diff --git a/client/src/components/ConnectionPlaceholder.tsx b/client/src/components/ConnectionPlaceholder.tsx
index 06efcc2..7aca7b9 100644
--- a/client/src/components/ConnectionPlaceholder.tsx
+++ b/client/src/components/ConnectionPlaceholder.tsx
@@ -1,5 +1,6 @@
 import { useMemo } from "react";
 import { useDevice } from "@/contexts/DeviceContext";
+import { isLikelyNetworkFetchError } from "@/lib/networkError";
 import { Loader2, Wifi } from "lucide-react";
 import BottomNav from "@/components/BottomNav";
 import localeZh from "@/locales/data-zh.json";
@@ -50,7 +51,7 @@ export default function ConnectionPlaceholder() {
         <>
           <p className="text-[15px] text-white/80 mb-2">{text.failedTitle}</p>
           <p className="text-[13px] text-white/45 text-center max-w-xs">
-            {error ?? text.failedDesc}
+            {error && !isLikelyNetworkFetchError(error) ? error : text.failedDesc}
           </p>
           <p className="text-[12px] text-white/30 mt-3 text-center max-w-xs">{text.failedHint}</p>
         </>
diff --git a/client/src/contexts/DeviceContext.tsx b/client/src/contexts/DeviceContext.tsx
index 35885cd..7bead87 100644
--- a/client/src/contexts/DeviceContext.tsx
+++ b/client/src/contexts/DeviceContext.tsx
@@ -10,6 +10,7 @@ import {
   PeqState,
 } from "@/lib/luxsinApi";
 import { getDeviceIpFromUrl, resolveInitialDeviceIp } from "@/lib/deviceIp";
+import { isLikelyNetworkFetchError } from "@/lib/networkError";
 
 interface DeviceContextType {
   ip: string;
@@ -115,7 +116,11 @@ export function DeviceProvider({ children }: { children: React.ReactNode }) {
       setApi(newApi);
       setIsConnected(true);
     } catch (e) {
-      setError(`Connection failed: ${e instanceof Error ? e.message : String(e)}`);
+      setError(
+        isLikelyNetworkFetchError(e)
+          ? null
+          : `Connection failed: ${e instanceof Error ? e.message : String(e)}`,
+      );
       setIsConnected(false);
     } finally {
       setIsConnecting(false);
@@ -151,7 +156,11 @@ export function DeviceProvider({ children }: { children: React.ReactNode }) {
       await fetchState(apiInstance);
       await fetchPeqState(apiInstance).catch(() => undefined);
     } catch (e) {
-      setError(`Refresh failed: ${e instanceof Error ? e.message : String(e)}`);
+      setError(
+        isLikelyNetworkFetchError(e)
+          ? null
+          : `Refresh failed: ${e instanceof Error ? e.message : String(e)}`,
+      );
     }
   }, [api, isConnected, ip, isDemoMode, fetchState, fetchPeqState]);
 
diff --git a/client/src/lib/aiApi.ts b/client/src/lib/aiApi.ts
index deba230..eaa1412 100644
--- a/client/src/lib/aiApi.ts
+++ b/client/src/lib/aiApi.ts
@@ -11,6 +11,7 @@ import {
   dbToVolume,
   volumeToDb,
 } from "./luxsinApi";
+import { AI_NETWORK_ERROR_CODE, isLikelyNetworkFetchError } from "./networkError";
 
 // Allow override via Vite env / localStorage; default to same origin in prod.
