diff --git a/.env.example b/.env.example
index 78bbd5c..93cd0d5 100644
--- a/.env.example
+++ b/.env.example
@@ -6,6 +6,11 @@
 # 生成方式: python -c "import secrets; print(secrets.token_urlsafe(32))"
 JWT_SECRET_KEY=
 
+# 后台登录会话：空闲 24h 过期，绝对上限 7d（活跃请求自动续期，不会突破 7d）
+# 旧变量 ACCESS_TOKEN_EXPIRE_HOURS 仍可作为 ACCESS_TOKEN_IDLE_HOURS 的回退值。
+ACCESS_TOKEN_IDLE_HOURS=24
+ACCESS_TOKEN_MAX_HOURS=168
+
 # 敏感字段落盘加密密钥（生产环境必须设置且长期保持不变！）
 # 用于加密账号密码、邮箱密码、Cookie、代理密钥等数据库字段
 # 生成方式: python -c "import secrets; print(secrets.token_urlsafe(32))"
diff --git a/README.md b/README.md
index f3b68ad..09bebb3 100644
--- a/README.md
+++ b/README.md
@@ -110,6 +110,7 @@ python3 -c 'import secrets; print(secrets.token_urlsafe(32))'
 - `FISH_FIN_RECHARGE_*`：鱼翅供应商直充，只走环境变量，不入库、不回前端。
 - `MAIL_ROUNDCUBE_URL`：邮件验证码服务；不填则用代码默认 Roundcube 地址。
 - `CORS_ORIGINS`、`COOKIE_SECURE`：HTTPS 部署时按实际填写。
+- `ACCESS_TOKEN_IDLE_HOURS` / `ACCESS_TOKEN_MAX_HOURS`：后台登录滑动会话，默认 24h 空闲过期、7d 绝对上限；活跃请求自动续签，但不会突破 7d。
 
 应用宝扫码图和支付二维码只经后台授权接口返回。服务器只需要本仓库，不必再部署 `js_reverse`。Worker 任务数据在 `data/yyb-worker-jobs/`。
 
