diff --git a/apps/desktop/electron/main.ts b/apps/desktop/electron/main.ts
index 13d9deff4d..0affc0631c 100644
--- a/apps/desktop/electron/main.ts
+++ b/apps/desktop/electron/main.ts
@@ -415,7 +415,7 @@ import {
   windowsUpdatePrerequisiteError,
   wrapHandoffForDetachedConsole
 } from './updater-process'
-import { registerUserAccountIpc } from './user-account-ipc'
+import { PluginApiError, registerUserAccountIpc } from './user-account-ipc'
 import {
   formatBlockerMessage,
   formatProbeFailedMessage,
@@ -8009,7 +8009,39 @@ registerUserAccountIpc({
   },
   fetcher: fetch as any,
   readMachineBindingState: () =>
-    fs.readFileSync(path.join(resolveHermesHome(), 'mercury-relay', 'state.json'), 'utf8')
+    fs.readFileSync(path.join(resolveHermesHome(), 'mercury-relay', 'state.json'), 'utf8'),
+  // 本机 gateway 插件管理面（§21 DB-T4b）：经 dashboard 会话令牌走
+  // /api/plugins/mercury-relay/*；FastAPI {detail} 即稳定 code。
+  callPluginApi: async (apiPath: string, body: Record<string, unknown>) => {
+    let descriptor
+
+    try {
+      descriptor = await ensureBackend(primaryProfileKey(), { passive: true })
+    } catch {
+      throw new PluginApiError('plugin_unreachable', 0)
+    }
+
+    try {
+      return await fetchJson(`${descriptor.baseUrl}/api/plugins/mercury-relay/${apiPath}`, descriptor.token, {
+        method: 'POST',
+        body
+      })
+    } catch (error: any) {
+      const status = typeof error?.statusCode === 'number' ? error.statusCode : 0
+      let code = status > 0 ? 'server' : 'plugin_unreachable'
+
+      try {
+        const detail = JSON.parse(String(error?.message || '').replace(/^\d+:\s*/, ''))?.detail
+
+        if (typeof detail === 'string' && /^[a-z][a-z0-9_]{1,63}$/.test(detail)) {code = detail}
+      } catch {
+        // 非 JSON 错误体：保留归纳码
+      }
+
+      throw new PluginApiError(code, status)
+    }
+  },
+  machineName: os.hostname()
 })
 
 function _loadNativeTokens(baseUrl: string): NativeTokenSet | null {
diff --git a/apps/desktop/electron/preload.ts b/apps/desktop/electron/preload.ts
index bafd3dd58b..b2d598b231 100644
--- a/apps/desktop/electron/preload.ts
+++ b/apps/desktop/electron/preload.ts
@@ -44,7 +44,10 @@ contextBridge.exposeInMainWorld('hermesDesktop', {
     registerStart: payload => ipcRenderer.invoke('hermes:account:register-start', payload),
     registerResend: payload => ipcRenderer.invoke('hermes:account:register-resend', payload),
     resetRequest: payload => ipcRenderer.invoke('hermes:account:reset-request', payload),
-    resetConfirm: payload => ipcRenderer.invoke('hermes:account:reset-confirm', payload)
+    resetConfirm: payload => ipcRenderer.invoke('hermes:account:reset-confirm', payload),
+    bindingStatus: () => ipcRenderer.invoke('hermes:account:binding-status'),
+    bindMachine: () => ipcRenderer.invoke('hermes:account:bind-machine'),
+    unbindMachine: () => ipcRenderer.invoke('hermes:account:unbind-machine')
   },
   // Registry-scoped backend resolution: { connectionId, profile } → descriptor.
   getConnectionFor: payload => ipcRenderer.invoke('hermes:connection:for', payload),
diff --git a/apps/desktop/electron/relay-account.ts b/apps/desktop/electron/relay-account.ts
index 4efb3c3d8b..24402cb95d 100644
--- a/apps/desktop/electron/relay-account.ts
+++ b/apps/desktop/electron/relay-account.ts
@@ -294,3 +294,24 @@ export async function relayAccountBindingOwner(
     throw error
   }
 }
+
+/**
+ * U-6 解绑前置：用户会话撤销自己的 installation（202 受理即成功）。
+ * 404 not_visible = 已不在名下，幂等放行；其余错误照常抛。
+ */
+export async function relayAccountDeleteInstallation(
+  site: string,
+  accessToken: string,
+  installationId: string,
+  fetcher: FetchLike
+): Promise<void> {
+  try {
+    await request(fetcher, `${site}/api/v2/installations/${encodeURIComponent(installationId)}`, {
+      method: 'DELETE',
+      headers: { authorization: `Bearer ${accessToken}` }
+    })
+  } catch (error) {
+    if (error instanceof RelayAccountError && error.status === 404) {return}
+    throw error
+  }
+}
diff --git a/apps/desktop/electron/user-account-ipc.test.ts b/apps/desktop/electron/user-account-ipc.test.ts
index 8483a2b235..00ef1f15e3 100644
--- a/apps/desktop/electron/user-account-ipc.test.ts
+++ b/apps/desktop/electron/user-account-ipc.test.ts
@@ -87,7 +87,7 @@ test('login 持久化会话并返回 profile；token 不出 IPC 返回值', asyn
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher } = loginOkFetcher()
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
 
