diff --git a/src/components/auth/RoutePermissionGuard.test.tsx b/src/components/auth/RoutePermissionGuard.test.tsx
new file mode 100644
index 0000000..08f8051
--- /dev/null
+++ b/src/components/auth/RoutePermissionGuard.test.tsx
@@ -0,0 +1,54 @@
+import { render, screen } from "@testing-library/react";
+
+import { useAccessStore } from "@/store/accessStore";
+import { useAuthStore } from "@/store/authStore";
+import { RoutePermissionGuard } from "./RoutePermissionGuard";
+
+jest.mock("next/navigation", () => ({
+  usePathname: () => "/network-simulation",
+}));
+
+describe("RoutePermissionGuard", () => {
+  beforeEach(() => {
+    useAccessStore.setState({
+      context: null,
+      permissions: [],
+      loading: false,
+    });
+    useAuthStore.setState({
+      accessToken: null,
+      sessionExpired: false,
+      sessionExpiryReason: null,
+    });
+  });
+
+  it("prioritizes an expired session over a missing route permission", () => {
+    useAuthStore.setState({
+      sessionExpired: true,
+      sessionExpiryReason: "unauthorized",
+    });
+
+    render(
+      <RoutePermissionGuard>
+        <div>受保护内容</div>
+      </RoutePermissionGuard>,
+    );
+
+    expect(screen.getByText("登录状态已失效")).toBeInTheDocument();
+    expect(screen.getByText("正在跳转到登录页面…")).toBeInTheDocument();
+    expect(screen.queryByText("无权访问此功能")).not.toBeInTheDocument();
+    expect(screen.queryByText(/simulation\.view/)).not.toBeInTheDocument();
+    expect(screen.queryByText("受保护内容")).not.toBeInTheDocument();
+  });
+
+  it("shows the permission error when the session is still valid", () => {
+    render(
+      <RoutePermissionGuard>
+        <div>受保护内容</div>
+      </RoutePermissionGuard>,
+    );
+
+    expect(screen.getByText("无权访问此功能")).toBeInTheDocument();
+    expect(screen.getByText(/simulation\.view/)).toBeInTheDocument();
+  });
+});
diff --git a/src/components/auth/RoutePermissionGuard.tsx b/src/components/auth/RoutePermissionGuard.tsx
index 0c455c0..4894fb1 100644
--- a/src/components/auth/RoutePermissionGuard.tsx
+++ b/src/components/auth/RoutePermissionGuard.tsx
@@ -7,6 +7,7 @@ import type { ReactNode } from "react";
 
 import { permissionForPath } from "@/lib/permissions";
 import { useAccessStore } from "@/store/accessStore";
+import { useAuthStore } from "@/store/authStore";
 
 export const RoutePermissionGuard = ({
   children,
@@ -16,8 +17,24 @@ export const RoutePermissionGuard = ({
   const pathname = usePathname();
   const permissions = useAccessStore((state) => state.permissions);
   const loading = useAccessStore((state) => state.loading);
+  const sessionExpired = useAuthStore((state) => state.sessionExpired);
   const requiredPermission = permissionForPath(pathname);
 
+  if (sessionExpired) {
+    return (
+      <Box sx={{ p: 3 }}>
+        <Alert severity="warning">
+          <Stack spacing={0.5}>
+            <Typography variant="body1">登录状态已失效</Typography>
+            <Typography variant="body2">
+              正在跳转到登录页面…
+            </Typography>
+          </Stack>
+        </Alert>
+      </Box>
+    );
+  }
+
   if (requiredPermission && loading) {
     return (
       <Box sx={{ minHeight: 320, display: "grid", placeItems: "center" }}>
diff --git a/src/components/auth/SessionExpiryDialog.test.tsx b/src/components/auth/SessionExpiryDialog.test.tsx
index ab1e778..b43e8d3 100644
--- a/src/components/auth/SessionExpiryDialog.test.tsx
+++ b/src/components/auth/SessionExpiryDialog.test.tsx
@@ -1,5 +1,6 @@
 import { createTheme, ThemeProvider } from "@mui/material/styles";
-import { act, render, screen } from "@testing-library/react";
+import { act, fireEvent, render, screen } from "@testing-library/react";
+import { signIn } from "next-auth/react";
 
 import { useAuthStore } from "@/store/authStore";
 import { SessionExpiryDialog } from "./SessionExpiryDialog";
@@ -10,6 +11,8 @@ jest.mock("next-auth/react", () => ({
 
 describe("SessionExpiryDialog", () => {
   beforeEach(() => {
+    jest.useFakeTimers();
+    jest.mocked(signIn).mockReset().mockResolvedValue(undefined);
     useAuthStore.setState({
       accessToken: null,
       sessionExpired: true,
@@ -19,6 +22,7 @@ describe("SessionExpiryDialog", () => {
 