diff --git a/docker-compose.yml b/docker-compose.yml
index b6ade33..1c951ee 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -39,6 +39,9 @@ services:
       - DB_POOL_RECYCLE=${DB_POOL_RECYCLE:-1800}
       # JWT 密钥（生产环境务必修改，可用 python -c "import secrets; print(secrets.token_urlsafe(32))" 生成）
       - JWT_SECRET_KEY=${JWT_SECRET_KEY:-}
+      # 后台登录滑动会话：24h 空闲过期，7d 绝对上限。
+      - ACCESS_TOKEN_IDLE_HOURS=${ACCESS_TOKEN_IDLE_HOURS:-24}
+      - ACCESS_TOKEN_MAX_HOURS=${ACCESS_TOKEN_MAX_HOURS:-168}
       # 敏感字段落盘加密密钥（生产环境务必长期保持不变）
       - APP_ENCRYPTION_KEY=${APP_ENCRYPTION_KEY:-}
       # 默认管理员账号密码（仅首次启动建库时生效）
diff --git a/tests/test_auth_sliding_session.py b/tests/test_auth_sliding_session.py
new file mode 100644
index 0000000..3b26540
--- /dev/null
+++ b/tests/test_auth_sliding_session.py
@@ -0,0 +1,118 @@
+"""后台登录滑动会话：24h 空闲 + 7d 绝对上限。"""
+
+from datetime import UTC, datetime, timedelta
+from types import SimpleNamespace
+
+from jose import jwt
+from starlette.responses import Response
+
+from web.backend import security
+from web.backend.session import _should_renew, set_session_cookie
+
+NOW = datetime.now(UTC).replace(microsecond=0)
+
+
+def test_issue_token_uses_24h_idle_window():
+    issued = security.issue_access_token({"sub": "7"}, now=NOW)
+    payload = security.decode_access_token(issued.token)
+
+    assert payload is not None
+    assert payload["iat"] == int(NOW.timestamp())
+    assert issued.expires_at == NOW + timedelta(hours=24)
+    assert not security.is_session_expired(payload, now=NOW + timedelta(hours=23))
+    assert security.is_session_expired(payload, now=NOW + timedelta(hours=24))
+
+
+def test_renew_extends_idle_window_but_keeps_session_start():
+    issued = security.issue_access_token({"sub": "7"}, now=NOW)
+    renewed = security.renew_access_token(issued.token, now=NOW + timedelta(hours=23))
+
+    assert renewed is not None
+    assert renewed.issued_at == NOW
+    assert renewed.expires_at == NOW + timedelta(hours=47)
+    payload = security.decode_access_token(renewed.token)
+    assert payload is not None
+    assert payload["iat"] == int(NOW.timestamp())
+
+
+def test_renew_never_passes_seven_day_absolute_cap():
+    # 模拟一个已经连续续期到第 6 天 23:30 的会话（仍有效），
+    # 下一次续期只能把 exp 顶到 7d，不能推到 7d23h。
+    near_cap = jwt.encode(
+        {
+            "sub": "7",
+            "iat": NOW,
+            "exp": NOW + timedelta(days=6, hours=23, minutes=30),
+        },
+        security.SECRET_KEY_TYPED,
+        algorithm=security.ALGORITHM,
+    )
+    renewed = security.renew_access_token(
+        near_cap, now=NOW + timedelta(days=6, hours=23)
+    )
+
+    assert renewed is not None
+    assert renewed.expires_at == NOW + timedelta(days=7)
+    payload = security.decode_access_token(renewed.token)
+    assert payload is not None
+    assert security.is_session_expired(payload, now=NOW + timedelta(days=7))
+
+    # 已经顶到绝对上限后不再续签。
+    assert (
+        security.renew_access_token(
+            renewed.token, now=NOW + timedelta(days=6, hours=23, minutes=30)
+        )
+        is None
+    )
+
+
+def test_legacy_token_without_iat_anchors_cap_to_original_issue_time():
+    legacy = jwt.encode(
+        {
+            "sub": "7",
+            "exp": NOW + timedelta(hours=1),
+        },
+        security.SECRET_KEY_TYPED,
+        algorithm=security.ALGORITHM,
+    )
+
+    renewed = security.renew_access_token(legacy, now=NOW)
+
+    assert renewed is not None
+    # 旧 Token 固定 24h，因此签发时间 = exp - 24h。
+    assert renewed.issued_at == NOW - timedelta(hours=23)
+    assert renewed.expires_at == NOW + timedelta(hours=24)
+
+
+def test_set_session_cookie_matches_token_expiry():
+    response = Response()
+    expires_at = NOW + timedelta(hours=24)
+
+    set_session_cookie(response, "token-value", expires_at, now=NOW)
+
+    cookie = response.headers["set-cookie"].lower()
+    assert "access_token=token-value" in cookie
+    assert "httponly" in cookie
+    assert "samesite=lax" in cookie
+    assert "max-age=86400" in cookie
+    assert "path=/" in cookie
+
+
+def test_should_renew_only_authenticated_api_requests():
+    request = SimpleNamespace(
+        url=SimpleNamespace(path="/api/accounts"),
+        state=SimpleNamespace(current_user=object()),
+    )
+    assert _should_renew(request, 200)
+    assert _should_renew(request, 403)
+    assert not _should_renew(request, 401)
+
+    request.url.path = "/api/auth/logout"
+    assert not _should_renew(request, 200)
+
+    request.url.path = "/assets/app.js"
+    assert not _should_renew(request, 200)
+
+    request.url.path = "/api/accounts"
+    request.state.current_user = None
+    assert not _should_renew(request, 200)
diff --git a/web/backend/deps.py b/web/backend/deps.py
index f976025..5e68aae 100644
--- a/web/backend/deps.py
+++ b/web/backend/deps.py
@@ -8,7 +8,8 @@ from sqlalchemy.orm import Session
 from .database import SessionLocal, get_db
 from .models import User
 from .permissions import get_user_permissions
-from .security import decode_access_token
+from .security import decode_access_token, is_session_expired
+from .session import SESSION_COOKIE_NAME
 
