diff --git a/frontend/src/app/activity/page.test.tsx b/frontend/src/app/activity/page.test.tsx
new file mode 100644
index 0000000..af5cec2
--- /dev/null
+++ b/frontend/src/app/activity/page.test.tsx
@@ -0,0 +1,55 @@
+import React from "react";
+import { describe, expect, it, vi } from "vitest";
+import { render, screen } from "@testing-library/react";
+
+import ActivityPage from "./page";
+import { AuthProvider } from "@/components/providers/AuthProvider";
+import { QueryProvider } from "@/components/providers/QueryProvider";
+
+vi.mock("next/link", () => {
+  return {
+    default: ({ href, children, ...props }: any) => (
+      <a href={typeof href === "string" ? href : "#"} {...props}>
+        {children}
+      </a>
+    ),
+  };
+});
+
+// Make Clerk components explode if we ever try to render them without the provider.
+// The regression we want to catch is: AuthProvider skips <ClerkProvider/>, but the
+// wrappers still render <SignedOut/> from @clerk/nextjs (which crashes in real builds).
+vi.mock("@clerk/nextjs", () => {
+  return {
+    ClerkProvider: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+    SignedIn: () => {
+      throw new Error("@clerk/nextjs SignedIn rendered (unexpected in secretless mode)");
+    },
+    SignedOut: () => {
+      throw new Error("@clerk/nextjs SignedOut rendered without ClerkProvider");
+    },
+    SignInButton: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+    SignOutButton: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+    useAuth: () => ({ isLoaded: true, isSignedIn: false }),
+    useUser: () => ({ isLoaded: true, isSignedIn: false, user: null }),
+  };
+});
+
+describe("/activity auth boundary", () => {
+  it("renders without ClerkProvider runtime errors when publishable key is a placeholder", () => {
+    // Simulate CI/secretless env where an arbitrary placeholder value may be present.
+    // AuthProvider should treat this as disabled, and the auth wrappers must not render
+    // Clerk SignedOut/SignedIn components.
+    process.env.NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY = "placeholder";
+
+    render(
+      <AuthProvider>
+        <QueryProvider>
+          <ActivityPage />
+        </QueryProvider>
+      </AuthProvider>,
+    );
+
+    expect(screen.getByText(/sign in to view the feed/i)).toBeInTheDocument();
+  });
+});
diff --git a/frontend/vitest.config.ts b/frontend/vitest.config.ts
index 197150a..880f1c3 100644
--- a/frontend/vitest.config.ts
+++ b/frontend/vitest.config.ts
@@ -1,6 +1,13 @@
+import path from "node:path";
+
 import { defineConfig } from "vitest/config";
 
 export default defineConfig({
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "./src"),
+    },
+  },
   test: {
     environment: "jsdom",
     setupFiles: ["./src/setupTests.ts"],