fix(ui): stop treating a failed background model refetch as unverifiable

react-query keeps the last successful list around when a later refetch fails: data stays populated, but isError flips true. presetAvailability read isError alone, so once a caller had a good cached list, any subsequent refetch hiccup (window refocus, a manual retry that itself fails, etc.) made every preset unverifiable again, wrongly blocked an already-selected preset at the new submit-time check, and showed a "models are no longer available" toast for models that were, per the cache, still there. Only treat the state as unverifiable when there has never been a successful fetch (data is still undefined); otherwise keep trusting the cached list, matching how react-query itself treats stale-but-valid data.

ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.test.tsx

@@ -1,5 +1,5 @@
 import { renderWithProviders, screen, waitFor, testQueryClient } from "../../../tests/test-utils";
-import { fireEvent } from "@testing-library/react";
+import { act, fireEvent } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { vi } from "vitest";
 import AddAutoRouterTab from "./add_auto_router_tab";
@@ -200,6 +200,31 @@ describe("AddAutoRouterTab", () => {
     expect(mockFetchAvailableModels).toHaveBeenCalledTimes(2);
   });
 
+  // react-query keeps the last successful list when a later refetch fails, so a background
+  // refetch error must not treat an already-verified, still-cached preset as unverifiable: the
+  // caller never sees a stale error message, and a preset they already picked stays submittable.
+  it("keeps a selected preset submit-reachable when a background refetch fails but cached models remain valid", async () => {
+    const user = userEvent.setup();
+    mockFetchAvailableModels.mockResolvedValueOnce(ALL_FAMILY_MODELS).mockRejectedValue(new Error("boom"));
+
+    renderWithProviders(<Harness />);
+    openTemplateDropdown();
+    await waitFor(() => expect(isOptionDisabled(optionByLabel("Anthropic Family")!)).toBe(false));
+    fireEvent.click(optionByLabel("Anthropic Family")!);
+
+    await act(async () => {
+      await testQueryClient.refetchQueries({ queryKey: ["availableModels", "autoRouter", "token"] });
+    });
+
+    await user.type(screen.getByPlaceholderText(/smart_router/i), "resilient-router");
+    await user.click(screen.getByRole("button", { name: /add auto router/i }));
+
+    await waitFor(() => expect(mockHandleAddAutoRouterSubmit).toHaveBeenCalled());
+    expect(NotificationManager.fromBackend).not.toHaveBeenCalledWith(
+      "This template's models are no longer available. Please reselect a template or switch to Custom.",
+    );
+  });
+
   // The headline behavior: selecting a preset must pre-fill the tier config so the created
   // router carries the preset's models. Real tier validation runs here (getMissingTiersError is
   // not stubbed), so if selection stopped pre-filling, the empty tiers would either block the

ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.tsx

@@ -106,7 +106,7 @@ const AddAutoRouterTab: React.FC<AddAutoRouterTabProps> = ({
   }, [accessToken]);
 
   const {
-    data: modelInfo = [],
+    data,
     isLoading: modelsLoading,
     isError: modelsError,
     refetch: refetchModels,
@@ -115,6 +115,11 @@ const AddAutoRouterTab: React.FC<AddAutoRouterTabProps> = ({
     queryFn: () => fetchAvailableModels(accessToken),
     enabled: Boolean(accessToken),
   });
+  const modelInfo = React.useMemo(() => data ?? [], [data]);
+  // react-query keeps the last successful list around when a later refetch fails, so isError
+  // alone can't tell "never loaded" apart from "loaded, then a background refetch errored" - only
+  // the former leaves us with nothing trustworthy to verify a preset's models against.
+  const modelsUnverifiable = modelsError && data === undefined;
 
   const isAdmin = all_admin_roles.includes(userRole);
 
@@ -133,7 +138,7 @@ const AddAutoRouterTab: React.FC<AddAutoRouterTabProps> = ({
   // makes the load-race (pick during loading, then discover a missing model) unrepresentable.
   const presetAvailability = (preset: AutoRouterPreset): PresetAvailability => {
     if (modelsLoading) return { kind: "loading" };
-    if (modelsError) return { kind: "unverifiable" };
+    if (modelsUnverifiable) return { kind: "unverifiable" };
     const missing = getMissingModelsInPreset(preset, availableModelSet);
     return missing.length > 0 ? { kind: "missing_models", models: missing } : { kind: "available" };
   };
@@ -372,7 +377,7 @@ const AddAutoRouterTab: React.FC<AddAutoRouterTabProps> = ({
             {showValidationErrors && !selectedPreset && (
               <div className="text-xs mt-1 text-red-500">Please select a template</div>
             )}
-            {modelsError && (
+            {modelsUnverifiable && (
               <div className="text-xs mt-1 text-red-500">
                 Could not load available models.{" "}
                 <button type="button" className="underline" onClick={() => refetchModels()}>