diff --git a/src/api.ts b/src/api.ts
index 1c0a576..3e17570 100644
--- a/src/api.ts
+++ b/src/api.ts
@@ -70,6 +70,10 @@ export const api = {
     auth.fetch(`${BASE}/api/cards/${cardId}/pin`, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ pinned }) }).then(r => json<{ card: ActivityCard }>(r)),
   cardDismiss: (cardId: string) =>
     auth.fetch(`${BASE}/api/cards/${cardId}/dismiss`, { method: 'POST' }).then(r => json<{ card: ActivityCard }>(r)),
+  listProjectCards: (projectId: string) =>
+    auth.fetch(`${BASE}/api/projects/${projectId}/cards`).then(r => json<{ cards: ActivityCard[] }>(r)).then(d => d.cards ?? []),
+  cardToProject: (cardId: string) =>
+    auth.fetch(`${BASE}/api/cards/${cardId}/to_project`, { method: 'POST' }).then(r => json<{ card: ActivityCard; origin: ActivityCard }>(r)),
 
   upload: (projectId: string, file: File) => {
     const fd = new FormData()
@@ -114,13 +118,17 @@ export interface SSEHandlers {
   onError?: (err: Error) => void
 }
 
-export function connectEvents(conversationId: string, since: number, handlers: SSEHandlers): { close: () => void } {
+export function connectEvents(conversationId: string, since: number, handlers: SSEHandlers, projectId?: string): { close: () => void } {
   let closed = false
   let es: EventSource | null = null
 
   const connect = () => {
     if (closed) return
-    es = new EventSource(auth.withKey(`${BASE}/api/events?conversationId=${encodeURIComponent(conversationId)}&since=${since}`))
+    // 项目流（CF3/D50）：scope=project 订阅项目频道（伪会话键，信封带 ProjectID）。
+    const url = projectId
+      ? `${BASE}/api/events?scope=project&projectId=${encodeURIComponent(projectId)}&since=${since}`
+      : `${BASE}/api/events?conversationId=${encodeURIComponent(conversationId)}&since=${since}`
+    es = new EventSource(auth.withKey(url))
     es.onopen = () => handlers.onOpen?.()
     es.onerror = () => {
       if (closed) return
@@ -131,7 +139,8 @@ export function connectEvents(conversationId: string, since: number, handlers: S
     // 同时监听具名事件与默认（服务端 event: 字段）。
     const types = ['message.delta', 'thinking.delta', 'tool.call', 'tool.result', 'run.phase',
       'hitl.request', 'hitl.resolved', 'plan.update', 'todo.update', 'agent.spawn', 'agent.progress',
-      'agent.result', 'artifact.created', 'artifact.updated', 'run.completed', 'run.failed', 'error']
+      'agent.result', 'artifact.created', 'artifact.updated', 'run.completed', 'run.failed', 'error',
+      'card.created', 'card.updated', 'card.status', 'card.resolved']
     for (const t of types) es.addEventListener(t, ev => handle(t, (ev as MessageEvent).data))
   }
 
diff --git a/src/components/TaskSidebar.tsx b/src/components/TaskSidebar.tsx
index 60b71fa..308ffaf 100644
--- a/src/components/TaskSidebar.tsx
+++ b/src/components/TaskSidebar.tsx
@@ -51,7 +51,9 @@ export function TaskSidebar() {
   const org = useStore(s => s.ui.taskOrg)
   const showArchived = useStore(s => s.ui.showArchived)
   const theme = useStore(s => s.ui.theme)
-  const pendingBadge = useStore(s => s.cards.filter(c => c.status === 'action_required').length)
+  const pendingBadge = useStore(s =>
+    s.cards.filter(c => c.status === 'action_required').length +
+    s.projectCards.filter(c => c.status === 'action_required').length)
 
   const [q, setQ] = useState('')
   const [collapsed, setCollapsed] = useState<Record<string, boolean>>(loadCollapsed)
diff --git a/src/components/Workbench.tsx b/src/components/Workbench.tsx
index 2cb8c41..c5d7788 100644
--- a/src/components/Workbench.tsx
+++ b/src/components/Workbench.tsx
@@ -15,11 +15,44 @@ export const docBridge: DocBridge = {
   },
 }
 
