diff --git a/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue b/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue
index 4ab551e7..fa5ff760 100644
--- a/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue
+++ b/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue
@@ -9,14 +9,22 @@ import { traceDisplayRows, type TraceEventRow } from "../../../../../tools/src/h
 
 const props = defineProps<{ trace?: RunnerTrace | null; defaultExpanded?: boolean; storageKey?: string; autoExpanded?: boolean | null }>();
 
+const TRACE_RENDER_ROW_WINDOW = 120;
 const listRef = ref<HTMLOListElement | null>(null);
 const expanded = ref(false);
 const { following, keepBottomAfterUpdate, onScroll, scrollToBottom } = useBottomFollowScroll(listRef, { threshold: 24 });
 
 const events = computed(() => Array.isArray(props.trace?.events) ? props.trace.events : []);
 const eventCount = computed(() => props.trace?.eventCount ?? events.value.length);
-const rawReadableRows = computed(() => traceDisplayRows(traceRecord(props.trace), events.value as Record<string, unknown>[], { formatClock: formatDisplayClock }));
+const rawReadableRows = computed(() => expanded.value ? traceDisplayRows(traceRecord(props.trace), events.value as Record<string, unknown>[], { formatClock: formatDisplayClock }) : []);
 const readableRows = computed(() => rawReadableRows.value);
+const hiddenRowCount = computed(() => Math.max(0, readableRows.value.length - TRACE_RENDER_ROW_WINDOW));
+const renderedRows = computed(() => hiddenRowCount.value > 0 ? readableRows.value.slice(-TRACE_RENDER_ROW_WINDOW) : readableRows.value);
+const traceSummaryLabel = computed(() => {
+  const count = eventCount.value;
+  if (count <= 0) return String(props.trace?.status ?? "").trim() || "pending";
+  return `${count} events`;
+});
 const projectionDiagnosticLabel = computed(() => {
   const projection = props.trace?.projection ?? null;
   const health = projection?.projectionHealth ?? props.trace?.projectionHealth;
@@ -128,14 +136,16 @@ function firstNonEmptyString(...values: unknown[]): string | null {
 
 <template>
   <section v-if="trace" class="trace-timeline" :data-trace-id="trace.traceId || undefined" :data-status="trace.status" :data-projection-health="trace.projection?.projectionHealth || trace.projectionHealth || undefined" :data-following="following ? 'true' : 'false'">
-    <details class="trace-disclosure" :open="expanded" @toggle="onDisclosureToggle">
+    <details class="trace-disclosure" :open="expanded" :data-event-count="eventCount" :data-readable-row-count="readableRows.length" :data-rendered-row-count="renderedRows.length" :data-row-windowed="hiddenRowCount > 0 ? 'true' : 'false'" @toggle="onDisclosureToggle">
       <summary class="trace-disclosure-summary" aria-label="折叠运行记录">
         <span class="trace-disclosure-caret" aria-hidden="true" />
         <span class="trace-disclosure-label">运行记录</span>
+        <span class="trace-disclosure-count">{{ traceSummaryLabel }}</span>
       </summary>
-      <div class="trace-disclosure-body">
-        <ol ref="listRef" @scroll="onScroll">
-          <li v-for="(row, index) in readableRows" :key="rowKey(row, index)" class="trace-render-row" data-testid="trace-render-row" :data-trace-id="trace.traceId || undefined" :data-projected-seq="row.seq ?? undefined" :data-event-kind="row.rowId" :data-event-status="row.tone" :data-terminal="row.terminal ? 'true' : 'false'" :data-row-kind="rowIsTool(row) ? 'tool' : 'message'" :data-row-id="row.rowId" :aria-posinset="row.seq ?? index + 1">
+      <div v-if="expanded" class="trace-disclosure-body">
+        <p v-if="hiddenRowCount > 0" class="trace-window-notice">显示最近 {{ renderedRows.length }} / {{ readableRows.length }} 行</p>
+        <ol v-if="renderedRows.length > 0" ref="listRef" @scroll="onScroll">
+          <li v-for="(row, index) in renderedRows" :key="rowKey(row, index)" class="trace-render-row" data-testid="trace-render-row" :data-trace-id="trace.traceId || undefined" :data-projected-seq="row.seq ?? undefined" :data-event-kind="row.rowId" :data-event-status="row.tone" :data-terminal="row.terminal ? 'true' : 'false'" :data-row-kind="rowIsTool(row) ? 'tool' : 'message'" :data-row-id="row.rowId" :aria-posinset="row.seq ?? hiddenRowCount + index + 1">
             <details v-if="rowIsTool(row)" class="trace-tool-details">
               <summary>
                 <code>{{ row.header }}</code>
diff --git a/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue b/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue
index f78934d4..652b1b62 100644
--- a/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue
+++ b/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue
@@ -34,10 +34,8 @@ const traceTimelinePolicy = computed(() => workbenchTraceTimelinePolicy());
 const scrollSignature = computed(() => workbench.activeMessages.map((message) => [
   message.id,
   message.status,
-  visibleMessageText(message).length,
-  message.updatedAt ?? "",
-  message.runnerTrace?.eventCount ?? message.runnerTrace?.events?.length ?? 0
-].join(":")));
+  visibleMessageText(message).length
+].join(":")).join("|"));
 
