fix(host): 根因——spawn 的 detached:true 让 PowerShell 起来即退；feat: 三种跟随方式（默认跟随前台）

根因（对照实验）：spawn('powershell', [...], {detached:true}) 在 Windows 上 → 子进程 exit 0、
脚本一行没跑（日志里连 start 都没有），表现就是『点打开没反应』；detached:false 完全正常。
现在 spawnShell：绝对路径优先 + 不 detached + 等心跳确认，失败把原因写进 status notes。

跟随方式（用户需求：切到哪个会话就跟哪个，且可配置）：
- front（默认）跟随前台：客户端半订阅 uiSession.current，会话一换就上报 /window{action:front}
- latest 跟随最新事件；pinned 固定在 ⇄ 里选中的会话
设置入口：设置→悬浮窗（模式三选一）；浮窗 ⇄ 里点会话=切到 pinned
快照新增 follow/front 字段；/window 支持 action=follow|front

lib/client.js

@@ -49,17 +49,17 @@ window.__ModuleLoader__.load({
     })
     const muted = { opacity: 0.7, fontSize: 12, lineHeight: 1.7 }
 
-    /** 宿主可达性 + 浮窗存活状态 */
+    /** 宿主可达性 + 浮窗存活状态 + 跟随方式 */
     function useStatus() {
-      const [status, setStatus] = React.useState({ ok: false, alive: false, text: '', session: null })
+      const [status, setStatus] = React.useState({ ok: false, alive: false, text: '', session: null, follow: 'front' })
       const [busy, setBusy] = React.useState(false)
       const refresh = React.useCallback(async () => {
         try {
           const r = await callHost('status')
           const s = await readState().catch(() => null)
-          setStatus({ ok: true, alive: !!r.alive, text: r.text || '', session: s })
+          setStatus({ ok: true, alive: !!r.alive, text: r.text || '', session: s, follow: r.follow || (s && s.follow) || 'front' })
         } catch (e) {
-          setStatus({ ok: false, alive: false, text: String(e && e.message || e), session: null })
+          setStatus({ ok: false, alive: false, text: String(e && e.message || e), session: null, follow: 'front' })
         }
       }, [])
       React.useEffect(() => {
@@ -72,7 +72,18 @@ window.__ModuleLoader__.load({
         try { await callHost(action) } catch (e) { /* 宿主离线：状态轮询会显示 */ }
         setTimeout(() => { setBusy(false); refresh() }, 800)
       }, [refresh])
-      return { status, busy, act, refresh }
+      const setFollow = React.useCallback(async (mode) => {
+        setBusy(true)
+        try {
+          await fetch(`${ROUTE}/window`, {
+            method: 'POST',
+            headers: { 'content-type': 'application/json' },
+            body: JSON.stringify({ action: 'follow', mode }),
+          })
+        } catch (e) { }
+        setTimeout(() => { setBusy(false); refresh() }, 500)
+      }, [refresh])
+      return { status, busy, act, setFollow, refresh }
     }
 
