feat(ui): team leader processing indicator and announce run streaming

- Add team.leader.processing backend event (emitted from onDrain before
  announce run starts) so all WS clients show processing status
- Capture announce run.started events to stream leader's summarization
  in real-time (thinking, tool calls, text)
- Add leader_processing phase to ActivityIndicator and ChatTopBar
- isBusy stays true during leader processing → stop button visible

cmd/gateway.go

@@ -143,6 +143,16 @@ func runGateway() {
 				for _, item := range items {
 					batchMedia = append(batchMedia, item.Media...)
 				}
+				// Notify clients that leader is processing team results
+				// (bridges UI gap between last task.completed and announce run.started).
+				msgBus.Broadcast(bus.Event{
+					Name: protocol.EventTeamLeaderProcessing,
+					Payload: map[string]any{
+						"agentId": meta.ParentAgent,
+						"tasks":   len(items),
+					},
+				})
+
 				msgBus.PublishInbound(bus.InboundMessage{
 					Channel:  "system",
 					SenderID: senderID,

pkg/protocol/events.go

@@ -52,6 +52,9 @@ const (
 	EventTeamTaskDeleted   = "team.task.deleted"
 	EventTeamTaskStale     = "team.task.stale"
 
+	// Emitted when leader starts processing completed team task results (before announce run).
+	EventTeamLeaderProcessing = "team.leader.processing"
+
 	// Team CRUD events (admin operations).
 	EventTeamCreated       = "team.created"
 	EventTeamUpdated       = "team.updated"

ui/web/src/api/protocol.ts

@@ -206,6 +206,9 @@ export const Events = {
   TEAM_TASK_DISPATCHED: "team.task.dispatched",
   TEAM_TASK_DELETED: "team.task.deleted",
 
+  // Team leader processing (bridges gap between last task.completed and announce run.started)
+  TEAM_LEADER_PROCESSING: "team.leader.processing",
+
   // Team messages
   TEAM_MESSAGE_SENT: "team.message.sent",
 

ui/web/src/components/chat/active-run-zone.tsx

@@ -63,7 +63,7 @@ export function ActiveRunZone({
           </div>
         )}
 
-        {isRunning && (
+        {(isRunning || activity?.phase === "leader_processing") && (
           <ActivityIndicator activity={activity} isRunning={isRunning} />
         )}
       </div>

ui/web/src/components/chat/activity-indicator.tsx

@@ -1,4 +1,4 @@
-import { Brain, Wrench, Pencil, Archive, RefreshCw } from "lucide-react";
+import { Brain, Wrench, Pencil, Archive, RefreshCw, Users } from "lucide-react";
 import type { RunActivity } from "@/types/chat";
 
 interface ActivityIndicatorProps {
@@ -7,7 +7,7 @@ interface ActivityIndicatorProps {
 }
 
 export function ActivityIndicator({ activity, isRunning }: ActivityIndicatorProps) {
-  if (!isRunning) return null;
+  if (!isRunning && activity?.phase !== "leader_processing") return null;
 
   if (!activity) {
     return (
@@ -51,6 +51,8 @@ function getPhaseConfig(activity: RunActivity) {
         color: "text-orange-500",
         label: `Retrying (${activity.retryAttempt ?? 0}/${activity.retryMax ?? 0})...`,
       };
+    case "leader_processing":
+      return { icon: Users, color: "text-emerald-500", label: "Processing team results..." };
     default:
       return { icon: Brain, color: "text-muted-foreground", label: "Working..." };
   }

ui/web/src/components/chat/chat-top-bar.tsx

@@ -19,6 +19,7 @@ const phaseLabels: Record<RunActivity["phase"], string> = {
   streaming: "Responding…",
   compacting: "Compacting…",
   retrying: "Retrying…",
+  leader_processing: "Processing team results…",
 };
 
 export function ChatTopBar({ agentId, isRunning, isBusy, activity, teamTasks }: ChatTopBarProps) {

ui/web/src/pages/chat/hooks/use-chat-messages.ts

@@ -433,14 +433,24 @@ export function useChatMessages(sessionKey: string, agentId: string) {
   useWsEvent(Events.TEAM_TASK_PROGRESS, onTaskProgress);
   useWsEvent(Events.TEAM_TASK_ASSIGNED, onTaskAssigned);
 
+  // Leader processing: backend emits when announce queue drains (before announce run starts).
+  const handleLeaderProcessing = useCallback((payload: unknown) => {
+    const event = payload as { agentId?: string; tasks?: number };
+    if (event?.agentId === agentIdRef.current) {
+      activityRef.current = { phase: "leader_processing" };
+      setActivity(activityRef.current);
+    }
+  }, []);
+  useWsEvent(Events.TEAM_LEADER_PROCESSING, handleLeaderProcessing);
+
   // Add a local message optimistically (shown immediately, replaced on next loadHistory)
   const addLocalMessage = useCallback((msg: ChatMessage) => {
     setMessages((prev) => [...prev, msg]);
   }, []);
 
-  // isBusy: true when main agent is running OR team tasks are active.
-  // Used for stop button visibility, top bar status, empty state check.
-  const isBusy = isRunning || teamTasks.length > 0;
+  // isBusy: true when main agent is running, team tasks are active,
+  // or leader is processing team results before announce run starts.
+  const isBusy = isRunning || teamTasks.length > 0 || activity?.phase === "leader_processing";
 
   return {
     messages,

ui/web/src/types/chat.ts

@@ -4,7 +4,7 @@ import type { Message } from "./session";
 
 /** Activity phase tracking during agent run */
 export interface RunActivity {
-  phase: "thinking" | "tool_exec" | "streaming" | "compacting" | "retrying";
+  phase: "thinking" | "tool_exec" | "streaming" | "compacting" | "retrying" | "leader_processing";
   tool?: string;
   tools?: string[];
   iteration?: number;