 watch(scrollSignature, async () => {
   await keepBottomAfterUpdate();
diff --git a/web/hwlab-cloud-web/src/components/workbench/message-rendering.ts b/web/hwlab-cloud-web/src/components/workbench/message-rendering.ts
index 186caefa..2409537e 100644
--- a/web/hwlab-cloud-web/src/components/workbench/message-rendering.ts
+++ b/web/hwlab-cloud-web/src/components/workbench/message-rendering.ts
@@ -5,14 +5,34 @@ import { firstNonEmptyString } from "@/utils";
 
 marked.setOptions({ async: false, breaks: true, gfm: true });
 
+const MARKDOWN_RENDER_CACHE_LIMIT = 160;
+const markdownRenderCache = new Map<string, string>();
+
 export function renderSafeMarkdown(source: string | null | undefined): string {
   const text = source?.trim();
   if (!text) return "";
+  const cached = markdownRenderCache.get(text);
+  if (cached !== undefined) {
+    markdownRenderCache.delete(text);
+    markdownRenderCache.set(text, cached);
+    return cached;
+  }
   const rendered = marked.parse(text) as string;
-  return sanitizeHtml(rendered, {
+  const html = sanitizeHtml(rendered, {
     ADD_ATTR: ["target", "rel"],
     USE_PROFILES: { html: true }
   });
+  rememberMarkdownRender(text, html);
+  return html;
+}
+
+function rememberMarkdownRender(source: string, html: string): void {
+  markdownRenderCache.set(source, html);
+  while (markdownRenderCache.size > MARKDOWN_RENDER_CACHE_LIMIT) {
+    const oldest = markdownRenderCache.keys().next().value;
+    if (typeof oldest !== "string") break;
+    markdownRenderCache.delete(oldest);
+  }
 }
 
 interface HtmlSanitizeConfig {
diff --git a/web/hwlab-cloud-web/src/stores/workbench.ts b/web/hwlab-cloud-web/src/stores/workbench.ts
index 6c5f5ff4..66d704a0 100644
--- a/web/hwlab-cloud-web/src/stores/workbench.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench.ts
@@ -15,13 +15,13 @@ import { createWorkbenchServerState, reduceWorkbenchServerState, selectActiveMes
 
 const DEFAULT_CODE_AGENT_TIMEOUT_MS = 1_800_000;
 const DEFAULT_GATEWAY_TIMEOUT_MS = 120_000;
-const TRACE_HYDRATION_PAGE_LIMIT = 100;
-const TRACE_HYDRATION_MAX_PAGES = 60;
+const TRACE_HYDRATION_PAGE_LIMIT = 50;
+const TRACE_HYDRATION_MAX_PAGES = 4;
 const TRACE_HYDRATION_MAX_ATTEMPTS = 3;
 const TRACE_HYDRATION_RETRY_DELAY_MS = 700;
-const TRACE_HYDRATION_AUTO_QUEUE_LIMIT = 12;
-const TRACE_HYDRATION_BACKGROUND_CONCURRENCY = 2;
-const TRACE_HYDRATION_BACKGROUND_DELAY_MS = 150;
+const TRACE_HYDRATION_AUTO_QUEUE_LIMIT = 4;
+const TRACE_HYDRATION_BACKGROUND_CONCURRENCY = 1;
+const TRACE_HYDRATION_BACKGROUND_DELAY_MS = 400;
 const SESSION_LIST_PAGE_LIMIT = 20;
 const WORKBENCH_READ_HYDRATION_CONCURRENCY = 3;
 const WORKBENCH_READ_FAILURE_COOLDOWN_MS = 5_000;
diff --git a/web/hwlab-cloud-web/src/styles/workbench.css b/web/hwlab-cloud-web/src/styles/workbench.css
index 8bd6a70e..5b16f7ef 100644
--- a/web/hwlab-cloud-web/src/styles/workbench.css
+++ b/web/hwlab-cloud-web/src/styles/workbench.css
@@ -1391,6 +1391,13 @@
   line-height: 1;
 }
 
+.trace-disclosure-count {
+  color: #64748b;
+  font-size: 10px;
+  font-weight: 700;
+  line-height: 1;
+}
+
 .trace-disclosure-body {
   display: grid;
   gap: 5px;
@@ -1535,6 +1542,18 @@
   color: #92400e;
 }
 
+.trace-window-notice {
+  margin: 0;
+  border: 1px solid #d8e1eb;
+  border-radius: 3px;
+  background: white;
+  color: #64748b;
+  font-size: 11px;
+  font-weight: 700;
+  line-height: 1.4;
+  padding: 5px 7px;
+}
+
 .trace-empty {
   border: 1px solid #d8e1eb;
   background: white;