stromcom · stromcom · Aug 14, 2026 · Aug 14, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## [0.5.0] - 2026-08-14
+### Added
+- `language` option on `ConfOptions` — sets the widget UI language through `conf()`, mirroring `theme`. Values: `null` (follows the browser, falling back to English), `en`, `cs`, `sk`. Unlike the `snippet()` parameter it can be changed at runtime; when both are given, the conf value wins
+
 ## [0.4.0] - 2026-08-07
 ### Added
 - `entityResolve` callback option on `ConfOptions` — resolves business-entity detail for the message editor's chip hover-card

diff --git a/README.md b/README.md
@@ -284,11 +284,16 @@ See the full list of parameters in [`src/Options/ConfOptions.php`](src/Options/C
 | `pageCSSPath` | `?string` | CSS file URL injected into the snippet iframe. |
 | `notificationElementTargetElement` | `?string` | JS expression returning the target DOM element. |
 | `notificationElementPosition` | `?int` | Icon position: 1=top-left, 2=top-right, 3=bottom-right, 4=bottom-left. |
+| `language` | `?string` | UI language of the app. Values: `null` (follows the browser, falling back to English), `en`, `cs`, `sk`. |
 | `theme` | `?string` | Light/dark mode for the app. Values: `null` (follows browser preference), `stromcom-light`, `stromcom-dark`. |
 | `entityResolve` | `?string` | JS callback resolving business-entity detail (order, ticket…) for the message editor's chip hover-card. Receives `{type, id}`, returns (or resolves to) `{title, url?, fields: [{label, value}]}`. |
 
 ### UI language
-Pass a language code to `snippet()` to force the widget UI language (`cs`, `en`, `sk`…). When omitted, the widget detects it from the browser, falling back to English.
+Set the language on `ConfOptions`, the same way as the theme. When omitted, the widget detects it from the browser, falling back to English.
+```php
+echo $client->conf(new ConfOptions(language: 'cs'))->getHTML();
+```
+`snippet()` also takes a language code, which sets the initial value before `conf()` runs. Use it when the language is known at page render and you want the widget to boot into it without waiting for `conf()`; `ConfOptions::$language` wins whenever both are given.
 ```php
 echo $client->snippet('cs')->getHTML();
 ```

diff --git a/src/Options/ConfOptions.php b/src/Options/ConfOptions.php
@@ -45,6 +45,9 @@ class ConfOptions extends SnippetOptions {
   #[Docs('Callback invoked after the notification element is rendered', null, true, 'Function|null')]
   private ?string $notificationElementAfterRender = null;
 
+  #[Docs('UI language of the app. Null follows the browser, falling back to English. Available: en, cs, sk', 'cs', true)]
+  private ?string $language = null;
+
   #[Docs('Theme name applied to the host page via data-theme on <html>. Available: stromcom-default, stromcom-dark', 'stromcom-dark', true)]
   private ?string $theme = null;
 
@@ -67,6 +70,9 @@ public function __construct(
     ?string $homeBeforeRender = null,
     ?string $theme = null,
     ?string $entityResolve = null,
+    // Appended last on purpose — inserting it next to $theme would shift the
+    // positional arguments of existing callers.
+    ?string $language = null,
   ) {
     $this->notificationRenderer             = $notificationRenderer;
     $this->onNotification                   = $onNotification;
@@ -80,6 +86,7 @@ public function __construct(
     $this->notificationElementBeforeRender  = $notificationElementBeforeRender;
     $this->notificationElementAfterRender   = $notificationElementAfterRender;
     $this->homeBeforeRender                 = $homeBeforeRender;
+    $this->language                         = $language;
     $this->theme                            = $theme;
     $this->entityResolve                    = $entityResolve;
   }
@@ -157,6 +164,10 @@ public function renderNotificationElementAfterRender(): ?JsValue {
     return $this->wrapJsValue($this->notificationElementAfterRender);
   }
 
+  public function getLanguage(): ?string {
+    return $this->language;
+  }
+
   public function getTheme(): ?string {
     return $this->theme;
   }

diff --git a/src/SnippetClient.php b/src/SnippetClient.php
@@ -61,6 +61,8 @@ public function csp(): CspPolicy {
    *
    * @param string|null $language UI language (e.g. "cs", "en", "sk"). Null (default) lets the
    *                              widget detect it from the browser, falling back to English.
+   *                              This is the initial value only — `ConfOptions::$language`
+   *                              overrides it and can be changed later at runtime.
    *
    * @throws SnippetGenerationException
    */

diff --git a/tests/Options/ConfOptionsTest.php b/tests/Options/ConfOptionsTest.php
@@ -104,6 +104,20 @@ public function entity_resolve_null_renders_as_null(): void {
     $this->assertNull($options->renderEntityResolve());
   }
 
+  #[Test]
+  public function language_is_included_when_set(): void {
+    $options = new ConfOptions(language: 'cs');
+    $result  = $options->getOptions();
+
+    $this->assertArrayHasKey('language', $result);
+    $this->assertSame('cs', $result['language']);
+  }
+
+  #[Test]
+  public function language_is_not_included_when_null(): void {
+    $this->assertArrayNotHasKey('language', (new ConfOptions())->getOptions());
+  }
+
   #[Test]
   public function get_options_with_docs_returns_all_property_schemas(): void {
     $schema = ConfOptions::getOptionsWithDocs();

diff --git a/tests/SnippetClientTest.php b/tests/SnippetClientTest.php
@@ -80,6 +80,12 @@ public function conf_output_contains_conf_call(): void {
     $this->assertStringContainsString('stromCom.conf(', $code);
   }
 
+  #[Test]
+  public function conf_output_contains_language(): void {
+    $code = $this->client->conf(new ConfOptions(language: 'cs'))->getCode();
+    $this->assertStringContainsString('"language": "cs"', $code);
+  }
+
   #[Test]
   public function conf_output_with_docs_contains_on_load(): void {
     $code = $this->client->conf(new ConfOptions(), true)->getCode();