docs: add additional behaviors for layout stability in CloudFront configuration

Author: skeptrunedev

advanced/subpath/route53-cloudfront.mdx

@@ -158,6 +158,29 @@ Lastly, we're going to edit the `Default (*)` behavior.
 
 2. Select **Save changes**.
 
+### Additional behaviors for layout stability
+
+To prevent layout shifts and ensure smooth navigation, add these additional behaviors for static asset handling:
+
+#### `/mintlify-assets/_next/static/*`
+
+Create a behavior with a **Path pattern** of `/mintlify-assets/_next/static/*` to serve static assets efficiently:
+
+- Set **Origin and origin groups** to your `.mintlify.dev` URL
+- Set **Cache policy** to **CachingOptimized** 
+- Set **Origin request policy** to **AllViewerExceptHostHeader**
+
+This behavior should be ordered **above** the default behavior in your behaviors list, as CloudFront evaluates them in order.
+
+#### Update default behavior for app router navigation
+
+For your **Default (*)** behavior, ensure these settings to handle HTML and app router navigation properly:
+
+- Set **Cache policy** to **CachingDisabled** (since RSC ?_rsc= payloads vary and shouldn't be cached)
+- Set **Origin request policy** to **AllViewerExceptHostHeader**
+
+These configurations prevent the sidenav from snapping up and down during navigation by ensuring only the new page's MDX content is fetched while keeping layout assets stable.
+
 ### Check behaviors are set up correctly
 
 If you follow the above steps, your behaviors should look like this:
@@ -208,4 +231,4 @@ Now, we're going to bring the functionality of the CloudFront distribution into
 
 Your documentation is now live at `/docs` for your primary domain.
 
-<Propagating />
+<Propagating />