diff --git a/browse/test/build.test.ts b/browse/test/build.test.ts
new file mode 100644
index 00000000..050f3576
--- /dev/null
+++ b/browse/test/build.test.ts
@@ -0,0 +1,28 @@
+import { describe, test, expect } from 'bun:test';
+import { execSync } from 'child_process';
+import * as fs from 'fs';
+import * as path from 'path';
+
+const DIST_DIR = path.resolve(__dirname, '..', 'dist');
+const SERVER_NODE = path.join(DIST_DIR, 'server-node.mjs');
+
+describe('build: server-node.mjs', () => {
+  test('passes node --check if present', () => {
+    if (!fs.existsSync(SERVER_NODE)) {
+      // browse/dist is gitignored; no build has run in this checkout.
+      // Skip rather than fail so plain `bun test` without a prior build passes.
+      return;
+    }
+    expect(() => execSync(`node --check ${SERVER_NODE}`, { stdio: 'pipe' })).not.toThrow();
+  });
+
+  test('does not inline @ngrok/ngrok (must be external)', () => {
+    if (!fs.existsSync(SERVER_NODE)) return;
+    const bundle = fs.readFileSync(SERVER_NODE, 'utf-8');
+    // Dynamic imports of externalized packages show up as string literals in the bundle,
+    // not as inlined module code. The heuristic: ngrok's native binding loader would
+    // reference its own internals. If any ngrok internal identifier appears, the module
+    // got inlined despite the --external flag.
+    expect(bundle).not.toMatch(/ngrok_napi|ngrokNapi|@ngrok\/ngrok-darwin|@ngrok\/ngrok-linux|@ngrok\/ngrok-win32/);
+  });
+});