Render saved surfaces in the preview pane with refresh recovery

Why: U4 read-only experience - surface.updated events project into a
surfaces slice with a strict revision guard (stale/duplicate events
never overwrite; server snapshot is the single owner), preview tabs
gain a surface: kind that renders SurfaceView (doc-refs bridge into
artifact previews), a new page auto-opens a tab without stealing the
user's active non-surface tab, and opening a conversation reloads the
authoritative surface list so refresh/断线 restores pages.

Evidence: tsc clean; vitest 87/87 including new surface projection
tests (stale/duplicate/multi-surface); UI SurfaceView suite green in
its repo.

Impact: Frontend-only; no backend or contract changes.

Refs: Core PRs #27/#28; UI PRs #42/#43/#44; Dev task
feature/generative-ui-u4

src/api.ts

@@ -30,6 +30,8 @@ export const api = {
   setPermissionMode: (id: string, permissionMode: string) => auth.fetch(`${BASE}/api/conversations/${id}`, { method: 'PATCH', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ permissionMode }) }).then(r => { if (!r.ok) throw new Error(`${r.status}: ${r.statusText}`) }),
   checkpoints: (id: string, messageId: string) => auth.fetch(`${BASE}/api/conversations/${id}/checkpoints?messageId=${encodeURIComponent(messageId)}`).then(r => json<{ restored?: string[]; skipped?: string[] }>(r)),
   rewindFiles: (id: string, messageId: string) => auth.fetch(`${BASE}/api/conversations/${id}/rewind`, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ messageId }) }).then(r => json<{ restored?: string[]; skipped?: string[] }>(r)),
+  surfaceList: (convId: string) => auth.fetch(`${BASE}/api/conversations/${convId}/surfaces`).then(r => json<any[]>(r)),
+  surfaceGet: (id: string) => auth.fetch(`${BASE}/api/surfaces/${id}`).then(r => json<any>(r)),
   me: () => auth.fetch(`${BASE}/api/me`).then(r => json<{ owner: string; name: string; auth: boolean; isAdmin?: boolean; mustChangePassword?: boolean }>(r)),
   // ---- 认证与会话（管理员发放制，R2）----
   login: (owner: string, password: string) => auth.fetch(`${BASE}/api/auth/login`, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ owner, password }) }).then(async r => {
@@ -160,7 +162,7 @@ const streamEventListeners: Record<StreamEventType, true> = {
   'card.created': true,
   'card.updated': true,
   'card.status': true,
-  'card.resolved': true,
+  'card.resolved': true, 'surface.updated': true,
 }
 
 export function connectEvents(conversationId: string, since: number, handlers: SSEHandlers, projectId?: string): { close: () => void } {

src/components/PreviewPane.tsx

@@ -1,7 +1,7 @@
 // 第三栏「文件」入口的多标签预览：打开/切换/关闭标签、编辑保存、展开铺满与下载。
 // 列表 ⇄ 预览在同一入口内切换；宽度档（阅读档 420–1100）由 App 的分隔条控制。
 import { useEffect, useState } from 'react'
-import { Btn, FilePreview, Icon, TabStrip } from '@ui'
+import { Btn, FilePreview, Icon, SurfaceView, TabStrip } from '@ui'
 import { api } from '../api'
 import type { Artifact } from '../contracts'
 import { humanSize } from '../messageparts'
@@ -15,6 +15,10 @@ export function PreviewPane() {
   const artifacts = useStore(s => s.artifacts)
   const expanded = useStore(s => s.ui.previewExpanded)
   const active = tabs.find(t => t.id === activeId) ?? tabs[0]
+  const surfaces = useStore(s => s.surfaces)
+  const surfaceSnap = active?.id.startsWith('surface:')
+    ? surfaces.find(x => 'surface:' + String(x.identity.surfaceId) === active.id)
+    : undefined
   const art = active ? artifacts.find(a => a.id === active.id) : undefined
   const textKind = !!art && isTextKind(art)
   const [content, setContent] = useState<string | null>(null)
@@ -35,6 +39,32 @@ export function PreviewPane() {
   }, [art?.id])
 
   if (!active) return null
+  if (active.id.startsWith('surface:')) {
+    return (
+      <div className="preview-pane">
+        <TabStrip
+          tabs={tabs.map(t => ({ id: t.id, label: t.name }))}
+          activeId={active.id}
+          onActivate={id => store.activatePreview(id)}
+          onClose={id => store.closePreview(id)}
+        />
+        <div className="preview-pane-bar">
+          <button type="button" className="icon-btn" title="返回文件列表" onClick={() => store.setUI({ filesView: 'list', previewExpanded: false })}>
+            <Icon name="list" size={14} />
+          </button>
+          <span className="preview-pane-name" title={active.name}>{active.name}</span>
+        </div>
+        <div className="preview-pane-body">
+          {surfaceSnap
+            ? <SurfaceView snapshot={surfaceSnap} docBridge={{ onOpenDoc: docId => {
+                const art = artifacts.find(a => a.id === docId)
+                if (art) store.requestPreview(art)
+              } }} />
+            : <p className="surface-view-empty">页面快照不可用（可能已被移除或无权限）。</p>}
+        </div>
+      </div>
+    )
+  }
   return (
     <div className="preview-pane">
       <TabStrip