 # auto_error=False: 允许 token 为空（后续从 cookie 读取）
 oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login", auto_error=False)
@@ -25,13 +26,15 @@ def get_current_user(
         headers={"WWW-Authenticate": "Bearer"},
     )
     # 优先从 Authorization Bearer header 读取，回退到 httpOnly cookie
+    from_cookie = False
     if not token:
-        token = request.cookies.get("access_token")
+        token = request.cookies.get(SESSION_COOKIE_NAME)
+        from_cookie = True
     if not token:
         raise credentials_exc
     try:
         payload = decode_access_token(token)
-        if payload is None:
+        if payload is None or is_session_expired(payload):
             raise credentials_exc
         user_id_raw = payload.get("sub")
         if user_id_raw is None:
@@ -43,6 +46,10 @@ def get_current_user(
     user = db.query(User).filter(User.id == int(user_id)).first()
     if user is None or not user.is_active:
         raise credentials_exc
+    # 中间件据此只在「已通过认证的请求」上续签 Cookie；Bearer 客户端不写 Cookie。
+    request.state.current_user = user
+    if from_cookie:
+        request.state.auth_cookie_token = token
     return user
 
 
@@ -66,11 +73,13 @@ def authenticate_websocket(websocket: WebSocket) -> User | None:
     Returns:
         User 如果认证成功，None 如果失败。
     """
-    token = websocket.cookies.get("access_token") or websocket.query_params.get("token")
+    token = websocket.cookies.get(SESSION_COOKIE_NAME) or websocket.query_params.get(
+        "token"
+    )
     if not token:
         return None
     payload = decode_access_token(token)
-    if not payload or not payload.get("sub"):
+    if not payload or is_session_expired(payload) or not payload.get("sub"):
         return None
     db = SessionLocal()
     try:
diff --git a/web/backend/main.py b/web/backend/main.py
index 6b197ef..dbdff3e 100644
--- a/web/backend/main.py
+++ b/web/backend/main.py
@@ -36,6 +36,7 @@ from .routers import (
     yyb,
 )
 from .schemas import AppInfo
+from .session import SessionRenewalMiddleware
 from .version import get_app_version
 
 
@@ -149,6 +150,9 @@ class SecurityHeadersMiddleware(BaseHTTPMiddleware):
 
 app.add_middleware(SecurityHeadersMiddleware)
 
+# 后台登录滑动续期：24h 空闲过期，7d 绝对上限。
+app.add_middleware(SessionRenewalMiddleware)
+
 # 注册路由
 app.include_router(auth.router)
 app.include_router(users.router)
diff --git a/web/backend/routers/auth.py b/web/backend/routers/auth.py
index 91082ff..8327909 100644
--- a/web/backend/routers/auth.py
+++ b/web/backend/routers/auth.py
@@ -2,8 +2,6 @@
 
 from __future__ import annotations
 
-import os
-
 from fastapi import APIRouter, Depends, Request, Response
 from sqlalchemy.orm import Session
 
@@ -21,7 +19,7 @@ from ..schemas import (
     SmsCodeResponse,
     TokenResponse,
 )
-from ..security import ACCESS_TOKEN_EXPIRE_HOURS, create_access_token, verify_password
+from ..security import issue_access_token, verify_password
 from ..services.dc_auth_service import (
     APP_ID,
     CHALLENGE_PURPOSE,
@@ -37,12 +35,10 @@ from ..services.login_sms_service import (
     send_login_sms_code,
     verify_login_sms_code,
 )
+from ..session import clear_session_cookie, set_session_cookie
 
 router = APIRouter(prefix="/api/auth", tags=["认证"])
 
-# Cookie 安全配置（生产环境 HTTPS 部署时设置 COOKIE_SECURE=true）
-_COOKIE_SECURE = os.getenv("COOKIE_SECURE", "false").lower() == "true"
-
 
 def _find_user(db: Session, username_value: str) -> User | None:
     """用户名只 trim，不做大小写折叠、不限制字符集。
@@ -75,18 +71,6 @@ def _request_origin(request: Request) -> str:
     return str(request.base_url).rstrip("/")
 
