diff --git a/ui/web/src/i18n/locales/en/agents.json b/ui/web/src/i18n/locales/en/agents.json
index 5d7f0bbe..8ef6dcc6 100644
--- a/ui/web/src/i18n/locales/en/agents.json
+++ b/ui/web/src/i18n/locales/en/agents.json
@@ -724,7 +724,10 @@
     "retrying": "Retrying...",
     "done": "done",
     "fileLabelSOUL": "Soul & Personality",
-    "fileLabelIDENTITY": "Identity Card"
+    "fileLabelIDENTITY": "Identity Card",
+    "takingTooLong": "Taking too long?",
+    "cancel": "Cancel",
+    "cancelling": "Cancelling..."
   },
   "configGroups": {
     "core": "Core",
diff --git a/ui/web/src/i18n/locales/vi/agents.json b/ui/web/src/i18n/locales/vi/agents.json
index cec9d42a..34ecd77b 100644
--- a/ui/web/src/i18n/locales/vi/agents.json
+++ b/ui/web/src/i18n/locales/vi/agents.json
@@ -709,7 +709,10 @@
     "retrying": "Đang thử lại...",
     "done": "xong",
     "fileLabelSOUL": "Linh hồn & Tính cách",
-    "fileLabelIDENTITY": "Thẻ danh tính"
+    "fileLabelIDENTITY": "Thẻ danh tính",
+    "takingTooLong": "Mất quá nhiều thời gian?",
+    "cancel": "Huỷ",
+    "cancelling": "Đang huỷ..."
   },
   "configGroups": {
     "core": "Cốt lõi",
diff --git a/ui/web/src/i18n/locales/zh/agents.json b/ui/web/src/i18n/locales/zh/agents.json
index cb1470d8..59e4e86f 100644
--- a/ui/web/src/i18n/locales/zh/agents.json
+++ b/ui/web/src/i18n/locales/zh/agents.json
@@ -709,7 +709,10 @@
     "retrying": "重试中...",
     "done": "完成",
     "fileLabelSOUL": "灵魂与个性",
-    "fileLabelIDENTITY": "身份卡"
+    "fileLabelIDENTITY": "身份卡",
+    "takingTooLong": "耗时过长？",
+    "cancel": "取消",
+    "cancelling": "正在取消..."
   },
   "configGroups": {
     "core": "核心",
diff --git a/ui/web/src/pages/agents/agent-detail/agent-detail-page.tsx b/ui/web/src/pages/agents/agent-detail/agent-detail-page.tsx
index dd2fd350..6692a235 100644
--- a/ui/web/src/pages/agents/agent-detail/agent-detail-page.tsx
+++ b/ui/web/src/pages/agents/agent-detail/agent-detail-page.tsx
@@ -35,7 +35,7 @@ export function AgentDetailPage({ agentId, onBack }: AgentDetailPageProps) {
   const navigate = useNavigate();
   const { agent, files, loading, updateAgent, getFile, setFile, regenerateAgent, resummonAgent, refresh } =
     useAgentDetail(agentId);
-  const { deleteAgent: deleteAgentById } = useAgents();
+  const { deleteAgent: deleteAgentById, cancelSummonAgent } = useAgents();
   const hb = useAgentHeartbeat(agentId);
   const [summoningOpen, setSummoningOpen] = useState(false);
   const [activeTab, setActiveTab] = useState("agent");
@@ -161,6 +161,7 @@ export function AgentDetailPage({ agentId, onBack }: AgentDetailPageProps) {
         agentName={title}
         onCompleted={() => {}}
         onResummon={async () => { await resummonAgent(); }}
+        onCancel={cancelSummonAgent}
       />
 
       {heartbeatOpen && (
diff --git a/ui/web/src/pages/agents/agents-page.tsx b/ui/web/src/pages/agents/agents-page.tsx
index 6f9ce2c7..700130ba 100644
--- a/ui/web/src/pages/agents/agents-page.tsx
+++ b/ui/web/src/pages/agents/agents-page.tsx
@@ -31,7 +31,7 @@ export function AgentsPage() {
   const { t } = useTranslation("agents");
   const { id: detailId } = useParams<{ id: string }>();
   const navigate = useNavigate();
-  const { agents, loading, createAgent, deleteAgent, refresh, resummonAgent } = useAgents();
+  const { agents, loading, createAgent, deleteAgent, refresh, resummonAgent, cancelSummonAgent } = useAgents();
   const showSkeleton = useDeferredLoading(loading && agents.length === 0);
 
   const [search, setSearch] = useState("");
@@ -288,6 +288,7 @@ export function AgentsPage() {
           agentName={summoningAgent.name}
           onCompleted={refresh}
           onResummon={resummonAgent}
+          onCancel={cancelSummonAgent}
         />
       )}
     </div>
diff --git a/ui/web/src/pages/agents/hooks/use-agents.ts b/ui/web/src/pages/agents/hooks/use-agents.ts
index a96660f7..7fc0f474 100644
--- a/ui/web/src/pages/agents/hooks/use-agents.ts
+++ b/ui/web/src/pages/agents/hooks/use-agents.ts
@@ -113,5 +113,12 @@ export function useAgents() {
     [http],
   );
 
