diff --git a/web/hwlab-cloud-web/src/stores/workbench-live-kafka-event.ts b/web/hwlab-cloud-web/src/stores/workbench-live-kafka-event.ts
index ad101f47..5d8e1e04 100644
--- a/web/hwlab-cloud-web/src/stores/workbench-live-kafka-event.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench-live-kafka-event.ts
@@ -43,8 +43,7 @@ export function reduceWorkbenchLiveKafkaMessageState(previous: WorkbenchLiveMess
   if (previous.terminal) return previous;
   const terminal = workbenchLiveKafkaEventIsTerminal(event);
   const status = terminal ? firstNonEmptyString(event.status, "completed") ?? "completed" : "running";
-  const lifecycleEvents = [...previousEvents, event];
-  const assistantText = traceAssistantLifecycleEventIsSuperseded(event, lifecycleEvents, lifecycleEvents.length - 1)
+  const assistantText = traceAssistantLifecycleEventIsSuperseded(event, previousEvents, previousEvents.length)
     ? null
     : workbenchLiveKafkaAssistantText(event);
   return {
diff --git a/web/hwlab-cloud-web/src/stores/workbench-server-state.ts b/web/hwlab-cloud-web/src/stores/workbench-server-state.ts
index 9360cde2..45b9252e 100644
--- a/web/hwlab-cloud-web/src/stores/workbench-server-state.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench-server-state.ts
@@ -134,24 +134,23 @@ function reduceSessionDetail(state: WorkbenchServerState, session: WorkbenchSess
 
 function reduceSessionList(state: WorkbenchServerState, sessions: WorkbenchSessionRecord[]): WorkbenchServerState {
   const sessionIds = sessions.map((session) => session.sessionId).filter((sessionId): sessionId is string => Boolean(sessionId));
-  const next = sessions.reduce((current, session) => reduceSessionListItem(current, session), state);
-  return { ...next, sessionOrder: unique(sessionIds) };
-}
-
-function reduceSessionListItem(state: WorkbenchServerState, session: WorkbenchSessionRecord): WorkbenchServerState {
-  const sessionId = session.sessionId;
-  if (!sessionId) return state;
-  const existing = state.sessionsById[sessionId];
-  const existingMessages = state.messagesBySessionId[sessionId] ?? existing?.messages;
-  const messages = Array.isArray(existingMessages) ? existingMessages : Array.isArray(session.messages) ? session.messages : [];
-  const merged = mergeSessionRecord(existing, { ...session, messages });
-  const sessionStatus = sessionStatusAuthorityFromDetail(session);
+  const sessionsById = { ...state.sessionsById };
+  const sessionStatusById = { ...state.sessionStatusById };
+  for (const session of sessions) {
+    const sessionId = session.sessionId;
+    if (!sessionId) continue;
+    const existing = sessionsById[sessionId];
+    const existingMessages = state.messagesBySessionId[sessionId] ?? existing?.messages;
+    const messages = Array.isArray(existingMessages) ? existingMessages : Array.isArray(session.messages) ? session.messages : [];
+    sessionsById[sessionId] = mergeSessionRecord(existing, { ...session, messages });
+    const sessionStatus = sessionStatusAuthorityFromDetail(session);
+    if (sessionStatus) sessionStatusById[sessionId] = mergeSessionStatusAuthority(sessionStatusById[sessionId], sessionStatus);
+  }
   return {
     ...state,
-    sessionsById: { ...state.sessionsById, [sessionId]: merged },
-    sessionStatusById: sessionStatus
-      ? { ...state.sessionStatusById, [sessionId]: mergeSessionStatusAuthority(state.sessionStatusById[sessionId], sessionStatus) }
-      : state.sessionStatusById
+    sessionOrder: unique(sessionIds),
+    sessionsById,
+    sessionStatusById
   };
 }
 
diff --git a/web/hwlab-cloud-web/src/stores/workbench-session.ts b/web/hwlab-cloud-web/src/stores/workbench-session.ts
index 08d5eaae..40f0d381 100644
--- a/web/hwlab-cloud-web/src/stores/workbench-session.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench-session.ts
@@ -146,13 +146,14 @@ export function shouldShowSessionDetailLoading(input: {
 
