feat: 原生系统提示词只读展示、会话末尾 fork、深浅色主题

apps/desktop/src/main/index.ts

@@ -1,4 +1,4 @@
-import { app, BrowserWindow, ipcMain, Menu, shell } from 'electron'
+import { app, BrowserWindow, ipcMain, Menu, nativeTheme, shell } from 'electron'
 import { existsSync } from 'node:fs'
 import { join } from 'node:path'
 import { registerIpc } from './ipc'
@@ -32,13 +32,16 @@ function registerWindowControls(): void {
 }
 
 async function createWindow(): Promise<void> {
+  // 窗口底色跟随深浅色（加载/resize 时不闪白）；构造函数里已按持久化偏好设置过
+  // nativeTheme.themeSource，这里用实际生效值
+  const dark = nativeTheme.shouldUseDarkColors
   const win = new BrowserWindow({
     width: 1280,
     height: 840,
     minWidth: 960,
     minHeight: 640,
     show: false,
-    backgroundColor: '#ffffff',
+    backgroundColor: dark ? '#212121' : '#ffffff',
     title: 'Inkreach Agent',
     // 窗口/任务栏图标（Windows/Linux；macOS 打包时由 build 配置提供 icns）
     ...(existsSync(APP_ICON) ? { icon: APP_ICON } : {}),
@@ -52,6 +55,11 @@ async function createWindow(): Promise<void> {
     }
   })
 
+  // 深浅色切换时同步窗口底色（避免暗色下 resize/加载闪白块）
+  nativeTheme.on('updated', () => {
+    win.setBackgroundColor(nativeTheme.shouldUseDarkColors ? '#212121' : '#ffffff')
+  })
+
   // 最大化状态同步给渲染层（切换「最大化/还原」字形）
   const sendWinState = (): void => win.webContents.send('win:state', win.isMaximized())
   win.on('maximize', sendWinState)

apps/desktop/src/main/ipc.ts

@@ -178,19 +178,25 @@ export function registerIpc(): AgentService {
     )
   })
 
+  // 会话末尾分叉为新会话（pi fork，原会话保留）
+  ipcMain.handle('session:fork', () => pass(() => service.forkSession()))
+
   // ---- 应用设置 ----
   ipcMain.handle('settings:get', () => service.getSettings())
 
-  ipcMain.handle('settings:setPrompt', (_event, text: unknown) => {
-    if (typeof text !== 'string') throw new Error('invalid prompt')
-    return pass(() => service.setSystemPrompt(text))
-  })
+  // 当前生效的系统提示词（pi 原生 + 技能注入，只读展示）
+  ipcMain.handle('settings:getSystemPrompt', () => service.getSystemPrompt())
 
   ipcMain.handle('settings:setTheme', (_event, id: unknown) => {
     if (typeof id !== 'string' || !id.trim()) throw new Error('invalid theme id')
     service.setThemeColor(id.trim())
   })
 
+  ipcMain.handle('settings:setThemeMode', (_event, mode: unknown) => {
+    if (mode !== 'light' && mode !== 'dark' && mode !== 'system') throw new Error('invalid theme mode')
+    service.setThemeMode(mode)
+  })
+
   // ---- 工作区 ----
   ipcMain.handle('workspaces:list', () =>
     service.listWorkspaces().catch((err: unknown) => {

apps/desktop/src/main/pi/agent-service.ts

@@ -1,4 +1,5 @@
 import { app, dialog, shell } from 'electron'
+import { nativeTheme } from 'electron'
 import { existsSync, mkdirSync, readFileSync, readdirSync, statSync, writeFileSync } from 'node:fs'
 import { dirname, join } from 'node:path'
 import {
@@ -39,6 +40,7 @@ import type {
   SessionStatsInfo,
   SkillDetail,
   ThinkingLevel,
+  ThemeMode,
   WorkspaceFile,
   WorkspaceMeta
 } from '@shared/types'
@@ -63,7 +65,7 @@ export class AgentService {
   private flushTimer: NodeJS.Timeout | null = null
   private attached: AgentSession | null = null
   private unsubscribeAttached: (() => void) | null = null
-  private settings: AppSettings = { systemPrompt: '' }
+  private settings: AppSettings = {}
   /** 当前工作区目录（agent cwd），会话按目录隔离 */
   private workspaceDir = ''
   private approvalsRegistered = false
@@ -73,6 +75,13 @@ export class AgentService {
   private skillsEstimate: { cwd: string; value: number } | null = null
   readonly approvals = new ApprovalService()
 
