fix(splash): reuse latest chat message preview

src/app/chat/chat-screen.tsx

@@ -35,6 +35,7 @@ import { useChatUnlockNavigationFlow } from "./hooks/use-chat-unlock-navigation-
 import { useChatGuestLogin } from "./hooks/use-chat-guest-login";
 import { useChatMessageLimitBanner } from "./hooks/use-chat-message-limit-banner";
 import { useChatPromotionBootstrap } from "./hooks/use-chat-promotion-bootstrap";
+import { useSplashLatestMessageSync } from "./hooks/use-splash-latest-message-sync";
 
 const chatShellStyle = {
   "--chat-message-font-size": "clamp(16px, 3.333vw, 18px)",
@@ -47,6 +48,11 @@ export function ChatScreen() {
   const state = useChatState();
   const authState = useAuthState();
   const authDispatch = useAuthDispatch();
+  useSplashLatestMessageSync({
+    historyLoaded: state.historyLoaded,
+    loginStatus: authState.loginStatus,
+    messages: state.historyMessages,
+  });
   const isPromotionBootstrapReady = useChatPromotionBootstrap();
   const visibleMessages = isPromotionBootstrapReady
     ? state.messages

src/app/chat/hooks/use-splash-latest-message-sync.ts

@@ -0,0 +1,53 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+
+import type { LoginStatus } from "@/data/dto/auth";
+import type { UiMessage } from "@/data/dto/chat";
+import { resolveSplashLatestMessageCacheIdentity } from "@/lib/chat/splash_latest_message";
+import { getLatestSplashMessagePreview } from "@/lib/chat/splash_latest_message_preview";
+import { useSplashLatestMessageCache } from "@/providers/splash-latest-message-provider";
+
+export interface UseSplashLatestMessageSyncInput {
+  historyLoaded: boolean;
+  loginStatus: LoginStatus;
+  messages: readonly UiMessage[];
+}
+
+export function useSplashLatestMessageSync({
+  historyLoaded,
+  loginStatus,
+  messages,
+}: UseSplashLatestMessageSyncInput): void {
+  const cache = useSplashLatestMessageCache();
+  const hasObservedInitialSnapshotRef = useRef(false);
+  const identityPromiseRef = useRef<Promise<string | null> | null>(null);
+
+  useEffect(() => {
+    hasObservedInitialSnapshotRef.current = false;
+    identityPromiseRef.current = null;
+  }, [loginStatus]);
+
+  useEffect(() => {
+    if (!historyLoaded) return;
+
+    if (!hasObservedInitialSnapshotRef.current) {
+      hasObservedInitialSnapshotRef.current = true;
+      return;
+    }
+
+    const preview = getLatestSplashMessagePreview(messages);
+    let cancelled = false;
+
+    identityPromiseRef.current ??= resolveSplashLatestMessageCacheIdentity();
+    void identityPromiseRef.current.then((identity) => {
+      if (!cancelled && identity) {
+        cache.set(identity, preview);
+      }
+    });
+
+    return () => {
+      cancelled = true;
+    };
+  }, [cache, historyLoaded, messages]);
+}

src/app/splash/__tests__/splash-latest-message.helpers.test.ts

@@ -1,6 +1,9 @@
 import { describe, expect, it } from "vitest";
 
-import { getSplashLatestMessagePreview } from "@/lib/chat/splash_latest_message_preview";
+import {
+  getLatestSplashMessagePreview,
+  getSplashLatestMessagePreview,
+} from "@/lib/chat/splash_latest_message_preview";
 
 describe("getSplashLatestMessagePreview", () => {
   it("uses text content for text messages", () => {
@@ -34,6 +37,15 @@ describe("getSplashLatestMessagePreview", () => {
     ).toBe("[图片]");
   });
 
+  it("uses image placeholder for a mapped UI image message", () => {
+    expect(
+      getSplashLatestMessagePreview({
+        content: "",
+        imageUrl: "https://example.com/image.jpg",
+      }),
+    ).toBe("[图片]");
+  });
+
   it("uses voice placeholder for voice messages", () => {
     expect(
       getSplashLatestMessagePreview({
@@ -54,6 +66,35 @@ describe("getSplashLatestMessagePreview", () => {
     ).toBe("[语音]");
   });
 
