diff --git a/core/backend_log.py b/core/backend_log.py
index b25faec0..4bb4fa9b 100644
--- a/core/backend_log.py
+++ b/core/backend_log.py
@@ -90,6 +90,10 @@ def _memory():
     try:
         import app.logger as comfy_log
     except Exception:  # noqa: BLE001
+        # Without ComfyUI on the path, `app` resolves to our own folder (a namespace package) and stays cached,
+        # which would later hide ComfyUI's real `app` package. Forget it.
+        if getattr(sys.modules.get("app"), "__file__", True) is None:
+            sys.modules.pop("app", None)
         return None
     logs = comfy_log.logs
     if logs is not None and not isinstance(logs, Kept):
diff --git a/core/tests/test_backend_log_app_import.py b/core/tests/test_backend_log_app_import.py
new file mode 100644
index 00000000..8901766e
--- /dev/null
+++ b/core/tests/test_backend_log_app_import.py
@@ -0,0 +1,15 @@
+import subprocess
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def test_failed_comfy_logger_import_leaves_no_stale_app_package():
+    """Outside ComfyUI, `app` is our own folder; it must not stay cached and hide ComfyUI's real `app` later."""
+    code = (
+        "import sys; sys.path.insert(0, %r); import core.backend_log; "
+        "print('app' in sys.modules and getattr(sys.modules['app'], '__file__', 1) is None)"
+    ) % str(ROOT)
+    out = subprocess.run([sys.executable, "-I", "-c", code], capture_output=True, text=True, cwd=str(ROOT))
+    assert out.stdout.strip().endswith("False"), out.stdout + out.stderr