some comments..

packages/builder/src/pages/[application]/backend/model/_layout.svelte

@@ -8,6 +8,8 @@
   }
 
   onMount(async () => {
+    // navigate to first model in list, if not already selected
+    // and this is the final url (i.e. no selectedModel)
     if (!$leftover && $backendUiStore.models.length > 0 && (!$backendUiStore.selectedModel || !$backendUiStore.selectedModel._id)) {
       $goto(`./${$backendUiStore.models[0]._id}`)
     }

packages/builder/src/pages/[application]/backend/model/index.svelte

@@ -8,7 +8,10 @@
   }
 
   onMount(async () => {
+     // navigate to first model in list, if not already selected
+    // and this is the final url (i.e. no selectedModel)
     if (!$leftover && $backendUiStore.models.length > 0 && (!$backendUiStore.selectedModel || !$backendUiStore.selectedModel._id)) {
+      // this file routes as .../models/index, so, go up one.
       $goto(`../${$backendUiStore.models[0]._id}`)
     }
   })