   const result = await handlers.get('hermes:account:login')!(null, {
     site: 'https://relay.example.com/',
@@ -108,7 +108,7 @@ test('status 未登录返回 loggedIn:false', async () => {
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher } = loginOkFetcher()
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   assert.deepEqual(await handlers.get('hermes:account:status')!(null), { loggedIn: false })
 })
 
@@ -134,7 +134,7 @@ test('me 401 → 自动 refresh 一次重试成功，轮换后的令牌落盘',
     return { status: 200, body: {} }
   })
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
   const me = await handlers.get('hermes:account:me')!(null)
   assert.equal(me.profile.email, 'u@example.com')
@@ -164,7 +164,7 @@ test('refresh 也被拒 = 硬会话终点：本地清零并上报 sessionExpired
     return { status: 200, body: {} }
   })
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
   const status = await handlers.get('hermes:account:status')!(null)
   assert.deepEqual(status, { loggedIn: false, sessionExpired: true })
@@ -186,7 +186,7 @@ test('relay 不可达但本地会话在：status 标离线并回缓存 profile +
     return { ok: true, status: 200, json: async () => ME, text: async () => '' }
   }
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
   online = false
   const status = await handlers.get('hermes:account:status')!(null)
@@ -210,7 +210,7 @@ test('logout 尽力通知服务端，本地清零；服务端 401 不阻塞', as
     return { status: 200, body: {} }
   })
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
   const result = await handlers.get('hermes:account:logout')!(null)
   assert.deepEqual(result, { ok: true })
@@ -218,6 +218,20 @@ test('logout 尽力通知服务端，本地清零；服务端 401 不阻塞', as
   assert.deepEqual(await handlers.get('hermes:account:status')!(null), { loggedIn: false })
 })
 
+function register(deps: {
+  ipcMain: ReturnType<typeof fakeIpcMain>['ipcMain']
+  io: UserAccountStoreIo
+  fetcher: FetchLike
+  readMachineBindingState: () => string
+  callPluginApi?: (path: string, body: Record<string, unknown>) => Promise<any>
+}): void {
+  registerUserAccountIpc({
+    ...deps,
+    callPluginApi: deps.callPluginApi ?? (async () => { throw new Error('unexpected plugin api call') }),
+    machineName: 'test-machine'
+  })
+}
+
 function unbound(): string {
   throw new Error('ENOENT')
 }
@@ -257,7 +271,7 @@ test('U-5：本机绑定属于登录者本人 → 放行', async () => {
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher } = u5Fetcher('u@example.com', ['inst-1'])
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
+  register({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
 
   const result = await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u@example.com', password: 'pw' })
   assert.equal(result.ok, true)
@@ -268,7 +282,7 @@ test('U-5：他账号登录 → 当场销毁会话，返回锁码 + 绑定者邮
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher, calls } = u5Fetcher('owner@example.com', ['inst-other'])
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
+  register({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
 
   const result = await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'intruder@example.com', password: 'pw' })
   assert.deepEqual(result, { ok: false, code: 'machine_bound_to_other', binderEmail: 'owner@example.com' })
@@ -282,7 +296,7 @@ test('U-5：绑定在别的站点 → 同样拒绝', async () => {
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher } = u5Fetcher(null, [])
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
+  register({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
 
