From e2460374dee914eae8d1edfbbb8d9e2309432fc3 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 25 May 2026 13:24:11 +0000
Subject: [PATCH] fix(i18n): normalize html language tags in client detection

Agent-Logs-Url: https://github.com/trails-cool/trails/sessions/7546ba18-5628-4f50-bc8b-104fa7ba6afe

Co-authored-by: stigi <13815+stigi@users.noreply.github.com>
---
 packages/i18n/src/client.test.ts | 16 ++++++++++++++++
 packages/i18n/src/index.ts       |  1 +
 2 files changed, 17 insertions(+)
 create mode 100644 packages/i18n/src/client.test.ts

diff --git a/packages/i18n/src/client.test.ts b/packages/i18n/src/client.test.ts
new file mode 100644
index 0000000..c7b0d28
--- /dev/null
+++ b/packages/i18n/src/client.test.ts
@@ -0,0 +1,16 @@
+/**
+ * @vitest-environment jsdom
+ */
+import { describe, expect, it } from "vitest";
+import { i18n, initI18nClient } from "./index.ts";
+
+describe("initI18nClient", () => {
+  it("normalizes regional html lang tags to supported languages", () => {
+    document.documentElement.lang = "de-DE";
+
+    initI18nClient();
+
+    expect(i18n.language).toBe("de");
+    expect(i18n.t("journal:nav.login")).toBe("Anmelden");
+  });
+});
diff --git a/packages/i18n/src/index.ts b/packages/i18n/src/index.ts
index 5db3adb..7634071 100644
--- a/packages/i18n/src/index.ts
+++ b/packages/i18n/src/index.ts
@@ -64,6 +64,7 @@ export function initI18nClient() {
       ...commonOptions,
       detection: {
         order: ["htmlTag", "navigator"],
+        convertDetectedLanguage: (lng: string) => matchSupportedLng(lng),
         caches: [],
       },
     });