fix: treat invalid or missing dashboard timestamps as stale

apps/web/package.json

@@ -8,7 +8,7 @@
     "dev": "vite",
     "build": "vite build",
     "preview": "vite preview",
-    "test": "node --import tsx --test src/demo/trace-health-check.test.ts src/lib/config.test.ts src/dashboard/fixture-health-check.test.ts src/lib/round-status.test.ts src/components/dashboard/RoundStatusCard.test.tsx",
+    "test": "node --import tsx --test src/demo/trace-health-check.test.ts src/lib/config.test.ts src/dashboard/fixture-health-check.test.ts src/lib/round-status.test.ts src/components/dashboard/RoundStatusCard.test.tsx src/hooks/useDashboardData.test.ts",
     "typecheck": "tsc --noEmit -p tsconfig.json"
   },
   "dependencies": {

apps/web/src/hooks/useDashboardData.test.ts

@@ -0,0 +1,55 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+import { isStale } from "./useDashboardData";
+
+// Mirrors STALE_THRESHOLD_MS in useDashboardData.ts (5 minutes). Kept as a
+// local constant rather than imported so these tests pin the *contract*
+// (fresh below the threshold, stale above it) without depending on that
+// value being exported.
+const STALE_THRESHOLD_MS = 5 * 60 * 1000;
+const NOW_MS = Date.parse("2026-06-15T12:00:00.000Z");
+
+test("invalid or missing timestamps are treated as stale", () => {
+  assert.equal(isStale("not-a-date", NOW_MS), true, "unparseable string");
+  assert.equal(isStale("", NOW_MS), true, "empty string");
+  assert.equal(isStale("abcdef", NOW_MS), true, "garbage string");
+  assert.equal(isStale("2026-13-45T00:00:00Z", NOW_MS), true, "invalid calendar date");
+  assert.equal(isStale(null, NOW_MS), true, "null");
+  assert.equal(isStale(undefined, NOW_MS), true, "undefined");
+});
+
+test("valid fresh timestamps are not stale", () => {
+  const fetchedAt = new Date(NOW_MS - 30_000).toISOString(); // 30s ago
+  assert.equal(isStale(fetchedAt, NOW_MS), false);
+});
+
+test("valid old timestamps beyond the threshold are stale", () => {
+  const fetchedAt = new Date(NOW_MS - STALE_THRESHOLD_MS - 60_000).toISOString(); // 6 min ago
+  assert.equal(isStale(fetchedAt, NOW_MS), true);
+});
+
+test("a timestamp equal to now is fresh", () => {
+  const fetchedAt = new Date(NOW_MS).toISOString();
+  assert.equal(isStale(fetchedAt, NOW_MS), false);
+});
+
+test("a future timestamp is fresh (unchanged pre-existing behavior)", () => {
+  const fetchedAt = new Date(NOW_MS + 60_000).toISOString(); // 1 min in the future
+  assert.equal(isStale(fetchedAt, NOW_MS), false);
+});
+
+test("boundary: exactly at the stale threshold is still fresh (strict greater-than)", () => {
+  const fetchedAt = new Date(NOW_MS - STALE_THRESHOLD_MS).toISOString();
+  assert.equal(isStale(fetchedAt, NOW_MS), false);
+});
+
+test("boundary: one millisecond past the stale threshold is stale", () => {
+  const fetchedAt = new Date(NOW_MS - STALE_THRESHOLD_MS - 1).toISOString();
+  assert.equal(isStale(fetchedAt, NOW_MS), true);
+});
+
+test("boundary: one millisecond inside the stale threshold is fresh", () => {
+  const fetchedAt = new Date(NOW_MS - STALE_THRESHOLD_MS + 1).toISOString();
+  assert.equal(isStale(fetchedAt, NOW_MS), false);
+});

apps/web/src/hooks/useDashboardData.ts

@@ -16,8 +16,27 @@ export interface UseDashboardDataResult {
   refetch: () => void;
 }
 
-function isStale(fetchedAt: string, nowMs: number): boolean {
+/**
+ * Determine whether dashboard data fetched at `fetchedAt` should be treated
+ * as stale relative to `nowMs`.
+ *
+ * A missing or unparseable `fetchedAt` is treated as stale rather than
+ * fresh: `Date.parse()` returns `NaN` for invalid input, and every
+ * comparison against `NaN` (including `>`) evaluates to `false` in
+ * JavaScript -- so without an explicit check, malformed timestamp data
+ * would silently be reported as fresh instead of triggering the staleness
+ * warning it's meant to guard against.
+ */
+export function isStale(fetchedAt: string | null | undefined, nowMs: number): boolean {
+  if (!fetchedAt) {
+    return true;
+  }
+
   const fetchedTime = Date.parse(fetchedAt);
+  if (!Number.isFinite(fetchedTime)) {
+    return true;
+  }
+
   return nowMs - fetchedTime > STALE_THRESHOLD_MS;
 }