diff --git a/desktop/src/main.cjs b/desktop/src/main.cjs
index b01d844..f0428e8 100644
--- a/desktop/src/main.cjs
+++ b/desktop/src/main.cjs
@@ -1359,6 +1359,34 @@ function getRendererConsoleLogPath() {
   }
 }
 
+function getRendererDebugLogPath() {
+  try {
+    const dir = app.getPath("userData");
+    fs.mkdirSync(dir, { recursive: true });
+    return path.join(dir, "renderer-debug.log");
+  } catch {
+    return null;
+  }
+}
+
+function appendRendererDebugLog(line) {
+  const logPath = getRendererDebugLogPath();
+  if (!logPath) return;
+  try {
+    fs.appendFileSync(logPath, line, { encoding: "utf8" });
+  } catch {}
+}
+
+function stringifyDebugDetails(details) {
+  if (details == null) return "";
+  if (typeof details === "string") return details;
+  try {
+    return JSON.stringify(details);
+  } catch (err) {
+    return `[unserializable:${err?.message || err}]`;
+  }
+}
+
 function setupRendererConsoleLogging(win) {
   if (!debugEnabled()) return;
 
@@ -1575,6 +1603,15 @@ function registerWindowIpc() {
     }
   });
 
+  ipcMain.on("debug:log", (event, payload) => {
+    const scope = String(payload?.scope || "renderer").trim() || "renderer";
+    const message = String(payload?.message || "").trim() || "(empty)";
+    const url = String(payload?.url || event?.sender?.getURL?.() || "").trim();
+    const details = stringifyDebugDetails(payload?.details);
+    const suffix = details ? ` details=${details}` : "";
+    appendRendererDebugLog(`[${nowIso()}] [${scope}] ${message} url=${url}${suffix}\n`);
+  });
+
   ipcMain.handle("app:setCloseBehavior", (_event, behavior) => {
     try {
       const next = setCloseBehavior(behavior);
diff --git a/desktop/src/preload.cjs b/desktop/src/preload.cjs
index 501d0e3..33ab114 100644
--- a/desktop/src/preload.cjs
+++ b/desktop/src/preload.cjs
@@ -1,5 +1,65 @@
 const { contextBridge, ipcRenderer } = require("electron");
 
+function sendDebugLog(scope, message, details) {
+  try {
+    ipcRenderer.send("debug:log", {
+      scope: String(scope || "renderer"),
+      message: String(message || ""),
+      details: details == null ? {} : details,
+      url: typeof location !== "undefined" ? String(location.href || "") : "",
+    });
+  } catch {}
+}
+
+sendDebugLog("preload", "script-start", {
+  userAgent: typeof navigator !== "undefined" ? String(navigator.userAgent || "") : "",
+});
+
+if (typeof document !== "undefined") {
+  document.addEventListener("readystatechange", () => {
+    sendDebugLog("preload", "document-readystate", {
+      readyState: String(document.readyState || ""),
+    });
+  });
+}
+
+if (typeof window !== "undefined") {
+  window.addEventListener("DOMContentLoaded", () => {
+    sendDebugLog("preload", "dom-content-loaded");
+  });
+
+  window.addEventListener("load", () => {
+    sendDebugLog("preload", "window-load");
+  });
+
+  window.addEventListener("error", (event) => {
+    sendDebugLog("preload", "window-error", {
+      message: String(event?.message || ""),
+      filename: String(event?.filename || ""),
+      lineno: Number(event?.lineno || 0),
+      colno: Number(event?.colno || 0),
+    });
+  });
+
+  window.addEventListener("unhandledrejection", (event) => {
+    const reason = event?.reason;
+    sendDebugLog("preload", "window-unhandledrejection", {
+      reason:
+        reason instanceof Error
+          ? {
+              name: String(reason.name || "Error"),
+              message: String(reason.message || ""),
+              stack: String(reason.stack || ""),
+            }
+          : String(reason || ""),
+    });
+  });
+
+  window.setTimeout(() => {
+    sendDebugLog("preload", "set-timeout-0");
+  }, 0);
+}
+
 contextBridge.exposeInMainWorld("wechatDesktop", {
   // Marker used by the frontend to distinguish the Electron desktop shell from the pure web build.
   __brand: "WeChatDataAnalysisDesktop",
@@ -8,6 +68,7 @@ contextBridge.exposeInMainWorld("wechatDesktop", {
   close: () => ipcRenderer.invoke("window:close"),
   isMaximized: () => ipcRenderer.invoke("window:isMaximized"),
   isDebugEnabled: () => ipcRenderer.invoke("app:isDebugEnabled"),
+  logDebug: (scope, message, details = {}) => sendDebugLog(scope, message, details),
 
