],
+			['site', VersionId::changes(), 'content/_changes/site.txt'],
+			['site', VersionId::published(), 'content/site.txt'],
+			['user', VersionId::changes(), 'site/accounts/abcdefgh/_changes/user.txt'],
+			['user', VersionId::published(), 'site/accounts/abcdefgh/user.txt'],
+		];
+	}
+
+	/**
+	 * @covers ::contentFile
+	 */
+	public function testContentFileDraft()
+	{
+		$this->setUpSingleLanguage();
 
 		$model = new Page([
-			'kirby' => $app,
+			'kirby' => $this->app,
 			'isDraft' => true,
 			'slug' => 'a-page',
 			'template' => 'article'
 		]);
 
 		$storage = new PlainTextContentStorageHandler($model);
-		$this->assertSame(static::TMP . '/' . $expected, $storage->contentFile(VersionId::changes(), $language));
+		$this->assertSame(static::TMP . '/content/_drafts/a-page/article.txt', $storage->contentFile(VersionId::changes(), Language::single()));
 	}
 
 	/**
 	 * @covers ::contentFile
-	 * @dataProvider contentFileDraftProvider
 	 */
-	public function testContentFileDraftPublished(string $language, string $expected)
+	public function testContentFileDraftPublished()
 	{
-		$app = new App([
-			'roots' => [
-				'index' => static::TMP
-			]
-		]);
+		$this->setUpSingleLanguage();
 
 		$model = new Page([
-			'kirby' => $app,
+			'kirby' => $this->app,
 			'root' => static::TMP,
 			'isDraft' => true,
 			'slug' => 'a-page',
@@ -514,36 +653,19 @@ public function testContentFileDraftPublished(string $language, string $expected
 
 		$this->expectException(LogicException::class);
 		$this->expectExceptionMessage('Drafts cannot have a published content file');
-		$storage->contentFile(VersionId::published(), $language);
+		$storage->contentFile(VersionId::published(), Language::single());
 	}
 
-	public static function contentFileDraftProvider(): array
-	{
-		return [
-			['default', 'content/_drafts/a-page/article.txt'],
-			['en', 'content/_drafts/a-page/article.en.txt'],
-		];
-	}
 	/**
 	 * @covers ::contentFiles
 	 */
 	public function testContentFilesChangesMultiLang()
 	{
-		new App([
-			'languages' => [
-				[
-					'code' => 'en',
-					'default' => true
-				],
-				[
-					'code' => 'de'
-				]
-			]
-		]);
+		$this->setUpMultiLanguage();
 
 		$this->assertSame([
-			static::TMP . '/_changes/article.en.txt',
-			static::TMP . '/_changes/article.de.txt'
+			$this->model->root() . '/_changes/article.en.txt',
+			$this->model->root() . '/_changes/article.de.txt'
 		], $this->storage->contentFiles(VersionId::changes()));
 	}
 
@@ -552,8 +674,10 @@ public function testContentFilesChangesMultiLang()
 	 */
 	public function testContentFilesChangesSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$this->assertSame([
-			static::TMP . '/_changes/article.txt'
+			$this->model->root() . '/_changes/article.txt'
 		], $this->storage->contentFiles(VersionId::changes()));
 	}
 
@@ -562,21 +686,11 @@ public function testContentFilesChangesSingleLang()
 	 */
 	public function testContentFilesPublishedMultiLang()
 	{
-		new App([
-			'languages' => [
-				[
-					'code' => 'en',
-					'default' => true
-				],
-				[
-					'code' => 'de'
-				]
-			]
-		]);
+		$this->setUpMultiLanguage();
 
 		$this->assertSame([
-			static::TMP . '/article.en.txt',
-			static::TMP . '/article.de.txt'
+			$this->model->root() . '/article.en.txt',
+			$this->model->root() . '/article.de.txt'
 		], $this->storage->contentFiles(VersionId::published()));
 	}
 
@@ -585,8 +699,10 @@ public function testContentFilesPublishedMultiLang()
 	 */
 	public function testContentFilesPublishedSingleLang()
 	{
+		$this->setUpSingleLanguage();
+
 		$this->assertSame([
-			static::TMP . '/article.txt'
+			$this->model->root() . '/article.txt'
 		], $this->storage->contentFiles(VersionId::published()));
 	}
 }