+const inboxCallbacks = {
+  onAction: (c: ActivityCard, id: string) => store.cardAction(c, id),
+  onPin: (c: ActivityCard, p: boolean) => store.cardPin(c, p),
+  onDismiss: (c: ActivityCard) => store.cardDismiss(c),
+  onLocate: (c: ActivityCard) => store.locateMessage(c.anchorMessageId),
+  onArchive: (c: ActivityCard) => store.cardToProject(c),
+}
+
+/** 项目收件箱视图（CF3/D49/D51）：项目级卡片 ∪ 其他会话待办（done 不聚合）。 */
+function ProjectInbox({ cards }: { cards: ActivityCard[] }) {
+  const own = cards.filter(c => !c.conversationId)
+  const cross = cards.filter(c => !!c.conversationId)
+  if (cards.length === 0) {
+    return <div className="inbox-empty">项目收件箱为空——「留档到项目」的产物卡与其他会话的待办会聚合在这里。</div>
+  }
+  return (
+    <>
+      <div className="inbox-zone-label">📁 项目级卡片（跨会话可见）</div>
+      {own.length > 0
+        ? <InboxList cards={own} callbacks={inboxCallbacks} docBridge={docBridge} />
+        : <div className="inbox-empty" style={{ padding: '4px 14px' }}>暂无——会话卡点 🗂 即留档至此</div>}
+      {cross.length > 0 && (
+        <>
+          <div className="inbox-zone-label">🕓 其他会话待办</div>
+          <InboxList cards={cross} callbacks={inboxCallbacks} docBridge={docBridge} showPinnedZone={false} />
+        </>
+      )}
+    </>
+  )
+}
+
 export function Workbench() {
   const cards = useStore(s => s.cards)
   const plan = useStore(s => s.plan)
   const todos = useStore(s => s.todos)
-  const pending = pendingCount(cards)
+  const inboxScope = useStore(s => s.inboxScope)
+  const projectCards = useStore(s => s.projectCards)
+  const pending = pendingCount(cards) + pendingCount(projectCards)
   const rightTab = useStore(s => s.ui.rightTab)
   const railId = useStore(s => s.ui.railPreviewId)
   const railArtifact = useStore(s => (railId ? s.artifacts.find(a => a.id === railId) : undefined))
@@ -61,12 +94,15 @@ export function Workbench() {
       ) : (
         <div className="tab-body">
           <CurrentTaskCard plan={plan} todos={todos} />
-          <InboxList cards={cards} docBridge={docBridge} callbacks={{
-            onAction: (c: ActivityCard, id: string) => store.cardAction(c, id),
-            onPin: (c: ActivityCard, p: boolean) => store.cardPin(c, p),
-            onDismiss: (c: ActivityCard) => store.cardDismiss(c),
-            onLocate: (c: ActivityCard) => store.locateMessage(c.anchorMessageId),
-          }} />
+          <div className="inbox-scope" role="tablist" aria-label="收件箱范围">
+            <button className={inboxScope === 'conv' ? 'active' : ''} onClick={() => store.setInboxScope('conv')}>本会话</button>
+            <button className={inboxScope === 'project' ? 'active' : ''} onClick={() => store.setInboxScope('project')}>
+              项目{pendingCount(projectCards) > 0 ? ` ${pendingCount(projectCards)}` : ''}
+            </button>
+          </div>
+          {inboxScope === 'project'
+            ? <ProjectInbox cards={projectCards} />
+            : <InboxList cards={cards} docBridge={docBridge} callbacks={inboxCallbacks} />}
         </div>
       )}
     </>
diff --git a/src/store.ts b/src/store.ts
index 960b8b0..d43c306 100644
--- a/src/store.ts
+++ b/src/store.ts
@@ -64,6 +64,8 @@ interface AppState {
   todos: TodoList | null
   artifacts: Artifact[]
   cards: ActivityCard[]
+  projectCards: ActivityCard[]
+  inboxScope: 'conv' | 'project'
   profiles: AgentProfile[]
   pluginPanels: PluginPanel[]
   serverWorkspaces: { id: string; title: string; icon?: string; shortcut?: string; body?: any[] }[]
@@ -106,7 +108,7 @@ let state: AppState = {
   contextObs: {},
   projects: [], currentProjectId: null, tasks: [], me: null, currentConvId: null,
   messages: [], runs: [], activeHitl: [], lastSeq: 0, live: null,
-  plan: null, todos: null, artifacts: [], cards: [], profiles: [], pluginPanels: [],
+  plan: null, todos: null, artifacts: [], cards: [], projectCards: [], inboxScope: 'conv', profiles: [], pluginPanels: [],
   serverWorkspaces: [],
   ui: loadUI(), connected: false, error: null, toast: null,
 }
@@ -131,6 +133,8 @@ function applyTheme(theme: string) {
 }
 
 let sse: { close: () => void } | null = null
+let projectSse: { close: () => void } | null = null
+let projectSeq = 0
 
 export function useStore<T>(selector: (s: AppState) => T): T {
   return useSyncExternalStore(
@@ -173,6 +177,10 @@ export const store = {
 
   async openProject(projectId: string) {
     set({ currentProjectId: projectId })
+    if (store.getState().inboxScope === 'project') {
+      store.loadProjectCards()
+      store.connectProject()
+    }
     store.setUI({ lastProjectId: projectId })
     await store.refreshArtifacts(projectId)
   },
@@ -224,7 +232,7 @@ export const store = {
 