+  it("uses media placeholders for mapped UI lock reasons", () => {
+    expect(
+      getSplashLatestMessagePreview({
+        content: "",
+        lockReason: "voice_message",
+      }),
+    ).toBe("[语音]");
+    expect(
+      getSplashLatestMessagePreview({
+        content: "",
+        lockReason: "image_paywall",
+      }),
+    ).toBe("[图片]");
+  });
+
+  it("skips synthetic messages when selecting the latest preview", () => {
+    expect(
+      getLatestSplashMessagePreview([
+        { content: "Real message" },
+        { content: "Greeting", isSynthetic: true },
+      ]),
+    ).toBe("Real message");
+    expect(
+      getLatestSplashMessagePreview([
+        { content: "Greeting", isSynthetic: true },
+      ]),
+    ).toBeNull();
+  });
+
   it("falls back when the latest message has no displayable content", () => {
     expect(
       getSplashLatestMessagePreview({

src/app/splash/hooks/use-splash-latest-message.ts

@@ -3,7 +3,8 @@
 import { useEffect, useState } from "react";
 
 import type { LoginStatus } from "@/data/dto/auth";
-import { fetchSplashLatestMessagePreview } from "@/lib/chat/splash_latest_message";
+import { loadSplashLatestMessagePreview } from "@/lib/chat/splash_latest_message";
+import { useSplashLatestMessageCache } from "@/providers/splash-latest-message-provider";
 import { Logger, Result } from "@/utils";
 
 const log = new Logger("SplashLatestMessage");
@@ -30,6 +31,7 @@ export function useSplashLatestMessage({
   isAuthLoading,
   loginStatus,
 }: UseSplashLatestMessageInput): UseSplashLatestMessageOutput {
+  const cache = useSplashLatestMessageCache();
   const [state, setState] = useState<SplashLatestMessageState>({
     key: "",
     loaded: false,
@@ -45,7 +47,7 @@ export function useSplashLatestMessage({
     let cancelled = false;
 
     const loadLatestMessage = async () => {
-      const result = await fetchSplashLatestMessagePreview();
+      const result = await loadSplashLatestMessagePreview({ cache });
       if (cancelled) return;
 
       if (Result.isErr(result)) {
@@ -69,7 +71,7 @@ export function useSplashLatestMessage({
     return () => {
       cancelled = true;
     };
-  }, [requestKey, shouldLoad]);
+  }, [cache, requestKey, shouldLoad]);
 
   if (!shouldLoad) return { message: null, isLoading: false };
   if (state.key !== requestKey || !state.loaded) {

src/data/dto/chat/ui_message.ts

@@ -13,6 +13,8 @@ export const UiMessageSchema = z.object({
   isFromAI: z.boolean(),
   /** 日期分隔条使用的本地日期（YYYY-MM-DD） */
   date: z.string(),
+  /** 前端生成的辅助消息，不应作为服务端聊天预览。 */
+  isSynthetic: z.boolean().optional(),
   /** 图片 URL（base64 data URL 或 http URL） */
   imageUrl: z.string().optional(),
   /** true = 图片可在列表展示，但全屏查看时需要会员解锁 */

src/lib/chat/__tests__/splash_latest_message.test.ts

@@ -8,7 +8,11 @@ vi.mock("@/data/repositories/chat_repository", () => ({
   getChatRepository: () => ({ getHistory: getHistoryMock }),
 }));
 
-import { fetchSplashLatestMessagePreview } from "../splash_latest_message";
+import {
+  fetchSplashLatestMessagePreview,
+  loadSplashLatestMessagePreview,
+} from "../splash_latest_message";
+import { createSplashLatestMessageCache } from "../splash_latest_message_cache";
 
