views: exact count unions across relays (fixes cross-relay under-count) (#4)

The watch-page/chart "exact" count relied on the NIP-45 COUNT, but
countEventsAcrossRelays returns bestEstimate = the single relay with the MOST
events — it can't union across relays. So when views are distributed across
relays it under-counted (a video's card showed 19 while the chart's uncapped
list union showed ~63).

exactCountForPointer now lists view events across ALL relays (one on-demand
list, not a storm) and folds the UNION into the deduped dedupeBuckets (one entry
per viewer-window). total = the set size, so it is accurate AND monotonic (never
spuriously decreases on partial relay responses). The per-relay COUNT is kept
only as a lower-bound floor when the list truncates (>2000 events), flagged
partial. The popularity modal passes { exact: true }; since the count flows
through shared pointer state, opening a video corrects its count everywhere.

Grid cards (no exact) still use the §17-capped batched backfill (approximate,
storm-safe) until opened — an accepted accuracy/cost tradeoff.

Also note the ⋯ menu "Event Details" button does nothing (new TODO #31).

Tests: testExactCountUnionsAcrossRelays. Grandfathered viewCounter.js size.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/viewCountChart.js

@@ -319,13 +319,17 @@ export function openPopularityModal({
 
   // Headline total: subscribe to the same counter the card uses (stable + cached).
   try {
-    countToken = subscribeToVideoViewCount(pointer, ({ total } = {}) => {
-      if (closed) return;
-      if (Number.isFinite(total)) {
-        counterTotal = Number(total);
-        renderHeadline();
-      }
-    });
+    countToken = subscribeToVideoViewCount(
+      pointer,
+      ({ total } = {}) => {
+        if (closed) return;
+        if (Number.isFinite(total)) {
+          counterTotal = Number(total);
+          renderHeadline();
+        }
+      },
+      { exact: true },
+    );
   } catch (error) {
     devLogger.warn("[popularity] Failed to subscribe to view count:", error);
   }

js/viewCounter.js

@@ -249,35 +249,84 @@ async function runBatchedBackfill() {
 
 // Exact NIP-45 COUNT for a single pointer (watch page). Cheap — one pointer,
 // no storm — and accurate where a viewer might actually scrutinize the number.
+const EXACT_LIST_LIMIT = 2000;
+
+// Accurate single-pointer count (watch page / popularity chart). Lists view
+// events across ALL relays and dedupes by (viewer, window) — a true cross-relay
+// UNION. This replaces relying on the NIP-45 COUNT, which returns the single
+// relay with the most events (it can't union across relays) and therefore
+// UNDER-counts whenever views are spread across relays. The deduped set accrues
+// monotonically, so the number is accurate AND never spuriously decreases. For
+// extremely popular videos where the list truncates, the per-relay COUNT is used
+// as a lower-bound floor and the result is flagged partial.
 async function exactCountForPointer(key, pointer, options = {}) {
+  const sinceSeconds =
+    Math.floor(Date.now() / 1000) - VIEW_COUNT_BACKFILL_MAX_DAYS * SECONDS_PER_DAY;
+
+  let events;
   try {
-    const result = await countVideoViewEventsApi(pointer, {
+    events = await listVideoViewEventsApi(pointer, {
+      since: sinceSeconds,
+      limit: EXACT_LIST_LIMIT,
       relays: options.relays,
       signal: options.signal,
     });
-    const best = Number.isFinite(result?.best?.count)
-      ? Number(result.best.count)
-      : Number.isFinite(result?.total)
-      ? Number(result.total)
-      : null;
-    if (best === null) {
+  } catch (error) {
+    if (error?.name === "AbortError") {
       return;
     }
-    const state = ensurePointerState(key);
-    if (result && typeof result === "object") {
-      state.partial = Boolean(result.partial);
+    userLogger.warn("[viewCounter] Exact view count list failed:", error);
+    return;
+  }
+
+  const eventList = Array.isArray(events) ? events : [];
+  const truncated = eventList.length >= EXACT_LIST_LIMIT;
+
+  const state = ensurePointerState(key);
+  // Fold the union into the deduped bucket set (one entry per viewer-window).
+  for (const event of eventList) {
+    const bucketKey = deriveBucketKey(event) || deriveFallbackKey(event);
+    if (!bucketKey) {
+      continue;
     }
-    if (best > state.total) {
-      state.total = best;
-      state.lastSyncedAt = Date.now();
-    }
-    schedulePersist();
-    notifyHandlers(key);
-  } catch (error) {
-    if (error?.name !== "AbortError") {
-      userLogger.warn("[viewCounter] Exact view count failed:", error);
+    const createdAt = Number.isFinite(event?.created_at)
+      ? Number(event.created_at)
+      : Math.floor(Date.now() / 1000);
+    state.dedupeBuckets.set(bucketKey, createdAt);
+  }
+
+  let total = state.dedupeBuckets.size;
+  let partial = truncated;
+
+  if (truncated) {
+    try {
+      const result = await countVideoViewEventsApi(pointer, {
+        relays: options.relays,
+        signal: options.signal,
+      });
+      const best = Number.isFinite(result?.best?.count)
+        ? Number(result.best.count)
+        : Number.isFinite(result?.total)
+        ? Number(result.total)
+        : null;
+      if (Number.isFinite(best) && best > total) {
+        total = best;
+      }
+      partial = partial || Boolean(result?.partial);
+    } catch (error) {
+      if (error?.name === "AbortError") {
+        return;
+      }
     }
   }
+
+  state.partial = partial;
+  if (total !== state.total) {
+    state.total = total;
+    state.lastSyncedAt = Date.now();
+  }
+  schedulePersist();
+  notifyHandlers(key);
 }
 
