Reduce duplicate terminal detail loads

frontend/components/dashboard/scan-terminal/LiveTemperatureThresholdChart.tsx

@@ -56,6 +56,7 @@ const PEAK_GLOW_BADGE_CLASS = {
 } as const;
 
 const PROBABILITY_REFRESH_AFTER_PATCH_MS = 60_000;
+const FOREGROUND_FULL_DETAIL_REFRESH_DEDUP_MS = 90_000;
 const DETAIL_LOAD_BATCH_DELAY_MS = 0;
 
 const TemperatureChartCanvas = dynamic(
@@ -165,6 +166,7 @@ export function LiveTemperatureThresholdChart({
   const lastPatchAtRef = useRef<number>(Date.now());
   const lastAppliedPatchRevisionRef = useRef<number>(0);
   const lastProbabilityRefreshAtRef = useRef<number>(0);
+  const lastForegroundRefreshAtRef = useRef<number>(0);
   const localDayRolloverFetchDateRef = useRef<string>("");
   const [isChartVisible, setIsChartVisible] = useState(
     () => typeof IntersectionObserver === "undefined",
@@ -197,6 +199,7 @@ export function LiveTemperatureThresholdChart({
     lastPatchAtRef.current = Date.now();
     lastAppliedPatchRevisionRef.current = 0;
     lastProbabilityRefreshAtRef.current = 0;
+    lastForegroundRefreshAtRef.current = 0;
     localDayRolloverFetchDateRef.current = "";
     setCurrentCityLocalDate(formatCityLocalDate(row?.tz_offset_seconds));
   }, [city]);
@@ -395,7 +398,19 @@ export function LiveTemperatureThresholdChart({
     let cancelled = false;
 
     const refreshForegroundFullDetail = () => {
-      lastPatchAtRef.current = Date.now();
+      const now = Date.now();
+      const cacheKey = `${city}:${targetResolution}`;
+      const cached = _hourlyCache.get(cacheKey);
+      const cacheAge = cached ? now - Number(cached.ts || 0) : Number.POSITIVE_INFINITY;
+      if (
+        now - lastForegroundRefreshAtRef.current < FOREGROUND_FULL_DETAIL_REFRESH_DEDUP_MS ||
+        (cacheAge >= 0 && cacheAge < FOREGROUND_FULL_DETAIL_REFRESH_DEDUP_MS)
+      ) {
+        return;
+      }
+
+      lastForegroundRefreshAtRef.current = now;
+      lastPatchAtRef.current = now;
 
       fetchHourlyForecastForCity(city, { ignoreCache: true, resolution: targetResolution })
         .then((data) => {

frontend/components/dashboard/scan-terminal/__tests__/refreshCadencePolicy.test.ts

@@ -102,6 +102,10 @@ export async function runTests() {
       chartLogicSource.includes("primeCityDetailCache"),
     "visible terminal chart detail fetches should be coalesced into one batch request and prime the shared chart cache",
   );
+  assert(
+    chartLogicSource.includes("CITY_DETAIL_BATCH_WINDOW_MS = 100"),
+    "visible terminal chart detail fetches should use a wide enough batch window to coalesce cards mounted across adjacent frames",
+  );
   assert(
     chartLogicSource.includes("partial?: boolean") &&
       chartLogicSource.includes("missing?: string[]"),

frontend/components/dashboard/scan-terminal/__tests__/ssePatchArchitecture.test.ts

@@ -198,8 +198,9 @@ export function runTests() {
   assert(
     foregroundRefreshBlock.includes("ignoreCache: true") &&
       foregroundRefreshBlock.includes("fetchHourlyForecastForCity") &&
+      foregroundRefreshBlock.includes("FOREGROUND_FULL_DETAIL_REFRESH_DEDUP_MS") &&
       !foregroundRefreshBlock.includes("setIsHourlyLoading(true)"),
-    "foreground resume refresh should update full detail immediately in the background without showing the loading overlay",
+    "foreground resume refresh should update full detail in the background without showing the loading overlay or refetching fresh detail",
   );
   assert(
     !chart.includes("/api/city/${encodeURIComponent(city)}/summary"),

frontend/components/dashboard/scan-terminal/temperature-chart-logic.ts

@@ -988,7 +988,7 @@ type CityDetailBatchQueue = {
   timer: ReturnType<typeof setTimeout> | null;
 };
 
-const CITY_DETAIL_BATCH_WINDOW_MS = 25;
+const CITY_DETAIL_BATCH_WINDOW_MS = 100;
 const CITY_DETAIL_BATCH_MAX_CITIES = 12;
 const _cityDetailBatchQueues = new Map<string, CityDetailBatchQueue>();