   const result = await handlers.get('hermes:account:login')!(null, { site: 'https://other', email: 'u@example.com', password: 'pw' })
   assert.equal(result.ok, false)
@@ -294,7 +308,7 @@ test('U-5：绑定状态损坏 fail-closed，新会话一并销毁', async () =>
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher, calls } = u5Fetcher(null, [])
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: () => '{broken json' })
+  register({ ipcMain, io, fetcher, readMachineBindingState: () => '{broken json' })
 
   const result = await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u@example.com', password: 'pw' })
   assert.deepEqual(result, { ok: false, code: 'binding_state_invalid' })
@@ -306,7 +320,7 @@ test('login 预期失败走结构化返回：invalid_credentials / login_rate_li
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher } = makeFetcher(() => ({ status: 401, text: 'invalid_credentials' }))
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   assert.deepEqual(await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' }), {
     ok: false,
     code: 'invalid_credentials'
@@ -318,7 +332,7 @@ test('register/reset 四通道透传路径与参数', async () => {
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher, calls } = makeFetcher(() => ({ status: 202, body: { status: 'verification_sent' } }))
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
 
   assert.deepEqual(await handlers.get('hermes:account:register-start')!(null, { site: 'https://r', email: 'u@e.c', password: 'pw' }), { ok: true })
   assert.deepEqual(await handlers.get('hermes:account:register-resend')!(null, { site: 'https://r', email: 'u@e.c' }), { ok: true })
@@ -341,7 +355,7 @@ test('register-start 失败码透传（weak_password / registration_rate_limited
   const { handlers, ipcMain } = fakeIpcMain()
   const { io } = fakeIo()
   const { fetcher } = makeFetcher(() => ({ status: 400, text: 'weak_password' }))
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   assert.deepEqual(await handlers.get('hermes:account:register-start')!(null, { site: 'https://r', email: 'u@e.c', password: 'x' }), {
     ok: false,
     code: 'weak_password'
@@ -364,7 +378,7 @@ test('update-profile：PATCH /me 白名单三字段，合并回完整快照落
     return { status: 200, body: {} }
   })
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
 
   const result = await handlers.get('hermes:account:update-profile')!(null, {
@@ -399,7 +413,7 @@ test('update-profile：空补丁不出网；服务端拒绝码透传', async ()
     return { status: 200, body: {} }
   })
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
   const before = calls.length
   assert.deepEqual(await handlers.get('hermes:account:update-profile')!(null, { email: 'x@y.z' }), {
@@ -423,7 +437,7 @@ test('update-profile：服务端 403 profile_self_service_disabled 结构化透
     return { status: 200, body: {} }
   })
 
