diff --git a/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue b/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue
index c94de355..219fd3a1 100644
--- a/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue
+++ b/web/hwlab-cloud-web/src/components/workbench/ConversationPanel.vue
@@ -27,6 +27,7 @@ const panelRef = ref<HTMLElement | null>(null);
 const { following, keepBottomAfterUpdate, onScroll: onPanelScroll, scrollToBottom } = useBottomFollowScroll(panelRef, { threshold: 56 });
 const detailMessageId = ref<string | null>(null);
 const displayedDurationFloorMs = new Map<string, number>();
+const sealedDurationMs = new Map<string, number>();
 const visibleMessages = computed(() => workbench.sessionDetailLoading ? [] : workbench.activeMessages);
 const hasRunningAgentMessages = computed(() => visibleMessages.value.some(isRunningMessage));
 const { nowMs } = useWorkbenchNowTicker(hasRunningAgentMessages);
@@ -62,6 +63,9 @@ watch(visibleMessages, (messages) => {
   for (const key of Array.from(displayedDurationFloorMs.keys())) {
     if (!visibleKeys.has(key)) displayedDurationFloorMs.delete(key);
   }
+  for (const key of Array.from(sealedDurationMs.keys())) {
+    if (!visibleKeys.has(key)) sealedDurationMs.delete(key);
+  }
 }, { immediate: true });
 
 function openDetails(message: ChatMessage): void {
@@ -256,13 +260,14 @@ function messageDurationMeta(message: ChatMessage): { text: string; label: strin
   if (message.role !== "agent") return null;
   const timing = messageTimingForDisplay(message);
   const rawDurationMs = isRunningMessage(message) ? durationSince(timing?.startedAt) : terminalMessageDurationMs(message, timing);
-  if (rawDurationMs === null) return null;
   const durationMs = isRunningMessage(message) ? monotonicDisplayDurationMs(message, rawDurationMs) : sealedDisplayDurationMs(message, rawDurationMs);
+  if (durationMs === null) return null;
   const value = formatDuration(durationMs);
   return { text: `耗时 ${value}`, label: `总耗时：${value}` };
 }
 
-function monotonicDisplayDurationMs(message: ChatMessage, durationMs: number): number {
+function monotonicDisplayDurationMs(message: ChatMessage, durationMs: number | null): number | null {
+  if (durationMs === null) return null;
   const key = messageDurationFloorKey(message);
   const previous = displayedDurationFloorMs.get(key);
   const next = previous === undefined ? durationMs : Math.max(previous, durationMs);
@@ -270,8 +275,13 @@ function monotonicDisplayDurationMs(message: ChatMessage, durationMs: number): n
   return next;
 }
 
-function sealedDisplayDurationMs(message: ChatMessage, durationMs: number): number {
-  displayedDurationFloorMs.delete(messageDurationFloorKey(message));
+function sealedDisplayDurationMs(message: ChatMessage, durationMs: number | null): number | null {
+  const key = messageDurationFloorKey(message);
+  displayedDurationFloorMs.delete(key);
+  const previous = sealedDurationMs.get(key);
+  if (previous !== undefined) return previous;
+  if (durationMs === null) return null;
+  sealedDurationMs.set(key, durationMs);
   return durationMs;
 }
 
@@ -302,10 +312,11 @@ function terminalMessageDurationMs(message: ChatMessage, timing: ChatMessage["ti
 }
 
 function elapsedTerminalDurationMs(message: ChatMessage, timing: ChatMessage["timing"]): number | null {
+  const messageRecord = message as Record<string, unknown>;
   const trace = message.runnerTrace as Record<string, unknown> | null | undefined;
   const traceTiming = trace?.timing as Record<string, unknown> | null | undefined;
   const startedAt = timestampMs(timing?.startedAt ?? message.startedAt ?? traceTiming?.startedAt ?? trace?.startedAt);
-  const endedAt = timestampMs(timing?.finishedAt ?? message.finishedAt ?? traceTiming?.finishedAt ?? trace?.finishedAt ?? timing?.lastEventAt ?? message.lastEventAt ?? traceTiming?.lastEventAt ?? trace?.lastEventAt);
+  const endedAt = timestampMs(timing?.finishedAt ?? message.finishedAt ?? messageRecord.completedAt ?? traceTiming?.finishedAt ?? trace?.finishedAt ?? traceTiming?.completedAt ?? trace?.completedAt);
   if (startedAt === null || endedAt === null || endedAt < startedAt) return null;
   return Math.trunc(endedAt - startedAt);
 }