     /** 侧边栏底部按钮（设置按钮上方那一排） */
@@ -98,9 +109,15 @@ window.__ModuleLoader__.load({
 
     /** 设置 →「悬浮窗」整页 */
     function FloatSettingsSection() {
-      const { status, busy, act } = useStatus()
+      const { status, busy, act, setFollow } = useStatus()
       const s = status.session || {}
       const m = s.metrics || {}
+      const mode = status.follow || 'front'
+      const modeBtn = (key, label, hint) => h('button', {
+        key, style: btn(mode === key), disabled: busy,
+        title: hint,
+        onClick: () => setFollow(key),
+      }, label)
       return h('div', { style: { padding: '4px 2px', display: 'flex', flexDirection: 'column', gap: 14, maxWidth: 640 } }, [
         h('div', { key: 'h', style: { fontSize: 15, fontWeight: 600 } }, '悬浮窗（会话镜像小窗）'),
         h('div', { key: 'd', style: muted }, '始终置顶、可固定位置/尺寸、抓屏时自动隐身的小窗；把主界面切到后台也能盯着 Agent 干活。'),
@@ -119,6 +136,15 @@ window.__ModuleLoader__.load({
             h('button', { key: 'close', style: btn(false), disabled: busy, onClick: () => act('close') }, '关闭'),
           ]),
         ]),
+        h('div', { key: 'follow', style: card }, [
+          h('div', { key: 't', style: { fontWeight: 600, fontSize: 13 } }, '镜像跟随方式'),
+          h('div', { key: 'row', style: { display: 'flex', gap: 8, flexWrap: 'wrap' } }, [
+            modeBtn('front', '跟随前台（推荐）', '主界面显示哪个会话，浮窗就镜像哪个；切换会话自动跟上'),
+            modeBtn('latest', '跟随最新事件', '哪个会话最新有动静就镜像哪个（多任务并行时会来回跳）'),
+            modeBtn('pinned', '固定某个会话', '固定在浮窗 ⇄ 里选中的那个会话'),
+          ]),
+          h('div', { key: 'hint', style: muted }, '当前：' + (mode === 'front' ? '跟随前台当前对话' : mode === 'latest' ? '跟随最新事件' : '固定在选中的会话')),
+        ]),
         h('div', { key: 'st', style: card }, [
           h('div', { key: 't', style: { fontWeight: 600, fontSize: 13 } }, '当前会话'),
           h('div', { key: 'n', style: muted }, s.title ? String(s.title) : (s.sessionId || '还没有会话')),
@@ -128,7 +154,31 @@ window.__ModuleLoader__.load({
       ])
     }
 
-    const inject = ['slots']
+    const inject = ['slots', 'uiSession']
+
+    /** 把"当前显示的会话"上报给宿主 —— 「跟随前台」就是靠这个做到"切哪个跟哪个" */
+    function reportFront(ctx) {
+      try {
+        const ui = ctx.get('uiSession')
+        const read = () => {
+          try {
+            const cur = ui?.current
+            const id = cur?.value?.key ?? cur?.value?.sessionId ?? cur?.key ?? null
+            if (!id || id === lastFront) return
+            lastFront = id
+            fetch(`${ROUTE}/window`, {
+              method: 'POST',
+              headers: { 'content-type': 'application/json' },
+              body: JSON.stringify({ action: 'front', sessionId: id }),
+            }).catch(() => { })
+          } catch { }
+        }
+        read()
+        // uiSession.current 是 binding source，订阅它就能在切换会话时立刻跟上
+        try { return ui?.current?.subscribe?.(read) || ui?.subscribe?.(read) || null } catch { return null }
+      } catch (e) { console.warn('[float-window] uiSession unavailable', e); return null }
+    }
+    let lastFront = null
 
     /** 客户端半接管 UI 后，把宿主注入的备用按钮摘掉，避免出现两个入口 */
     function claimUi() {
@@ -141,6 +191,7 @@ window.__ModuleLoader__.load({
 
     function apply(ctx) {
       let registered = 0
+      reportFront(ctx)
       try {
         ctx.slots.inject('sidebar.footer.action', () => {
           try {

lib/host.js

@@ -233,7 +233,11 @@ export function apply(ctx, config) {
   const titles = new Map() // sessionId -> 会话标题（来自 session/title 事件）
   const contextWindows = new Map() // sessionId -> 上下文窗口（来自 request/context 事件）
   let lastSessionId = null
-  let pinnedSessionId = null // 用户在浮窗里选中的会话：多会话并行时不再被最新事件抢走
+  let pinnedSessionId = null // 「固定」模式：用户在浮窗里选中的会话，不再被任何事件抢走
+  let frontSessionId = null // 「跟随前台」模式：客户端半上报的当前显示会话（uiSession.current）
+  // 跟随方式：front=跟随前台当前对话（默认）；latest=跟随最新事件；pinned=固定某个会话
+  let followMode = ['front', 'latest', 'pinned'].includes(floatCfg.follow) ? floatCfg.follow : 'front'
+  const activeSessionId = () => (followMode === 'pinned' ? pinnedSessionId : (followMode === 'front' ? (frontSessionId || pinnedSessionId || lastSessionId) : lastSessionId))
 
