diff --git a/.env.example b/.env.example
index e0ab2f0..430234a 100644
--- a/.env.example
+++ b/.env.example
@@ -1,6 +1,8 @@
 GOOGLE_CLIENT_ID=your-google-oauth-client-id.apps.googleusercontent.com
 GOOGLE_CLIENT_SECRET=your-google-oauth-client-secret
+# OMS(orderlist) 와 SSO 하려면 양쪽 .env 에 동일한 값으로 설정
 SESSION_SECRET_KEY=replace-with-a-long-random-secret
+SESSION_COOKIE_NAME=session
 SESSION_COOKIE_SECURE=true
 PUBLIC_BASE_URL=https://dbx.no1king.freeddns.org
 CS_ORDER_URL=https://cs.example.com
diff --git a/app/main.py b/app/main.py
index 4f4ee2a..b981044 100644
--- a/app/main.py
+++ b/app/main.py
@@ -11,6 +11,9 @@ from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
 from starlette.middleware.sessions import SessionMiddleware
 
+# OMS(orderlist) 와 공유하는 세션 키. SessionMiddleware 의 session_cookie 도 동일 이름.
+SESSION_COOKIE_DEFAULT = "session"
+
 
 load_dotenv()
 
@@ -45,9 +48,11 @@ app = FastAPI(title="DBX 메인 페이지")
 app.add_middleware(
     SessionMiddleware,
     secret_key=env("SESSION_SECRET_KEY", "change-this-session-secret"),
+    session_cookie=env("SESSION_COOKIE_NAME", SESSION_COOKIE_DEFAULT),
     https_only=env("SESSION_COOKIE_SECURE", "true").lower() == "true",
     same_site="lax",
     max_age=60 * 60 * 8,
+    path="/",
 )
 app.mount("/static", StaticFiles(directory=str(BASE_DIR / "static")), name="static")
 
@@ -64,7 +69,26 @@ def public_url_for(request: Request, route_name: str) -> str:
 
 def get_user(request: Request) -> dict[str, Any] | None:
     user = request.session.get("user")
-    return user if isinstance(user, dict) else None
+    if isinstance(user, dict):
+        return user
+    # OMS 가 top-level user_email 만 채워놓은 SSO 세션도 인정
+    email = request.session.get("user_email")
+    if email:
+        return {
+            "email": str(email),
+            "name": request.session.get("user_name") or str(email),
+            "picture": "",
+        }
+    return None
+
+
+def safe_next(raw: str | None) -> str:
+    """Open redirect 방지: 같은 호스트의 절대 경로만 허용."""
+    if not raw:
+        return "/"
+    if not raw.startswith("/") or raw.startswith("//") or raw.startswith("/\\"):
+        return "/"
+    return raw
 
 
 def render_template(
@@ -140,6 +164,9 @@ async def login(request: Request):
             status_code=500,
         )
 
+    # SSO: ?next= 로 들어온 목적지를 OAuth 콜백 뒤에 사용하기 위해 세션에 임시 보관
+    request.session["_post_login_next"] = safe_next(request.query_params.get("next"))
+
     redirect_uri = public_url_for(request, "auth_google")
     return await oauth.google.authorize_redirect(
         request,
@@ -174,12 +201,19 @@ async def auth_google(request: Request):
             status_code=403,
         )
 
+    email = str(userinfo.get("email", "")).lower().strip()
+    name = userinfo.get("name") or email
+    # OMS 와 공유하는 top-level 키 (SSO 계약)
+    request.session["user_email"] = email
+    request.session["user_name"] = name
+    # 기존 코드/템플릿 호환용 dict
     request.session["user"] = {
-        "email": str(userinfo.get("email", "")).lower().strip(),
-        "name": userinfo.get("name") or userinfo.get("email"),
+        "email": email,
+        "name": name,
         "picture": userinfo.get("picture", ""),
     }
-    return RedirectResponse(url="/", status_code=303)
+    next_url = safe_next(request.session.pop("_post_login_next", "/"))
+    return RedirectResponse(url=next_url, status_code=303)
 
 
 @app.get("/logout")