fix(ui): fix Router Settings Loadbalancing tab save (LIT-4057)

The Loadbalancing tab rendered routing_groups as a generic text input and
sent its array value back as the JSON string "[]", which fails Pydantic
list validation on POST /config/update and returns 422. routing_groups has
its own dedicated Routing Groups tab, so this tab must neither render nor
write it; exclude it the same way retry_policy and model_group_retry_policy
are excluded for the Model Retry Settings tab.

The save was also fire-and-forget: setCallbacksCall was not awaited, so the
rejected promise escaped the try/catch and the success toast fired
unconditionally, showing success even when the backend rejected the change.
Await the call, gate the success toast on resolution, and surface the error.

ui/litellm-dashboard/src/components/router_settings/ReliabilityRetriesSection.tsx

@@ -20,14 +20,15 @@ const ReliabilityRetriesSection: React.FC<ReliabilityRetriesSectionProps> = ({
       <div className="grid grid-cols-1 gap-6 lg:grid-cols-2 xl:grid-cols-3">
         {Object.entries(routerSettings)
           .filter(
-            ([param, value]) =>
+            ([param]) =>
               param != "fallbacks" &&
               param != "context_window_fallbacks" &&
               param != "routing_strategy_args" &&
               param != "routing_strategy" &&
               param != "enable_tag_filtering" &&
               param != "retry_policy" &&
-              param != "model_group_retry_policy",
+              param != "model_group_retry_policy" &&
+              param != "routing_groups",
           )
           .map(([param, value]) => (
             <div key={param} className="space-y-2">

ui/litellm-dashboard/src/components/router_settings/index.test.tsx

@@ -146,4 +146,44 @@ describe("RouterSettings", () => {
 
     expect(NotificationsManager.success).toHaveBeenCalledWith("router settings updated successfully");
   });
+
+  it("should not render or save routing_groups (owned by the Routing Groups tab) (LIT-4057)", async () => {
+    const user = userEvent.setup();
+    vi.mocked(getCallbacksCall).mockResolvedValue({
+      router_settings: {
+        routing_strategy: "simple-shuffle",
+        num_retries: 3,
+        routing_groups: [{ group_name: "g1", models: ["gpt-4"], routing_strategy: "simple-shuffle" }],
+      },
+    });
+    renderWithProviders(<RouterSettings {...defaultProps} />);
+
+    await waitFor(() => {
+      expect(screen.getByTestId("strategy-select")).toBeInTheDocument();
+    });
+    expect(document.querySelector('input[name="routing_groups"]')).toBeNull();
+
+    await user.click(screen.getByRole("button", { name: /save changes/i }));
+
+    const payload = vi.mocked(setCallbacksCall).mock.calls[0][1] as {
+      router_settings: Record<string, unknown>;
+    };
+    expect(payload.router_settings).not.toHaveProperty("routing_groups");
+  });
+
+  it("should surface an error and not claim success when saving fails (LIT-4057)", async () => {
+    const user = userEvent.setup();
+    vi.mocked(setCallbacksCall).mockRejectedValue(new Error("422 Unprocessable Entity"));
+    renderWithProviders(<RouterSettings {...defaultProps} />);
+
+    await waitFor(() => {
+      expect(screen.getByTestId("strategy-select")).toBeInTheDocument();
+    });
+    await user.click(screen.getByRole("button", { name: /save changes/i }));
+
+    await waitFor(() => {
+      expect(NotificationsManager.fromBackend).toHaveBeenCalled();
+    });
+    expect(NotificationsManager.success).not.toHaveBeenCalled();
+  });
 });

ui/litellm-dashboard/src/components/router_settings/index.tsx

@@ -81,7 +81,7 @@ const RouterSettings: React.FC<RouterSettingsProps> = ({ accessToken, userRole,
     });
   }, [accessToken, userRole, userID]);
 
-  const handleSaveChanges = () => {
+  const handleSaveChanges = async () => {
     if (!accessToken) {
       return;
     }
@@ -91,9 +91,9 @@ const RouterSettings: React.FC<RouterSettingsProps> = ({ accessToken, userRole,
 
     const numberKeys = new Set(["allowed_fails", "cooldown_time", "num_retries", "timeout", "retry_after"]);
     const jsonKeys = new Set(["model_group_alias"]);
-    // retry_policy and model_group_retry_policy are owned exclusively by the
-    // Model Retry Settings tab; this page must not read or write them.
-    const tabOwnedKeys = new Set(["retry_policy", "model_group_retry_policy"]);
+    // retry_policy and model_group_retry_policy are owned by the Model Retry Settings tab;
+    // routing_groups is owned by the Routing Groups tab. This page must not read or write them.
+    const tabOwnedKeys = new Set(["retry_policy", "model_group_retry_policy", "routing_groups"]);
 
     const parseInputValue = (key: string, raw: string | undefined, fallback: unknown) => {
       if (raw === undefined) return fallback;
@@ -172,12 +172,11 @@ const RouterSettings: React.FC<RouterSettingsProps> = ({ accessToken, userRole,
     };
 
     try {
-      setCallbacksCall(accessToken, payload);
+      await setCallbacksCall(accessToken, payload);
+      NotificationsManager.success("router settings updated successfully");
     } catch (error) {
       NotificationsManager.fromBackend("Failed to update router settings: " + error);
     }
-
-    NotificationsManager.success("router settings updated successfully");
   };
 
   if (!accessToken) {