diff --git a/changelog.d/fixes/16059-locale-refresh-regression.md b/changelog.d/fixes/16059-locale-refresh-regression.md
new file mode 100644
index 000000000000..3bebe52b81ea
--- /dev/null
+++ b/changelog.d/fixes/16059-locale-refresh-regression.md
@@ -0,0 +1 @@
+- **Tests:** preserve the first-visit locale refresh ordering regression, checking that cookie, local storage, language and text direction are persisted before refreshing server content; isolate mock and React-root cleanup between cases (#16059).
diff --git a/tests/unit/ui/LocaleAutoDetect-refresh.test.tsx b/tests/unit/ui/LocaleAutoDetect-refresh.test.tsx
index 576edf84d4df..bf5223ea9a40 100644
--- a/tests/unit/ui/LocaleAutoDetect-refresh.test.tsx
+++ b/tests/unit/ui/LocaleAutoDetect-refresh.test.tsx
@@ -23,9 +23,11 @@ describe("LocaleAutoDetect refresh gating", () => {
     (
       globalThis as typeof globalThis & { IS_REACT_ACT_ENVIRONMENT?: boolean }
     ).IS_REACT_ACT_ENVIRONMENT = true;
-    refresh.mockClear();
+    refresh.mockReset();
     // Fresh visit: no locale cookie.
     document.cookie = "NEXT_LOCALE=; path=/; expires=Thu, 01 Jan 1970 00:00:00 GMT";
+    localStorage.removeItem("NEXT_LOCALE");
+    document.documentElement.dir = "ltr";
     Object.defineProperty(navigator, "languages", { value: ["en-US"], configurable: true });
   });
 
@@ -42,7 +44,7 @@ describe("LocaleAutoDetect refresh gating", () => {
       root.render(React.createElement(LocaleAutoDetect));
     });
     cleanups.push(() => {
-      root.unmount();
+      act(() => root.unmount());
       container.remove();
     });
   }
@@ -59,6 +61,21 @@ describe("LocaleAutoDetect refresh gating", () => {
     expect(refresh).toHaveBeenCalledTimes(1);
   });
 
+  it("persists the detected locale before refreshing server content on a first visit", async () => {
+    document.documentElement.lang = "en";
+    Object.defineProperty(navigator, "languages", { value: ["ar"], configurable: true });
+    refresh.mockImplementation(() => {
+      expect(document.cookie).toContain("NEXT_LOCALE=ar");
+      expect(localStorage.getItem("NEXT_LOCALE")).toBe("ar");
+      expect(document.documentElement.lang).toBe("ar");
+      expect(document.documentElement.dir).toBe("rtl");
+    });
+
+    await mount();
+
+    expect(refresh).toHaveBeenCalledTimes(1);
+  });
+
   // Alias wiring guard: the component must hand `LOCALE_ALIASES` to
   // `detectBrowserLocale`. `fil` (Filipino) is the discriminating input — no
   // locale code starts with `fil`, so with the real config it resolves to `phi`