 export function getAIBaseUrl(): string {
@@ -120,7 +121,13 @@ export interface QuestionPayload {
 // REST helpers
 // ============================================================
 async function jsonFetch<T>(url: string, init?: RequestInit): Promise<T> {
-  const res = await fetch(url, init);
+  let res: Response;
+  try {
+    res = await fetch(url, init);
+  } catch (error) {
+    if (isLikelyNetworkFetchError(error)) throw new Error(AI_NETWORK_ERROR_CODE);
+    throw error;
+  }
   if (!res.ok) throw new Error(`HTTP ${res.status}: ${await res.text()}`);
   return res.json();
 }
@@ -293,7 +300,7 @@ export function streamQuestion(payload: QuestionPayload, cb: StreamCallbacks): A
       cb.onDone?.();
     } catch (e: any) {
       if (e?.name === "AbortError") return;
-      cb.onError?.(e?.message ?? String(e));
+      cb.onError?.(isLikelyNetworkFetchError(e) ? AI_NETWORK_ERROR_CODE : (e?.message ?? String(e)));
     }
   })();
 
@@ -472,6 +479,12 @@ export async function executeFrontendTool(
         return { ok: false, message: `Unsupported tool: ${block.name}` };
     }
   } catch (e: any) {
+    if (isLikelyNetworkFetchError(e)) {
+      return {
+        ok: false,
+        message: "Device is not reachable. Ask the user to reconnect the device on the same network, then retry.",
+      };
+    }
     return { ok: false, message: e?.message ?? String(e) };
   }
 }
diff --git a/client/src/lib/networkError.ts b/client/src/lib/networkError.ts
new file mode 100644
index 0000000..e0b6de2
--- /dev/null
+++ b/client/src/lib/networkError.ts
@@ -0,0 +1,33 @@
+/** Browser / WebView fetch failures are usually TypeError with an opaque message. */
+
+export const AI_NETWORK_ERROR_CODE = "AI_UNREACHABLE";
+
+const NETWORK_FETCH_HINTS = [
+  "failed to fetch",
+  "networkerror",
+  "network request failed",
+  "load failed",
+  "internet connection appears to be offline",
+];
+
+export function isLikelyNetworkFetchError(error: unknown): boolean {
+  const name = error instanceof Error ? error.name : "";
+  const msg = (error instanceof Error ? error.message : String(error ?? "")).toLowerCase();
+  if (msg === AI_NETWORK_ERROR_CODE.toLowerCase()) return true;
+  if (NETWORK_FETCH_HINTS.some((hint) => msg.includes(hint))) return true;
+  // Some WebViews surface a bare TypeError when fetch cannot complete.
+  return name === "TypeError" && !msg;
+}
+
+export function formatNetworkAwareMessage(
+  template: string,
+  error: unknown,
+  networkCopy: string,
+): string {
+  const raw = error instanceof Error ? error.message : String(error ?? "");
+  const message = isLikelyNetworkFetchError(error) || isLikelyNetworkFetchError(raw) ? networkCopy : raw;
+  if (template.includes("{message}")) {
+    return template.split("{message}").join(String(message));
+  }
+  return isLikelyNetworkFetchError(error) || isLikelyNetworkFetchError(raw) ? networkCopy : template;
+}
diff --git a/client/src/locales/data-de.json b/client/src/locales/data-de.json
index 3d43350..3e10010 100644
--- a/client/src/locales/data-de.json
+++ b/client/src/locales/data-de.json
@@ -4,7 +4,7 @@
     "ipMissingDesc": "Bitte fügen Sie die Geräte-IP in der Adressleiste hinzu, bevor Sie diese Seite öffnen, zum Beispiel:",
     "connecting": "Verbindung zu {ip}…",
     "failedTitle": "Verbindung fehlgeschlagen",
-    "failedDesc": "Überprüfen Sie die Geräte-IP und Ihre Netzwerkverbindung.",
