Fix busted tests

frontend/src/components/MessageList.tsx

@@ -602,11 +602,22 @@ export function MessageList({
 
     let frames = 0;
     let raf = 0;
+    let lastAppliedTop: number | null = null;
     const step = () => {
       const list = listRef.current;
       if (!pendingBottomScrollRef.current || !list) return;
 
+      // Something other than us moved the scroll (a programmatic scrollTop, a
+      // restored position, assistive tech). Gesture handlers only catch a human
+      // at the wheel, so also bail when the position we last set has been moved
+      // upward — the pin must never fight another writer.
+      if (lastAppliedTop !== null && list.scrollTop < lastAppliedTop - 1) {
+        pendingBottomScrollRef.current = false;
+        return;
+      }
+
       scrollToIndex(sortedMessages.length - 1, 'end');
+      lastAppliedTop = list.scrollTop;
 
       const atBottom = list.scrollHeight - list.scrollTop - list.clientHeight <= 1;
       if (atBottom || (frames += 1) >= BOTTOM_SCROLL_FRAME_BUDGET) {

tests/e2e/specs/channel-info-and-search.spec.ts

@@ -37,8 +37,10 @@ test.describe('Channel info pane', () => {
     await page.goto(`/#channel/${channelKey}/flightless`);
     await expect(page.getByRole('status', { name: 'Radio OK' })).toBeVisible();
 
-    // Wait for messages to load
-    await expect(page.getByText('seed-0')).toBeVisible({ timeout: 15_000 });
+    // Wait for messages to load. Assert on the newest seeded message, not the
+    // oldest: the list is virtualized, so it opens at the bottom and only the
+    // visible window is in the DOM — seed-0 is 30 rows up and legitimately absent.
+    await expect(page.getByText(`seed-${SEED_COUNT - 1}`)).toBeVisible({ timeout: 15_000 });
 
     // Click the channel name in the header to open info pane
     const headerTitle = page.locator('h2').filter({ hasText: '#flightless' });

tests/e2e/specs/pagination.spec.ts

@@ -25,13 +25,20 @@ test.describe('Message pagination ordering/dedup', () => {
 
     const list = page.locator('div.h-full.overflow-y-auto').first();
 
-    // Scroll to top to trigger older fetch
-    await list.evaluate((el) => {
-      el.scrollTop = 0;
-    });
-
-    // Wait for oldest message to appear after pagination
-    await expect(page.getByText('seed-0')).toBeVisible({ timeout: 15_000 });
+    // Scroll to top repeatedly until the oldest message renders.
+    //
+    // One scroll is not enough with a virtualized list: reaching the top fetches
+    // the older page, and the list then anchors to the message that was on top so
+    // the reader keeps their place, which leaves seed-0 fifty rows further up and
+    // unmounted. A reader scrolls again to get there; so does this. (Before
+    // virtualization every loaded row was in the DOM, so a single scroll made
+    // seed-0 findable regardless of where the viewport actually was.)
+    await expect(async () => {
+      await list.evaluate((el) => {
+        el.scrollTop = 0;
+      });
+      await expect(page.getByText('seed-0')).toBeVisible({ timeout: 1_000 });
+    }).toPass({ timeout: 20_000 });
 
     // Spot-check ordering: seed-249 appears above seed-200; seed-50 above seed-10
     // Fetch from API to validate ordering and dedup