Add chart freshness diagnostics

tests/test_sse_replay.py

@@ -4,6 +4,7 @@ from fastapi.testclient import TestClient
 
 from web.app import app
 from web.routers import sse_router
+from web.sse_manager import SseManager
 
 
 def _decode_sse_events(text: str):
@@ -15,6 +16,25 @@ def _decode_sse_events(text: str):
     return events
 
 
+def test_sse_format_event_stamps_emit_time_for_latency_diagnostics(monkeypatch):
+    monkeypatch.setattr("web.sse_manager.time.time", lambda: 1780750904.5)
+
+    frame = SseManager._format_event(
+        {
+            "type": "city_observation_patch.v1",
+            "revision": 123,
+            "city": "busan",
+            "source": "amos",
+            "ts": 1780750864062,
+            "payload": {"temp": 23.0},
+        }
+    )
+
+    event = _decode_sse_events(frame)[0]
+    assert event["sse_emitted_at_ms"] == 1780750904500
+    assert event["payload"]["temp"] == 23.0
+
+
 def test_events_endpoint_replays_only_requested_cities(monkeypatch):
     captured = {}
 

tests/test_web_observability.py

@@ -1012,6 +1012,13 @@ def test_city_detail_batch_returns_busy_when_global_builder_slot_is_full(monkeyp
     assert payload["busy"] is True
     assert payload["details"] == {}
     assert payload["missing"] == ["paris", "shanghai"]
+    assert payload["diagnostics"]["partial_reason"] == "busy"
+    assert payload["diagnostics"]["response_source"] == "busy"
+    assert payload["diagnostics"]["requested_count"] == 2
+    assert payload["diagnostics"]["completed_count"] == 0
+    assert payload["diagnostics"]["missing_count"] == 2
+    assert payload["diagnostics"]["city_status"]["paris"]["status"] == "busy"
+    assert payload["diagnostics"]["city_status"]["shanghai"]["status"] == "busy"
     assert build_calls == 0
 
 
@@ -1102,6 +1109,17 @@ def test_city_detail_batch_returns_completed_details_when_one_city_is_slow(monke
     assert payload["partial"] is True
     assert payload["missing"] == ["slow"]
     assert payload["errors"] == {}
+    assert payload["diagnostics"]["partial_reason"] == "timeout"
+    assert payload["diagnostics"]["requested_count"] == 3
+    assert payload["diagnostics"]["completed_count"] == 2
+    assert payload["diagnostics"]["missing_count"] == 1
+    assert payload["diagnostics"]["error_count"] == 0
+    assert payload["diagnostics"]["batch_concurrency"] == 2
+    assert payload["diagnostics"]["partial_timeout_ms"] == 20
+    assert payload["diagnostics"]["city_status"]["fast"]["status"] == "ok"
+    assert payload["diagnostics"]["city_status"]["other"]["status"] == "ok"
+    assert payload["diagnostics"]["city_status"]["slow"]["status"] == "timeout"
+    assert isinstance(payload["diagnostics"]["city_status"]["fast"]["duration_ms"], (int, float))
     assert "slow" not in completed