fix backend bug

app.py

@@ -887,7 +887,20 @@ async def meccog_results() -> dict[str, Any]:
 
     if isinstance(results_resp, Exception) or not results_resp.is_success:
         err = str(results_resp) if isinstance(results_resp, Exception) else results_resp.text[:200]
-        raise HTTPException(502, f"Backend API error: {err}")
+        log.warning("Backend API error on /v1/results: %s", err)
+        # The bucket-sync API is a separate service and can be briefly down or
+        # slow to wake — degrade to the last known-good payload rather than
+        # taking the whole Results tab down with a 502, mirroring how
+        # _SingleFlightCache serves stale data for /api/messages etc.
+        if _meccog_cache["data"] is not None:
+            stale = dict(_meccog_cache["data"])
+            stale["error"] = f"Backend API error (showing cached data): {err}"
+            return stale
+        return {
+            "results": [], "leaderboard": [], "coverage": {},
+            "consensus": {}, "hyp_order": HYP_ORDER, "hypotheses": HYPOTHESES,
+            "fetched_at": "", "error": f"Backend API error: {err}",
+        }
 
     results_raw: list[dict] = results_resp.json().get("items", [])
     lb_rows: list[dict] = (

static/index.html

@@ -3454,12 +3454,19 @@ function renderMeccogTab(d) {
   if (!d) return;
   const { coverage, consensus, results, agents, hyp_order, hypotheses, fetched_at, error } = d;
 
-  if (error) {
+  // An `error` alongside empty data means there's nothing to show (e.g.
+  // BACKEND_API_URL unset, or the very first fetch failed with no cache
+  // yet to fall back to). An `error` alongside populated data means the
+  // backend is having trouble but we're showing the last known-good
+  // snapshot — render it rather than blanking the tab.
+  if (error && !results?.length && !hyp_order?.length) {
     meccogStatus.textContent = 'not configured';
     hypGridEl.innerHTML = `<div class="mc-empty" style="grid-column:1/-1">${escapeHtml(error)}</div>`;
     return;
   }
-  meccogStatus.textContent = fetched_at ? `updated ${fetched_at}` : '';
+  meccogStatus.textContent = error
+    ? `⚠ ${error}`
+    : (fetched_at ? `updated ${fetched_at}` : '');
 
   // Populate the submission activity chart on the leaderboard tab.
   if (results?.length) renderSubmissionsChart(results);