fix: skip locale prefix for absolute and protocol-relative Link hrefs

packages/vinext/src/shims/link.tsx

@@ -283,6 +283,12 @@ function applyLocaleToHref(href: string, locale: string | false | undefined): st
     return href;
   }
 
+  // Absolute and protocol-relative URLs must not be prefixed — locale
+  // only applies to local paths.
+  if (href.startsWith("http://") || href.startsWith("https://") || href.startsWith("//")) {
+    return href;
+  }
+
   // locale is a string: prepend the locale prefix if not already present
   const defaultLocale = getDefaultLocale();
   // For the default locale, Next.js doesn't add a prefix

packages/vinext/src/shims/router.ts

@@ -124,6 +124,11 @@ function resolveUrl(url: string | UrlObject): string {
  */
 export function applyNavigationLocale(url: string, locale?: string): string {
   if (!locale || typeof window === "undefined") return url;
+  // Absolute and protocol-relative URLs must not be prefixed — locale
+  // only applies to local paths.
+  if (url.startsWith("http://") || url.startsWith("https://") || url.startsWith("//")) {
+    return url;
+  }
   const defaultLocale = window.__VINEXT_DEFAULT_LOCALE__;
   // Default locale doesn't get a prefix
   if (locale === defaultLocale) return url;

tests/link.test.ts

@@ -242,6 +242,30 @@ describe("Link locale handling", () => {
     // Should not become /fr/fr/about
     expect(html).toContain('href="/fr/about"');
   });
+
+  it("locale does not mangle absolute same-origin URLs", () => {
+    // An absolute URL like https://example.com/about should not become
+    // /fr/https://example.com/about — locale prefix only applies to paths
+    const html = ReactDOMServer.renderToString(
+      React.createElement(Link, { href: "https://example.com/about", locale: "fr" } as any, "x"),
+    );
+    expect(html).toContain('href="https://example.com/about"');
+  });
+
+  it("locale does not mangle protocol-relative URLs", () => {
+    // //example.com/about should not become /fr///example.com/about
+    const html = ReactDOMServer.renderToString(
+      React.createElement(Link, { href: "//example.com/about", locale: "fr" } as any, "x"),
+    );
+    expect(html).toContain('href="//example.com/about"');
+  });
+
+  it("locale does not mangle http:// URLs", () => {
+    const html = ReactDOMServer.renderToString(
+      React.createElement(Link, { href: "http://example.com/path", locale: "de" } as any, "x"),
+    );
+    expect(html).toContain('href="http://example.com/path"');
+  });
 });
 
 // ─── toSameOriginPath ────────────────────────────────────────────────────

tests/shims.test.ts

@@ -6795,6 +6795,55 @@ describe("Pages Router router helpers", () => {
       expect(isHashOnlyChange("https://example.com#foo")).toBe(false);
     });
   });
+
+  describe("applyNavigationLocale", () => {
+    it("does not prefix absolute https:// URLs", async () => {
+      const { applyNavigationLocale } = await import("../packages/vinext/src/shims/router.js");
+      // Simulate a browser-like window so the locale guard is reached
+      (globalThis as any).window = { __VINEXT_DEFAULT_LOCALE__: "en" };
+      try {
+        expect(applyNavigationLocale("https://example.com/about", "fr")).toBe(
+          "https://example.com/about",
+        );
+      } finally {
+        delete (globalThis as any).window;
+      }
+    });
+
+    it("does not prefix absolute http:// URLs", async () => {
+      const { applyNavigationLocale } = await import("../packages/vinext/src/shims/router.js");
+      (globalThis as any).window = { __VINEXT_DEFAULT_LOCALE__: "en" };
+      try {
+        expect(applyNavigationLocale("http://example.com/path", "de")).toBe(
+          "http://example.com/path",
+        );
+      } finally {
+        delete (globalThis as any).window;
+      }
+    });
+
+    it("does not prefix protocol-relative // URLs", async () => {
+      const { applyNavigationLocale } = await import("../packages/vinext/src/shims/router.js");
+      (globalThis as any).window = { __VINEXT_DEFAULT_LOCALE__: "en" };
+      try {
+        expect(applyNavigationLocale("//cdn.example.com/img.png", "fr")).toBe(
+          "//cdn.example.com/img.png",
+        );
+      } finally {
+        delete (globalThis as any).window;
+      }
+    });
+
+    it("prefixes local paths with locale", async () => {
+      const { applyNavigationLocale } = await import("../packages/vinext/src/shims/router.js");
+      (globalThis as any).window = { __VINEXT_DEFAULT_LOCALE__: "en" };
+      try {
+        expect(applyNavigationLocale("/about", "fr")).toBe("/fr/about");
+      } finally {
+        delete (globalThis as any).window;
+      }
+    });
+  });
 });
 
 describe("next/server enhancements", () => {