+  constructor() {
+    // 设置同步读入 + 应用持久化的深浅色偏好（nativeTheme 会影响渲染层
+    // prefers-color-scheme 与原生控件配色；窗口创建前生效可避免首帧闪错色）
+    this.loadSettings()
+    nativeTheme.themeSource = this.settings.themeMode ?? 'system'
+  }
+
   /** 工作区根目录：文档/Inkreach，每个子目录 = 一个工作区 */
   get workspacesRoot(): string {
     return join(app.getPath('documents'), 'Inkreach')
@@ -94,7 +103,6 @@ export class AgentService {
     try {
       const raw = JSON.parse(readFileSync(this.settingsFile, 'utf8')) as Partial<AppSettings>
       this.settings = {
-        systemPrompt: typeof raw.systemPrompt === 'string' ? raw.systemPrompt : '',
         workspace: typeof raw.workspace === 'string' ? raw.workspace : undefined,
         customWorkspaces: Array.isArray(raw.customWorkspaces)
           ? raw.customWorkspaces.filter((p): p is string => typeof p === 'string')
@@ -102,10 +110,11 @@ export class AgentService {
         // 历史版本存过 autoEdit/plan，统一收敛回 confirm
         permissionMode:
           raw.permissionMode === 'full' ? 'full' : 'confirm',
-        themeColor: typeof raw.themeColor === 'string' ? raw.themeColor : undefined
+        themeColor: typeof raw.themeColor === 'string' ? raw.themeColor : undefined,
+        themeMode: raw.themeMode === 'light' || raw.themeMode === 'dark' ? raw.themeMode : 'system'
       }
     } catch {
-      this.settings = { systemPrompt: '', permissionMode: this.permissionMode }
+      this.settings = { permissionMode: this.permissionMode, themeMode: 'system' }
     }
     this.permissionMode = this.settings.permissionMode ?? 'confirm'
     this.initWorkspaces()
@@ -258,7 +267,6 @@ export class AgentService {
         cwd: targetCwd,
         agentDir: targetAgentDir,
         resourceLoaderOptions: {
-          ...(this.settings.systemPrompt.trim() ? { systemPrompt: this.settings.systemPrompt } : {}),
           extensionFactories: [
             createApprovalExtension(this.approvals, TOOLS_REQUIRING_APPROVAL, () => this.permissionMode)
           ]
@@ -1054,17 +1062,45 @@ export class AgentService {
     this.emitSwitched(session)
   }
 
+  /** 在会话末尾分叉出新会话（pi fork：复制到新会话文件，原会话保留不动）。
+   * fork 后 runtime 重挂新会话，rebind 回调负责发 session_switched。 */
+  async forkSession(): Promise<void> {
+    const runtime = await this.getRuntime()
+    const session = runtime.session
+    if (session.isStreaming) {
+      await session.abort()
+    }
+    const leafId = session.sessionManager.getLeafId()
+    if (!leafId) {
+      throw new Error('会话还没有可分叉的内容')
+    }
+    const result = await runtime.fork(leafId, { position: 'at' })
+    if (result.cancelled) return
+  }
+
   // ---- 应用设置 ----
 
   getSettings(): AppSettings {
     return { ...this.settings }
   }
 
-  /** 更新系统提示词后重建运行时（continueRecent 重新挂载当前最近会话，历史保留） */
-  async setSystemPrompt(text: string): Promise<void> {
-    this.settings = { ...this.settings, systemPrompt: text }
+  /** 当前生效的系统提示词（pi 原生提示词 + 技能注入，只读展示用） */
+  async getSystemPrompt(): Promise<string> {
+    const runtime = await this.getRuntime()
+    return runtime.session.systemPrompt
+  }
+
+  /** 深浅色模式：写入 Electron nativeTheme（渲染层 prefers-color-scheme 随之变化）并持久化 */
+  setThemeMode(mode: ThemeMode): void {
+    this.settings = { ...this.settings, themeMode: mode }
+    this.saveSettings()
+    nativeTheme.themeSource = mode
+  }
+
+  /** 主题色偏好（纯外观，仅持久化；渲染层负责应用） */
+  setThemeColor(id: string): void {
+    this.settings = { ...this.settings, themeColor: id }
     this.saveSettings()
-    await this.rebuildRuntime()
   }
 
   /** 切换权限模式：即时生效（审批扩展每笔工具调用实时读取），并广播给渲染层 */
@@ -1078,12 +1114,6 @@ export class AgentService {
     }
   }
 
-  /** 主题色偏好（纯外观，仅持久化；渲染层负责应用） */
-  setThemeColor(id: string): void {
-    this.settings = { ...this.settings, themeColor: id }
-    this.saveSettings()
-  }
-
   private async rebuildRuntime(): Promise<void> {
     const old = this.runtime
     this.runtime = null