-  registerUserAccountIpc({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
   await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
   assert.deepEqual(await handlers.get('hermes:account:update-profile')!(null, { nickname: 'x' }), {
     ok: false,
@@ -432,3 +446,249 @@ test('update-profile：服务端 403 profile_self_service_disabled 结构化透
   // 失败不落盘改动
   assert.equal(loadUserAccount(io)?.profile?.nickname, '小赫')
 })
+
+// ---------- DB-T4b：绑定打通 + U-6 解绑全清（§21） ----------------------------
+
+test('binding-status：未绑定 / 已绑定只回 site+installationId / 损坏 fail-closed 标记', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher } = loginOkFetcher()
+  register({ ipcMain, io, fetcher, readMachineBindingState: unbound })
+  assert.deepEqual(await handlers.get('hermes:account:binding-status')!(null), { bound: false })
+})
+
+test('binding-status：已绑定不含凭据字段；损坏报 stateInvalid', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher } = loginOkFetcher()
+  register({ ipcMain, io, fetcher, readMachineBindingState: () => BINDING_STATE })
+  const bound = await handlers.get('hermes:account:binding-status')!(null)
+  assert.deepEqual(bound, { bound: true, site: 'https://r', installationId: 'inst-1' })
+  assert.equal(JSON.stringify(bound).includes('SHOULD-NOT-BE-READ'), false)
+
+  const { handlers: h2, ipcMain: i2 } = fakeIpcMain()
+  register({ ipcMain: i2, io: fakeIo().io, fetcher, readMachineBindingState: () => '{broken' })
+  assert.deepEqual(await h2.get('hermes:account:binding-status')!(null), { bound: false, stateInvalid: true })
+})
+
+test('bind-machine：插件收到 site+session_token(Bearer 等价物)+suggested_name；不落 email/password', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher } = loginOkFetcher()
+  const pluginCalls: { path: string; body: any }[] = []
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: unbound,
+    callPluginApi: async (path, body) => {
+      pluginCalls.push({ path, body })
+
+      return { state: 'bound', created: true }
+    }
+  })
+  await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
+
+  const result = await handlers.get('hermes:account:bind-machine')!(null)
+  assert.deepEqual(result, { ok: true, state: 'bound' })
+  assert.equal(pluginCalls.length, 1)
+  assert.equal(pluginCalls[0].path, 'identity/login')
+  assert.equal(pluginCalls[0].body.site, 'https://r')
+  assert.equal(pluginCalls[0].body.session_token, 'AT-1')
+  assert.equal(pluginCalls[0].body.suggested_name, 'test-machine')
+  assert.equal('password' in pluginCalls[0].body, false)
+})
+
+test('bind-machine：已绑定不出网（already_bound）；未登录 not_logged_in', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher } = loginOkFetcher()
+  let pluginCalls = 0
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: () => BINDING_STATE,
+    callPluginApi: async () => {
+      pluginCalls += 1
+
+      return { state: 'bound' }
+    }
+  })
+  assert.deepEqual(await handlers.get('hermes:account:bind-machine')!(null), { ok: false, code: 'already_bound' })
+  assert.equal(pluginCalls, 0)
+})
+
+test('bind-machine：binding_pending 原样透传确认码', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher } = loginOkFetcher()
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: unbound,
+    callPluginApi: async () => ({ state: 'binding_pending', code: 'MR-7K2P-Q9', expires_at: '2026-09-19T12:00:00Z' })
+  })
+  await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
+  assert.deepEqual(await handlers.get('hermes:account:bind-machine')!(null), {
+    ok: true,
+    state: 'binding_pending',
+    code: 'MR-7K2P-Q9',
+    expiresAt: '2026-09-19T12:00:00Z'
+  })
+})
+
+test('unbind-machine（U-6）：服务端撤销 → 插件 purge → 删所有会话；本地会话清零', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+
+  const { fetcher, calls } = makeFetcher(url => {
+    if (url.endsWith('/auth/login')) {return { status: 200, body: TOKENS }}
+
+    if (url.endsWith('/me')) {return { status: 200, body: ME }}
+
+    if (url.endsWith('/installations')) {return { status: 200, body: { items: [{ id: 'inst-1' }] } }}
+
+    if (url.includes('/installations/')) {return { status: 202, body: { status: 'requested' } }}
+
+    return { status: 200, body: {} }
+  })
+
+  const pluginCalls: string[] = []
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: () => BINDING_STATE,
+    callPluginApi: async path => {
+      pluginCalls.push(path)
