diff --git a/e2e/auth.test.ts b/e2e/auth.test.ts
new file mode 100644
index 0000000..ce19e79
--- /dev/null
+++ b/e2e/auth.test.ts
@@ -0,0 +1,112 @@
+import { test, expect, type CDPSession, type Page } from "@playwright/test";
+
+// Virtual authenticator helpers
+async function setupVirtualAuthenticator(cdp: CDPSession) {
+  await cdp.send("WebAuthn.enable");
+  const { authenticatorId } = await cdp.send("WebAuthn.addVirtualAuthenticator", {
+    options: {
+      protocol: "ctap2",
+      transport: "internal",
+      hasResidentKey: true,
+      hasUserVerification: true,
+      isUserVerified: true,
+    },
+  });
+  return authenticatorId;
+}
+
+async function removeVirtualAuthenticator(cdp: CDPSession, authenticatorId: string) {
+  await cdp.send("WebAuthn.removeVirtualAuthenticator", { authenticatorId });
+  await cdp.send("WebAuthn.disable");
+}
+
+async function registerUser(page: Page, email: string, username: string) {
+  await page.goto("/auth/register");
+  await expect(page.getByRole("heading", { name: "Register" })).toBeVisible();
+  await page.getByLabel("Email").click();
+  await page.getByLabel("Email").fill(email);
+  await page.getByLabel("Username").click();
+  await page.getByLabel("Username").fill(username);
+  // Verify both fields retained values before submitting
+  await expect(page.getByLabel("Email")).toHaveValue(email);
+  await expect(page.getByLabel("Username")).toHaveValue(username);
+  await page.getByRole("button", { name: /Register with Passkey/ }).click();
+}
+
+async function logout(page: Page) {
+  await page.getByRole("navigation").getByRole("button", { name: "Log Out" }).click();
+  await expect(page.getByRole("navigation").getByRole("link", { name: "Sign In" })).toBeVisible({ timeout: 5000 });
+}
+
+test.describe("Passkey Authentication", () => {
+  test("register with passkey and sign in", async ({ page }) => {
+    const cdp = await page.context().newCDPSession(page);
+    const authenticatorId = await setupVirtualAuthenticator(cdp);
+
+    const email = `test-${Date.now()}@example.com`;
+    const username = `testuser${Date.now()}`;
+
+    // Register
+    await registerUser(page, email, username);
+    await expect(page).toHaveURL("/", { timeout: 10000 });
+    await expect(page.getByRole("navigation").getByText(username)).toBeVisible({ timeout: 5000 });
+
+    // Log out
+    await logout(page);
+
+    // Sign in with passkey
+    await page.goto("/auth/login");
+    await page.getByRole("button", { name: /Sign in with Passkey/ }).click();
+    await expect(page).toHaveURL("/", { timeout: 10000 });
+    await expect(page.getByRole("navigation").getByText(username)).toBeVisible({ timeout: 5000 });
+
+    await removeVirtualAuthenticator(cdp, authenticatorId);
+  });
+
+  test("passkey login fails with no registered credential", async ({ page }) => {
+    const cdp = await page.context().newCDPSession(page);
+    const authenticatorId = await setupVirtualAuthenticator(cdp);
+
+    await page.goto("/auth/login");
+    await page.getByRole("button", { name: /Sign in with Passkey/ }).click();
+    await expect(page.getByText(/No passkey found/i)).toBeVisible({ timeout: 10000 });
+
+    await removeVirtualAuthenticator(cdp, authenticatorId);
+  });
+
+  test("register rejects duplicate email", async ({ page }) => {
+    const cdp = await page.context().newCDPSession(page);
+    const authenticatorId = await setupVirtualAuthenticator(cdp);
+
+    const email = `dup-${Date.now()}@example.com`;
+
+    // Register first user
+    await registerUser(page, email, `first${Date.now()}`);
+    await expect(page).toHaveURL("/", { timeout: 10000 });
+    await logout(page);
+
+    // Try to register with same email
+    await registerUser(page, email, `second${Date.now()}`);
+    await expect(page.getByText(/already in use/i)).toBeVisible({ timeout: 10000 });
+
+    await removeVirtualAuthenticator(cdp, authenticatorId);
+  });
+
+  test("register rejects duplicate username", async ({ page }) => {
+    const cdp = await page.context().newCDPSession(page);
+    const authenticatorId = await setupVirtualAuthenticator(cdp);
+
+    const username = `uniq${Date.now()}`;
+
+    // Register first user
+    await registerUser(page, `first-${Date.now()}@example.com`, username);
+    await expect(page).toHaveURL("/", { timeout: 10000 });
+    await logout(page);
+
+    // Try to register with same username
+    await registerUser(page, `second-${Date.now()}@example.com`, username);
+    await expect(page.getByText(/already taken/i)).toBeVisible({ timeout: 10000 });
+
+    await removeVirtualAuthenticator(cdp, authenticatorId);
+  });
+});
diff --git a/playwright.config.ts b/playwright.config.ts
index b8a79dc..ff32d8b 100644
--- a/playwright.config.ts
+++ b/playwright.config.ts
@@ -31,6 +31,14 @@ export default defineConfig({
         baseURL: "http://localhost:3001",
       },
     },
+    {
+      name: "auth",
+      testMatch: "auth.test.ts",
+      use: {
+        ...devices["Desktop Chrome"],
+        baseURL: "http://localhost:3000",
+      },
+    },
     {
       name: "integration",
       testMatch: "integration.test.ts",