From 87ab74d1b94c6bc6318df07fc8ec9d276859986a Mon Sep 17 00:00:00 2001
From: Frank Song <franksong2702@gmail.com>
Date: Tue, 23 Jun 2026 00:11:51 +0800
Subject: [PATCH] fix(ui): preserve thinking detail scroll on rebuild

---
 static/ui.js                       | 20 ++++++++++++++++++--
 tests/test_ui_tool_call_cleanup.py | 24 ++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/static/ui.js b/static/ui.js
index 4ee97f61..9ea475ae 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -8224,6 +8224,10 @@ function _worklogDetailBaseKey(el){
 function _worklogDetailDisclosureIsOpen(el){
   return !!(el&&el.classList&&el.classList.contains('open'));
 }
+function _worklogDetailScrollableBody(el){
+  if(!el||!el.querySelector) return null;
+  return el.querySelector('.thinking-card-body,.tool-card-detail');
+}
 function _setWorklogDetailDisclosureOpen(el, open){
   if(!el||!el.classList) return;
   el.classList.toggle('open', !!open);
@@ -8252,7 +8256,12 @@ function _captureWorklogDetailDisclosureState(root){
   const counts=Object.create(null);
   root.querySelectorAll(_worklogDetailDisclosureSelector).forEach(el=>{
     const key=_worklogDetailDisclosureKeyForElement(el, counts);
-    if(key) state.set(key, _worklogDetailDisclosureIsOpen(el));
+    if(!key) return;
+    const body=_worklogDetailScrollableBody(el);
+    state.set(key,{
+      open:_worklogDetailDisclosureIsOpen(el),
+      scrollTop:body?Math.max(0,Number(body.scrollTop)||0):0,
+    });
   });
   return state;
 }
@@ -8264,7 +8273,14 @@ function _restoreWorklogDetailDisclosureState(root, state){
   root.querySelectorAll(_worklogDetailDisclosureSelector).forEach(el=>{
     const key=_worklogDetailDisclosureKeyForElement(el, counts);
     if(!key||!state.has(key)) return;
-    _setWorklogDetailDisclosureOpen(el, state.get(key));
+    const saved=state.get(key);
+    const open=(saved&&typeof saved==='object'&&'open' in saved)?saved.open:saved;
+    _setWorklogDetailDisclosureOpen(el, open);
+    const scrollTop=(saved&&typeof saved==='object')?Number(saved.scrollTop):0;
+    if(open&&Number.isFinite(scrollTop)&&scrollTop>0){
+      const body=_worklogDetailScrollableBody(el);
+      if(body) body.scrollTop=Math.min(scrollTop, Math.max(0, body.scrollHeight-body.clientHeight));
+    }
   });
 }
 function _thinkingCardHtml(text, open){
diff --git a/tests/test_ui_tool_call_cleanup.py b/tests/test_ui_tool_call_cleanup.py
index d3b4ceae..4e6dea61 100644
--- a/tests/test_ui_tool_call_cleanup.py
+++ b/tests/test_ui_tool_call_cleanup.py
@@ -279,6 +279,30 @@ class TestToolCallGroupingStatic:
             "Restoring multi-tool groups must sync both CSS state and accessibility state."
         )
 
+    def test_render_rebuild_preserves_nested_worklog_detail_scroll_position(self):
+        capture_fn = _function_body(UI_JS, "_captureWorklogDetailDisclosureState")
+        restore_fn = _function_body(UI_JS, "_restoreWorklogDetailDisclosureState")
+        body_fn = _function_body(UI_JS, "_worklogDetailScrollableBody")
+
+        assert ".thinking-card-body,.tool-card-detail" in body_fn, (
+            "Nested scroll preservation must cover Thinking bodies and Tool details."
+        )
+        assert "_worklogDetailScrollableBody(el)" in capture_fn, (
+            "The rebuild-state capture must inspect each detail's nested scroll container."
+        )
+        assert "scrollTop:body?Math.max(0,Number(body.scrollTop)||0):0" in capture_fn, (
+            "The captured Worklog detail state must retain the nested scrollTop value."
+        )
+        assert "const saved=state.get(key)" in restore_fn, (
+            "Restoration should read the structured state object for each detail."
+        )
+        assert "const open=(saved&&typeof saved==='object'&&'open' in saved)?saved.open:saved" in restore_fn, (
+            "Restoration must remain backward-compatible with legacy boolean snapshots."
+        )
+        assert "body.scrollTop=Math.min(scrollTop, Math.max(0, body.scrollHeight-body.clientHeight))" in restore_fn, (
+            "Restoration must reapply nested scrollTop after the rebuilt detail is opened."
+        )
+
     def test_worklog_detail_keys_stay_stable_while_streaming_content_grows(self):
         key_fn = _function_body(UI_JS, "_worklogDetailBaseKey")
         append_thinking_fn = _function_body(UI_JS, "appendThinking")