fix(usage-stats): avoid partial stats on initial SSE race

Skip creating partial stats from SSE before the initial REST load
completes, keeping real-time merges limited to existing full stats.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/shared/components/UsageStats.js

@@ -204,6 +204,7 @@ export default function UsageStats({ period: periodProp, setPeriod: setPeriodPro
   const [providers, setProviders] = useState([]);
   const [periodLocal, setPeriodLocal] = useState("today");
   const isInitialLoad = useRef(true);
+  const hasLoadedStats = useRef(false);
   const period = periodProp ?? periodLocal;
   const setPeriod = setPeriodProp ?? setPeriodLocal;
 
@@ -242,14 +243,17 @@ export default function UsageStats({ period: periodProp, setPeriod: setPeriodPro
     fetch(`/api/usage/stats?period=${period}`)
       .then((r) => r.ok ? r.json() : null)
       .then((data) => {
-        if (data) setStats((prev) => ({ ...prev, ...data }));
+        if (data) {
+          hasLoadedStats.current = true;
+          setStats((prev) => ({ ...prev, ...data }));
+        }
       })
       .catch(() => {})
       .finally(() => {
         setLoading(false);
         setFetching(false);
       });
-  }, [period]); // eslint-disable-line react-hooks/exhaustive-deps
+  }, [period]);
 
   // SSE connection - real-time updates for activeRequests + recentRequests only
   useEffect(() => {
@@ -259,14 +263,17 @@ export default function UsageStats({ period: periodProp, setPeriod: setPeriodPro
       try {
         const data = JSON.parse(e.data);
         // Always merge only real-time fields, never overwrite full stats from REST
-        setStats((prev) => ({
-          ...(prev || {}),
-          activeRequests: data.activeRequests,
-          recentRequests: data.recentRequests,
-          errorProvider: data.errorProvider,
-          pending: data.pending,
-        }));
-        setLoading(false);
+        setStats((prev) => {
+          if (!prev) return prev;
+          return {
+            ...prev,
+            activeRequests: data.activeRequests,
+            recentRequests: data.recentRequests,
+            errorProvider: data.errorProvider,
+            pending: data.pending,
+          };
+        });
+        if (hasLoadedStats.current) setLoading(false);
       } catch (err) {
         console.error("[SSE CLIENT] parse error:", err);
       }