+
+      return { state: 'purged' }
+    }
+  })
+  await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
+  assert.notEqual(loadUserAccount(io), null)
+
+  const result = await handlers.get('hermes:account:unbind-machine')!(null)
+  assert.deepEqual(result, { ok: true })
+  // 1. 服务端撤销带用户 Bearer
+  const revoke = calls.find(c => c.url.includes('/installations/'))
+  assert.equal(revoke?.init?.method, 'DELETE')
+  assert.equal(revoke?.init?.headers?.authorization, 'Bearer AT-1')
+  assert.ok(revoke!.url.endsWith('/installations/inst-1'))
+  // 2. 插件 purge
+  assert.deepEqual(pluginCalls, ['identity/purge'])
+  // 3. 会话清零 + 尽力服务端吊销
+  assert.equal(loadUserAccount(io), null)
+  assert.ok(calls.some(c => c.url.endsWith('/auth/logout')))
+  assert.deepEqual(await handlers.get('hermes:account:status')!(null), { loggedIn: false })
+})
+
+test('unbind-machine：服务端撤销失败不阻塞本地全清（尽力语义）', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+
+  const { fetcher } = makeFetcher(url => {
+    if (url.endsWith('/auth/login')) {return { status: 200, body: TOKENS }}
+
+    if (url.endsWith('/me')) {return { status: 200, body: ME }}
+
+    if (url.endsWith('/installations')) {return { status: 200, body: { items: [{ id: 'inst-1' }] } }}
+
+    if (url.includes('/installations/')) {return { status: 503, text: 'server' }}
+
+    return { status: 200, body: {} }
+  })
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: () => BINDING_STATE,
+    callPluginApi: async () => ({ state: 'purged' })
+  })
+  await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
+  assert.deepEqual(await handlers.get('hermes:account:unbind-machine')!(null), { ok: true })
+  assert.equal(loadUserAccount(io), null)
+})
+
+test('unbind-machine：插件不可达则结构化失败且会话保留（不留半清假象）', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+
+  const { fetcher } = makeFetcher(url => {
+    if (url.endsWith('/auth/login')) {return { status: 200, body: TOKENS }}
+
+    if (url.endsWith('/me')) {return { status: 200, body: ME }}
+
+    if (url.endsWith('/installations')) {return { status: 200, body: { items: [{ id: 'inst-1' }] } }}
+
+    return { status: 200, body: {} }
+  })
+
+  const { PluginApiError } = await import('./user-account-ipc')
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: () => BINDING_STATE,
+    callPluginApi: async () => {
+      throw new PluginApiError('plugin_unreachable', 0)
+    }
+  })
+  await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
+  assert.deepEqual(await handlers.get('hermes:account:unbind-machine')!(null), { ok: false, code: 'plugin_unreachable' })
+  assert.notEqual(loadUserAccount(io), null)
+})
+
+test('unbind-machine：未绑定 not_bound，不出网', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher, calls } = loginOkFetcher()
+  let pluginCalls = 0
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: unbound,
+    callPluginApi: async () => {
+      pluginCalls += 1
+
+      return {}
+    }
+  })
+  assert.deepEqual(await handlers.get('hermes:account:unbind-machine')!(null), { ok: false, code: 'not_bound' })
+  assert.equal(pluginCalls, 0)
+  assert.equal(calls.some(c => c.url.includes('/installations/')), false)
+})
+
+test('登出≠解绑：logout 绝不碰插件 API 与 installation 端点', async () => {
+  const { handlers, ipcMain } = fakeIpcMain()
+  const { io } = fakeIo()
+  const { fetcher, calls } = loginOkFetcher()
+  let pluginCalls = 0
+
+  register({
+    ipcMain,
+    io,
+    fetcher,
+    readMachineBindingState: () => BINDING_STATE,
+    callPluginApi: async () => {
+      pluginCalls += 1
+
+      return {}
+    }
+  })
+  await handlers.get('hermes:account:login')!(null, { site: 'https://r', email: 'u', password: 'p' })
+  calls.length = 0
+  await handlers.get('hermes:account:logout')!(null)
+  assert.equal(pluginCalls, 0)
+  assert.equal(calls.some(c => c.url.includes('/installations/')), false)
+})
diff --git a/apps/desktop/electron/user-account-ipc.ts b/apps/desktop/electron/user-account-ipc.ts
index 66d24eaf7b..8cd255362b 100644
--- a/apps/desktop/electron/user-account-ipc.ts
+++ b/apps/desktop/electron/user-account-ipc.ts
@@ -21,6 +21,7 @@ import {
   canonicalizeRelaySite,
   type FetchLike,
   relayAccountBindingOwner,
+  relayAccountDeleteInstallation,
   RelayAccountError,
   relayAccountFetchMe,
   relayAccountListInstallationIds,
@@ -43,17 +44,37 @@ import {
 