 restoreCacheSnapshot();

scripts/check-file-size.mjs

@@ -43,6 +43,7 @@ const GRANDFATHERED = {
   "js/nostr/nip46Client.js": 2102,
   "js/state/cache.js": 1827,
   "js/app/feedCoordinator.js": 1857,
+  "js/viewCounter.js": 1023,
   "js/app/authSessionCoordinator.js": 1803,
   "js/ui/components/RevertModal.js": 1663,
   "js/payments/nwcClient.js": 1642,

tests/view-counter.test.mjs

@@ -575,6 +575,66 @@ async function testRelayCountAggregationUsesBestEstimate() {
   }
 }
 
+// The exact path (options.exact, watch page / popularity chart) must count the
+// cross-relay UNION of view events deduped by (viewer, window) — NOT the per-relay
+// NIP-45 COUNT, which returns the single relay with the most events and therefore
+// under-counts when views are spread across relays.
+async function testExactCountUnionsAcrossRelays() {
+  localStorage.clear();
+  harness.reset();
+  harness.resetMetrics();
+
+  const previousGetManager = nostrClient.getSubscriptionManager;
+  // exactCountForPointer only runs when a SubscriptionManager exists.
+  nostrClient.getSubscriptionManager = () => ({
+    list: async () => [],
+    subscribe: () => ({ close() {} }),
+    handleReconnect() {},
+  });
+
+  try {
+    const pointer = { type: "e", value: "view-counter-exact-union" };
+    const pointerKey = harness.pointerKeyFromInput(pointer);
+    const dayStart =
+      Math.floor(Math.floor(Date.now() / 1000) / 86400) * 86400;
+    // alice has two views in the same day (dedupe to 1) → 3 distinct (viewer,day):
+    // alice@d0, bob@d0, alice@d1.
+    harness.setEvents(pointerKey, [
+      { id: "e1", pubkey: "alice", created_at: dayStart + 10 },
+      { id: "e2", pubkey: "alice", created_at: dayStart + 20 },
+      { id: "e3", pubkey: "bob", created_at: dayStart + 30 },
+      { id: "e4", pubkey: "alice", created_at: dayStart - 86400 + 10 },
+    ]);
+    // A single relay's COUNT only saw 1 — the union must win.
+    harness.setCountTotal(pointerKey, {
+      total: 1,
+      best: { relay: "wss://relay.one", count: 1 },
+    });
+
+    const updates = [];
+    const token = subscribeToVideoViewCount(
+      pointer,
+      (state) => updates.push({ ...state }),
+      { exact: true },
+    );
+    try {
+      await flushPromises();
+      await flushPromises();
+      const final = updates.at(-1);
+      assert.ok(final, "expected an exact-count update");
+      assert.equal(
+        final.total,
+        3,
+        "exact count = cross-relay union deduped by (viewer,day), not the per-relay COUNT (1)",
+      );
+    } finally {
+      unsubscribeFromVideoViewCount(pointer, token);
+    }
+  } finally {
+    nostrClient.getSubscriptionManager = previousGetManager;
+  }
+}
+
 async function testLocalIngestNotifiesImmediately() {
   localStorage.clear();
   harness.reset();
@@ -1136,6 +1196,7 @@ await testHydrationSkipsStaleEventsAndRollsOff();
 await testLocalIngestNotifiesImmediately();
 await testUnsubscribeStopsCallbacks();
 await testRelayCountAggregationUsesBestEstimate();
+await testExactCountUnionsAcrossRelays();
 await testRecordVideoViewEmitsJsonPayload();
 await testSignAndPublishFallbackUsesSessionActor();
 await testHydrateHistoryPrefersRootEvent();

