fix(news): keep the feed cursor in step with the list and drop Local reads for an area left

Co-Authored-By: Claude Fable 5.2 <[email protected]>

src/layers/news/index.js

@@ -190,6 +190,7 @@ export function createNewsLayer({
     request = null,
     feedRequest = null,
     inViewRequest = null,
+    inViewRequestKey = null,
     areaRequest = null,
     settleTimer = null,
     pulseTimer = null,
@@ -958,7 +959,9 @@ export function createNewsLayer({
       // clears it, not only the next refresh.
       needs = { ...needs, conflicts: null };
       feed = {
-        ...mergeFeedPage(feed, page, mode, now(), undefined, windowMs),
+        // Kept for the server's whole window (the shown one filters the
+        // view), so the rows between the head and the cursor are never lost.
+        ...mergeFeedPage(feed, page, mode, now(), undefined, maxWindowMs),
         loading: false,
         error: null,
       };
@@ -1039,18 +1042,24 @@ export function createNewsLayer({
     // The section changed, or the layer went off, while the area was read.
     if (!local() || !enabled) return;
     const readKey = inView.area?.key ?? '';
-    if (
-      !force &&
-      inView.readKey === readKey &&
-      (inView.minor || inViewRequest)
-    ) {
+    const held = inView.readKey === readKey && inView.minor;
+    if (!force && (inViewRequest ? inViewRequestKey === readKey : held)) {
       render();
       notify();
       return;
     }
+    // A read still out for another area must not land over this one.
     inViewRequest?.abort();
+    if (!force && held) {
+      inViewRequest = null;
+      inView = { ...inView, loading: false };
+      render();
+      notify();
+      return;
+    }
     const controller = new AbortController();
     inViewRequest = controller;
+    inViewRequestKey = readKey;
     inView = { ...inView, loading: true };
     notify();
     try {

src/layers/news/layer.test.mjs

@@ -852,3 +852,107 @@ test('a failed read keeps the layer on with an error; disable clears the overlay
   assert.deepEqual(entries.at(-1), []);
   assert.deepEqual(layer.getRowControls().feed.items, []);
 });
+
+test('narrowing the window and widening it again loses no report already read', async (t) => {
+  const { layer } = fixture(t, {
+    source: {
+      // Two pages: the head page, and an older one behind its cursor.
+      getFeed: async ({ before } = {}) =>
+        before
+          ? {
+              reports: [
+                report('earlier', { publishedAt: '2026-10-28T05:00:00.000Z' }),
+              ],
+              nextBefore: null,
+            }
+          : {
+              reports: [
+                report('recent', { publishedAt: '2026-10-28T09:30:00.000Z' }),
+              ],
+              nextBefore: '2026-10-28T09:30:00.000Z',
+            },
+    },
+  });
+  const shown = () => layer.getRowControls().feed.items.map((item) => item.id);
+  layer.enable();
+  await layer.update();
+  for (let i = 0; i < 3; i++) await settle();
+  assert.deepEqual(shown(), ['recent', 'earlier']);
+  layer.setParams({ filters: { hours: 1 } });
+  for (let i = 0; i < 3; i++) await settle();
+  assert.deepEqual(shown(), ['recent']);
+  layer.setParams({ filters: { hours: 24 } });
+  for (let i = 0; i < 3; i++) await settle();
+  assert.deepEqual(shown(), ['recent', 'earlier']);
+});
+
+test("a slower Local read for the area just left never replaces the current area's reports", async (t) => {
+  t.mock.timers.enable({ apis: ['setTimeout'] });
+  let centre = { lat: 49, lon: 36 };
+  const pending = [];
+  const russia = {
+    area: { key: 'RU', name: 'Russia', kind: 'country', country: 'RU' },
+    polygons: [
+      {
+        outer: [
+          [38, 48],
+          [40, 48],
+          [40, 50.5],
+          [38, 50.5],
+        ],
+        holes: [],
+      },
+    ],
+    borders: [],
+    disputed: [],
+  };
+  const { layer, camera } = fixture(t, {
+    height: 1_000_000,
+    centre: () => centre,
+    source: {
+      getAreaOutline: async (point) => (point.lon < 37.5 ? ukraine : russia),
+      getFeed: (query) => {
+        if (!(query.relevance === '' && query.limit === 500))
+          return Promise.resolve({ reports: [], nextBefore: null });
+        if (query.at.lon < 37.5)
+          return Promise.resolve({
+            reports: [report('kharkiv', { severity: 1 })],
+            nextBefore: null,
+          });
+        // Russia's read is slow.
+        return new Promise((resolve) => pending.push(resolve));
+      },
+    },
+  });
+  const look = async (at) => {
+    centre = at;
+    camera.moveEnd.raiseEvent();
+    t.mock.timers.tick(800);
+    await flush();
+  };
+  const shown = () =>
+    layer.getRowControls().feed.inView.items.map((item) => item.id);
+  layer.enable();
+  await layer.update();
+  await flush();
+  layer.setParams({ filters: { section: 'local' } });
+  await flush();
+  assert.deepEqual(shown(), ['kharkiv']);
+  await look({ lat: 49, lon: 39 });
+  assert.equal(pending.length, 1);
+  await look({ lat: 49, lon: 36 });
+  pending[0]({
+    reports: [
+      report('belgorod', {
+        severity: 1,
+        pins: [{ lat: 49, lon: 39, place: 'Rossosh', mappable: true }],
+      }),
+    ],
+    nextBefore: null,
+  });
+  await flush();
+  const view = layer.getRowControls().feed;
+  assert.equal(view.inView.area, 'Ukraine');
+  assert.equal(view.inView.loading, false);
+  assert.deepEqual(shown(), ['kharkiv']);
+});

src/layers/news/model.js

@@ -617,6 +617,8 @@ export function reportMarkerPosition(report, pin = 0) {
  * only the window and at most `max` rows (a long session does not grow
  * the list). `mode` 'head' refreshes the top and keeps the older cursor;
  * 'append' adds an older page and takes its cursor; 'replace' starts over.
+ * A head page that has older pages behind it and shares no row with the list
+ * left a gap (more than a page arrived since), so it starts over too.
  */
 export function mergeFeedPage(
   feed,
@@ -627,6 +629,10 @@ export function mergeFeedPage(
   windowMs = NEWS_WINDOW_MS,
 ) {
   const byId = new Map();
+  if (mode === 'head' && page.nextBefore && feed.items.length) {
+    const held = new Set(feed.items.map((item) => item.id));
+    if (!page.reports.some((item) => held.has(item.id))) mode = 'replace';
+  }
   const items =
     mode === 'replace'
       ? page.reports

src/layers/news/model.test.mjs

@@ -318,6 +318,23 @@ test('feed pages merge newest first without duplicates', () => {
   );
 });
 
+test('a head page that does not reach the rows held starts the list over', () => {
+  const held = report('h', '2026-10-28T06:00:00Z');
+  const fresh = report('n', '2026-10-28T09:30:00Z');
+  // More than a page arrived since the last refresh (a suspended tab): the
+  // reports between this page and the rows held are behind its cursor.
+  const feed = mergeFeedPage(
+    { items: [held], nextBefore: 'OLD' },
+    { reports: [fresh], nextBefore: 'NEW' },
+    'head',
+    NOW,
+  );
+  assert.deepEqual(
+    [feed.items.map((r) => r.id), feed.nextBefore],
+    [['n'], 'NEW'],
+  );
+});
+
 test('the feed list keeps only the last 24 hours and at most its cap', () => {
   const fresh = report('f', '2026-10-28T09:00:00Z');
   const stale = report('s', '2026-10-27T09:00:00Z');