diff --git a/web-admin/src/features/organizations/user-management/dialogs/AddGuestsDialog.svelte b/web-admin/src/features/organizations/user-management/dialogs/AddGuestsDialog.svelte
index e2f13f2600c..9838f58d81c 100644
--- a/web-admin/src/features/organizations/user-management/dialogs/AddGuestsDialog.svelte
+++ b/web-admin/src/features/organizations/user-management/dialogs/AddGuestsDialog.svelte
@@ -43,6 +43,14 @@
   let projectDropdownOpen = false;
   let selectedRole: "admin" | "editor" | "viewer" = "viewer";
   let roleDropdownOpen = false;
+  let hasAutoSelectedProject = false;
+
+  function resetDialogState() {
+    failedInvites = [];
+    selectedProjects = [];
+    selectedRole = "viewer";
+    hasAutoSelectedProject = false;
+  }
 
   // Projects list
   $: projectsQuery = createAdminServiceListProjectsForOrganization(
@@ -63,6 +71,20 @@
   $: selectedRoleLabel =
     ORG_ROLES_OPTIONS.find((o) => o.value === selectedRole)?.label ?? "";
 
+  $: selectedProjectsLabel = (() => {
+    if (selectedProjects.length === 0) return "Select projects";
+    if (selectedProjects.length === 1) return selectedProjects[0];
+    return `${selectedProjects.length} Project${selectedProjects.length > 1 ? "s" : ""}`;
+  })();
+
+  $: if (open && !hasAutoSelectedProject && projects.length > 0) {
+    const firstProjectName = projects[0]?.name;
+    if (firstProjectName) {
+      selectedProjects = [firstProjectName];
+      hasAutoSelectedProject = true;
+    }
+  }
+
   function toggleProjectSelection(projectName: string) {
     const idx = selectedProjects.indexOf(projectName);
     if (idx >= 0) {
@@ -153,8 +175,7 @@
 
         if (failedInvites.length === 0) {
           open = false;
-          selectedProjects = [];
-          selectedRole = "viewer";
+          resetDialogState();
         }
       },
       validationMethod: "oninput",
@@ -173,15 +194,11 @@
   onOutsideClick={(e) => {
     e.preventDefault();
     open = false;
-    failedInvites = [];
-    selectedProjects = [];
-    selectedRole = "viewer";
+    resetDialogState();
   }}
-  onOpenChange={(open) => {
-    if (!open) {
-      failedInvites = [];
-      selectedProjects = [];
-      selectedRole = "viewer";
+  onOpenChange={(dialogOpen) => {
+    if (!dialogOpen) {
+      resetDialogState();
     }
   }}
 >
@@ -231,16 +248,17 @@
         {:else if projects.length === 0}
           <div class="text-xs text-slate-500">No projects</div>
         {:else}
-          <Dropdown.Root bind:open={projectDropdownOpen}>
+          <Dropdown.Root
+            bind:open={projectDropdownOpen}
+            closeOnItemClick={false}
+          >
             <Dropdown.Trigger
               class="min-w-[260px] flex flex-row justify-between gap-1 items-center rounded-sm border border-gray-300 {projectDropdownOpen
                 ? 'bg-slate-200'
                 : 'hover:bg-slate-100'} px-2 py-1"
             >
               <span>
-                {selectedProjects.length > 0
-                  ? `${selectedProjects.length} Project${selectedProjects.length > 1 ? "s" : ""}`
-                  : "Select projects"}
+                {selectedProjectsLabel}
               </span>
               {#if projectDropdownOpen}
                 <CaretUpIcon size="12px" />
@@ -253,7 +271,7 @@
                 <Dropdown.CheckboxItem
                   class="font-normal flex items-center overflow-hidden"
                   checked={selectedProjects.includes(p.name)}
-                  on:click={() => toggleProjectSelection(p.name)}
+                  onCheckedChange={() => toggleProjectSelection(p.name)}
                 >
                   <span class="truncate w-full" title={p.name}>{p.name}</span>
                 </Dropdown.CheckboxItem>