   getAutoLaunch: () => ipcRenderer.invoke("app:getAutoLaunch"),
   setAutoLaunch: (enabled) => ipcRenderer.invoke("app:setAutoLaunch", !!enabled),
diff --git a/frontend/composables/chat/useChatMessages.js b/frontend/composables/chat/useChatMessages.js
index 7acb0fd..4d710da 100644
--- a/frontend/composables/chat/useChatMessages.js
+++ b/frontend/composables/chat/useChatMessages.js
@@ -36,6 +36,9 @@ export const useChatMessages = ({
 
   const logMessagePhase = (phase, details = {}) => {
     if (!isDesktopRenderer()) return
+    try {
+      window.wechatDesktop?.logDebug?.('chat-messages', phase, details)
+    } catch {}
     console.info(`[chat-messages] ${phase}`, {
       account: String(selectedAccount.value || '').trim(),
       selectedUsername: String(selectedContact.value?.username || '').trim(),
diff --git a/frontend/pages/chat/[[username]].vue b/frontend/pages/chat/[[username]].vue
index 3188acc..83631bf 100644
--- a/frontend/pages/chat/[[username]].vue
+++ b/frontend/pages/chat/[[username]].vue
@@ -94,6 +94,9 @@ const shouldLogChatBootstrap = () => isDesktopShell() || desktopDebugEnabled.val
 
 const logChatBootstrap = (phase, details = {}) => {
   if (!shouldLogChatBootstrap()) return
+  try {
+    window.wechatDesktop?.logDebug?.('chat-bootstrap', phase, details)
+  } catch {}
   console.info(`[chat-bootstrap] ${phase}`, {
     elapsedMs: chatBootstrapElapsedMs(),
     route: route.fullPath,
diff --git a/frontend/plugins/desktop-debug.client.js b/frontend/plugins/desktop-debug.client.js
new file mode 100644
index 0000000..065e94c
--- /dev/null
+++ b/frontend/plugins/desktop-debug.client.js
@@ -0,0 +1,83 @@
+const isDesktopShell = () => {
+  if (typeof window === 'undefined') return false
+  return !!window.wechatDesktop?.__brand
+}
+
+const formatError = (error) => {
+  if (!error) return ''
+  if (error instanceof Error) {
+    return {
+      name: String(error.name || 'Error'),
+      message: String(error.message || ''),
+      stack: String(error.stack || '')
+    }
+  }
+  if (typeof error === 'object') {
+    try {
+      return JSON.parse(JSON.stringify(error))
+    } catch {}
+  }
+  return String(error)
+}
+
+const logDesktopDebug = (phase, details = {}) => {
+  if (!isDesktopShell()) return
+  try {
+    window.wechatDesktop?.logDebug?.('nuxt-bootstrap', phase, {
+      href: String(window.location?.href || ''),
+      ...details
+    })
+  } catch {}
+  try {
+    console.info(`[nuxt-bootstrap] ${phase}`, details)
+  } catch {}
+}
+
+export default defineNuxtPlugin((nuxtApp) => {
+  logDesktopDebug('plugin:setup')
+
+  if (typeof window !== 'undefined') {
+    window.addEventListener('error', (event) => {
+      logDesktopDebug('window:error', {
+        message: String(event?.message || ''),
+        filename: String(event?.filename || ''),
+        lineno: Number(event?.lineno || 0),
+        colno: Number(event?.colno || 0),
+        error: formatError(event?.error)
+      })
+    })
+
+    window.addEventListener('unhandledrejection', (event) => {
+      logDesktopDebug('window:unhandledrejection', {
+        reason: formatError(event?.reason)
+      })
+    })
+  }
+
+  nuxtApp.hook('app:created', () => {
+    logDesktopDebug('app:created')
+  })
+
+  nuxtApp.hook('app:beforeMount', () => {
+    logDesktopDebug('app:beforeMount')
+  })
+
+  nuxtApp.hook('app:mounted', () => {
+    logDesktopDebug('app:mounted')
+  })
+
+  nuxtApp.hook('page:start', () => {
+    logDesktopDebug('page:start')
+  })
+
+  nuxtApp.hook('page:finish', () => {
+    logDesktopDebug('page:finish')
+  })
+
+  nuxtApp.hook('vue:error', (error, _instance, info) => {
+    logDesktopDebug('vue:error', {
+      info: String(info || ''),
+      error: formatError(error)
+    })
+  })
+})