diff --git a/tools/src/hwlab-cli/trace-renderer.ts b/tools/src/hwlab-cli/trace-renderer.ts
index ce92154e..2504944b 100644
--- a/tools/src/hwlab-cli/trace-renderer.ts
+++ b/tools/src/hwlab-cli/trace-renderer.ts
@@ -121,12 +121,12 @@ function traceEventsForDisplay(events: TraceEvent[] = []): TraceEvent[] {
 }
 
 function traceEventDisplaySeq(event: TraceEvent | null | undefined): number | null {
-  return numberOrNull(event?.projectedSeq) ?? numberOrNull(event?.seq);
+  return numberOrNull(event?.projectedSeq);
 }
 
 function traceEventIdentityToken(event: TraceEvent): string | number | null {
   const seq = traceEventDisplaySeq(event);
-  return seq ?? nonEmptyString(event.projectedSeq ?? event.seq);
+  return seq ?? nonEmptyString(event.projectedSeq);
 }
 
 function isToolTraceRow(row: TraceEventRow): boolean {
diff --git a/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts b/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts
index ab439b05..90af4616 100644
--- a/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts
+++ b/web/hwlab-cloud-web/src/composables/useTraceSubscription.ts
@@ -218,14 +218,17 @@ function traceEventSortSeq(event: TraceEvent): number {
 
 function traceEventIdentity(event: TraceEvent): string | null {
   const label = typeof event.label === "string" ? event.label : typeof event.type === "string" ? event.type : "";
-  const seqValue = event.projectedSeq ?? event.seq;
+  const seqValue = event.projectedSeq;
   const seq = typeof seqValue === "number" || typeof seqValue === "string" ? String(seqValue) : "";
   if (seq) return `projected:${seq}:${label || "event"}`;
+  const source = typeof event.source === "string" ? event.source : "";
+  const sourceSeq = typeof event.sourceSeq === "number" || typeof event.sourceSeq === "string" ? String(event.sourceSeq) : "";
+  if (source && sourceSeq) return `source:${source}:${sourceSeq}:${label || "event"}`;
   return null;
 }
 
 function traceEventProjectedSeq(event: TraceEvent): number {
-  const seq = Number(event.projectedSeq ?? event.seq);
+  const seq = Number(event.projectedSeq);
   return Number.isFinite(seq) ? Math.trunc(seq) : Number.NaN;
 }
 
diff --git a/web/hwlab-cloud-web/src/stores/workbench.ts b/web/hwlab-cloud-web/src/stores/workbench.ts
index 0fbb983b..112ff0e5 100644
--- a/web/hwlab-cloud-web/src/stores/workbench.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench.ts
@@ -832,23 +832,19 @@ function nonBlockingProjection(projection: ProjectionDiagnostic | null): Project
   async function cancelAgentMessage(message: ChatMessage): Promise<void> {
     const traceId = message.traceId ?? message.runnerTrace?.traceId;
     if (!traceId) return;
+    const sessionId = message.sessionId ?? selectedSessionId.value;
     const response = await api.agent.cancelAgentMessage({ traceId, sessionId: message.sessionId ?? selectedSessionId.value, threadId: message.threadId ?? selectedThreadId.value });
-    const payload = response.data as AgentChatResultResponse | null;
-    const status = normalizedStatusText(payload?.status) ?? "canceled";
-    const terminal = payload?.terminal === true || isTerminalMessageStatus(status);
-    if (response.ok && payload) {
-      applyTurnStatusSnapshot(traceId, payload);
-      if (terminal) completeTrace(traceId, payload);
-    } else {
-      applyTurnStatusSnapshot(traceId, { traceId, status: "canceled", running: false, terminal: true, sessionId: message.sessionId ?? selectedSessionId.value ?? undefined, threadId: message.threadId ?? selectedThreadId.value ?? undefined } as AgentChatResultResponse);
-    }
-    if (status === "canceled" || status === "cancelled") {
-      markMessage(traceId, { status: "canceled", text: "用户已取消该 turn。" });
-      void clearActiveTrace(traceId, "cancel-agent-message");
+    if (!response.ok) {
+      applyProjectionDiagnostic(traceId, projectionDiagnosticFromApiFailure(response, { code: "code_agent_cancel_failed", message: response.error ?? "Code Agent 取消请求失败，当前 turn 状态保持 canonical projection。", health: response.status === 0 ? "unavailable" : "degraded" }));
+      return;
     }
+    recordActivity("cancel:accepted");
     if (message.status === "running") chatPending.value = false;
     currentRequest.value = null;
-    scheduleSessionListRefresh(message.sessionId ?? selectedSessionId.value, SESSION_LIST_TERMINAL_REFRESH_DELAY_MS);
+    void clearActiveTrace(traceId, "cancel-agent-message");
+    void refreshMessageProjectionForTrace(sessionId, traceId);
+    if (sessionId) void hydrateTraceEvents(serverState.value.messagesBySessionId[sessionId] ?? messages.value);
+    scheduleSessionListRefresh(sessionId, SESSION_LIST_TERMINAL_REFRESH_DELAY_MS);
   }
 
   async function cancelRunningTrace(): Promise<void> {
@@ -2231,7 +2227,7 @@ function traceNextProjectedSeq(result: AgentChatResultResponse, fallback: number
 }
 
 function traceEventProjectedSeq(event: TraceEvent): number {
-  const seq = Number(event.projectedSeq ?? event.seq);
+  const seq = Number(event.projectedSeq);
   return Number.isFinite(seq) ? Math.trunc(seq) : Number.NaN;
 }