Retry transient chart detail misses

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

@@ -64,6 +64,7 @@ const PROBABILITY_REFRESH_AFTER_PATCH_MS = DASHBOARD_REFRESH_POLICY_MS.metar;
 const FOREGROUND_FULL_DETAIL_REFRESH_DEDUP_MS = 90_000;
 const NO_PATCH_CACHED_DETAIL_REFRESH_MS = DASHBOARD_REFRESH_POLICY_MS.observation;
 const DETAIL_LOAD_BATCH_DELAY_MS = 0;
+const TRANSIENT_DETAIL_RETRY_DELAY_MS = 3_000;
 const INITIAL_DETAIL_LOAD_SLOTS = 3;
 const DEFERRED_DETAIL_LOAD_DELAY_MS = 1_200;
 const DEFERRED_DETAIL_LOAD_GROUP_SIZE = 3;
@@ -792,13 +793,41 @@ export function LiveTemperatureThresholdChart({
     setIsHourlyLoading(true);
     markDetailRequest("network");
     let cancelled = false;
+    let retryScheduled = false;
+    let retryTimer: ReturnType<typeof setTimeout> | null = null;
+
+    const scheduleTransientDetailRetry = () => {
+      retryScheduled = true;
+      markDetailDegraded();
+      retryTimer = setTimeout(() => {
+        if (cancelled) return;
+        markDetailRequest("network");
+        fetchHourlyForecastForCity(city, { bypassLocalCache: true, resolution: targetResolution })
+          .then((data) => {
+            if (cancelled) return;
+            if (!data) {
+              markDetailDegraded({ showUserError: true });
+              return;
+            }
+            applySuccessfulHourlyDetail(data);
+          })
+          .catch(() => {
+            if (!cancelled) {
+              markDetailDegraded({ showUserError: true });
+            }
+          })
+          .finally(() => {
+            if (!cancelled) setIsHourlyLoading(false);
+          });
+      }, TRANSIENT_DETAIL_RETRY_DELAY_MS);
+    };
 
     const timer = setTimeout(() => {
       fetchHourlyForecastForCity(city, { resolution: targetResolution })
         .then((data) => {
           if (cancelled) return;
           if (!data) {
-            markDetailDegraded({ showUserError: true });
+            scheduleTransientDetailRetry();
             return;
           }
           applySuccessfulHourlyDetail(data);
@@ -809,13 +838,14 @@ export function LiveTemperatureThresholdChart({
           }
         })
         .finally(() => {
-          if (!cancelled) setIsHourlyLoading(false);
+          if (!cancelled && !retryScheduled) setIsHourlyLoading(false);
         });
     }, DETAIL_LOAD_BATCH_DELAY_MS);
 
     return () => {
       cancelled = true;
       clearTimeout(timer);
+      if (retryTimer !== null) clearTimeout(retryTimer);
     };
   }, [
     city,

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

@@ -299,6 +299,13 @@ export async function runTests() {
       chartCanvasSourceIncludes(chartSource, "handleRetryDetail"),
     "city detail charts should show stale cache first and expose a retryable unavailable state",
   );
+  assert(
+    chartSource.includes("TRANSIENT_DETAIL_RETRY_DELAY_MS") &&
+      chartSource.includes("scheduleTransientDetailRetry") &&
+      chartSource.includes("fetchHourlyForecastForCity(city, { bypassLocalCache: true, resolution: targetResolution })") &&
+      chartSource.includes("!retryScheduled"),
+    "cold partial detail-batch misses should stay in loading state and retry cached detail once before showing unavailable",
+  );
   const successfulHourlyDetailBlock =
     /const applySuccessfulHourlyDetail = useCallback\([\s\S]*?\n  \}, \[row\]\);/.exec(chartSource)?.[0] || "";
   assert(