From 75d0c4824a6081b1754bc37c6a3aac9b9455cc46 Mon Sep 17 00:00:00 2001
From: YeungKC <11473691+YeungKC@users.noreply.github.com>
Date: Thu, 9 Jul 2026 10:36:39 +0900
Subject: [PATCH] Fix chat scroll reset animation race

---
 lib/ui/home/chat/chat_scroll_coordinator.dart | 14 +++++
 .../chat/chat_scroll_coordinator_test.dart    | 51 +++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/lib/ui/home/chat/chat_scroll_coordinator.dart b/lib/ui/home/chat/chat_scroll_coordinator.dart
index 7025044108..f9fc2c784f 100644
--- a/lib/ui/home/chat/chat_scroll_coordinator.dart
+++ b/lib/ui/home/chat/chat_scroll_coordinator.dart
@@ -189,6 +189,7 @@ class ChatScrollCoordinator {
             _animateNextRestore ||
             animateLatestReset);
     if (reset) {
+      _cancelProgrammaticScrollBeforeReset();
       _animatedRestoreMessageId = null;
       _animatedRestoreDirection = null;
       _animatedRestoreComplete = null;
@@ -225,6 +226,19 @@ class ChatScrollCoordinator {
     });
   }
 
+  void _cancelProgrammaticScrollBeforeReset() {
+    _followTailAfterProgrammaticScroll = false;
+    _tailFollowAnchorSnapshot = null;
+    if (!scrollController.hasClients) return;
+    if (_programmaticScrollDepth <= 0 && _programmaticBottomScrollDepth <= 0) {
+      return;
+    }
+    final position = scrollController.position;
+    if (!position.isScrollingNotifier.value) return;
+    traceChatJump('cancel programmatic scroll before reset');
+    scrollController.jumpTo(position.pixels);
+  }
+
   void _resetCenteredOffsetBeforePaint() {
     if (!scrollController.hasClients) return;
     if (scrollController.offset.abs() <= _jumpToTolerance) return;
diff --git a/test/ui/home/chat/chat_scroll_coordinator_test.dart b/test/ui/home/chat/chat_scroll_coordinator_test.dart
index 3cb88eccb2..14451d784f 100644
--- a/test/ui/home/chat/chat_scroll_coordinator_test.dart
+++ b/test/ui/home/chat/chat_scroll_coordinator_test.dart
@@ -602,6 +602,57 @@ void main() {
     );
   });
 
+  testWidgets('reset restore cancels pending latest animation', (tester) async {
+    final coordinator = ChatScrollCoordinator();
+    final messages = List.generate(30, testMessage);
+    final top = List.generate(8, testMessage);
+    final bottom = List.generate(8, (index) => testMessage(index + 100));
+    final nextMessages = [...top, ...bottom];
+    final keysByMessageId = {
+      for (final message in [...messages, ...nextMessages])
+        message.messageId: GlobalKey(),
+    };
+    final centerKey = GlobalKey();
+
+    addTearDown(coordinator.dispose);
+    await pumpFullyBuiltScrollableMessages(
+      tester,
+      coordinator,
+      messages,
+      keysByMessageId,
+    );
+    coordinator.scrollController.jumpTo(
+      coordinator.scrollController.position.maxScrollExtent - 120,
+    );
+
+    unawaited(coordinator.scrollToBottomIfInLoadedWindow(animated: true));
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(
+      coordinator.scrollController.position.isScrollingNotifier.value,
+      true,
+    );
+
+    await pumpCenteredScrollableMessages(
+      tester,
+      coordinator,
+      centerKey: centerKey,
+      top: top,
+      bottom: bottom,
+      keysByMessageId: keysByMessageId,
+    );
+    coordinator.scheduleRestore(
+      messages: nextMessages,
+      keysByMessageId: keysByMessageId,
+      reset: true,
+      isLatest: false,
+      hasCenteredAnchor: true,
+      traceTargetMessageId: bottom.first.messageId,
+    );
+    await tester.pumpAndSettle();
+
+    expect(coordinator.scrollController.offset, 0);
+  });
+
   testWidgets(
     'scheduleRestore animates tail-follow without jump notifications',
     (tester) async {