 
-def _set_auth_cookie(response: Response, token: str) -> None:
-    response.set_cookie(
-        key="access_token",
-        value=token,
-        httponly=True,
-        secure=_COOKIE_SECURE,
-        samesite="lax",
-        max_age=ACCESS_TOKEN_EXPIRE_HOURS * 3600,
-        path="/",
-    )
-
-
 def _issue_session(
     db: Session,
     response: Response,
@@ -94,8 +78,8 @@ def _issue_session(
     method: str,
     device_id: str = "",
 ) -> TokenResponse:
-    token = create_access_token({"sub": str(user.id), "role": user.role})
-    _set_auth_cookie(response, token)
+    issued = issue_access_token({"sub": str(user.id), "role": user.role})
+    set_session_cookie(response, issued.token, issued.expires_at)
 
     detail = f"method={method}"
     if device_id:
@@ -112,7 +96,7 @@ def _issue_session(
     db.commit()
 
     return TokenResponse(
-        access_token=token,
+        access_token=issued.token,
         role=user.role,
         username=user.username,
         permissions=get_user_permissions(user),
@@ -252,7 +236,7 @@ def logout(
     current_user: User = Depends(get_current_user),
     db: Session = Depends(get_db),
 ):
-    response.delete_cookie(key="access_token", path="/")
+    clear_session_cookie(response)
     db.add(
         AuditLog(
             user_id=current_user.id,
diff --git a/web/backend/security.py b/web/backend/security.py
index af17e15..2452f1f 100644
--- a/web/backend/security.py
+++ b/web/backend/security.py
@@ -1,8 +1,18 @@
-"""安全模块：密码哈希 + JWT"""
+"""安全模块：密码哈希 + JWT。
+
+后台登录采用「滑动会话」：
+
+- ``ACCESS_TOKEN_IDLE_HOURS``：空闲多久失效，默认 24 小时；
+- ``ACCESS_TOKEN_MAX_HOURS``：从首次登录起算的绝对上限，默认 7 天。
+
+每个带有效会话的 API 请求都会续签 Cookie，但 ``iat`` 保持不变，
+因此活跃用户最多也只能维持 7 天，之后必须重新登录。
+"""
 
 import os
 import secrets
 import warnings
+from dataclasses import dataclass
 from datetime import UTC, datetime, timedelta
 
 import bcrypt
@@ -20,7 +30,22 @@ if not SECRET_KEY:
 assert SECRET_KEY is not None
 SECRET_KEY_TYPED: str = SECRET_KEY
 ALGORITHM = "HS256"
-ACCESS_TOKEN_EXPIRE_HOURS = int(os.getenv("ACCESS_TOKEN_EXPIRE_HOURS", "24"))
+
+# 兼容旧部署：只配置了 ACCESS_TOKEN_EXPIRE_HOURS 时，把它当作空闲时长。
+ACCESS_TOKEN_IDLE_HOURS = int(
+    os.getenv("ACCESS_TOKEN_IDLE_HOURS", os.getenv("ACCESS_TOKEN_EXPIRE_HOURS", "24"))
+)
+ACCESS_TOKEN_MAX_HOURS = int(os.getenv("ACCESS_TOKEN_MAX_HOURS", str(7 * 24)))
+ACCESS_TOKEN_EXPIRE_HOURS = ACCESS_TOKEN_IDLE_HOURS
+
+
+@dataclass(frozen=True)
+class AccessToken:
+    """一次签发结果：Token 本体 + 会话起点 + 过期时刻。"""
+
+    token: str
+    issued_at: datetime
+    expires_at: datetime
 
 
 def hash_password(password: str) -> str:
@@ -37,13 +62,75 @@ def verify_password(plain: str, hashed: str) -> bool:
         return False
 
