fix(splash): reuse latest chat message preview

src/providers/root-providers.tsx

@@ -3,12 +3,13 @@
 /**
  * 根级 Client Providers 包装
  *
- * 这里只保留跨路由的 Auth、User 和 viewport Provider。Chat、Payment、
- * PrivateRoom 状态机由对应路由 layout 按需挂载。
+ * 这里只保留跨路由的 Auth、User、消息预览和 viewport Provider。Chat、
+ * Payment、PrivateRoom 状态机由对应路由 layout 按需挂载。
  */
 
 import type { ReactNode } from "react";
 
+import { SplashLatestMessageProvider } from "@/providers/splash-latest-message-provider";
 import { ViewportCssVarsProvider } from "@/providers/viewport-css-vars-provider";
 import { AppNavigationGuard } from "@/router/app-navigation-guard";
 import { AuthProvider } from "@/stores/auth/auth-context";
@@ -28,11 +29,13 @@ export function RootProviders({ children }: RootProvidersProps) {
         <AuthStatusChecker />
         <OAuthSessionSync />
         <AppNavigationGuard />
-        <UserProvider>
-          <UserAuthSync />
-          {children}
-          <div id="toast-portal" />
-        </UserProvider>
+        <SplashLatestMessageProvider>
+          <UserProvider>
+            <UserAuthSync />
+            {children}
+            <div id="toast-portal" />
+          </UserProvider>
+        </SplashLatestMessageProvider>
       </AuthProvider>
     </ViewportCssVarsProvider>
   );

src/providers/splash-latest-message-provider.tsx

@@ -0,0 +1,73 @@
+"use client";
+
+import {
+  createContext,
+  type ReactNode,
+  useContext,
+  useEffect,
+  useRef,
+  useState,
+} from "react";
+
+import {
+  createSplashLatestMessageCache,
+  type SplashLatestMessageCache,
+} from "@/lib/chat/splash_latest_message_cache";
+import { useAuthState } from "@/stores/auth/auth-context";
+
+const SplashLatestMessageCacheContext =
+  createContext<SplashLatestMessageCache | null>(null);
+
+export function SplashLatestMessageProvider({
+  children,
+}: {
+  children: ReactNode;
+}) {
+  const [cache] = useState(createSplashLatestMessageCache);
+
+  return (
+    <SplashLatestMessageCacheContext.Provider value={cache}>
+      <SplashLatestMessageAuthSync cache={cache} />
+      {children}
+    </SplashLatestMessageCacheContext.Provider>
+  );
+}
+
+export function useSplashLatestMessageCache(): SplashLatestMessageCache {
+  const cache = useContext(SplashLatestMessageCacheContext);
+  if (!cache) {
+    throw new Error(
+      "useSplashLatestMessageCache must be used within SplashLatestMessageProvider.",
+    );
+  }
+  return cache;
+}
+
+function SplashLatestMessageAuthSync({
+  cache,
+}: {
+  cache: SplashLatestMessageCache;
+}) {
+  const authState = useAuthState();
+  const previousLoginStatusRef = useRef<string | null>(null);
+
+  useEffect(() => {
+    if (!authState.hasInitialized || authState.isLoading) return;
+
+    const previousLoginStatus = previousLoginStatusRef.current;
+    if (
+      previousLoginStatus !== null &&
+      previousLoginStatus !== authState.loginStatus
+    ) {
+      cache.clear();
+    }
+    previousLoginStatusRef.current = authState.loginStatus;
+  }, [
+    authState.hasInitialized,
+    authState.isLoading,
+    authState.loginStatus,
+    cache,
+  ]);
+
+  return null;
+}