 describe("fetchSplashLatestMessagePreview", () => {
   beforeEach(() => {
@@ -39,3 +43,87 @@ describe("fetchSplashLatestMessagePreview", () => {
     expect(Result.isOk(result) && result.data).toBeNull();
   });
 });
+
+describe("loadSplashLatestMessagePreview", () => {
+  it("reuses a successful result for the same identity", async () => {
+    const cache = createSplashLatestMessageCache();
+    const fetchPreview = vi.fn().mockResolvedValue(Result.ok("Hello again"));
+    const resolveIdentity = vi.fn().mockResolvedValue(Result.ok("user:1"));
+
+    const first = await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity,
+    });
+    const second = await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity,
+    });
+
+    expect(Result.isOk(first) && first.data).toBe("Hello again");
+    expect(Result.isOk(second) && second.data).toBe("Hello again");
+    expect(fetchPreview).toHaveBeenCalledTimes(1);
+  });
+
+  it("treats a cached empty history as a cache hit", async () => {
+    const cache = createSplashLatestMessageCache();
+    cache.set("user:empty", null);
+    const fetchPreview = vi.fn();
+
+    const result = await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity: vi
+        .fn()
+        .mockResolvedValue(Result.ok("user:empty")),
+    });
+
+    expect(Result.isOk(result) && result.data).toBeNull();
+    expect(fetchPreview).not.toHaveBeenCalled();
+  });
+
+  it("does not cache failed requests", async () => {
+    const cache = createSplashLatestMessageCache();
+    const fetchPreview = vi
+      .fn()
+      .mockResolvedValueOnce(Result.err(new Error("offline")))
+      .mockResolvedValueOnce(Result.ok("Recovered"));
+    const resolveIdentity = vi.fn().mockResolvedValue(Result.ok("user:1"));
+
+    await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity,
+    });
+    const retry = await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity,
+    });
+
+    expect(Result.isOk(retry) && retry.data).toBe("Recovered");
+    expect(fetchPreview).toHaveBeenCalledTimes(2);
+  });
+
+  it("bypasses the cache when the identity is unavailable", async () => {
+    const cache = createSplashLatestMessageCache();
+    const fetchPreview = vi.fn().mockResolvedValue(Result.ok("Network"));
+    const resolveIdentity = vi
+      .fn()
+      .mockResolvedValue(Result.err(new Error("missing identity")));
+
+    await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity,
+    });
+    await loadSplashLatestMessagePreview({
+      cache,
+      fetchPreview,
+      resolveIdentity,
+    });
+
+    expect(fetchPreview).toHaveBeenCalledTimes(2);
+  });
+});

src/lib/chat/__tests__/splash_latest_message_cache.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+
+import { createSplashLatestMessageCache } from "../splash_latest_message_cache";
+
+describe("splash latest message cache", () => {
+  it("isolates previews by chat identity", () => {
+    const cache = createSplashLatestMessageCache();
+
+    cache.set("user:1", "First user");
+    cache.set("user:2", "Second user");
+
+    expect(cache.get("user:1")?.message).toBe("First user");
+    expect(cache.get("user:2")?.message).toBe("Second user");
+    expect(cache.get("user:3")).toBeUndefined();
+  });
+
+  it("clears all session previews", () => {
+    const cache = createSplashLatestMessageCache();
+    cache.set("user:1", null);
+
+    cache.clear();
+
+    expect(cache.get("user:1")).toBeUndefined();
+  });
+});

src/lib/chat/splash_latest_message.ts

@@ -1,9 +1,47 @@
 "use client";
 
 import { getChatRepository } from "@/data/repositories/chat_repository";
+import {
+  resolveChatCacheOwnerKey,
+  type ChatCacheIdentityResolver,
+} from "@/data/repositories/chat_cache_identity";
 import { Result, type Result as ResultT } from "@/utils";
 
-import { getSplashLatestMessagePreview } from "./splash_latest_message_preview";
+import type { SplashLatestMessageCache } from "./splash_latest_message_cache";
+import { getLatestSplashMessagePreview } from "./splash_latest_message_preview";
+
+export interface LoadSplashLatestMessagePreviewInput {
+  cache: SplashLatestMessageCache;
+  fetchPreview?: () => Promise<ResultT<string | null>>;
+  resolveIdentity?: ChatCacheIdentityResolver;
+}
+
+export async function resolveSplashLatestMessageCacheIdentity(): Promise<
+  string | null
+> {
+  const result = await resolveChatCacheOwnerKey();
+  return Result.isOk(result) ? result.data : null;
+}
+
+export async function loadSplashLatestMessagePreview({
+  cache,
+  fetchPreview = fetchSplashLatestMessagePreview,
+  resolveIdentity = resolveChatCacheOwnerKey,
+}: LoadSplashLatestMessagePreviewInput): Promise<ResultT<string | null>> {
+  const identityResult = await resolveIdentity();
+  const identity = Result.isOk(identityResult) ? identityResult.data : null;
+
+  if (identity) {
+    const cached = cache.get(identity);
+    if (cached) return Result.ok(cached.message);
+  }
+
+  const result = await fetchPreview();
+  if (identity && Result.isOk(result)) {
+    cache.set(identity, result.data);
+  }
+  return result;
+}
 
 export async function fetchSplashLatestMessagePreview(): Promise<
   ResultT<string | null>
@@ -11,6 +49,5 @@ export async function fetchSplashLatestMessagePreview(): Promise<
   const result = await getChatRepository().getHistory(1, 0);
   if (Result.isErr(result)) return Result.err(result.error);
 
