diff --git a/scripts/cursor-hooks.js b/scripts/cursor-hooks.js
index 8d222bd5e..1ccc8f6d0 100644
--- a/scripts/cursor-hooks.js
+++ b/scripts/cursor-hooks.js
@@ -36,8 +36,18 @@ function readConfig(file) {
   } catch (e) {
     if (e.code !== 'ENOENT') throw e;
   }
-  if (!config || typeof config !== 'object' || Array.isArray(config)) config = {};
-  if (!config.hooks || typeof config.hooks !== 'object' || Array.isArray(config.hooks)) config.hooks = {};
+  if (!config || typeof config !== 'object' || Array.isArray(config)) {
+    throw new Error(file + ' must contain a JSON object; nothing was changed');
+  }
+  if (config.hooks === undefined) config.hooks = {};
+  if (!config.hooks || typeof config.hooks !== 'object' || Array.isArray(config.hooks)) {
+    throw new Error(file + ': hooks must be an object; nothing was changed');
+  }
+  for (const [event, entries] of Object.entries(config.hooks)) {
+    if (!Array.isArray(entries)) {
+      throw new Error(file + ': hooks.' + event + ' must be an array; nothing was changed');
+    }
+  }
   return config;
 }
 
diff --git a/tests/cursor-hooks.test.js b/tests/cursor-hooks.test.js
index a604c817b..09f438cc5 100644
--- a/tests/cursor-hooks.test.js
+++ b/tests/cursor-hooks.test.js
@@ -315,3 +315,20 @@ test('installer refuses to touch a malformed hooks.json', () => {
     assert.equal(fs.readFileSync(file, 'utf8'), broken, 'malformed file must be left byte-for-byte intact');
   }
 });
+
+for (const [name, config] of Object.entries({
+  'root-array': [{ command: 'keep me' }],
+  'hooks-array': { hooks: [{ command: 'keep me' }] },
+  'event-string': { hooks: { sessionStart: 'node custom-hook.js' } },
+})) {
+  test(`installer refuses ${name} without overwriting hooks.json`, () => {
+    const c = cursorEnv(`invalid-${name}`);
+    const file = path.join(c.home, '.cursor', 'hooks.json');
+    fs.mkdirSync(path.dirname(file), { recursive: true });
+    const original = JSON.stringify(config, null, 2) + '\n';
+    fs.writeFileSync(file, original);
+    const result = cli(['install'], c.env);
+    assert.notEqual(result.status, 0, 'invalid config must not be silently rewritten');
+    assert.equal(fs.readFileSync(file, 'utf8'), original);
+  });
+}