 export const USER_ACCOUNT_CLIENT_ID = 'hermes-desktop'
 
+/** 插件管理面（/api/plugins/mercury-relay/*）失败的结构化形态。 */
+export class PluginApiError extends Error {
+  readonly code: string
+  readonly status: number
+
+  constructor(code: string, status: number) {
+    super(code)
+    this.code = code
+    this.status = status
+  }
+}
+
 export interface UserAccountIpcDeps {
   ipcMain: { handle: (channel: string, fn: (event: any, payload?: any) => Promise<any>) => void }
   io: UserAccountStoreIo
   fetcher: FetchLike
   /** 插件 state.json 原文；ENOENT 抛错视为未绑定。 */
   readMachineBindingState: () => string
+  /**
+   * 调本机 gateway 的插件管理 API（路径如 'identity/login'）。
+   * 非 2xx 必须抛 PluginApiError（detail 即 code）；gateway 不可达抛
+   * PluginApiError('plugin_unreachable', 0)。
+   */
+  callPluginApi: (path: string, body: Record<string, unknown>) => Promise<any>
+  /** 绑定时的 suggested_name（本机显示名）。 */
+  machineName: string
 }
 
 /** 预期内的失败走结构化返回（renderer 按 code 上文案）；意外仍抛。 */
 function failure(error: unknown): { ok: false; code: string } {
-  if (error instanceof RelayAccountError) {
+  if (error instanceof RelayAccountError || error instanceof PluginApiError) {
     return { ok: false, code: error.code }
   }
 
@@ -61,7 +82,7 @@ function failure(error: unknown): { ok: false; code: string } {
 }
 
 export function registerUserAccountIpc(deps: UserAccountIpcDeps): void {
-  const { ipcMain, io, fetcher, readMachineBindingState } = deps
+  const { ipcMain, io, fetcher, readMachineBindingState, callPluginApi, machineName } = deps
   let cached: StoredUserAccount | null = null
 
   function current(): StoredUserAccount | null {
@@ -241,6 +262,115 @@ export function registerUserAccountIpc(deps: UserAccountIpcDeps): void {
     }
   })
 
+  ipcMain.handle('hermes:account:binding-status', async () => {
+    let binding
+
+    try {
+      binding = loadMachineBinding(readMachineBindingState)
+    } catch (error) {
+      if (error instanceof MachineBindingError) {return { bound: false, stateInvalid: true }}
+
+      throw error
+    }
+
+    if (!binding) {return { bound: false }}
+
+    return { bound: true, site: binding.site, installationId: binding.installationId }
+  })
+
+  /**
+   * U-1/RL-A1 免口令绑定：用当前用户会话 access token 让本机插件完成
+   * 绑定（口令永远不再经手）。插件 401（会话失效）并入 withSession 的
+   * 刷新重试链。binding_pending（双因素）原样透传给 UI。
+   */
+  ipcMain.handle('hermes:account:bind-machine', async () => {
+    let existing
+
+    try {
+      existing = loadMachineBinding(readMachineBindingState)
+    } catch (error) {
+      if (error instanceof MachineBindingError) {return { ok: false, code: 'binding_state_invalid' }}
+
+      throw error
+    }
+
+    if (existing) {return { ok: false, code: 'already_bound' }}
+
+    try {
+      const result = await withSession(async session => {
+        try {
+          return await callPluginApi('identity/login', {
+            site: session.site,
+            session_token: session.accessToken,
+            suggested_name: machineName
+          })
+        } catch (error) {
+          if (error instanceof PluginApiError && error.status === 401) {
+            throw new RelayAccountError(error.code, 401)
+          }
+
+          throw error
+        }
+      })
+
+      if (result?.state === 'binding_pending') {
+        return {
+          ok: true,
+          state: 'binding_pending',
+          code: typeof result.code === 'string' ? result.code : '',
+          expiresAt: typeof result.expires_at === 'string' ? result.expires_at : ''
+        }
+      }
+
+      if (result?.state !== 'bound') {return { ok: false, code: 'server' }}
+
+      return { ok: true, state: 'bound' }
+    } catch (error) {
+      return failure(error)
+    }
+  })
+
+  /**
+   * U-6 解绑 = 全清：服务端撤销 installation（尽力，404 幂等；会话死/
+   * 网络断不阻塞）→ 插件 purge（清绑定含 R + 抹 H，机器回裸态）→
+   * 删除所有会话（本地用户槽清零 + 尽力服务端吊销）。插件不可达时
+   * 结构化失败、会话保留，用户可重试——不留下"半清"的确定态假象。
+   */
+  ipcMain.handle('hermes:account:unbind-machine', async () => {
+    let binding
+
+    try {
+      binding = loadMachineBinding(readMachineBindingState)
+    } catch (error) {
+      if (error instanceof MachineBindingError) {return { ok: false, code: 'binding_state_invalid' }}
+
+      throw error
+    }
+
+    if (!binding) {return { ok: false, code: 'not_bound' }}
+
+    try {
+      await withSession(session => relayAccountDeleteInstallation(session.site, session.accessToken, binding.installationId, fetcher))
+    } catch {
+      // 尽力撤销：本地清零照旧
+    }
+
+    try {
+      await callPluginApi('identity/purge', {})
+    } catch (error) {
+      return failure(error)
+    }
+
+    const account = current()
+
+    if (account) {
+      await relayAccountLogout(account.session, fetcher)
+      store(null)
+    }
+
+    return { ok: true }
+  })
+
   ipcMain.handle('hermes:account:logout', async () => {
     const account = current()
 
