Show background notices without blocking the composer

Why: A background child should not look like the conversation is busy, and its completion note needs a compact row instead of a full assistant bubble.
Evidence: vitest run passed, including design-guard. tsc -b passed.
Impact: The stop button cancels the conversation run. System notices fold with the shared Collapsible.
Refs: feature/agent-harness-p3b
Co-authored-by: Cursor <cursoragent@cursor.com>

src/components/Conversation.tsx

@@ -341,6 +341,19 @@ function OutboxPanel() {
   )
 }
 
+export function NoticeMessage({ msg }: { msg: Message }) {
+  const text = msg.parts.filter(p => p.type === 'text').map(p => p.text).join('\n')
+  const preview = text.replace(/<\/?system-reminder>/g, '').trim().split('\n').find(line => line.trim()) ?? '系统通知'
+  return (
+    <div className="msg notice" data-msg-id={msg.id}>
+      <Collapsible id={`notice:${msg.id}`} triggerClassName="notice-summary"
+        trigger={<span className="notice-label">通知 · {preview}</span>}>
+        <div className="notice-body">{text}</div>
+      </Collapsible>
+    </div>
+  )
+}
+
 export function Conversation() {
   const currentConvId = useStore(s => s.currentConvId)
   const conversation = useStore(s => s.tasks.find(c => c.id === s.currentConvId))
@@ -447,6 +460,7 @@ export function Conversation() {
               </div>
             )
           }
+          if (m.role === 'system') return <NoticeMessage key={m.id} msg={m} />
           return <AssistantMessage key={m.id} msg={m} live={live?.runId === m.runId ? live : null} />
         })}
         {live && !messages.some(m => m.runId === live.runId) &&

src/contracts.ts

@@ -210,6 +210,8 @@ export interface PromptModule {
   body: string; outputContract?: string;
   source?: 'builtin' | 'plugin' | 'user'; owner?: string;
   basedOnVersion?: number; drifted?: boolean; disabled?: boolean;
+  /** 子代理 profile。只对 agent.sub.* 有意义；空字段表示沿用内置。 */
+  tools?: string[]; model?: string; maxTurns?: number;
 }
 
 export interface PromptBlock { moduleId: string; version: number; layer: string; body: string; }

src/store.ts

@@ -487,7 +487,7 @@ export const store = {
   },
 
   async cancelActive() {
-    const active = state.runs.find(r => !isTerminal(r.status))
+    const active = activeRun(state.runs)
     if (!active) return
     await api.cancelRun(active.id).catch(() => undefined)
     setTimeout(() => store.reconcile(), 200)
@@ -721,5 +721,5 @@ function isConversationBusy(err: unknown): boolean {
 }
 
 export function activeRun(runs: Run[]): Run | undefined {
-  return runs.find(r => !isTerminal(r.status))
+  return runs.find(r => r.kind !== 'subagent' && !isTerminal(r.status))
 }

src/styles.css

@@ -67,6 +67,9 @@ button { font-family: inherit; font-size: inherit; color: inherit; }
 .msg { margin-bottom: 20px; animation: mk-rise-in .18s var(--ease-out); }
 .msg-role { font-size: var(--fs-ui-sm); color: var(--text-faint); margin-bottom: 6px; display: flex; gap: 8px; align-items: center; }
 .msg-role .role-mark { width: 18px; height: 18px; border-radius: 5px; display: inline-flex; align-items: center; justify-content: center; color: var(--text-dim); background: var(--bg-raised); border: 1px solid var(--border); }
+.msg.notice { margin-bottom: 12px; }
+.notice-summary { font-size: var(--fs-ui-sm); color: var(--text-dim); background: none; border: none; padding: 0; cursor: pointer; }
+.notice-body { font-size: var(--fs-ui-sm); color: var(--text-dim); white-space: pre-wrap; margin-top: 4px; }
 .msg.user .bubble {
   background: var(--accent-soft); border: 1px solid transparent;
   border-radius: var(--radius-lg); padding: 11px 16px; white-space: pre-wrap;

