Guarantee route and autogenerated sidebar sort order

.changeset/shy-parrots-dance.md

@@ -0,0 +1,5 @@
+---
+"@astrojs/starlight": patch
+---
+
+Guarantee route and autogenerated sidebar sort order

docs/src/content/docs/reference/configuration.md

@@ -97,6 +97,11 @@ starlight({
 });
 ```
 
+:::note[Sorting]
+Autogenerated sidebar groups are sorted by filename alphabetically.
+For example, a page generated from `astro.md` would appear above the page for `starlight.md`.
+:::
+
 #### `SidebarGroup`
 
 ```ts

packages/starlight/utils/routing.ts

@@ -76,7 +76,10 @@ function getRoutes(): Route[] {
     }
   }
 
-  return routes;
+  // Sort alphabetically by page slug to guarantee order regardless of platform.
+  return routes.sort((a, b) =>
+    a.slug < b.slug ? -1 : a.slug > b.slug ? 1 : 0
+  );
 }
 export const routes = getRoutes();