diff --git a/.jules/bolt.md b/.jules/bolt.md
index 31adfad..e21defa 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -12,3 +12,11 @@ The default Express `express.json()` middleware limits incoming JSON payloads to
 
 Action:
 Increased the JSON payload limit in `src/index.js` to 10mb, and added an explicit error handler to intercept `err.type === 'entity.too.large'` and return a standardized `413 Payload Too Large` JSON response.
+
+## 2024-05-24 — Improve array validation and bound computationCache memory map size
+
+Learning:
+Unbounded Map caches in repeated serverless or long-running operations can cause memory leaks. Also, `req.body.messages` without `Array.isArray()` validation can lead to crashes if a string is provided and later mapped.
+
+Action:
+Added strict `!Array.isArray(messages)` validation to the `/v1/chat/completions` API route, and restricted the `computationCache` Map size to 1000 items in `src/index.js` to ensure long-term stability and resilience.
diff --git a/src/index.js b/src/index.js
index 59961d9..8f2c17f 100644
--- a/src/index.js
+++ b/src/index.js
@@ -37,8 +37,8 @@ app.use((err, req, res, next) => {
 // API endpoints
 app.post('/v1/chat/completions', (req, res) => {
   const { model, messages } = req.body || {};
-  if (!model || !messages) {
-    return res.status(400).json({ error: 'Missing model or messages' });
+  if (!model || !messages || !Array.isArray(messages)) {
+    return res.status(400).json({ error: 'Missing or invalid model or messages' });
   }
 
   // Mock unified response
@@ -91,6 +91,11 @@ function heavyComputation(iterations) {
     return computationCache.get(iterations);
   }
 
+  // Prevent memory leak from unbounded cache growth
+  if (computationCache.size >= 1000) {
+    computationCache.clear();
+  }
+
   let sum = 0;
   for (let i = 0; i < iterations; i++) {
     sum += Math.sqrt(i) * Math.sin(i * 0.01);
diff --git a/tests/api.test.js b/tests/api.test.js
index e184779..29ed2eb 100644
--- a/tests/api.test.js
+++ b/tests/api.test.js
@@ -33,7 +33,19 @@ test('POST /v1/chat/completions fails without model', async () => {
     });
 
   assert.strictEqual(res.status, 400);
-  assert.strictEqual(res.body.error, 'Missing model or messages');
+  assert.strictEqual(res.body.error, 'Missing or invalid model or messages');
+});
+
+test('POST /v1/chat/completions fails when messages is not an array', async () => {
+  const res = await request(app)
+    .post('/v1/chat/completions')
+    .send({
+      model: 'gpt-4',
+      messages: "Hello!"
+    });
+
+  assert.strictEqual(res.status, 400);
+  assert.strictEqual(res.body.error, 'Missing or invalid model or messages');
 });
 
 test('POST /v1/chat/completions fails with invalid JSON gracefully', async () => {
diff --git a/tests/api_robustness.test.js b/tests/api_robustness.test.js
index 0575486..59f5d70 100644
--- a/tests/api_robustness.test.js
+++ b/tests/api_robustness.test.js
@@ -10,7 +10,7 @@ test('POST /v1/chat/completions handles undefined req.body (e.g. non-JSON conten
     .send('some text');
 
   assert.strictEqual(res.status, 400);
-  assert.strictEqual(res.body.error, 'Missing model or messages');
+  assert.strictEqual(res.body.error, 'Missing or invalid model or messages');
 });
 
 test('POST /v1/chat/completions handles payload too large gracefully', async () => {