diff --git a/apps/web/public/sw.js b/apps/web/public/sw.js
deleted file mode 100644
index cbd0915..0000000
--- a/apps/web/public/sw.js
+++ /dev/null
@@ -1,25 +0,0 @@
-const CACHE_NAME = "cents-shell-v3";
-const APP_SHELL = ["/", "/manifest.webmanifest"];
-
-self.addEventListener("install", (event) => {
-  event.waitUntil(caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL)));
-});
-
-self.addEventListener("activate", (event) => {
-  event.waitUntil(
-    caches
-      .keys()
-      .then((keys) => Promise.all(keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key)))),
-  );
-});
-
-self.addEventListener("fetch", (event) => {
-  if (event.request.method !== "GET") return;
-
-  event.respondWith(
-    caches.match(event.request).then((cached) => {
-      if (cached) return cached;
-      return fetch(event.request).catch(() => caches.match("/"));
-    }),
-  );
-});
diff --git a/apps/web/src/App.vue b/apps/web/src/App.vue
index 4be8965..edf8a5e 100644
--- a/apps/web/src/App.vue
+++ b/apps/web/src/App.vue
@@ -1,4 +1,19 @@
+<script setup lang="ts">
+import { onBeforeUnmount, onMounted } from "vue";
+import { useAuthStore } from "./stores/auth";
+
+const auth = useAuthStore();
+const retrySession = () => {
+  if (typeof navigator === "undefined" || navigator.onLine) void auth.loadSession(true);
+};
+
+onMounted(() => window.addEventListener("online", retrySession));
+onBeforeUnmount(() => window.removeEventListener("online", retrySession));
+</script>
+
 <template>
   <RouterView />
+  <div v-if="auth.unavailable && auth.user" class="offline-status" role="status">
+    服务暂不可用，当前显示本地数据
+  </div>
 </template>
-
diff --git a/apps/web/src/stores/auth.ts b/apps/web/src/stores/auth.ts
index fa7d741..810b64e 100644
--- a/apps/web/src/stores/auth.ts
+++ b/apps/web/src/stores/auth.ts
@@ -5,6 +5,27 @@ import { closeUserDb } from "../data/db";
 export type SessionUser = { id: string; name: string };
 
 let sessionPromise: Promise<void> | null = null;
+const LAST_SESSION_KEY = "cents:last-session-user";
+
+function readLastSession(): SessionUser | null {
+  try {
+    const value = localStorage.getItem(LAST_SESSION_KEY);
+    if (!value) return null;
+    const user = JSON.parse(value) as SessionUser;
+    return user?.id && user?.name ? user : null;
+  } catch {
+    return null;
+  }
+}
+
+function writeLastSession(user: SessionUser | null) {
+  try {
+    if (user) localStorage.setItem(LAST_SESSION_KEY, JSON.stringify(user));
+    else localStorage.removeItem(LAST_SESSION_KEY);
+  } catch {
+    // Storage can be disabled by the browser; server auth still works.
+  }
+}
 
 export const useAuthStore = defineStore("auth", {
   state: () => ({
@@ -21,8 +42,9 @@ export const useAuthStore = defineStore("auth", {
           const result = await apiRequest<{ user: SessionUser | null }>("/api/auth/session");
           this.user = result.user;
           this.unavailable = false;
+          writeLastSession(result.user);
         } catch {
-          this.user = null;
+          this.user = readLastSession();
           this.unavailable = true;
         } finally {
           this.loaded = true;
@@ -40,6 +62,7 @@ export const useAuthStore = defineStore("auth", {
         body: { name },
       });
       this.user = result.user;
+      writeLastSession(result.user);
     },
     async login(name: string, password: string) {
       const result = await apiRequest<{ user: SessionUser }>("/api/auth/login", {
@@ -49,6 +72,7 @@ export const useAuthStore = defineStore("auth", {
       this.user = result.user;
       this.loaded = true;
       this.unavailable = false;
+      writeLastSession(result.user);
     },
     async logout() {
       const userId = this.user?.id;
@@ -56,6 +80,7 @@ export const useAuthStore = defineStore("auth", {
       if (userId) closeUserDb(userId);
       this.user = null;
       this.loaded = true;
+      writeLastSession(null);
     },
   },
 });
diff --git a/apps/web/src/stores/ledgers.ts b/apps/web/src/stores/ledgers.ts
index 0cc3a80..ccb8bec 100644
--- a/apps/web/src/stores/ledgers.ts
+++ b/apps/web/src/stores/ledgers.ts
@@ -40,7 +40,15 @@ export const useLedgerStore = defineStore("ledgers", {
         const auth = useAuthStore();
         if (!auth.user) return;
         const db = await getUserDb(auth.user.id);
-        const result = await apiRequest<{ ledgers: LedgerRecord[] }>("/api/ledgers");
+        let serverLedgers: LedgerRecord[];
+        try {
+          const result = await apiRequest<{ ledgers: LedgerRecord[] }>("/api/ledgers");
+          serverLedgers = result.ledgers;
+        } catch (error) {
+          const cachedLedgers = await db.ledgers.toArray();
+          if (!cachedLedgers.length) throw error;
+          serverLedgers = cachedLedgers;
+        }
         const displayPreferences = await db.userPreferences
           .where("userId")
           .equals(auth.user.id)
@@ -57,17 +65,16 @@ export const useLedgerStore = defineStore("ledgers", {
         const summaryByLedger = new Map(
           summaryPreferences.map((preference) => [preference.id.split(":").at(-1), preference.value as LedgerSummaryRange]),
         );
-        const serverLedgers = result.ledgers.map((ledger) => ({
+        const hydratedLedgers = serverLedgers.map((ledger) => ({
           ...ledger,
           amountDisplay: displayByLedger.get(ledger.id) ?? "base",
           summaryRange: summaryByLedger.get(ledger.id) ?? "year",
         }));
-        this.ledgers = serverLedgers;
+        this.ledgers = hydratedLedgers;
 