 
-def create_access_token(
-    data: dict, expires_hours: int = ACCESS_TOKEN_EXPIRE_HOURS
-) -> str:
+def _utcnow() -> datetime:
+    return datetime.now(UTC).replace(microsecond=0)
+
+
+def _as_utc(value: object) -> datetime | None:
+    """把 JWT 里的时间字段（datetime / 时间戳）统一转成 UTC datetime。"""
+    if isinstance(value, datetime):
+        return (
+            value.replace(tzinfo=UTC) if value.tzinfo is None else value.astimezone(UTC)
+        )
+    if isinstance(value, (int, float)):
+        try:
+            return datetime.fromtimestamp(value, UTC)
+        except (OverflowError, OSError, ValueError):
+            return None
+    if isinstance(value, str):
+        try:
+            return datetime.fromtimestamp(float(value), UTC)
+        except (OverflowError, OSError, ValueError):
+            return None
+    return None
+
+
+def _session_start(payload: dict) -> datetime | None:
+    """会话起点：新 Token 用 ``iat``，旧 Token 用 ``exp - 24h`` 反推。
+
+    旧 Token 没有 ``iat``。上线后第一次续签必须把绝对上限锚定到真实登录时刻，
+    不能从「第一次续签」重新算 7 天，否则老会话会被额外延长。
+    """
+    issued_at = _as_utc(payload.get("iat"))
+    if issued_at is not None:
+        return issued_at
+    expires_at = _as_utc(payload.get("exp"))
+    if expires_at is None:
+        return None
+    return expires_at - timedelta(hours=ACCESS_TOKEN_IDLE_HOURS)
+
+
+def _absolute_expiry(issued_at: datetime) -> datetime:
+    return issued_at + timedelta(hours=ACCESS_TOKEN_MAX_HOURS)
+
+
+def issue_access_token(
+    data: dict,
+    *,
+    issued_at: datetime | None = None,
+    now: datetime | None = None,
+) -> AccessToken:
+    """签发新会话 Token：``exp = min(now + 空闲时长, 会话起点 + 7 天)``。"""
+    current = _utcnow() if now is None else now.replace(microsecond=0)
+    started = current if issued_at is None else issued_at.replace(microsecond=0)
+    expire = min(
+        current + timedelta(hours=ACCESS_TOKEN_IDLE_HOURS),
+        _absolute_expiry(started),
+    )
     to_encode = data.copy()
-    expire = datetime.now(UTC) + timedelta(hours=expires_hours)
-    to_encode.update({"exp": expire})
-    return jwt.encode(to_encode, SECRET_KEY_TYPED, algorithm=ALGORITHM)
+    to_encode.update({"iat": started, "exp": expire})
+    token = jwt.encode(to_encode, SECRET_KEY_TYPED, algorithm=ALGORITHM)
+    return AccessToken(token=token, issued_at=started, expires_at=expire)
+
+
+def create_access_token(
+    data: dict,
+    *,
+    issued_at: datetime | None = None,
+    now: datetime | None = None,
+) -> str:
+    """兼容旧调用：只返回 Token 字符串。"""
+    return issue_access_token(data, issued_at=issued_at, now=now).token
 
