diff --git a/middleware/01.redirect-to-custom-domain.ts b/middleware/01.redirect-to-custom-domain.ts
new file mode 100644
index 0000000..bc3ad16
--- /dev/null
+++ b/middleware/01.redirect-to-custom-domain.ts
@@ -0,0 +1,16 @@
+import { defineMiddleware } from "void";
+
+const LEGACY_HOST = "vp-setup.void.app";
+const CANONICAL_ORIGIN = "https://setup.viteplus.dev";
+
+export function buildRedirectTarget(host: string | undefined, requestUrl: string): string | null {
+  if (host !== LEGACY_HOST) return null;
+  const url = new URL(requestUrl);
+  return `${CANONICAL_ORIGIN}${url.pathname}${url.search}`;
+}
+
+export default defineMiddleware(async (c, next) => {
+  const target = buildRedirectTarget(c.req.header("host"), c.req.url);
+  if (target) return c.redirect(target, 301);
+  await next();
+});
diff --git a/tests/redirect.test.ts b/tests/redirect.test.ts
new file mode 100644
index 0000000..a7f572a
--- /dev/null
+++ b/tests/redirect.test.ts
@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vite-plus/test";
+import { buildRedirectTarget } from "../middleware/01.redirect-to-custom-domain";
+
+describe("buildRedirectTarget", () => {
+  it("redirects legacy host root to canonical origin", () => {
+    expect(buildRedirectTarget("vp-setup.void.app", "https://vp-setup.void.app/")).toBe(
+      "https://setup.viteplus.dev/",
+    );
+  });
+
+  it("preserves path and query string", () => {
+    expect(
+      buildRedirectTarget("vp-setup.void.app", "https://vp-setup.void.app/?tag=v1.2.3&arch=arm64"),
+    ).toBe("https://setup.viteplus.dev/?tag=v1.2.3&arch=arm64");
+  });
+
+  it("returns null for the custom domain (no redirect)", () => {
+    expect(buildRedirectTarget("setup.viteplus.dev", "https://setup.viteplus.dev/")).toBeNull();
+  });
+
+  it("returns null for localhost during dev", () => {
+    expect(buildRedirectTarget("localhost:5173", "http://localhost:5173/")).toBeNull();
+  });
+
+  it("returns null when host header is missing", () => {
+    expect(buildRedirectTarget(undefined, "https://vp-setup.void.app/")).toBeNull();
+  });
+
+  it("does not match preview/staging subdomains", () => {
+    expect(
+      buildRedirectTarget("vp-setup-staging.void.app", "https://vp-setup-staging.void.app/"),
+    ).toBeNull();
+  });
+});