 export function sessionToSessionTab(session: WorkbenchSessionRecord, activeSessionId: string | null, sessionStatusAuthority: SessionStatusAuthorityMap = {}): SessionTab {
   const sessionId = session.sessionId;
-  const updatedAt = sessionDisplayUpdatedAt(session);
-  const latestAgent = latestAgentMessage(session.messages);
+  const messageProjection = projectSessionTabMessages(session.messages);
+  const updatedAt = sessionDisplayUpdatedAtWithUserMessage(session, messageProjection.latestUserMessageAt);
+  const latestAgent = messageProjection.latestAgent;
   const status = resolveSessionTabStatus(session, sessionStatusAuthority[sessionId], latestAgent);
   const projection = projectionFromSession(session, sessionStatusAuthority[sessionId]);
   const projectionText = projectionDiagnosticText(projection);
-  const trace = firstNonEmptyString(latestAgent?.traceId, latestAgent?.runnerTrace?.traceId, session.messages?.at(-1)?.traceId, session.lastTraceId);
-  const userMessage = session.messages?.find((message) => message.role === "user");
+  const trace = firstNonEmptyString(latestAgent?.traceId, latestAgent?.runnerTrace?.traceId, messageProjection.lastMessageTraceId, session.lastTraceId);
+  const userMessage = messageProjection.firstUser;
   const running = isRunningIndicatorStatus(status);
   const preview = firstReadableSentence(
     session.firstUserMessagePreview,
@@ -316,7 +317,11 @@ function mergeSelectedSessionDetail(stable: WorkbenchSessionRecord[], selected:
 }
 
 function latestAgentMessage(messages: ChatMessage[] | undefined): ChatMessage | null {
-  return [...(messages ?? [])].reverse().find((message) => message.role === "agent") ?? null;
+  for (let index = (messages?.length ?? 0) - 1; index >= 0; index -= 1) {
+    const message = messages?.[index];
+    if (message?.role === "agent") return message;
+  }
+  return null;
 }
 
 function latestMessageForTrace(messages: ChatMessage[], traceId: string): ChatMessage | null {
@@ -443,8 +448,12 @@ function firstReadableSentence(...values: unknown[]): string | null {
 }
 
 export function sessionDisplayUpdatedAt(session: WorkbenchSessionRecord): string | null {
+  return sessionDisplayUpdatedAtWithUserMessage(session, latestUserMessageAtFromMessages(session.messages));
+}
+
+function sessionDisplayUpdatedAtWithUserMessage(session: WorkbenchSessionRecord, latestUserMessageAt: string | null): string | null {
   return firstNonEmptyString(
-    latestUserMessageAtFromMessages(session.messages ?? []),
+    latestUserMessageAt,
     session.lastUserMessageAt,
     session.snapshot?.lastUserMessageAt,
     session.startedAt,
@@ -454,22 +463,40 @@ export function sessionDisplayUpdatedAt(session: WorkbenchSessionRecord): string
 }
 
 export function latestUserMessageAtFromMessages(messages: ChatMessage[] | undefined): string | null {
-  const userMessageTimes = (messages ?? [])
-    .filter((message) => message.role === "user")
-    .map((message) => firstNonEmptyString(message.createdAt, message.updatedAt));
-  return latestTimestamp(...userMessageTimes);
+  let latest: { value: string; ms: number } | null = null;
+  let fallback: string | null = null;
+  for (const message of messages ?? []) {
+    if (message.role !== "user") continue;
+    const value = firstNonEmptyString(message.createdAt, message.updatedAt);
+    fallback ??= value;
+    if (!value) continue;
+    const ms = timestampMs(value);
+    if (ms && (!latest || ms > latest.ms)) latest = { value, ms };
+  }
+  return latest?.value ?? fallback;
 }
 
-function latestTimestamp(...values: unknown[]): string | null {
-  let latest: { value: string; ms: number } | null = null;
-  for (const value of values) {
-    const text = firstNonEmptyString(value);
-    if (!text) continue;
-    const ms = timestampMs(text);
-    if (!ms) continue;
-    if (!latest || ms > latest.ms) latest = { value: text, ms };
+function projectSessionTabMessages(messages: ChatMessage[] | undefined): { latestAgent: ChatMessage | null; firstUser: ChatMessage | null; latestUserMessageAt: string | null; lastMessageTraceId: string | null } {
+  let latestAgent: ChatMessage | null = null;
+  let firstUser: ChatMessage | null = null;
+  let latestUserMessageAt: { value: string; ms: number } | null = null;
+  let firstUserMessageAt: string | null = null;
+  for (const message of messages ?? []) {
+    if (message.role === "agent") latestAgent = message;
+    if (message.role !== "user") continue;
+    firstUser ??= message;
+    const value = firstNonEmptyString(message.createdAt, message.updatedAt);
+    firstUserMessageAt ??= value;
+    if (!value) continue;
+    const ms = timestampMs(value);
+    if (ms && (!latestUserMessageAt || ms > latestUserMessageAt.ms)) latestUserMessageAt = { value, ms };
   }
-  return latest?.value ?? firstNonEmptyString(...values) ?? null;
+  return {
+    latestAgent,
+    firstUser,
+    latestUserMessageAt: latestUserMessageAt?.value ?? firstUserMessageAt,
+    lastMessageTraceId: firstNonEmptyString(messages?.at(-1)?.traceId)
+  };
 }
 
 function readableSentence(value: unknown): string | null {