   afterEach(() => {
     act(() => useAuthStore.getState().clearSessionExpired());
+    jest.useRealTimers();
   });
 
   it("renders above every regular application overlay", () => {
@@ -36,4 +40,40 @@ describe("SessionExpiryDialog", () => {
       zIndex: theme.zIndex.tooltip + 1,
     });
   });
+
+  it("shows the expired state before automatically starting login", () => {
+    window.history.replaceState({}, "", "/network-simulation?tab=history");
+
+    render(<SessionExpiryDialog />);
+
+    expect(screen.getByText("登录已过期")).toBeInTheDocument();
+    expect(screen.getByText("即将自动跳转到登录页面。"))
+      .toBeInTheDocument();
+    expect(signIn).not.toHaveBeenCalled();
+
+    act(() => {
+      jest.advanceTimersByTime(2_000);
+    });
+
+    expect(signIn).toHaveBeenCalledTimes(1);
+    expect(signIn).toHaveBeenCalledWith("keycloak", {
+      callbackUrl: "/network-simulation?tab=history",
+      redirect: true,
+    });
+  });
+
+  it("allows a retry when starting automatic login fails", async () => {
+    jest.mocked(signIn)
+      .mockRejectedValueOnce(new Error("network unavailable"))
+      .mockResolvedValueOnce(undefined);
+
+    render(<SessionExpiryDialog />);
+
+    await act(async () => {
+      jest.advanceTimersByTime(2_000);
+    });
+    fireEvent.click(screen.getByRole("button", { name: "重新认证" }));
+
+    expect(signIn).toHaveBeenCalledTimes(2);
+  });
 });
diff --git a/src/components/auth/SessionExpiryDialog.tsx b/src/components/auth/SessionExpiryDialog.tsx
index c42ecd9..2f2e87d 100644
--- a/src/components/auth/SessionExpiryDialog.tsx
+++ b/src/components/auth/SessionExpiryDialog.tsx
@@ -1,6 +1,6 @@
 "use client";
 
-import { useEffect, useMemo, useState } from "react";
+import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { signIn } from "next-auth/react";
 import AccessTimeOutlinedIcon from "@mui/icons-material/AccessTimeOutlined";
 import {
@@ -18,6 +18,7 @@ import { useTheme } from "@mui/material/styles";
 import { useAuthStore } from "@/store/authStore";
 
 const WARNING_WINDOW_MS = 15 * 60 * 1000;
+const EXPIRED_REDIRECT_DELAY_MS = 2_000;
 
 type SessionExpiryDialogProps = {
   expiresAt?: number;
@@ -31,6 +32,7 @@ export const SessionExpiryDialog = ({
   const reason = useAuthStore((state) => state.sessionExpiryReason);
   const [now, setNow] = useState(() => Date.now());
   const [warningDismissed, setWarningDismissed] = useState(false);
+  const redirectStartedRef = useRef(false);
 
   useEffect(() => {
     const timer = window.setInterval(() => setNow(Date.now()), 30_000);
@@ -47,10 +49,27 @@ export const SessionExpiryDialog = ({
     [expiresAt, now, sessionExpired, warningDismissed],
   );
 
-  const handleReauthenticate = () => {
+  const handleReauthenticate = useCallback(() => {
+    if (redirectStartedRef.current) return;
+    redirectStartedRef.current = true;
     const callbackUrl = `${window.location.pathname}${window.location.search}`;
-    void signIn("keycloak", { callbackUrl, redirect: true });
-  };
+    void signIn("keycloak", { callbackUrl, redirect: true }).catch(() => {
+      redirectStartedRef.current = false;
+    });
+  }, []);
+
+  useEffect(() => {
+    if (!sessionExpired) {
+      redirectStartedRef.current = false;
+      return;
+    }
+
+    const timer = window.setTimeout(
+      handleReauthenticate,
+      EXPIRED_REDIRECT_DELAY_MS,
+    );
+    return () => window.clearTimeout(timer);
+  }, [handleReauthenticate, sessionExpired]);
 
   const isOpen = sessionExpired || isExpiringSoon;
   const title = sessionExpired ? "登录已过期" : "登录即将到期";
@@ -77,6 +96,11 @@ export const SessionExpiryDialog = ({
           <Typography variant="body2" color="text.secondary">
             重新认证不会自动重放已失败的写入请求；请在返回后确认内容并再次提交。
           </Typography>
+          {sessionExpired && (
+            <Typography variant="body2" color="text.secondary">
+              即将自动跳转到登录页面。
+            </Typography>
+          )}
         </Stack>
       </DialogContent>
       <DialogActions>