test/notice.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest'
+import { renderToStaticMarkup } from 'react-dom/server'
+import { createElement } from 'react'
+import { activeRun } from '../src/store'
+import { NoticeMessage } from '../src/components/Conversation'
+import type { Message, Run } from '../src/contracts'
+
+function run(kind: Run['kind'], status: Run['status']): Run {
+  return {
+    id: `${kind}-${status}`, conversationId: 'c', projectId: 'p',
+    kind, status, createdAt: '2026-10-01T00:00:00Z',
+  }
+}
+
+describe('activeRun', () => {
+  it('ignores background subagents so they do not block sending', () => {
+    const runs = [run('subagent', 'running'), run('conversation', 'completed')]
+    expect(activeRun(runs)).toBeUndefined()
+    expect(activeRun([run('conversation', 'running'), run('subagent', 'running')])?.kind).toBe('conversation')
+  })
+})
+
+describe('NoticeMessage', () => {
+  it('renders a compact notice row', () => {
+    const msg: Message = {
+      id: 'msg_notice', conversationId: 'c', role: 'system', createdAt: '2026-10-01T00:00:00Z',
+      parts: [{ type: 'text', text: '<system-reminder>\n后台子代理「检索」已结束。\n</system-reminder>' }],
+    }
+    const html = renderToStaticMarkup(createElement(NoticeMessage, { msg }))
+    expect(html).toContain('通知 · 后台子代理「检索」已结束。')
+    expect(html).toContain('msg notice')
+    expect(html).not.toContain('<details')
+  })
+})

tsconfig.tsbuildinfo

@@ -1 +1 @@
-{"root":["./src/App.tsx","./src/api.ts","./src/auth.ts","./src/contracts.ts","./src/live.ts","./src/main.tsx","./src/messageparts.ts","./src/outbox.ts","./src/passwords.ts","./src/previewsetup.ts","./src/previewtabs.ts","./src/store.ts","./src/tasklist.ts","./src/toolkind.ts","./src/components/AdminUsersModal.tsx","./src/components/AdminZone.tsx","./src/components/AgentTracker.tsx","./src/components/ArtifactsPanel.tsx","./src/components/Conversation.tsx","./src/components/DocViewer.tsx","./src/components/LoginPage.tsx","./src/components/PreviewPane.tsx","./src/components/ProcessTimeline.tsx","./src/components/ProjectSettingsModal.tsx","./src/components/SettingsModal.tsx","./src/components/TaskSidebar.tsx","./src/components/Workbench.tsx","./src/components/Workspaces.tsx","./src/components/adminSections.tsx","./test/auth.test.ts","./test/contracts.test.ts","./test/design-guard.test.ts","./test/live.test.ts","./test/messageparts.test.ts","./test/outbox.test.ts","./test/previewtabs.test.ts","./test/tasklist.test.ts","./test/toolkind.test.ts"],"version":"5.9.3"}
+{"root":["./src/App.tsx","./src/api.ts","./src/auth.ts","./src/contracts.ts","./src/live.ts","./src/main.tsx","./src/messageparts.ts","./src/outbox.ts","./src/passwords.ts","./src/pluginHost.ts","./src/previewsetup.ts","./src/previewtabs.ts","./src/store.ts","./src/tasklist.ts","./src/toolkind.ts","./src/components/AdminUsersModal.tsx","./src/components/AdminZone.tsx","./src/components/AgentTracker.tsx","./src/components/ArtifactsPanel.tsx","./src/components/Conversation.tsx","./src/components/DocViewer.tsx","./src/components/LoginPage.tsx","./src/components/PreviewPane.tsx","./src/components/ProcessTimeline.tsx","./src/components/ProjectSettingsModal.tsx","./src/components/SettingsModal.tsx","./src/components/TaskSidebar.tsx","./src/components/Workbench.tsx","./src/components/Workspaces.tsx","./src/components/adminSections.tsx","./test/auth.test.ts","./test/contracts.test.ts","./test/design-guard.test.ts","./test/live.test.ts","./test/messageparts.test.ts","./test/notice.test.ts","./test/outbox.test.ts","./test/previewtabs.test.ts","./test/tasklist.test.ts","./test/toolkind.test.ts"],"version":"5.9.3"}