Stabilize AMSC chart detail overlays

tests/test_latest_observation_overlay.py

@@ -46,3 +46,55 @@ def test_overlay_replaces_amos_when_old_local_time_string_looks_later_than_new_u
     assert result["amos"]["observation_time"] == "2026-06-14T17:23:00+00:00"
     assert result["amos"]["observation_time_local"] == "2026-06-15 01:23:00"
     assert result["amos"]["runway_obs"]["point_temperatures"][0]["runway"] == "17L/35R"
+
+
+def test_overlay_uses_latest_success_when_newer_status_row_has_no_observation():
+    class FakeDB:
+        def get_latest_raw_observation(self, source, city):
+            assert (source, city) == ("amsc_awos", "chengdu")
+            return {
+                "status": "no_results",
+                "observed_at": "",
+                "fetched_at": "2026-06-14T17:02:09+00:00",
+                "updated_at_ts": 1781456529.0,
+                "payload": {
+                    "source": "amsc_awos",
+                    "city": "chengdu",
+                    "status": "no_results",
+                    "error": "source returned no observation rows",
+                },
+            }
+
+        def list_latest_raw_observations_for_city(self, city, *, limit=100):
+            assert city == "chengdu"
+            return [
+                self.get_latest_raw_observation("amsc_awos", "chengdu"),
+                {
+                    "source": "amsc_awos",
+                    "city": "chengdu",
+                    "station_code": "ZUUU",
+                    "station_name": "Chengdu Shuangliu",
+                    "status": "ok",
+                    "observed_at": "2026-06-14T17:00:00+00:00",
+                    "fetched_at": "2026-06-14T17:00:30+00:00",
+                    "updated_at_ts": 1781456430.0,
+                    "payload": {
+                        "source": "amsc_awos",
+                        "source_label": "AMSC AWOS Chengdu Shuangliu (ZUUU)",
+                        "icao": "ZUUU",
+                        "temp_c": 25.8,
+                        "observation_time": "2026-06-14T17:00:00+00:00",
+                        "observation_time_local": "2026-06-15 01:00:00",
+                    },
+                },
+            ]
+
+    result = overlay_latest_amsc_observation(
+        FakeDB(),
+        "chengdu",
+        {"name": "chengdu", "temp_symbol": "°C", "amos": {}},
+    )
+
+    assert result["amos"]["temp_c"] == 25.8
+    assert result["current"]["temp"] == 25.8
+    assert result["airport_current"]["source_code"] == "amsc_awos"

tests/test_web_observability.py

@@ -1199,6 +1199,62 @@ def test_chart_data_cache_hit_starts_full_stale_refresh(monkeypatch):
     assert refresh_calls == ["paris"]
 
 
+def test_chart_data_cache_hit_overlays_latest_amsc_raw(monkeypatch):
+    import asyncio
+
+    class FakeCache:
+        def get_city_cache(self, kind, city):
+            assert kind == "full"
+            return {
+                "payload": {
+                    "name": city,
+                    "display_name": city.title(),
+                    "temp_symbol": "°C",
+                    "risk": {"icao": "ZUUU"},
+                    "current": {},
+                    "airport_current": {},
+                    "amos": {},
+                    "hourly": {"times": ["13:00"], "temps": [25.0]},
+                },
+            }
+
+        def get_runway_obs_recent(self, icao, minutes=60):
+            return []
+
+        def get_latest_raw_observation(self, source, city):
+            assert (source, city) == ("amsc_awos", "chengdu")
+            return {
+                "source": "amsc_awos",
+                "city": "chengdu",
+                "station_code": "ZUUU",
+                "station_name": "Chengdu Shuangliu",
+                "status": "ok",
+                "observed_at": "2026-06-14T17:00:00+00:00",
+                "fetched_at": "2026-06-14T17:00:30+00:00",
+                "payload": {
+                    "source": "amsc_awos",
+                    "source_label": "AMSC AWOS Chengdu Shuangliu (ZUUU)",
+                    "icao": "ZUUU",
+                    "temp_c": 25.8,
+                    "observation_time": "2026-06-14T17:00:00+00:00",
+                    "observation_time_local": "2026-06-15 01:00:00",
+                },
+            }
+
+    monkeypatch.setattr(city_api.legacy_routes, "_CACHE_DB", FakeCache())
+    monkeypatch.setattr(
+        city_api.legacy_routes,
+        "_overlay_latest_wunderground_current",
+        lambda city, payload: payload,
+    )
+
+    payload = asyncio.run(city_api._get_city_chart_data("chengdu", force_refresh=False))
+
+    assert payload["amos"]["temp_c"] == 25.8
+    assert payload["current"]["temp"] == 25.8
+    assert payload["airport_current"]["source_code"] == "amsc_awos"
+
+
 def test_chart_data_returns_cached_payload_when_optional_overlay_times_out(monkeypatch):
     import asyncio