From 545681ce4c7a61b7a5fbbfff334c61443c4cfb6e Mon Sep 17 00:00:00 2001
From: allenliang2022 <allenliang2022@users.noreply.github.com>
Date: Mon, 6 Jul 2026 13:01:40 +0800
Subject: [PATCH] =?UTF-8?q?refactor(webui):=20address=20review=20=E2=80=94?=
 =?UTF-8?q?=20drop=20dead=20field,=20rename,=20add=20fallback=20intent=20t?=
 =?UTF-8?q?est=20(#5637)?=
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Greptile review follow-ups (no behavior change):
- Remove the captured-but-never-read scrollTopAtCapture field from
  _captureMessageViewportAnchor; only scrollHeightAtCapture is consulted.
- Rename _grewAbove -> _grewSinceCapture in the realign guard (the check is
  overall scrollHeight growth since capture, not specifically above-viewport),
  matching the fallback guard's _grewSinceSnap.
- Add a mutation-checked fallback active-intent test: content grew but the reader
  has recent real input intent, so the absolute snapshot.top restore is kept.
---
 static/ui.js                               | 13 ++++++-------
 tests/test_issue5637_stale_anchor_guard.py | 14 ++++++++++++++
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/static/ui.js b/static/ui.js
index cb65ae87..63d592ee 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -953,12 +953,11 @@ function _captureMessageViewportAnchor(){
         key:row&&row.dataset?String(row.dataset.messageAnchorKey||''):'',
         topOffset:rect.top-containerRect.top,
         topPadBefore,
-        // Snapshot the scroll geometry at capture so a later realign can detect that
-        // content grew ABOVE the viewport between capture and restore — the streaming
-        // case where the anchor's topOffset is stale and realigning to it would yank a
-        // still reader backward (issue #5637).
+        // Snapshot the scroll height at capture so a later realign can detect that
+        // content grew between capture and restore — the streaming case where the
+        // anchor's topOffset is stale and realigning to it would yank a still reader
+        // backward (issue #5637).
         scrollHeightAtCapture:container.scrollHeight,
-        scrollTopAtCapture:container.scrollTop,
       };
     }
   }
@@ -1050,10 +1049,10 @@ function _restoreMessageViewportAnchor(anchor, rawIdxDelta){
   const _realignDelta=(rect.top-containerRect.top)-targetTop;
   const _shAtCap=Number(anchor.scrollHeightAtCapture);
   if(Number.isFinite(_shAtCap)){
-    const _grewAbove=(container.scrollHeight-_shAtCap)>4;
+    const _grewSinceCapture=(container.scrollHeight-_shAtCap)>4;
     const _activeIntent=(typeof _recentMessageScrollIntent==='function' && _recentMessageScrollIntent())
       || (typeof _recentMessageTouchScrollIntent==='function' && _recentMessageTouchScrollIntent());
-    if(_grewAbove&&!_activeIntent&&Math.abs(_realignDelta)>8){
+    if(_grewSinceCapture&&!_activeIntent&&Math.abs(_realignDelta)>8){
       return false;
     }
   }
diff --git a/tests/test_issue5637_stale_anchor_guard.py b/tests/test_issue5637_stale_anchor_guard.py
index 403cd661..93cada57 100644
--- a/tests/test_issue5637_stale_anchor_guard.py
+++ b/tests/test_issue5637_stale_anchor_guard.py
@@ -217,3 +217,17 @@ def test_fallback_backward_compatible_without_capture_scrollheight():
         active_intent=False,
     )))
     assert m["writes"] == [89577]
+
+
+def test_fallback_allows_snapshot_top_with_active_intent():
+    """Content grew since snapshot, but the reader has recent real input intent -> the
+    fallback keeps its legitimate absolute restore (an actively-scrolling reader owns the
+    snapshot). Mirrors the realign-guard active-intent case.
+    Mutation: drop the `!_activeIntent` term from the fallback guard and this fails
+    (the write would be wrongly refused)."""
+    m = json.loads(_run_node(_fallback_harness(
+        snapshot_scroll_height=90000, cur_scroll_height=90453, snapshot_top=89577,
+        active_intent=True,
+    )))
+    assert m["writes"] == [89577]
+