src/contracts.ts

@@ -99,7 +99,8 @@ export type StreamEventType =
   | 'agent.spawn' | 'agent.progress' | 'agent.result'
   | 'artifact.created' | 'artifact.updated'
   | 'run.completed' | 'run.failed' | 'error'
-  | 'card.created' | 'card.updated' | 'card.status' | 'card.resolved';
+  | 'card.created' | 'card.updated' | 'card.status' | 'card.resolved'
+  | 'surface.updated';
 
 export interface StreamEvent<P = unknown> {
   seq: number; runId?: ID; conversationId: ID; ts: string; v: number;
@@ -355,3 +356,45 @@ export interface UploadInfo {
   artifactId: ID; filename: string; mime?: string; size: number;
   parsed?: ParsedDocument;
 }
+
+// ---- Generative UI Surface（提案 U2/U4；与 Go surface.go 同步）----
+
+export interface SurfaceCompat {
+  schemaVersion: number;
+  catalogVersion: string;
+  pluginVersion?: string;
+}
+
+export interface SurfaceIdentity {
+  surfaceId: ID;
+  owner: string;
+  projectId?: ID;
+  conversationId?: ID;
+  sourceRunId?: ID;
+  pluginId: string;
+}
+
+export interface SurfaceSpec {
+  title: string;
+  nodes: UINode[];
+}
+
+export interface SurfaceSnapshot {
+  identity: SurfaceIdentity;
+  compat: SurfaceCompat;
+  revision: number;
+  baseRevision?: number;
+  contextVersion?: string;
+  activationEpoch: number;
+  spec: SurfaceSpec;
+  semanticText?: string;
+}
+
+export interface SurfaceMeta {
+  surfaceId: ID;
+  title: string;
+  pluginId: string;
+  revision: number;
+  conversationId?: ID;
+  updatedAt: string;
+}

src/store.ts

@@ -16,8 +16,19 @@ export function isFontSizeChoice(value: number): value is FontSizeChoice {
   return (FONT_SIZE_CHOICES as readonly number[]).includes(value)
 }
 import type {
-  Project, Conversation, Message, Run, Artifact, HITLCard, PlanSnapshot, TodoList,
-  AgentProfile, StreamEvent, PluginPanel, ActivityCard,
+  ActivityCard,
+  AgentProfile,
+  Artifact,
+  Conversation,
+  HITLCard,
+  Message,
+  PlanSnapshot,
+  PluginPanel,
+  Project,
+  Run,
+  StreamEvent,
+  SurfaceSnapshot,
+  TodoList
 } from './contracts'
 