 
 def decode_access_token(token: str) -> dict | None:
@@ -51,3 +138,48 @@ def decode_access_token(token: str) -> dict | None:
         return jwt.decode(token, SECRET_KEY_TYPED, algorithms=[ALGORITHM])
     except JWTError:
         return None
+
+
+def is_session_expired(payload: dict, *, now: datetime | None = None) -> bool:
+    """同时检查空闲过期与 7 天绝对上限。"""
+    current = now or _utcnow()
+    expires_at = _as_utc(payload.get("exp"))
+    if expires_at is None or current >= expires_at:
+        return True
+    issued_at = _session_start(payload)
+    return issued_at is not None and current >= _absolute_expiry(issued_at)
+
+
+def renew_access_token(
+    token: str, *, now: datetime | None = None
+) -> AccessToken | None:
+    """续签有效会话；已到 7 天绝对上限或 Token 本身无效时返回 ``None``。
+
+    续签保留原 ``iat``，只把 ``exp`` 推到 ``now + 24h``，且不超过绝对上限。
+    """
+    payload = decode_access_token(token)
+    if payload is None:
+        return None
+    current = (_utcnow() if now is None else now).replace(microsecond=0)
+    if is_session_expired(payload, now=current):
+        return None
+    issued_at = _session_start(payload)
+    if issued_at is None:
+        return None
+
+    absolute_expire = _absolute_expiry(issued_at)
+    if current >= absolute_expire:
+        return None
+    old_expire = _as_utc(payload.get("exp"))
+    new_expire = min(
+        current + timedelta(hours=ACCESS_TOKEN_IDLE_HOURS), absolute_expire
+    )
+    if old_expire is not None and new_expire <= old_expire:
+        # 已顶到绝对上限，或本次请求没有带来有意义的延长：不重发 Cookie。
+        return None
+
+    claims = payload.copy()
+    claims.pop("exp", None)
+    claims.update({"iat": issued_at, "exp": new_expire})
+    renewed = jwt.encode(claims, SECRET_KEY_TYPED, algorithm=ALGORITHM)
+    return AccessToken(token=renewed, issued_at=issued_at, expires_at=new_expire)
diff --git a/web/backend/session.py b/web/backend/session.py
new file mode 100644
index 0000000..9216276
--- /dev/null
+++ b/web/backend/session.py
@@ -0,0 +1,87 @@
+"""后台登录 Cookie 与滑动续期中间件。
+
+续期只发生在「已经通过 ``get_current_user`` 的请求」上：
+
+- ``get_current_user`` 把当前用户和「本次认证用的 Cookie Token」写进
+  ``request.state``；
+- 响应完成后，中间件读取该 Token，把 ``exp`` 推到 ``now + 24h``（不超过 7 天）；
+- 登录流程、登出、未认证请求、401 响应一律不续期。
+"""
+
+from __future__ import annotations
+
+import os
+from datetime import UTC, datetime
+
+from fastapi import Request, Response
+from starlette.middleware.base import BaseHTTPMiddleware, RequestResponseEndpoint
+
+from .security import AccessToken, renew_access_token
+
+SESSION_COOKIE_NAME = "access_token"
+
+# 生产环境 HTTPS 部署时设置 COOKIE_SECURE=true
+_COOKIE_SECURE = os.getenv("COOKIE_SECURE", "false").lower() == "true"
+
+# 登出会删除 Cookie，不能再被中间件补回来。
+_NO_RENEW_PATHS = frozenset({"/api/auth/logout"})
+
+
+def set_session_cookie(
+    response: Response,
+    token: str,
+    expires_at: datetime,
+    *,
+    now: datetime | None = None,
+) -> None:
+    """写入会话 Cookie；有效期跟随 JWT 的绝对过期时刻。"""
+    current = now or datetime.now(UTC)
+    max_age = int((expires_at - current).total_seconds())
+    if max_age <= 0:
+        return
+    response.set_cookie(
+        key=SESSION_COOKIE_NAME,
+        value=token,
+        httponly=True,
+        secure=_COOKIE_SECURE,
+        samesite="lax",
+        max_age=max_age,
+        expires=expires_at,
+        path="/",
+    )
+
+
+def clear_session_cookie(response: Response) -> None:
+    response.delete_cookie(key=SESSION_COOKIE_NAME, path="/")
+
+
+def _should_renew(request: Request, status_code: int) -> bool:
+    """只对「已认证的 API 请求 + 非 401 + 非登出」续期。"""
+    path = request.url.path.rstrip("/") or "/"
+    if status_code == 401:
+        return False
+    if not path.startswith("/api/"):
+        return False
+    if path in _NO_RENEW_PATHS:
+        return False
+    return getattr(request.state, "current_user", None) is not None
+
+
+class SessionRenewalMiddleware(BaseHTTPMiddleware):
+    """滑动续期：活跃请求自动延长 24h，但永不突破 7 天绝对上限。"""
+
+    async def dispatch(
+        self, request: Request, call_next: RequestResponseEndpoint
+    ) -> Response:
+        response = await call_next(request)
+        if not _should_renew(request, response.status_code):
+            return response
+
+        token = getattr(request.state, "auth_cookie_token", None)
+        if not token:
+            return response
+        renewed: AccessToken | None = renew_access_token(token)
+        if renewed is None:
+            return response
+        set_session_cookie(response, renewed.token, renewed.expires_at)
+        return response