diff --git a/tools/src/hwlab-cli/trace-renderer.ts b/tools/src/hwlab-cli/trace-renderer.ts
index e1e03769..2c2a1bf3 100644
--- a/tools/src/hwlab-cli/trace-renderer.ts
+++ b/tools/src/hwlab-cli/trace-renderer.ts
@@ -220,7 +220,7 @@ function traceCompletionSummaryRow(trace: Record<string, unknown>, event: TraceE
 
 function traceNoiseSummaryRow(trace: Record<string, unknown>, events: TraceEvent[], options: TraceDisplayRowsOptions): TraceEventRow {
   const lastEvent = events.at(-1);
-  const status = nonEmptyString(trace.status ?? trace.traceStatus ?? lastEvent?.status) ?? "running";
+  const status = nonEmptyString(trace.status ?? trace.traceStatus) ?? "running";
   const lastLabel = lastEvent ? readableTraceLabel(lastEvent) : "未观测";
   return {
     rowId: "trace-noise-summary",
diff --git a/web/hwlab-cloud-web/src/api/workbench.ts b/web/hwlab-cloud-web/src/api/workbench.ts
index 47d75aad..6b14409b 100644
--- a/web/hwlab-cloud-web/src/api/workbench.ts
+++ b/web/hwlab-cloud-web/src/api/workbench.ts
@@ -191,6 +191,9 @@ function normalizeTimingProjection(value: unknown): WorkbenchTurnTimingProjectio
   const lastEventAt = textValue(source.lastEventAt);
   const finishedAt = textValue(source.finishedAt);
   const durationMs = numberValue(source.durationMs);
+  // observedAt and lastEventAgeMs are server-side diagnostic snapshots.
+  // They must NOT be used as the user-visible relative time authority.
+  // Running relative time display must use startedAt/lastEventAt + browser local now().
   const observedAt = textValue(source.observedAt);
   const lastEventAgeMs = numberValue(source.lastEventAgeMs);
   if (!startedAt && !lastEventAt && !finishedAt && durationMs == null && lastEventAgeMs == null) return undefined;
diff --git a/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts b/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts
index 4123e272..95a4209f 100644
--- a/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts
+++ b/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts
@@ -89,7 +89,7 @@ export function snapshotToRunnerTrace(snapshot: TraceSnapshot): NonNullable<Chat
     eventSource: snapshot.eventSource ?? "trace-api",
     runnerKind: snapshot.agentRun?.adapter,
     sessionMode: snapshot.agentRun?.backendProfile,
-    lastEventLabel: snapshot.lastEventLabel ?? events.at(-1)?.label ?? events.at(-1)?.type,
+    lastEventLabel: snapshot.lastEventLabel ?? undefined,
     waitingFor: snapshot.waitingFor,
     timing: snapshot.timing ?? null,
     startedAt: snapshot.startedAt ?? snapshot.timing?.startedAt ?? null,
diff --git a/web/hwlab-cloud-web/src/stores/workbench.ts b/web/hwlab-cloud-web/src/stores/workbench.ts
index 00ac5769..00aa7099 100644
--- a/web/hwlab-cloud-web/src/stores/workbench.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench.ts
@@ -673,7 +673,7 @@ export const useWorkbenchStore = defineStore("workbench", () => {
     const ownerSessionId = traceOwnerSessionId(traceId, authoritySessionId);
     if (!ownerSessionId) return;
     const events = Array.isArray(result.events) ? result.events : Array.isArray(result.traceEvents) ? result.traceEvents : [];
-    const activityLabel = firstNonEmptyString(result.lastEventLabel, events.at(-1)?.label, events.at(-1)?.type, result.status);
+    const activityLabel = firstNonEmptyString(result.lastEventLabel, result.status);
     if (ownerSessionId === activeSessionId.value && (events.length > 0 || result.terminal === true || isTerminalMessageStatus(result.status))) recordActivity(`trace:${activityLabel ?? "hydrated"}`);
     markWorkbenchTraceEventsReceived({ traceId, events, transport: "rest_gap" });
     updateSessionMessages(ownerSessionId, (source) => source.map((message) => {
@@ -706,7 +706,7 @@ export const useWorkbenchStore = defineStore("workbench", () => {
         staleMs: result.staleMs ?? result.projection?.staleMs,
         blocker: result.blocker ?? result.projection?.blocker,
         ...messageTimingPatch(result),
-        lastEventLabel: result.lastEventLabel ?? events.at(-1)?.label ?? events.at(-1)?.type,
+        lastEventLabel: result.lastEventLabel ?? undefined,
         updatedAt: new Date().toISOString()
       } as NonNullable<ChatMessage["runnerTrace"]>;
       const runnerTrace = mergeRunnerTrace(message.runnerTrace, nextTrace);
@@ -1340,7 +1340,7 @@ function realtimeSnapshotToTraceSnapshot(traceId: string, snapshot: WorkbenchRea
     staleMs: firstFiniteNumber(source.staleMs, recordValue(source.projection)?.staleMs),
     blocker: recordValue(source.blocker) ?? recordValue(recordValue(source.projection)?.blocker) ?? undefined,
     ...messageTimingPatch(source),
-    lastEventLabel: firstNonEmptyString(source.lastEventLabel, source.lastEvent?.label, source.lastEvent?.type, events.at(-1)?.label, events.at(-1)?.type) ?? undefined,
+    lastEventLabel: firstNonEmptyString(source.lastEventLabel) ?? undefined,
     eventSource: "trace-api",
     updatedAt: firstNonEmptyString(source.updatedAt) ?? new Date().toISOString()
   } as TraceSnapshot;
@@ -1396,7 +1396,7 @@ function mergeTerminalResultTrace(previous: ChatMessage["runnerTrace"], result:
     durationMs: timing?.durationMs ?? null,
     runnerKind: firstNonEmptyString(agentRun?.adapter, resultTrace?.runnerKind, previous?.runnerKind) ?? undefined,
     sessionMode: firstNonEmptyString(agentRun?.backendProfile, resultTrace?.sessionMode, previous?.sessionMode) ?? undefined,
-    lastEventLabel: firstNonEmptyString(result.lastEventLabel, resultTrace?.lastEventLabel, previous?.lastEventLabel, events.at(-1)?.label, events.at(-1)?.type) ?? undefined,
+    lastEventLabel: firstNonEmptyString(result.lastEventLabel, resultTrace?.lastEventLabel, previous?.lastEventLabel) ?? undefined,
     updatedAt: new Date().toISOString()
   } as NonNullable<ChatMessage["runnerTrace"]>;
   if (traceDetailStatus) nextTrace.status = traceDetailStatus;