 export interface ContextObs {
@@ -86,6 +97,8 @@ interface AppState {
   plan: PlanSnapshot | null
   todos: TodoList | null
   artifacts: Artifact[]
+  /** generative-ui：会话内已保存页面（surface.updated 投影；按 surfaceId 存最新修订）。 */
+  surfaces: SurfaceSnapshot[]
   cards: ActivityCard[]
   projectCards: ActivityCard[]
   inboxScope: 'conv' | 'project'
@@ -153,7 +166,7 @@ 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: [], projectCards: [], inboxScope: 'conv', runtimeMock: false, profiles: [], pluginPanels: [],
+  plan: null, todos: null, artifacts: [], surfaces: [], cards: [], projectCards: [], inboxScope: 'conv', runtimeMock: false, profiles: [], pluginPanels: [],
   serverWorkspaces: [],
   ui: loadUI(), connected: false, posting: false, error: null, toast: null,
   outbox: [], outboxDraining: false,
@@ -359,7 +372,7 @@ 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: [], inboxScope: 'conv', outbox: [], outboxDraining: false, posting: false })
+    set({ currentConvId: convId, messages: [], runs: [], activeHitl: [], lastSeq: 0, live: null, plan: null, todos: null, cards: [], surfaces: [], inboxScope: 'conv', outbox: [], outboxDraining: false, posting: false })
     persistConvId(convId)
     // 空态时打开的预览标签（'_' 键）随会话进入一起迁移，不留在不可见的孤儿键下。
     if ((state.previewTabs['_'] ?? []).length > 0) {
@@ -369,6 +382,8 @@ export const store = {
         previewActive: { ...state.previewActive, [convId]: active },
       })
     }
+    // U4/R5：已保存页面从权威快照重载（刷新/断线恢复；事件流只做增量投影）。
+    api.surfaceList(convId).then(list => { if (state.currentConvId === convId) set({ surfaces: list ?? [] }) }).catch(() => {})
     const resumeSeq = await store.reconcile()
     store.connectLive(resumeSeq ?? state.lastSeq)
   },
@@ -490,6 +505,33 @@ export const store = {
         set({ todos: p.list })
         break
       }
+      case 'surface.updated': {
+        // KTD8：单一状态所有者——服务端快照为权威，本地按 revision 守卫：
+        // 旧修订/重复事件不覆盖新修订；切会话由 selectConversation 清空。
+        const p = e.payload as SurfaceSnapshot
+        if (!p?.identity?.surfaceId) break
+        const id = String(p.identity.surfaceId)
+        const surfaces = state.surfaces.filter(x => String(x.identity.surfaceId) !== id)
+        const existing = state.surfaces.find(x => String(x.identity.surfaceId) === id)
+        if (!existing || p.revision > existing.revision) {
+          surfaces.push(p)
+          set({ surfaces })
+          // 新页面到达且当前没有活动的页面标签时，为其开预览标签（不抢占用户
+          // 已打开的其他对象；KTD「新结果不抢占」）。
+          const conv = previewTabsKey(state.currentConvId)
+          const tabs = state.previewTabs[conv] ?? []
+          const activeId = state.previewActive[conv] ?? null
+          const hasSurfaceTab = tabs.some(t => t.id.startsWith('surface:'))
+          if (!hasSurfaceTab || (activeId ?? '').startsWith('surface:')) {
+            const opened = openPreviewTab(tabs, { id: 'surface:' + id, name: p.spec?.title || '页面' })
+            set({
+              previewTabs: { ...state.previewTabs, [conv]: opened.tabs },
+              previewActive: { ...state.previewActive, [conv]: opened.activeId },
+            })
+          }
+        }
+        break
+      }
       case 'card.created':
       case 'card.updated': {
         const p = e.payload as { card: ActivityCard }
@@ -846,6 +888,17 @@ export const store = {
     })
     syncFilesEntry(true)
   },
+  openSurface(surfaceId: string) {
+    // generative-ui：页面进预览第三栏（标签 id 带 surface: 前缀区分工件）。
+    const snap = state.surfaces.find(x => String(x.identity.surfaceId) === surfaceId)
+    const conv = previewTabsKey(state.currentConvId)
+    const opened = openPreviewTab(state.previewTabs[conv] ?? [], { id: 'surface:' + surfaceId, name: snap?.spec?.title || '页面' })
+    set({
+      previewTabs: { ...state.previewTabs, [conv]: opened.tabs },
+      previewActive: { ...state.previewActive, [conv]: opened.activeId },
+    })
+    syncFilesEntry(true)
+  },
   togglePreviewExpanded() { setUI({ previewExpanded: !state.ui.previewExpanded }) },
   activatePreview(id: string) {
     const conv = previewTabsKey(state.currentConvId)

src/surface.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from 'vitest'
+import { store } from './store'
+import type { StreamEvent, SurfaceSnapshot } from './contracts'
+
+// U4/R5：surface.updated 投影的 revision 守卫——旧修订/重复事件不得覆盖新修订；
+// 服务端快照是唯一权威（KTD8 单一状态所有者）。
+
+function surfEvent(seq: number, surfaceId: string, revision: number, title: string): StreamEvent<SurfaceSnapshot> {
+  return {
+    seq, conversationId: 'c1', ts: new Date().toISOString(), v: 1, type: 'surface.updated',
+    payload: {
+      identity: { surfaceId, owner: 'alice', pluginId: 'generative-ui', conversationId: 'c1' },
+      compat: { schemaVersion: 1, catalogVersion: 'ui-v1' },
+      revision, activationEpoch: 1,
+      spec: { title, nodes: [{ type: 'markdown', id: 'n1', markdown: 'x' }] },
+    },
+  }
+}
+
+describe('surface.updated projection', () => {
+  it('新事件入库；旧修订与重复事件不覆盖', () => {
+    store.applyEvent(surfEvent(1, 's1', 1, '初版'))
+    store.applyEvent(surfEvent(2, 's1', 2, '修订二'))
+    store.applyEvent(surfEvent(3, 's1', 1, '迟到的旧修订'))
+    store.applyEvent(surfEvent(4, 's1', 2, '重复事件'))
+    const list = store.getState().surfaces
+    expect(list).toHaveLength(1)
+    expect(list[0].revision).toBe(2)
+    expect(list[0].spec.title).toBe('修订二')
+  })
+
+  it('多页面并存，互不覆盖', () => {
+    store.applyEvent(surfEvent(5, 's2', 1, '页面二'))
+    const list = store.getState().surfaces
+    expect(list.filter(x => String(x.identity.surfaceId) === 's1')).toHaveLength(1)
+    expect(list.filter(x => String(x.identity.surfaceId) === 's2')).toHaveLength(1)
+  })
+})
+