-        const allowedIds = new Set(this.ledgers.map((ledger) => ledger.id));
         await db.transaction("rw", db.ledgers, async () => {
           await db.ledgers.clear();
-          if (serverLedgers.length) await db.ledgers.bulkPut(serverLedgers);
+          if (hydratedLedgers.length) await db.ledgers.bulkPut(hydratedLedgers);
         });
 
         const preferenceId = currentLedgerPreferenceId(auth.user.id);
@@ -76,7 +83,11 @@ export const useLedgerStore = defineStore("ledgers", {
         this.currentLedgerId = preferredLedger?.id ?? this.ledgers[0]?.id ?? "";
         if (this.currentLedgerId !== preference?.value) await this.persistCurrentLedger();
         this.loaded = true;
-        await this.loadCurrentMembers();
+        try {
+          await this.loadCurrentMembers();
+        } catch {
+          this.currentMembers = [];
+        }
       })();
       try {
         await ledgerLoadPromise;
@@ -116,10 +127,14 @@ export const useLedgerStore = defineStore("ledgers", {
         this.currentMembers = [];
         return;
       }
-      const result = await apiRequest<{ members: LedgerMember[] }>(
-        `/api/ledgers/${encodeURIComponent(this.currentLedgerId)}/members`,
-      );
-      this.currentMembers = result.members;
+      try {
+        const result = await apiRequest<{ members: LedgerMember[] }>(
+          `/api/ledgers/${encodeURIComponent(this.currentLedgerId)}/members`,
+        );
+        this.currentMembers = result.members;
+      } catch {
+        this.currentMembers = [];
+      }
     },
     memberName(userId: string) {
       return this.currentMembers.find((member) => member.id === userId)?.name ?? "历史用户";
diff --git a/apps/web/src/styles.css b/apps/web/src/styles.css
index d7fcb81..e0e205a 100644
--- a/apps/web/src/styles.css
+++ b/apps/web/src/styles.css
@@ -12,6 +12,23 @@
   box-sizing: border-box;
 }
 
+.offline-status {
+  position: fixed;
+  top: max(10px, env(safe-area-inset-top));
+  left: 50%;
+  z-index: 100;
+  max-width: calc(100% - 32px);
+  padding: 7px 12px;
+  border: 1px solid #e9c98d;
+  border-radius: 999px;
+  background: rgba(255, 248, 228, .96);
+  color: #795b19;
+  font-size: 11px;
+  line-height: 1.2;
+  pointer-events: none;
+  transform: translateX(-50%);
+}
+
 html,
 body,
 #app {
diff --git a/apps/web/vite.config.ts b/apps/web/vite.config.ts
index 12f66a6..fc2b629 100644
--- a/apps/web/vite.config.ts
+++ b/apps/web/vite.config.ts
@@ -81,9 +81,75 @@ function appIdentityPlugin(mode: string): Plugin {
   };
 }
 
+function offlineServiceWorkerPlugin(): Plugin {
+  const publicAssets = [
+    "/apple-touch-icon.png",
+    "/apple-touch-icon-dev.png",
+    "/icon-192.png",
+    "/icon-512.png",
+    "/icon-maskable-512.png",
+    "/icon-dev-192.png",
+    "/icon-dev-512.png",
+    "/icon-dev-maskable-512.png",
+  ];
+
+  return {
+    name: "cents-offline-service-worker",
+    generateBundle(_options, bundle) {
+      const bundledAssets = Object.keys(bundle)
+        .filter((fileName) => fileName !== "sw.js")
+        .map((fileName) => `/${fileName}`);
+      const precache = [...new Set([...bundledAssets, ...publicAssets])];
+      const source = `const CACHE_NAME = "cents-shell-v4";
+const PRECACHE = ${JSON.stringify(precache, null, 2)};
+
+self.addEventListener("install", (event) => {
+  event.waitUntil(caches.open(CACHE_NAME).then((cache) => cache.addAll(PRECACHE)).then(() => self.skipWaiting()));
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) => Promise.all(
+      keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key)),
+    )).then(() => self.clients.claim()),
+  );
+});
+
+self.addEventListener("fetch", (event) => {
+  if (event.request.method !== "GET") return;
+  const url = new URL(event.request.url);
+  if (url.origin !== self.location.origin || url.pathname.startsWith("/api/")) return;
+
+  if (event.request.mode === "navigate") {
+    event.respondWith(
+      fetch(event.request).then((response) => {
+        const copy = response.clone();
+        void caches.open(CACHE_NAME).then((cache) => cache.put("/", copy));
+        return response;
+      }).catch(() => caches.match("/")),
+    );
+    return;
+  }
+
+  event.respondWith(
+    caches.match(event.request).then((cached) => cached ?? fetch(event.request).then((response) => {
+      if (response.ok) {
+        const copy = response.clone();
+        void caches.open(CACHE_NAME).then((cache) => cache.put(event.request, copy));
+      }
+      return response;
+    })),
+  );
+});
+`;
+      this.emitFile({ type: "asset", fileName: "sw.js", source });
+    },
+  };
+}
+
 export default defineConfig(({ mode }) => ({
   envDir: monorepoRoot,
-  plugins: [vue(), appIdentityPlugin(mode)],
+  plugins: [vue(), appIdentityPlugin(mode), offlineServiceWorkerPlugin()],
   server: {
     allowedHosts: ["dev.cents.homemade.net.cn"],
     proxy: {