diff --git a/backend/tests/test_agent_guidance_check.py b/backend/tests/test_agent_guidance_check.py
index f0252235db..23dc886d45 100644
--- a/backend/tests/test_agent_guidance_check.py
+++ b/backend/tests/test_agent_guidance_check.py
@@ -54,6 +54,7 @@ EXPECTED_GUIDANCE_PATHS = {
     "backend/packages/harness/deerflow/utils/AGENTS.md",
     "frontend/src/AGENTS.md",
     "frontend/src/core/memory/AGENTS.md",
+    "frontend/tests/e2e/AGENTS.md",
     "scripts/AGENTS.md",
     "examples/deerflow-extension-agent-teams/AGENTS.md",
     "examples/deerflow-extension-workflows/AGENTS.md",
diff --git a/frontend/tests/e2e/AGENTS.md b/frontend/tests/e2e/AGENTS.md
new file mode 100644
index 0000000000..b62b8169fd
--- /dev/null
+++ b/frontend/tests/e2e/AGENTS.md
@@ -0,0 +1,10 @@
+# Browser E2E tests
+
+Virtualized lists do not keep every fetched row mounted. Assert the pagination
+request, then filter or scroll the loaded row into the rendered window before
+checking its content. Preserve the real scroll trigger and search-mode guard.
+
+For message ordering across compaction/refetch, poll an atomic DOM comparison
+until both nodes settle. Missing or reversed nodes must still fail; keep history,
+refresh and hidden-summary assertions. Avoid fixed sleeps and whole-test retries
+as substitutes for synchronization.
diff --git a/frontend/tests/e2e/thread-list-infinite-scroll.spec.ts b/frontend/tests/e2e/thread-list-infinite-scroll.spec.ts
index 763d3baa2d..cd93a308f5 100644
--- a/frontend/tests/e2e/thread-list-infinite-scroll.spec.ts
+++ b/frontend/tests/e2e/thread-list-infinite-scroll.spec.ts
@@ -64,6 +64,7 @@ test.describe("Thread list infinite scroll (issue #3482)", () => {
   test("chats list page loads more threads when scrolling to the bottom", async ({
     page,
   }) => {
+    const offsets = observeSearchOffsets(page);
     mockLangGraphAPI(page, { threads: THREADS });
 
     await page.goto("/workspace/chats");
@@ -80,7 +81,12 @@ test.describe("Thread list infinite scroll (issue #3482)", () => {
     // Scrolling the sentinel into view triggers the next page.
     const sentinel = page.getByTestId("chats-page-sentinel");
     await sentinel.scrollIntoViewIfNeeded();
+    await expect.poll(() => offsets).toContain(PAGE_SIZE);
 
+    // Crossing the virtualization threshold can unmount Conversation 051
+    // while the scroll anchor stays near the bottom of the expanded list.
+    // Filter the fetched rows to verify the next page reached the UI.
+    await page.getByPlaceholder("Search chats").fill(SECOND_PAGE_FIRST);
     await expect(main.getByText(SECOND_PAGE_FIRST)).toBeVisible({
       timeout: 15_000,
     });
diff --git a/frontend/tests/e2e/thread-ordering.spec.ts b/frontend/tests/e2e/thread-ordering.spec.ts
index 8399ba0101..a10a8e22df 100644
--- a/frontend/tests/e2e/thread-ordering.spec.ts
+++ b/frontend/tests/e2e/thread-ordering.spec.ts
@@ -395,28 +395,35 @@ test.describe("Thread message ordering", () => {
     });
     // DOM relative order, not viewport coordinates: stick-to-bottom smooth
     // scrolling makes two separate boundingBox reads race each other.
-    const questionBeforeAnswer = await page.evaluate(() => {
-      const list = document.querySelector('[data-testid="main-message-list"]');
-      if (!list) {
-        return null;
-      }
-      const leaf = (text: string) =>
-        [...list.querySelectorAll("div, p")].find(
-          (element) =>
-            element.children.length === 0 && element.textContent === text,
-        );
-      const question = leaf("final-turn question");
-      const answer = leaf("final-turn answer");
-      if (!question || !answer) {
-        return null;
-      }
-      return (
-        (question.compareDocumentPosition(answer) &
-          Node.DOCUMENT_POSITION_FOLLOWING) !==
-        0
-      );
-    });
-    expect(questionBeforeAnswer).toBe(true);
+    // Compaction and the finishing history refetch can briefly replace
+    // these nodes. Re-read both in one DOM snapshot until they settle.
+    await expect
+      .poll(() =>
+        page.evaluate(() => {
+          const list = document.querySelector(
+            '[data-testid="main-message-list"]',
+          );
+          if (!list) {
+            return null;
+          }
+          const leaf = (text: string) =>
+            [...list.querySelectorAll("div, p")].find(
+              (element) =>
+                element.children.length === 0 && element.textContent === text,
+            );
+          const question = leaf("final-turn question");
+          const answer = leaf("final-turn answer");
+          if (!question || !answer) {
+            return null;
+          }
+          return (
+            (question.compareDocumentPosition(answer) &
+              Node.DOCUMENT_POSITION_FOLLOWING) !==
+            0
+          );
+        }),
+      )
+      .toBe(true);
 
     // The finishing refetch observed the extended feed; the established
     // order — including the compacted head — is unchanged.