feat: make chat-style tasks the default experience (#11101)

ui/src/hooks/useClassicTaskInterfaceEnabled.ts

@@ -0,0 +1,42 @@
+import { useContext } from "react";
+import { QueryClient, QueryClientContext, useQuery } from "@tanstack/react-query";
+import { instanceSettingsApi } from "@/api/instanceSettings";
+import { queryKeys } from "@/lib/queryKeys";
+
+/**
+ * Fallback client for hosts that render gated components without a
+ * QueryClientProvider (isolated unit-test mounts, storybook-style renders).
+ * The query is disabled in that case, so this client never fetches — it only
+ * keeps `useQuery` from throwing. Created lazily so app code never pays for it.
+ */
+let detachedClient: QueryClient | null = null;
+function getDetachedClient(): QueryClient {
+  detachedClient ??= new QueryClient();
+  return detachedClient;
+}
+
+/**
+ * Classic Task Interface experimental flag (`enableClassicTaskInterface`).
+ *
+ * Wraps the shared experimental-settings query so gated call sites don't
+ * repeat the boilerplate. Fail-closed to chat-style: `enabled` stays false
+ * while the query is in flight, on fetch errors, and in renders without a
+ * QueryClientProvider (isolated unit-test mounts), so the default chat-style
+ * view is what renders unless the classic opt-in is provably on. `loaded`
+ * lets hosts that care distinguish "flag is off" from "flag not yet known".
+ */
+export function useClassicTaskInterfaceEnabled(): { enabled: boolean; loaded: boolean } {
+  const contextClient = useContext(QueryClientContext);
+  const { data, isFetched } = useQuery(
+    {
+      queryKey: queryKeys.instance.experimentalSettings,
+      queryFn: () => instanceSettingsApi.getExperimental(),
+      enabled: contextClient != null,
+    },
+    contextClient ?? getDetachedClient(),
+  );
+  if (!contextClient) {
+    return { enabled: false, loaded: true };
+  }
+  return { enabled: data?.enableClassicTaskInterface === true, loaded: isFetched };
+}