+    "failedDesc": "Das Gerät ist nicht erreichbar. Stellen Sie sicher, dass diese Seite und das Gerät im selben Netzwerk sind und die IP stimmt.",
     "failedHint": "Geben Sie das Gerät in der URL an, z.B. ?ip=10.0.0.119"
   },
   "home": {
@@ -623,6 +623,8 @@
     "thinking": "Denke…",
     "stopped": "(Gestoppt)",
     "requestFailed": "Anfrage fehlgeschlagen. Bitte versuchen Sie es später erneut.",
+    "deviceUnreachable": "Das Gerät ist nicht erreichbar. Prüfen Sie, ob diese Seite und das Gerät im selben Netzwerk sind, und versuchen Sie es erneut.",
+    "aiUnreachable": "Der Luxsin-KI-Dienst ist nicht erreichbar. Prüfen Sie Ihre Internetverbindung und versuchen Sie es erneut.",
     "ariaSend": "Senden",
     "ariaStop": "Stopp",
     "ariaNewChat": "Neuer Chat",
diff --git a/client/src/locales/data-en.json b/client/src/locales/data-en.json
index 1531a2e..034d2f2 100644
--- a/client/src/locales/data-en.json
+++ b/client/src/locales/data-en.json
@@ -4,7 +4,7 @@
     "ipMissingDesc": "Add the device IP in the address bar before opening this page, for example:",
     "connecting": "Connecting to {ip}…",
     "failedTitle": "Connection failed",
-    "failedDesc": "Check the device IP and your network connection.",
+    "failedDesc": "Can't reach the device. Make sure this page and the device are on the same network, and that the IP is correct.",
     "failedHint": "Specify the device in the URL, e.g. ?ip=10.0.0.119"
   },
   "home": {
@@ -623,6 +623,8 @@
     "thinking": "Thinking…",
     "stopped": "(Stopped)",
     "requestFailed": "Request failed. Please try again later.",
+    "deviceUnreachable": "Can't reach the device. Check that this page and the device are on the same network, then try again.",
+    "aiUnreachable": "Can't reach the Luxsin AI service. Check your internet connection and try again.",
     "ariaSend": "Send",
     "ariaStop": "Stop",
     "ariaNewChat": "New chat",
diff --git a/client/src/locales/data-es.json b/client/src/locales/data-es.json
index f0d6bc7..c1b2abc 100644
--- a/client/src/locales/data-es.json
+++ b/client/src/locales/data-es.json
@@ -4,7 +4,7 @@
     "ipMissingDesc": "Agregue la IP del dispositivo en la barra de direcciones antes de abrir esta página, por ejemplo:",
     "connecting": "Conectando a {ip}…",
     "failedTitle": "Error de conexión",
-    "failedDesc": "Verifique la IP del dispositivo y su conexión de red.",
+    "failedDesc": "No se puede alcanzar el dispositivo. Compruebe que esta página y el dispositivo estén en la misma red y que la IP sea correcta.",
     "failedHint": "Especifique el dispositivo en la URL, ej. ?ip=10.0.0.119"
   },
   "home": {
@@ -623,6 +623,8 @@
     "thinking": "Pensando…",
     "stopped": "(Detenido)",
     "requestFailed": "Error en la solicitud. Inténtelo de nuevo más tarde.",
+    "deviceUnreachable": "No se puede alcanzar el dispositivo. Compruebe que esta página y el dispositivo estén en la misma red e inténtelo de nuevo.",
+    "aiUnreachable": "No se puede alcanzar el servicio de Luxsin AI. Compruebe su conexión a Internet e inténtelo de nuevo.",
     "ariaSend": "Enviar",
     "ariaStop": "Detener",
     "ariaNewChat": "Nuevo chat",
diff --git a/client/src/locales/data-fr.json b/client/src/locales/data-fr.json
index 6b4f59c..0f2cd10 100644
--- a/client/src/locales/data-fr.json
+++ b/client/src/locales/data-fr.json
@@ -4,7 +4,7 @@
     "ipMissingDesc": "Veuillez ajouter l'IP de l'appareil dans la barre d'adresse avant d'ouvrir cette page, par exemple :",
     "connecting": "Connexion à {ip}…",
