diff --git a/backend/common/middleware.py b/backend/common/middleware.py
index 9e9855c..0f08f07 100644
--- a/backend/common/middleware.py
+++ b/backend/common/middleware.py
@@ -34,3 +34,22 @@ async def dispatch(self, request: Request, call_next):
                 status_code=500,
                 content={"detail": "Internal Server Error"}
             )
+
+class CORSLoggingMiddleware(BaseHTTPMiddleware):
+    """
+    Middleware to log potential CORS issues.
+    This should be added outside CORSMiddleware so it can see the final response headers.
+    """
+    async def dispatch(self, request: Request, call_next):
+        response = await call_next(request)
+
+        origin = request.headers.get("origin")
+        if origin:
+            allow_origin = response.headers.get("access-control-allow-origin")
+            if not allow_origin:
+                # If it's a 404/500, sometimes headers are missing if not handled correctly.
+                # But generally CORSMiddleware adds them even for errors.
+                logger = get_logger("backend.middleware.cors")
+                logger.warning(f"CORS Warning: Origin '{origin}' requested but no 'Access-Control-Allow-Origin' header in response. Status: {response.status_code}")
+
+        return response
diff --git a/backend/main.py b/backend/main.py
index c3f867d..96c0555 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -7,7 +7,7 @@
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
-from backend.common.middleware import PathRewriteMiddleware, ExceptionHandlingMiddleware
+from backend.common.middleware import PathRewriteMiddleware, ExceptionHandlingMiddleware, CORSLoggingMiddleware
 from backend.api.problems import router as problems_router
 from backend.api.sql import router as sql_router
 from backend.api.stats import router as stats_router
@@ -101,7 +101,7 @@ def start_scheduler_background():
 # Cloud Run 도메인 및 Regex 정의 (환경 무관하게 참조 가능하도록)
 cloud_origins = [
     "https://query-craft-frontend-53ngedkhia-uc.a.run.app",
-    "https://query-craft-frontend-758178119666.us-central1.run.app",
+    "https://query-craft-frontend-758178119666.us-central1.run.app", # Verified as per issue report
     "https://query-craft-frontend-758178119666.a.run.app", # 추가
     "https://querycraft.run.app",  # 커스텀 도메인 예비
 ]
@@ -133,6 +133,9 @@ def start_scheduler_background():
         allow_methods=["*"],
         allow_headers=["*"],
     )
+
+# CORS Logging Middleware (CORS 설정 이후에 추가하여 바깥쪽에서 감싸도록 함)
+app.add_middleware(CORSLoggingMiddleware)
     
 # 404 및 기타 에러 로깅 미들웨어
 @app.middleware("http")
diff --git a/tests/test_cors_config.py b/tests/test_cors_config.py
index 9a0f7c8..6d1288b 100644
--- a/tests/test_cors_config.py
+++ b/tests/test_cors_config.py
@@ -1,28 +1,39 @@
-
 import os
 import sys
 import pytest
+from unittest.mock import patch
+import importlib
 from fastapi.testclient import TestClient
 
-# Set ENV to production before importing backend.main to ensure production CORS settings are used
-os.environ["ENV"] = "production"
+@pytest.fixture(scope="module")
+def client():
+    """
+    Fixture to set ENV to production and reload backend.main
+    to apply production CORS settings.
+    Restores the original environment and reloads backend.main afterwards.
+    """
+    # Temporarily set ENV to production
+    with patch.dict(os.environ, {"ENV": "production"}):
+        import backend.main
+        importlib.reload(backend.main)
+        from backend.main import app
+        yield TestClient(app)
 
-try:
-    from backend.main import app
-except ImportError:
-    sys.path.append(os.getcwd())
-    from backend.main import app
+    # Reload backend.main to restore original (development) state
+    # This is crucial so other tests (like test_integration.py)
+    # don't see the production app instance or stale env settings.
+    import backend.main
+    importlib.reload(backend.main)
 
 class TestCORSConfig:
     """Test CORS configuration for the backend."""
 
-    def test_cors_specific_origin_allowed(self):
+    def test_cors_specific_origin_allowed(self, client):
         """
         Verify that the specific frontend origin reported in the issue is allowed.
         Origin: https://query-craft-frontend-758178119666.us-central1.run.app
         """
         origin = "https://query-craft-frontend-758178119666.us-central1.run.app"
-        client = TestClient(app)
 
         # 1. Test Preflight (OPTIONS)
         response = client.options(
@@ -38,7 +49,6 @@ def test_cors_specific_origin_allowed(self):
         assert response.headers.get("access-control-allow-credentials") == "true"
 
         # 2. Test GET request
-        # /auth/me might return 200 (logged_in=False) or 401 depending on logic, but headers must be present
         response = client.get(
             "/auth/me",
             headers={"Origin": origin}
@@ -46,10 +56,9 @@ def test_cors_specific_origin_allowed(self):
         assert response.headers.get("access-control-allow-origin") == origin
         assert response.headers.get("access-control-allow-credentials") == "true"
 
-    def test_cors_cloud_run_domain_regex(self):
+    def test_cors_cloud_run_domain_regex(self, client):
         """Verify that other Cloud Run domains matching the regex are also allowed."""
         origin = "https://query-craft-frontend-random-hash.a.run.app"
-        client = TestClient(app)
 
         response = client.options(
             "/auth/me",
@@ -61,10 +70,9 @@ def test_cors_cloud_run_domain_regex(self):
         assert response.status_code == 200
         assert response.headers.get("access-control-allow-origin") == origin
 
-    def test_cors_disallowed_origin(self):
+    def test_cors_disallowed_origin(self, client):
         """Verify that a random origin is NOT allowed."""
         origin = "https://evil-site.com"
-        client = TestClient(app)
 
         response = client.options(
             "/auth/me",
@@ -73,21 +81,14 @@ def test_cors_disallowed_origin(self):
                 "Access-Control-Request-Method": "GET",
             }
         )
-        # Standard behavior for disallowed origin in FastAPI CORSMiddleware is
-        # usually 200 OK but WITHOUT Access-Control-Allow-Origin header,
-        # or sometimes 400.
-        # Starlette CORSMiddleware just ignores it and processes request as normal non-CORS,
-        # or returns response without CORS headers.
-
         assert "access-control-allow-origin" not in response.headers
 
-    def test_path_rewrite_does_not_break_cors(self):
+    def test_path_rewrite_does_not_break_cors(self, client):
         """
         Verify that PathRewriteMiddleware (which rewrites /auth/me to /api/auth/me)
         does not interfere with CORS headers.
         """
         origin = "https://query-craft-frontend-758178119666.us-central1.run.app"
-        client = TestClient(app)
 
         # Send request to /auth/me (rewritten to /api/auth/me)
         response = client.get(