diff --git a/src/node/db/Pad.ts b/src/node/db/Pad.ts
index 30b18e6b542..54fd0bb645f 100644
--- a/src/node/db/Pad.ts
+++ b/src/node/db/Pad.ts
@@ -39,7 +39,7 @@ type PadSettings = {
   showChat: boolean;
   alwaysShowChat: boolean;
   chatAndUsers: boolean;
-  lang: string;
+  lang: string | null;
   view: PadViewSettings;
 };
 
@@ -91,7 +91,11 @@ class Pad {
         !!rawPadSettings.showChat,
       alwaysShowChat: !!rawPadSettings.alwaysShowChat,
       chatAndUsers: !!rawPadSettings.chatAndUsers,
-      lang: typeof rawPadSettings.lang === 'string' ? rawPadSettings.lang : 'en',
+      // Default to null (not 'en') so the client's l10n auto-detect chain
+      // (cookie -> navigator.language -> 'en' fallback) runs. Hardcoding 'en'
+      // forces English on every pad regardless of the browser's Accept-Language
+      // and broke #7586 (German system saw English pad UI in v2.7.0).
+      lang: typeof rawPadSettings.lang === 'string' ? rawPadSettings.lang : null,
       view: {
         showAuthorColors: rawView.showAuthorColors == null ? true : !!rawView.showAuthorColors,
         showLineNumbers: rawView.showLineNumbers == null ?
diff --git a/src/tests/backend/specs/Pad.ts b/src/tests/backend/specs/Pad.ts
index dd70a5127e1..13bc79e5ac3 100644
--- a/src/tests/backend/specs/Pad.ts
+++ b/src/tests/backend/specs/Pad.ts
@@ -159,4 +159,23 @@ describe(__filename, function () {
       assert.equal(pad!.text(), `${want}\n`);
     });
   });
+
+  describe('normalizePadSettings lang (issue #7586)', function () {
+    it('defaults lang to null when not provided, so client auto-detects locale', function () {
+      const ps = Pad.Pad.normalizePadSettings({});
+      assert.equal(ps.lang, null);
+    });
+
+    it('preserves an explicit string lang (creator override)', function () {
+      const ps = Pad.Pad.normalizePadSettings({lang: 'de'});
+      assert.equal(ps.lang, 'de');
+    });
+
+    it('drops non-string lang values to null rather than coercing to "en"', function () {
+      for (const bogus of [42, true, {}, [], null, undefined]) {
+        const ps = Pad.Pad.normalizePadSettings({lang: bogus});
+        assert.equal(ps.lang, null, `bogus input ${JSON.stringify(bogus)}`);
+      }
+    });
+  });
 });