-  return { agents, loading, error, refresh: invalidate, createAgent, updateAgent, deleteAgent, resummonAgent };
+  const cancelSummonAgent = useCallback(
+    async (id: string) => {
+      await http.post(`/v1/agents/${id}/cancel-summon`);
+    },
+    [http],
+  );
+
+  return { agents, loading, error, refresh: invalidate, createAgent, updateAgent, deleteAgent, resummonAgent, cancelSummonAgent };
 }
diff --git a/ui/web/src/pages/agents/summoning-modal.tsx b/ui/web/src/pages/agents/summoning-modal.tsx
index a76883a3..2f853895 100644
--- a/ui/web/src/pages/agents/summoning-modal.tsx
+++ b/ui/web/src/pages/agents/summoning-modal.tsx
@@ -17,10 +17,13 @@ interface SummoningModalProps {
   agentName: string;
   onCompleted: () => void;
   onResummon: (agentId: string) => Promise<void>;
+  onCancel?: (agentId: string) => Promise<void>;
   hideClose?: boolean;
   onContinue?: () => void;
 }
 
+const CANCEL_THRESHOLD_SEC = 60;
+
 const SUMMONING_FILES = [
   { name: "SOUL.md", required: true },
   { name: "IDENTITY.md", required: true },
@@ -33,6 +36,7 @@ export function SummoningModal({
   agentName,
   onCompleted,
   onResummon,
+  onCancel,
   hideClose = false,
   onContinue,
 }: SummoningModalProps) {
@@ -41,6 +45,7 @@ export function SummoningModal({
   const [status, setStatus] = useState<"summoning" | "completed" | "failed">("summoning");
   const [errorMsg, setErrorMsg] = useState("");
   const [retrying, setRetrying] = useState(false);
+  const [cancelling, setCancelling] = useState(false);
   const [elapsed, setElapsed] = useState(0);
   const timerRef = useRef<ReturnType<typeof setInterval> | null>(null);
 
@@ -100,6 +105,19 @@ export function SummoningModal({
 
   useWsEvent("agent.summoning", handleSummoningEvent);
 
+  const handleCancel = async () => {
+    if (!onCancel) return;
+    setCancelling(true);
+    try {
+      await onCancel(agentId);
+      // BE emits WS type=failed → existing handler closes modal
+    } catch {
+      // keep modal open
+    } finally {
+      setCancelling(false);
+    }
+  };
+
   const handleRetry = async () => {
     setRetrying(true);
     try {
@@ -235,6 +253,15 @@ export function SummoningModal({
             </p>
           )}
 
+          {status === "summoning" && elapsed >= CANCEL_THRESHOLD_SEC && onCancel && (
+            <div className="flex flex-col items-center gap-1">
+              <p className="text-xs text-muted-foreground">{t("summoning.takingTooLong")}</p>
+              <Button variant="ghost" size="sm" onClick={handleCancel} disabled={cancelling}>
+                {cancelling ? t("summoning.cancelling") : t("summoning.cancel")}
+              </Button>
+            </div>
+          )}
+
           {status === "completed" && onContinue && (
             <Button size="sm" onClick={onContinue}>
               {t("summoning.continue")}
diff --git a/ui/web/src/pages/setup/step-agent.tsx b/ui/web/src/pages/setup/step-agent.tsx
index c11cc66a..d291f78c 100644
--- a/ui/web/src/pages/setup/step-agent.tsx
+++ b/ui/web/src/pages/setup/step-agent.tsx
@@ -26,7 +26,7 @@ interface StepAgentProps {
 
 export function StepAgent({ provider, model, onComplete, onBack, existingAgent }: StepAgentProps) {
   const { t } = useTranslation("setup");
-  const { createAgent, updateAgent, deleteAgent, resummonAgent } = useAgents();
+  const { createAgent, updateAgent, deleteAgent, resummonAgent, cancelSummonAgent } = useAgents();
   const agentPresets = useAgentPresets();
 
   const isEditing = !!existingAgent;
@@ -274,6 +274,7 @@ export function StepAgent({ provider, model, onComplete, onBack, existingAgent }
           agentName={createdAgent.name}
           onCompleted={handleSummoningComplete}
           onResummon={resummonAgent}
+          onCancel={cancelSummonAgent}
           hideClose
           onContinue={summoningOutcome === "success" ? handleContinue : undefined}
         />