-  const latestMessage = result.data.messages.at(-1) ?? null;
-  return Result.ok(getSplashLatestMessagePreview(latestMessage));
+  return Result.ok(getLatestSplashMessagePreview(result.data.messages));
 }

src/lib/chat/splash_latest_message_cache.ts

@@ -0,0 +1,19 @@
+export interface SplashLatestMessageCacheEntry {
+  message: string | null;
+}
+
+export interface SplashLatestMessageCache {
+  clear(): void;
+  get(identity: string): SplashLatestMessageCacheEntry | undefined;
+  set(identity: string, message: string | null): void;
+}
+
+export function createSplashLatestMessageCache(): SplashLatestMessageCache {
+  const entries = new Map<string, SplashLatestMessageCacheEntry>();
+
+  return {
+    clear: () => entries.clear(),
+    get: (identity) => entries.get(identity),
+    set: (identity, message) => entries.set(identity, { message }),
+  };
+}

src/lib/chat/splash_latest_message_preview.ts

@@ -2,6 +2,9 @@ export interface SplashLatestMessageSource {
   type?: string | null;
   content?: string | null;
   audioUrl?: string | null;
+  imageUrl?: string | null;
+  isSynthetic?: boolean;
+  lockReason?: string | null;
   image?: {
     type?: string | null;
     url?: string | null;
@@ -18,7 +21,7 @@ const FALLBACK_PREVIEW_TEXT = "[消息]";
 export function getSplashLatestMessagePreview(
   message: SplashLatestMessageSource | null | undefined,
 ): string | null {
-  if (!message) return null;
+  if (!message || message.isSynthetic) return null;
 
   if (isVoiceMessage(message)) return VOICE_PREVIEW_TEXT;
   if (isImageMessage(message)) return IMAGE_PREVIEW_TEXT;
@@ -27,13 +30,25 @@ export function getSplashLatestMessagePreview(
   return content.length > 0 ? content : FALLBACK_PREVIEW_TEXT;
 }
 
+export function getLatestSplashMessagePreview(
+  messages: readonly SplashLatestMessageSource[],
+): string | null {
+  for (let index = messages.length - 1; index >= 0; index -= 1) {
+    const message = messages[index];
+    if (message && !message.isSynthetic) {
+      return getSplashLatestMessagePreview(message);
+    }
+  }
+  return null;
+}
+
 function isVoiceMessage(message: SplashLatestMessageSource): boolean {
   const type = normalizeMessageType(message.type);
   return (
     type === "voice" ||
     type === "audio" ||
     hasValue(message.audioUrl) ||
-    message.lockDetail?.reason === "voice_message"
+    getLockReason(message) === "voice_message"
   );
 }
 
@@ -41,12 +56,18 @@ function isImageMessage(message: SplashLatestMessageSource): boolean {
   const type = normalizeMessageType(message.type);
   return (
     type === "image" ||
+    hasValue(message.imageUrl) ||
     hasValue(message.image?.url) ||
     hasValue(message.image?.type) ||
-    message.lockDetail?.reason === "image"
+    getLockReason(message) === "image" ||
+    getLockReason(message) === "image_paywall"
   );
 }
 
+function getLockReason(message: SplashLatestMessageSource): string | null {
+  return message.lockReason ?? message.lockDetail?.reason ?? null;
+}
+
 function normalizeMessageType(value: string | null | undefined): string {
   return value?.trim().toLowerCase() ?? "";
 }

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 />
+        <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;
+}

src/stores/chat/chat-history-sync.ts

@@ -35,6 +35,7 @@ export function createGreetingMessage(): UiMessage {
       "Finally I can relax. How was your day out?",
     isFromAI: true,
     date: todayString(),
+    isSynthetic: true,
   };
 }