diff --git a/frontend/src/utils/cookie.ts b/frontend/src/utils/cookie.ts
new file mode 100644
index 0000000..92906b4
--- /dev/null
+++ b/frontend/src/utils/cookie.ts
@@ -0,0 +1,40 @@
+const COOKIE_NAME = "ai_agent_login";
+const COOKIE_DAYS = 7;
+
+export interface UserInfo {
+  user: string;
+  ts: number;
+}
+
+function setCookie(name: string, value: string, days: number) {
+  const expires = new Date(Date.now() + days * 864e5).toUTCString();
+  document.cookie = `${name}=${encodeURIComponent(value)};expires=${expires};path=/`;
+}
+
+function getCookie(name: string): string | null {
+  const match = document.cookie.match(new RegExp("(^| )" + name + "=([^;]+)"));
+  return match ? decodeURIComponent(match[2]) : null;
+}
+
+function deleteCookie(name: string) {
+  document.cookie = `${name}=;expires=Thu, 01 Jan 1970 00:00:00 GMT;path=/`;
+}
+
+export function setUserInfo(user: string) {
+  const info: UserInfo = { user, ts: Date.now() };
+  setCookie(COOKIE_NAME, JSON.stringify(info), COOKIE_DAYS);
+}
+
+export function getUserInfo(): UserInfo | null {
+  const raw = getCookie(COOKIE_NAME);
+  if (!raw) return null;
+  try {
+    return JSON.parse(raw) as UserInfo;
+  } catch {
+    return null;
+  }
+}
+
+export function clearUserInfo() {
+  deleteCookie(COOKIE_NAME);
+}