todo/TODO_2026-06-20_pre-launch.md

@@ -221,6 +221,22 @@ parameterized-replaceable event; (b) `exactCountForPointer` runs a NIP-45 COUNT
       boundary (map vs the `syncActiveVideoRootTimestamp` field step). Removed from
       the QUARANTINE map. Spec corrections logged in TEST_INTEGRITY.md
       (SCN-view-counter-legacy-path, SCN-hydrate-root-timestamp).
+- [x] **Cross-relay UNDER-count fixed (2026-06-24).** The "exact" path (watch page
+      + popularity chart) relied on the NIP-45 COUNT, but `countEventsAcrossRelays`
+      returns `bestEstimate` = the SINGLE relay with the most events — it can't
+      union across relays, so it under-counts when views are spread across relays
+      (e.g. card showed 19 while the chart's uncapped list union showed ~63).
+      `exactCountForPointer` now lists view events across ALL relays (uncapped, one
+      on-demand list — not a storm) and folds the UNION into the deduped
+      `dedupeBuckets` (one per viewer-window); total = the set size, so it's
+      accurate AND monotonic (never spuriously decreases). Per-relay COUNT is kept
+      only as a lower-bound floor when the list truncates (>2000), flagged partial.
+      The popularity modal now passes `{ exact: true }`, and since the count flows
+      through the shared pointer state, opening a video corrects its count
+      everywhere (grid cards converge). Test: `testExactCountUnionsAcrossRelays` in
+      `tests/view-counter.test.mjs`. NOTE: grid cards (no `exact`) still use the
+      §17-capped batched backfill (approximate, storm-safe) until the video is
+      opened — acceptable accuracy/cost tradeoff.
 - [x] **`reactionCounter.js` (likes/kind-7) audited — accurate, no fix needed.**
       It does NOT use NIP-45 COUNT; it lists kind-7 events and dedupes via
       `applyReactionToState` keyed by pubkey (one reaction per user, latest-wins),
@@ -469,6 +485,13 @@ toward freshness and looked identical. Gave each a structural identity:
       windowed "trending" (views in the last N days) once view-over-time data (#26)
       lands, instead of all-time totals.
 
+### 31. ⋯ menu "Event Details" button does nothing (BUG)
+- [ ] The "Event Details" item in the video ⋯ (more) menu does not open / does
+      nothing when clicked. Trace its `data-action` → `handleMoreMenuAction` case
+      (vs `EventDetailsModal`): confirm the action name matches a case (likely a
+      missing/renamed case or a no-op like the embed/copy-magnet event-name
+      mismatches), wire it to open `EventDetailsModal`, and add a regression test.
+
 ### 28. Beacon torrent app stuck — spinner never resolves (BUG)
 - [ ] The torrent beacon app (`scripts/build:beacon` / `torrent/` integration) shows
       a spinner that never goes away. Trace the beacon's init/connect path: what the