diff --git a/tests/test_city_payloads.py b/tests/test_city_payloads.py
new file mode 100644
index 00000000..772459af
--- /dev/null
+++ b/tests/test_city_payloads.py
@@ -0,0 +1,28 @@
+from web.services.city_payloads import build_city_summary_payload
+
+
+def test_city_summary_payload_preserves_deb_metadata():
+    payload = build_city_summary_payload(
+        {
+            "name": "shanghai",
+            "display_name": "Shanghai",
+            "temp_symbol": "°C",
+            "current": {},
+            "risk": {},
+            "deb": {
+                "prediction": 29.7,
+                "raw_prediction": 27.6,
+                "version": "deb_v1_recent_bias_corrected",
+                "bias_adjustment": 1.3,
+                "bias_samples": 18,
+            },
+        }
+    )
+
+    assert payload["deb"] == {
+        "prediction": 29.7,
+        "raw_prediction": 27.6,
+        "version": "deb_v1_recent_bias_corrected",
+        "bias_adjustment": 1.3,
+        "bias_samples": 18,
+    }
diff --git a/web/services/city_payloads.py b/web/services/city_payloads.py
index f2018590..081123ef 100644
--- a/web/services/city_payloads.py
+++ b/web/services/city_payloads.py
@@ -11,6 +11,7 @@ from web.core import _is_excluded_model_name
 TURKISH_MGM_CITIES = {"ankara", "istanbul"}
 
 def build_city_summary_payload(data: Dict[str, Any]) -> Dict[str, Any]:
+    deb = data.get("deb") if isinstance(data.get("deb"), dict) else {}
     return {
         "name": data.get("name"),
         "display_name": data.get("display_name"),
@@ -26,7 +27,7 @@ def build_city_summary_payload(data: Dict[str, Any]) -> Dict[str, Any]:
                 "settlement_source_label"
             ),
         },
-        "deb": {"prediction": data.get("deb", {}).get("prediction")},
+        "deb": dict(deb) if deb else {"prediction": None},
         "deviation_monitor": data.get("deviation_monitor") or {},
         "risk": {
             "level": data.get("risk", {}).get("level"),