diff --git a/apps/desktop/src/global.d.ts b/apps/desktop/src/global.d.ts
index 1a7349da3f..684ae270f7 100644
--- a/apps/desktop/src/global.d.ts
+++ b/apps/desktop/src/global.d.ts
@@ -13,6 +13,8 @@ import type {
 } from './store/pet-overlay'
 import type { QuickEntryStatePush, QuickEntryStatus, QuickEntrySubmitPayload } from './store/quick-entry'
 import type {
+  HermesUserAccountBindingStatus,
+  HermesUserAccountBindResult,
   HermesUserAccountLoginResult,
   HermesUserAccountOpResult,
   HermesUserAccountProfile,
@@ -57,6 +59,9 @@ declare global {
         registerResend: (payload: { site: string; email: string }) => Promise<HermesUserAccountOpResult>
         resetRequest: (payload: { site: string; email: string }) => Promise<HermesUserAccountOpResult>
         resetConfirm: (payload: { site: string; email: string; code: string; password: string }) => Promise<HermesUserAccountOpResult>
+        bindingStatus: () => Promise<HermesUserAccountBindingStatus>
+        bindMachine: () => Promise<HermesUserAccountBindResult>
+        unbindMachine: () => Promise<{ ok: boolean; code?: string }>
       }
       // Registry-scoped backend resolution: dial (connectionId, profile). An
       // empty/local connectionId delegates to the legacy getConnection path.
diff --git a/apps/desktop/src/store/user-account.ts b/apps/desktop/src/store/user-account.ts
index 42e2daa800..3d52869447 100644
--- a/apps/desktop/src/store/user-account.ts
+++ b/apps/desktop/src/store/user-account.ts
@@ -58,6 +58,16 @@ export type HermesUserAccountLoginResult =
   | { ok: true; site: string; profile: HermesUserAccountProfile }
   | { ok: false; code: string; binderEmail?: string | null }
 
+/** 本机绑定状态（§21 DB-T4b）：只含 site + installationId，凭据绝不出 main。 */
+export type HermesUserAccountBindingStatus =
+  | { bound: false; stateInvalid?: boolean }
+  | { bound: true; site: string; installationId: string }
+
+export type HermesUserAccountBindResult =
+  | { ok: true; state: 'bound' }
+  | { ok: true; state: 'binding_pending'; code: string; expiresAt: string }
+  | { ok: false; code: string }
+
 /** 登录/注册/找回的可预期失败码（renderer 按码上文案，绝不回显服务端原文）。 */
 export type UserAccountFailureCode =
   | 'account_locked'
@@ -187,3 +197,33 @@ export function userAccountDisplayName(profile: HermesUserAccountProfile | null)
 
   return at > 0 ? profile.email.slice(0, at) : profile.email
 }
+
+/** 本机绑定状态（只读插件 state.json 的非敏感二字段）。 */
+export function userAccountBindingStatus(): Promise<HermesUserAccountBindingStatus> {
+  return bridge().bindingStatus()
+}
+
+/** 绑定本机到当前账号（§21 U-1 免口令）。失败抛 UserAccountFailure；pending 返回确认码。 */
+export async function userAccountBindMachine(): Promise<{ state: 'bound' } | { state: 'binding_pending'; code: string; expiresAt: string }> {
+  const result = await bridge().bindMachine()
+
+  if (!result.ok) {throw new UserAccountFailure(result.code)}
+
+  if (result.state === 'binding_pending') {
+    return { state: 'binding_pending', code: result.code, expiresAt: result.expiresAt }
+  }
+
+  return { state: 'bound' }
+}
+
+/**
+ * U-6 解绑 = 全清：服务端撤销 + 插件 purge（含 H）+ 删所有会话。
+ * 成功后本地会话已不在，状态落 signed_out。
+ */
+export async function userAccountUnbindMachine(): Promise<void> {
+  const result = await bridge().unbindMachine()
+
+  if (!result.ok) {throw new UserAccountFailure(result.code ?? 'server')}
+
+  $userAccount.set({ status: 'signed_out' })
+}