   function counter(id) {
     let c = counts.get(id)
@@ -244,7 +248,8 @@ export function apply(ctx, config) {
   ctx.on('session/event', (session, event) => {
     try {
       const id = session?.id || session?.sessionId || 'unknown'
-      if (!pinnedSessionId) lastSessionId = id
+      // 「跟随前台」模式下，事件不再改变当前会话（前台由客户端半上报），但仍记录"最新事件"兜底
+      if (!pinnedSessionId || followMode === 'latest') lastSessionId = id
       const c = counter(id)
       const type = String(event?.type || '')
       const d2 = () => event?.data || event || {}
@@ -385,7 +390,7 @@ export function apply(ctx, config) {
 
   function snapshot() {
     const sessions = (() => { try { return ctx.get('sessions')?.list?.() || [] } catch { return [] } })()
-    const activeId = pinnedSessionId || lastSessionId
+    const activeId = activeSessionId()
     let session = sessions.find((s) => s?.id === activeId) || sessions[sessions.length - 1] || null
     const id = session?.id || activeId
     return {
@@ -393,6 +398,8 @@ export function apply(ctx, config) {
       at: Date.now(),
       sessionId: id || null,
       pinned: pinnedSessionId || null,
+      front: frontSessionId || null,
+      follow: followMode,
       title: (id && titles.get(id)) || session?.meta?.title || session?.title || null,
       messages: (id && rows.get(id)) || [],
       metrics: session ? metricsFor(session) : { turns: null, steps: null, tps: null, tokens: null, cacheHit: null, contextUsed: null },
@@ -471,9 +478,17 @@ export function apply(ctx, config) {
         await windowAction(msg.action)
       } else if (msg.cmd === 'watch') {
         // 浮窗切换跟随的会话：'' / null 表示回到"跟随最新"
+        if (msg.mode && ['front', 'latest', 'pinned'].includes(msg.mode)) followMode = msg.mode
         pinnedSessionId = msg.sessionId ? String(msg.sessionId) : null
-        if (pinnedSessionId) lastSessionId = pinnedSessionId
+        if (pinnedSessionId) { followMode = 'pinned'; lastSessionId = pinnedSessionId }
-        log('watch -> ' + (pinnedSessionId || 'latest'))
+        else if (!msg.mode) followMode = 'latest'
+        log(`watch -> mode=${followMode} session=${pinnedSessionId || 'auto'}`)
+      } else if (msg.cmd === 'follow') {
+        if (['front', 'latest', 'pinned'].includes(msg.mode)) {
+          followMode = msg.mode
+          if (msg.mode !== 'pinned') pinnedSessionId = null
+        }
+        log(`outbox follow -> ${followMode}`)
       } else if (msg.cmd === 'session' && msg.action === 'create') {
         const { value } = await hostCall('create', {
           sessionId: randomUUID(),
@@ -600,9 +615,25 @@ export function apply(ctx, config) {
         for await (const c of req) chunks.push(c)
         body = JSON.parse(Buffer.concat(chunks).toString('utf8') || '{}')
       } catch { }
+      // 客户端半的两条上报：前台会话 / 跟随方式
+      if (body.action === 'front') {
+        const sid = body.sessionId ? String(body.sessionId) : null
+        if (sid !== frontSessionId) log(`front -> ${sid || 'none'}`)
+        frontSessionId = sid
+        res.writeHead(200, { ...cors, 'Content-Type': 'application/json; charset=utf-8' })
+        res.end(JSON.stringify({ ok: true, follow: followMode, front: frontSessionId, alive: shellAlive() }))
+        return
+      }
+      if (body.action === 'follow') {
+        if (['front', 'latest', 'pinned'].includes(body.mode)) followMode = body.mode