     "failedTitle": "Échec de la connexion",
-    "failedDesc": "Vérifiez l'IP de l'appareil et votre connexion réseau.",
+    "failedDesc": "Impossible d'atteindre l'appareil. Vérifiez que cette page et l'appareil sont sur le même réseau, et que l'IP est correcte.",
     "failedHint": "Spécifiez l'appareil dans l'URL, par ex. ?ip=10.0.0.119"
   },
   "home": {
@@ -623,6 +623,8 @@
     "thinking": "Réflexion…",
     "stopped": "(Arrêté)",
     "requestFailed": "Échec de la requête. Veuillez réessayer plus tard.",
+    "deviceUnreachable": "Impossible d'atteindre l'appareil. Vérifiez que cette page et l'appareil sont sur le même réseau, puis réessayez.",
+    "aiUnreachable": "Impossible d'atteindre le service Luxsin AI. Vérifiez votre connexion Internet, puis réessayez.",
     "ariaSend": "Envoyer",
     "ariaStop": "Arrêter",
     "ariaNewChat": "Nouveau chat",
diff --git a/client/src/locales/data-zh-HK.json b/client/src/locales/data-zh-HK.json
index be0de66..1c23a7a 100644
--- a/client/src/locales/data-zh-HK.json
+++ b/client/src/locales/data-zh-HK.json
@@ -4,7 +4,7 @@
     "ipMissingDesc": "請在網址列加入裝置 IP 參數後再開啟本頁，例如：",
     "connecting": "正在連線 {ip}…",
     "failedTitle": "連線失敗",
-    "failedDesc": "請檢查裝置 IP 與網路連線。",
+    "failedDesc": "無法連接裝置。請確認本頁與裝置在同一網絡，並檢查裝置 IP 是否正確。",
     "failedHint": "透過網址列指定裝置，例如 ?ip=10.0.0.119"
   },
   "home": {
@@ -617,6 +617,8 @@
     "thinking": "思考中…",
     "stopped": "（已停止）",
     "requestFailed": "請求失敗，請稍後重試",
+    "deviceUnreachable": "無法連接裝置。請確認本頁與裝置在同一網絡後再試。",
+    "aiUnreachable": "無法連接 Luxsin AI 服務。請檢查網絡後再試。",
     "ariaSend": "發送",
     "ariaStop": "停止",
     "ariaNewChat": "新增會話",
diff --git a/client/src/locales/data-zh.json b/client/src/locales/data-zh.json
index acf495c..c52a9b9 100644
--- a/client/src/locales/data-zh.json
+++ b/client/src/locales/data-zh.json
@@ -4,7 +4,7 @@
     "ipMissingDesc": "请在地址栏添加设备 IP 参数后再打开本页，例如：",
     "connecting": "正在连接 {ip}…",
     "failedTitle": "连接失败",
-    "failedDesc": "请检查设备 IP 与网络连接。",
+    "failedDesc": "无法连接设备。请确认本页与设备在同一网络，并检查设备 IP 是否正确。",
     "failedHint": "通过地址栏指定设备，例如 ?ip=10.0.0.119"
   },
   "home": {
@@ -618,6 +618,8 @@
     "thinking": "思考中…",
     "stopped": "（已停止）",
     "requestFailed": "请求失败，请稍后重试",
+    "deviceUnreachable": "无法连接设备。请确认本页与设备在同一网络后再试。",
+    "aiUnreachable": "无法连接 Luxsin AI 服务。请检查网络后再试。",
     "ariaSend": "发送",
     "ariaStop": "停止",
     "ariaNewChat": "新建会话",
diff --git a/client/src/pages/AIPage.tsx b/client/src/pages/AIPage.tsx
index 7f018df..5e60368 100644
--- a/client/src/pages/AIPage.tsx
+++ b/client/src/pages/AIPage.tsx
@@ -39,6 +39,7 @@ import {
   streamQuestion,
   updateMessageApplied,
 } from "@/lib/aiApi";
+import { formatNetworkAwareMessage, isLikelyNetworkFetchError } from "@/lib/networkError";
 
 import { buildPeqSvgCurveData, getFilterType, PeqBandForResponse } from "@/lib/peqAudio";
 import { cn } from "@/lib/utils";
@@ -305,7 +306,7 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
       const list = await listChats(mac);
       setChats(list);
     } catch (e: any) {
-      toast.error(formatText(aiText.loadHistoryFailed, { message: e?.message ?? e }));
+      toast.error(formatNetworkAwareMessage(aiText.loadHistoryFailed, e, aiText.aiUnreachable));
     }
   }, [aiText, mac]);
 
@@ -357,7 +358,7 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
         setChatId(id);
         if (opts?.closePanel !== false) setHistoryOpen(false);
       } catch (e: any) {
