diff --git a/apps/web/e2e/smoke.spec.ts b/apps/web/e2e/smoke.spec.ts
new file mode 100644
index 0000000..db01fea
--- /dev/null
+++ b/apps/web/e2e/smoke.spec.ts
@@ -0,0 +1,48 @@
+/**
+ * Smoke test: verify the app loads without React errors.
+ *
+ * This test ensures that the Vite build resolves a single React
+ * instance (no duplicate React versions from pnpm transitive deps).
+ */
+import { test, expect } from "@playwright/test";
+
+test("app loads without React hook errors", async ({ page }) => {
+  const consoleErrors: string[] = [];
+  const pageErrors: string[] = [];
+
+  page.on("console", (msg) => {
+    if (msg.type() === "error") consoleErrors.push(msg.text());
+  });
+  page.on("pageerror", (err) => {
+    pageErrors.push(err.message);
+  });
+
+  await page.goto("/app", { waitUntil: "domcontentloaded", timeout: 10000 });
+  await page.waitForTimeout(5000);
+
+  // The critical check: no "Invalid hook call" or related React errors
+  const hookErrors = pageErrors.filter((e) =>
+    e.includes("Invalid hook call") ||
+    e.includes("useMemo") ||
+    e.includes("useRef") ||
+    e.includes("useContext") ||
+    e.includes("more than one copy of React")
+  );
+
+  expect(hookErrors).toEqual([]);
+
+  // Root element must exist
+  await expect(page.locator("#root")).toBeAttached();
+
+  // Should show either login form or app content (not a blank/dark screen)
+  const bodyText = await page.evaluate(() => document.body?.innerText || "");
+  const hasContent =
+    bodyText.includes("Sign in") ||
+    bodyText.includes("Anmelden") ||
+    bodyText.includes("EvOo") ||
+    bodyText.includes("Projekte") ||
+    bodyText.includes("Heute") ||
+    bodyText.includes("Team");
+
+  expect(hasContent).toBe(true);
+});
diff --git a/apps/web/vite.config.ts b/apps/web/vite.config.ts
index 33255f1..dccd5f2 100644
--- a/apps/web/vite.config.ts
+++ b/apps/web/vite.config.ts
@@ -226,6 +226,11 @@ function attachNovncProxy(server: ViteDevServer | PreviewServer, secret: string,
 }
 
 export default defineConfig(({ mode }) => {
+  const rootCwd = path.resolve(import.meta.dirname, "../..");
+  const reactPath = path.resolve(rootCwd, "node_modules/react");
+  const reactDomPath = path.resolve(rootCwd, "node_modules/react-dom");
+  const reactIndex = path.resolve(reactPath, "index.js");
+  const reactDomIndex = path.resolve(reactDomPath, "index.js");
   const rootEnv = loadEnv(mode, path.resolve(import.meta.dirname, "../.."), "");
   const api = process.env.API_PROXY_TARGET ?? rootEnv.API_PROXY_TARGET ?? "http://127.0.0.1:3100";
   const previewHost = process.env.RAKAZO_HOST ?? rootEnv.RAKAZO_HOST ?? "localhost";
@@ -298,6 +303,14 @@ export default defineConfig(({ mode }) => {
         },
       },
     ],
+    resolve: {
+      alias: {
+        "react": reactPath,
+        "react-dom": reactDomPath,
+        "react/jsx-runtime": reactPath,
+        "react/jsx-dev-runtime": reactPath,
+      },
+    },
     server: {
       host: "0.0.0.0",
       port: webPort,
diff --git a/packages/ui-web/package.json b/packages/ui-web/package.json
index 0f684ad..44c7c9e 100644
--- a/packages/ui-web/package.json
+++ b/packages/ui-web/package.json
@@ -32,7 +32,7 @@
     "vitest": "4.1.11"
   },
   "peerDependencies": {
-    "react": "19.2.3",
+    "react": ">=16.8.0",
     "react-dom": "19.2.3"
   }
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index a32807d..92c6b05 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -6498,6 +6498,10 @@ packages:
     resolution: {integrity: sha512-EQsFzMUJkCKGr1ePqlYADkIUmHW1s3ZXr5Yqy6wbGrfUCphpl2maM/kyOIRA2HpP3AaFQTZXD4ldjek+nccddA==}
     engines: {node: '>=14.14'}
 
+  fs-extra@11.4.1:
+    resolution: {integrity: sha512-KYAb4c9BJQI6QqGKthV68OHe0badztdXJWKo0WtBA9IuCFPTKvE5ZdUBglP833aMjhaSPNO4A5j/EkzZtGlKjA==}
+    engines: {node: '>=14.14'}
+
   fs-extra@7.0.1:
     resolution: {integrity: sha512-YJDaCJZEnBmcbw13fvdAM9AwNOJwOzrE4pqMqBq5nFiEqXUqHwlK4B+3pUw6JNvfSPtX05xFHtYy/1ni01eGCw==}
     engines: {node: '>=6 <7 || >=8'}
@@ -11433,7 +11437,7 @@ snapshots:
     dependencies:
       cross-dirname: 0.1.0
       debug: 4.4.3
-      fs-extra: 11.4.0
+      fs-extra: 11.4.1
       minimist: 1.2.8
       postject: 1.0.0-alpha.6
     transitivePeerDependencies:
@@ -16663,6 +16667,13 @@ snapshots:
       jsonfile: 6.2.1
       universalify: 2.0.1
 
+  fs-extra@11.4.1:
+    dependencies:
+      graceful-fs: 4.2.11
+      jsonfile: 6.2.1
+      universalify: 2.0.1
+    optional: true
+
   fs-extra@7.0.1:
     dependencies:
       graceful-fs: 4.2.11