diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 00000000..54c088f4
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2024-05-18 - Sanitize Third-Party Error Responses
+**Vulnerability:** The API upload endpoint was exposing detailed internal configuration state (e.g. missing Cloudinary credentials) and raw third-party error objects (`cloudinaryError`) directly to clients in HTTP 500 responses.
+**Learning:** Developers often pass full error objects from third-party services (like Cloudinary, AWS, etc) down to the client for debugging, inadvertently leaking internal architecture details and potentially sensitive configurations.
+**Prevention:** Always fail securely by catching exceptions, logging the detailed error object strictly server-side, and returning a generic, safe error message to the API consumer.
diff --git a/src/app/api/upload/route.ts b/src/app/api/upload/route.ts
index 1664e115..84197dd2 100644
--- a/src/app/api/upload/route.ts
+++ b/src/app/api/upload/route.ts
@@ -6,13 +6,15 @@ export async function POST(request: NextRequest) {
   try {
     // Verify Cloudinary configuration
     if (!process.env.CLOUDINARY_CLOUD_NAME || !process.env.CLOUDINARY_API_KEY || !process.env.CLOUDINARY_API_SECRET) {
+      // 🛡️ SECURITY: Log the detailed missing config server-side but do not expose
+      // internal service requirements (like Cloudinary) to the client.
       console.error('Missing Cloudinary credentials:', {
         cloud_name: !!process.env.CLOUDINARY_CLOUD_NAME,
         api_key: !!process.env.CLOUDINARY_API_KEY,
         api_secret: !!process.env.CLOUDINARY_API_SECRET
       });
       return NextResponse.json(
-        { error: 'Cloudinary is not configured. Please set environment variables.' },
+        { error: 'Image upload service configuration error.' },
         { status: 500 }
       );
     }
@@ -60,18 +62,16 @@ export async function POST(request: NextRequest) {
   } catch (error: any) {
     console.error('Upload error:', error);
 
-    // Return detailed error message
-    const errorMessage = error?.message || error?.error?.message || 'Failed to upload image';
-    const errorDetails = {
-      error: errorMessage,
+    // 🛡️ SECURITY: Log detailed errors (like 3rd party API objects) server-side
+    // and fail securely by providing only a generic error to the client.
+    console.error('Full error details:', {
+      message: error?.message || error?.error?.message || 'Failed to upload image',
       details: error?.http_code ? `HTTP ${error.http_code}` : undefined,
       cloudinaryError: error?.error || undefined
-    };
-
-    console.error('Full error details:', errorDetails);
+    });
 
     return NextResponse.json(
-      errorDetails,
+      { error: 'An error occurred during image upload.' },
       { status: 500 }
     );
   }