-        toast.error(formatText(aiText.loadChatFailed, { message: e?.message ?? e }));
+        toast.error(formatNetworkAwareMessage(aiText.loadChatFailed, e, aiText.aiUnreachable));
       }
     },
     [aiText, mapRowsToUI, settleRiskyConfirm],
@@ -429,7 +430,7 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
       newChat();
       toast.success(aiText.cleared);
     } catch (e: any) {
-      toast.error(formatText(aiText.clearFailed, { message: e?.message ?? e }));
+      toast.error(formatNetworkAwareMessage(aiText.clearFailed, e, aiText.aiUnreachable));
     }
   }, [aiText, chatId, newChat]);
 
@@ -445,7 +446,7 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
       toast.success(aiText.history.deleted);
     } catch (e: any) {
       toast.error(
-        formatText(aiText.history.deleteFailed, { message: e?.message ?? e }),
+        formatNetworkAwareMessage(aiText.history.deleteFailed, e, aiText.aiUnreachable),
       );
     }
   }, [aiText, chatId]);
@@ -514,14 +515,15 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
             msgCount: deviceState.msgCount ?? 0,
           };
         } catch (e: any) {
+          const text = isLikelyNetworkFetchError(e) ? aiText.deviceUnreachable : aiText.requestFailed;
           updateAssistant((m) => ({
             ...m,
             pending: false,
             error: true,
-            text: aiText.requestFailed,
+            text,
           }));
           setSending(false);
-          toast.error(formatText(aiText.requestFailed, { message: e?.message ?? e }));
+          toast.error(text);
           return;
         }
 
@@ -560,15 +562,16 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
             try {
               await sendToolResult(block.id, result);
             } catch (e: any) {
-              toast.error(formatText(aiText.toolResultFailed, { message: e?.message ?? e }));
+              toast.error(formatNetworkAwareMessage(aiText.toolResultFailed, e, aiText.aiUnreachable));
             }
           },
           onError: (msg) => {
+            const text = isLikelyNetworkFetchError(msg) ? aiText.aiUnreachable : (msg || aiText.requestFailed);
             updateAssistant((m) => ({
               ...m,
               pending: false,
               error: true,
-              text: m.text || msg || aiText.requestFailed,
+              text: m.text || text,
             }));
             setSending(false);
           },
@@ -779,7 +782,7 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
           nextApplied ? aiText.optimize.applySuccess : aiText.optimize.rollbackSuccess,
         );
       } catch (e: any) {
-        toast.error(formatText(aiText.optimize.applyFailed, { message: e?.message ?? e }));
+        toast.error(formatNetworkAwareMessage(aiText.optimize.applyFailed, e, aiText.deviceUnreachable));
       } finally {
         setApplyingId(null);
       }
@@ -812,7 +815,7 @@ export default function AIPage({ variant = "page", onClose }: AIPageProps = {})
         await updateSetting(bypassOn ? { peqEnable: 1, dsp_enable: 1 } : { peqEnable: 1 });
         await executeApplyToggle(msg);
       } catch (e: any) {
-        toast.error(formatText(aiText.optimize.applyFailed, { message: e?.message ?? e }));
+        toast.error(formatNetworkAwareMessage(aiText.optimize.applyFailed, e, aiText.deviceUnreachable));
       }
     },
     [aiText, deviceState?.dsp_enable, executeApplyToggle, updateSetting],