+        log(`follow mode -> ${followMode}`)
+        res.writeHead(200, { ...cors, 'Content-Type': 'application/json; charset=utf-8' })
+        res.end(JSON.stringify({ ok: true, follow: followMode, alive: shellAlive() }))
+        return
+      }
       const r = await windowAction(body.action)
       res.writeHead(200, { ...cors, 'Content-Type': 'application/json; charset=utf-8' })
-      res.end(JSON.stringify({ ...r, alive: shellAlive() }))
+      res.end(JSON.stringify({ ...r, alive: shellAlive(), follow: followMode }))
       return
     }
     res.writeHead(404, { ...cors, 'Content-Type': 'text/plain; charset=utf-8' })
@@ -644,14 +675,49 @@ export function apply(ctx, config) {
     // 直接起 powershell（隐藏窗口）。**不要**走 `cmd /c start`：那会弹出一个黑色控制台窗口
     // （用户已经看到过：标题 C:\WINDOWS\system32\cmd.exe，且批处理里的中文被 GBK 解析成乱码报错）。
     const ps1 = path.join(REPO, 'shell', 'float-window.ps1')
-    if (!fs.existsSync(ps1)) return { ok: false, error: `shell script not found: ${ps1}` }
+    if (!fs.existsSync(ps1)) {
-    try {
+      const msg = `shell script not found: ${ps1}`
+      log('spawnShell: ' + msg)
+      status.notes.push(`${new Date().toISOString()} spawnShell FAILED ${msg}`)
+      return { ok: false, error: msg }
+    }
+    // 绝对路径优先：DSH 应用进程的 PATH 未必和终端一致，裸名字可能找不到 powershell
+    const sysRoot = process.env.SystemRoot || 'C:\\Windows'
+    const candidates = [
+      path.join(sysRoot, 'System32', 'WindowsPowerShell', 'v1.0', 'powershell.exe'),
+      'powershell.exe',
+      'pwsh.exe',
+    ]
     const { spawn } = await import('node:child_process')
-      spawn('powershell.exe',
+    const before = aliveMtime()
-        ['-NoProfile', '-ExecutionPolicy', 'Bypass', '-WindowStyle', 'Hidden', '-File', ps1],
+    let lastErr = null
-        { detached: true, stdio: 'ignore', windowsHide: true }).unref()
+    for (const exe of candidates) {
-      return { ok: true, via: 'spawn powershell (hidden)' }
+      try {
-    } catch (e) { return { ok: false, error: String(e?.message || e) } }
+        // 注意：**不要**加 detached:true —— 实测在 Windows 上 detached(CREATE_NO_WINDOW) 会让
+        // PowerShell 宿主起来立刻退出（exit code 0、脚本一行都没跑），表现就是"点了打开没反应"。
+        const child = spawn(exe, ['-NoProfile', '-ExecutionPolicy', 'Bypass', '-WindowStyle', 'Hidden', '-File', ps1],
+          { stdio: 'ignore', windowsHide: true })
+        child.on('error', (e) => { lastErr = String(e?.message || e) })
+        child.unref()
+        // 等心跳确认：真的起来了才算成功（否则就是"点了没反应"）
+        for (let i = 0; i < 15; i++) {
+          await new Promise((r) => setTimeout(r, 400))
+          if (aliveMtime() > before) {
+            log(`spawnShell ok via ${exe}`)
+            status.notes.push(`${new Date().toISOString()} spawnShell ok via ${exe}`)
+            writeStatus()
+            return { ok: true, via: exe }
+          }
+          if (lastErr) break
+        }
+        log(`spawnShell: ${exe} produced no heartbeat${lastErr ? ' (' + lastErr + ')' : ''}`)
+      } catch (e) { lastErr = String(e?.message || e) }
+    }
+    const msg = `could not start float window (script=${ps1}, lastError=${lastErr || 'no heartbeat'})`
+    log('spawnShell FAILED: ' + msg)
+    status.notes.push(`${new Date().toISOString()} spawnShell FAILED ${msg}`)
+    writeStatus()
+    return { ok: false, error: msg }
   }
 
   /** 浮窗已经在跑就投递命令，否则按需拉起；投递后要等心跳确认，不能"发给死人" */