preserve conversation trace scroll

docs/reference/cloud-workbench.md

@@ -109,10 +109,11 @@ session identifiers, the visible detail must include a short redacted
 且非空的 assistant response 前，Workbench 不得暗示已有真实 assistant reply。
 
 Code Agent trace 在消息卡片内使用独立滚动容器展示。SSE、轮询或“回放 trace”
-更新只能刷新内容，不得重置用户已展开/折叠状态，也不得把
-`.message-trace-events` 的内部滚动位置跳回顶部；渲染前后必须按
-`messageId/traceId` 保存并恢复 trace list 的 `scrollTop/scrollLeft`。完整 trace
-可通过复制/下载获取，页面内默认保持“显示全部 + 内部滚动”的单一模式。
+更新只能刷新内容，不得重置用户已展开/折叠状态，也不得把 `#conversation-list`
+或 `.message-trace-events` 的滚动位置跳回顶部；渲染前后必须保存并恢复外层
+conversation list 和按 `messageId/traceId` 记录的 trace list
+`scrollTop/scrollLeft`。完整 trace 可通过复制/下载获取，页面内默认保持“显示全部
++ 内部滚动”的单一模式。
 
 ## Lightweight Checks
 

web/hwlab-cloud-web/app.mjs

@@ -180,6 +180,7 @@ const state = {
   chatMessages: [],
   traceStreams: new Map(),
   traceDetailsOpen: new Map(),
+  conversationScrollPosition: { top: 0, left: 0 },
   traceScrollPositions: new Map(),
   canceledTraces: new Set(),
   currentRequest: null,
@@ -792,6 +793,7 @@ function initCommandBar() {
     for (const close of state.traceStreams.values()) close();
     state.traceStreams.clear();
     state.traceDetailsOpen.clear();
+    state.conversationScrollPosition = { top: 0, left: 0 };
     state.traceScrollPositions.clear();
     state.chatMessages = [];
     state.conversationId = null;
@@ -2006,6 +2008,7 @@ function workbenchApiSurfaceStatus(live, coreProbes = [live.healthLive, live.res
 }
 
 function renderConversation() {
+  captureConversationScrollPosition();
   captureTraceScrollPositions();
   const introMessages = [
     {
@@ -2017,9 +2020,24 @@ function renderConversation() {
     codeAgentStatusMessage(state.codeAgentAvailability)
   ];
   replaceChildren(el.conversationList, ...[...introMessages, ...state.chatMessages].map(messageCard));
+  restoreConversationScrollPosition();
   restoreTraceScrollPositions();
 }
 
+function captureConversationScrollPosition() {
+  state.conversationScrollPosition = {
+    top: el.conversationList.scrollTop,
+    left: el.conversationList.scrollLeft
+  };
+}
+
+function restoreConversationScrollPosition() {
+  const position = state.conversationScrollPosition;
+  if (!position) return;
+  el.conversationList.scrollTop = Math.min(position.top, Math.max(0, el.conversationList.scrollHeight - el.conversationList.clientHeight));
+  el.conversationList.scrollLeft = Math.min(position.left, Math.max(0, el.conversationList.scrollWidth - el.conversationList.clientWidth));
+}
+
 function captureTraceScrollPositions(root = el.conversationList) {
   for (const list of root.querySelectorAll(".message-trace-events[data-trace-ui-key]")) {
     rememberTraceScrollPosition(list.dataset.traceUiKey, list);

web/hwlab-cloud-web/scripts/check.mjs

@@ -809,14 +809,20 @@ assert.match(app, /function messageTraceToolbar/);
 assert.match(app, /function messageTraceCountText/);
 assert.match(app, /显示全部\s+\$\{displayTotal\}\s+\/\s+原始\s+\$\{rawTotal\}/);
 assert.match(app, /traceDetailsOpen:\s*new Map\(\)/);
+assert.match(app, /conversationScrollPosition:\s*\{\s*top:\s*0,\s*left:\s*0\s*\}/);
 assert.match(app, /traceScrollPositions:\s*new Map\(\)/);
 assert.match(app, /state\.traceDetailsOpen\.clear\(\)/);
+assert.match(app, /state\.conversationScrollPosition\s*=\s*\{\s*top:\s*0,\s*left:\s*0\s*\}/);
 assert.match(app, /state\.traceScrollPositions\.clear\(\)/);
 assert.match(app, /function messageTraceUiKey/);
 assert.match(app, /function defaultTraceDetailsOpen/);
+assert.match(app, /function captureConversationScrollPosition/);
+assert.match(app, /function restoreConversationScrollPosition/);
 assert.match(app, /function captureTraceScrollPositions/);
 assert.match(app, /function restoreTraceScrollPositions/);
 assert.match(app, /function rememberTraceScrollPosition/);
+assert.match(functionBody(app, "renderConversation"), /captureConversationScrollPosition\(\)/);
+assert.match(functionBody(app, "renderConversation"), /restoreConversationScrollPosition\(\)/);
 assert.match(functionBody(app, "renderConversation"), /captureTraceScrollPositions\(\)/);
 assert.match(functionBody(app, "renderConversation"), /restoreTraceScrollPositions\(\)/);
 assert.match(functionBody(app, "messageTracePanel"), /state\.traceDetailsOpen\.get\(traceUiKey\)/);