   async openConversation(convId: string) {
     if (sse) { sse.close(); sse = null }
-    set({ currentConvId: convId, messages: [], runs: [], activeHitl: [], lastSeq: 0, live: null, plan: null, todos: null, cards: [] })
+    set({ currentConvId: convId, messages: [], runs: [], activeHitl: [], lastSeq: 0, live: null, plan: null, todos: null, cards: [], inboxScope: 'conv' })
     await store.reconcile()
     await store.connectLive()
   },
@@ -492,6 +500,72 @@ export const store = {
   toggleRight() { setUI({ rightCollapsed: !state.ui.rightCollapsed }) },
   openWorkspace(id: string) { setUI({ activeWorkspace: id }) },
   /** 收纳策略（T5）：一键收纳已完成卡（done→dismissed；resolved 盖章留痕不动）。 */
+  // 项目收件箱（CF3/D48-D51）：加载聚合视图 + 项目流订阅 + 留档。
+  async loadProjectCards() {
+    const pid = store.getState().currentProjectId
+    if (!pid) return
+    try { set({ projectCards: await api.listProjectCards(pid) }) } catch { /* 静默：切项目竞态 */ }
+  },
+
+  setInboxScope(scope: 'conv' | 'project') {
+    set({ inboxScope: scope })
+    if (scope === 'project') {
+      store.loadProjectCards()
+      store.connectProject()
+    } else if (projectSse) {
+      projectSse.close()
+      projectSse = null
+    }
+  },
+
+  connectProject() {
+    const pid = store.getState().currentProjectId
+    if (!pid) return
+    projectSse?.close()
+    projectSse = connectEvents('', projectSeq, { onEvent: e => store.applyProjectEvent(e) }, pid)
+  },
+
+  applyProjectEvent(e: StreamEvent) {
+    projectSeq = Math.max(projectSeq, e.seq)
+    const upsert = (card: ActivityCard) => {
+      const list = store.getState().projectCards
+      const i = list.findIndex(c => c.id === card.id)
+      set({ projectCards: i >= 0 ? list.map(c => (c.id === card.id ? card : c)) : [card, ...list] })
+    }
+    switch (e.type) {
+      case 'card.created':
+      case 'card.updated':
+        if ((e.payload as { card?: ActivityCard })?.card) upsert((e.payload as { card: ActivityCard }).card)
+        break
+      case 'card.status': {
+        const p = e.payload as { cardId: string; status: ActivityCard['status']; tone?: string }
+        const list = store.getState().projectCards
+        set({ projectCards: list.map(c => (c.id === p.cardId ? { ...c, status: p.status, tone: p.tone ?? c.tone } : c)) })
+        break
+      }
+      case 'card.resolved': {
+        const p = e.payload as { cardId: string }
+        const list = store.getState().projectCards
+        set({ projectCards: list.map(c => (c.id === p.cardId ? { ...c, status: 'resolved' as const } : c)) })
+        break
+      }
+    }
+  },
+
+  async cardToProject(card: ActivityCard) {
+    try {
+      const out = await api.cardToProject(card.id)
+      store.upsertCard(out.origin) // 会话视图：原卡 dismissed 留痕
+      const list = store.getState().projectCards
+      const i = list.findIndex(c => c.id === out.card.id)
+      set({ projectCards: i >= 0 ? list.map(c => (c.id === out.card.id ? out.card : c)) : [out.card, ...list] })
+      store.toast('已留档到项目收件箱')
+      store.setInboxScope('project')
+    } catch (e) {
+      store.toast(`留档失败：${e}`)
+    }
+  },
+
   async tidyCards() {
     const done = state.cards.filter(c => c.status === 'done')
     for (const c of done) {
diff --git a/src/styles.css b/src/styles.css
index ce2270a..b988522 100644
--- a/src/styles.css
+++ b/src/styles.css
@@ -404,3 +404,13 @@ button { font-family: inherit; font-size: inherit; color: inherit; }
 .tab-body[data-rail-preview] { display: flex; flex-direction: column; }
 .tab-body[data-rail-preview] .ui-fp { flex: 1; }
 .artifact-chip .ac-act { border: none; background: none; }
+
+/* 项目收件箱（CF3/D51）：会话/项目范围分段控件 */
+.inbox-scope {
+  display: flex; gap: 4px; padding: 6px 14px 2px;
+}
+.inbox-scope button {
+  border: 1px solid var(--border, #d8d8d8); background: transparent; color: inherit;
+  border-radius: 999px; padding: 2px 12px; font-size: 12px; cursor: pointer; opacity: .72;
+}
+.inbox-scope button.active { opacity: 1; font-weight: 600; background: var(--hover, rgba(0,0,0,.05)); }