diff --git a/src/client/Sidebar.tsx b/src/client/Sidebar.tsx
index 353b03c..51b44df 100644
--- a/src/client/Sidebar.tsx
+++ b/src/client/Sidebar.tsx
@@ -44,6 +44,7 @@ import type { TabDragPayload } from './TabBar.tsx'
 import { relativeTo } from './paths.ts'
 import { OrphanedTab } from './OrphanedTab.tsx'
 import { detectNewDirectSubagent } from './subagent-detect.ts'
+import { detectNewTask } from './subagent-tasks.ts'
 import { t } from './locales.ts'
 import { api, type SessionScope } from './api.ts'
 import css from './sidebar.module.css'
@@ -241,6 +242,28 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
     ctx.betterSidebar?.openTab({ type: 'subagent', title: t('subagent') })
   }, [sessionList, sessionId, store, ctx])
 
+  /**
+   * Task auto-activation: the moment a NEW background task appears for the
+   * current conversation (a task id the previous snapshot lacked), the
+   * auto-open pref is on, and the Tasks tab type is enabled, open the panel
+   * (if collapsed) and focus the Tasks page. Unlike the subagent trigger
+   * (0 → N only), ANY new task id triggers: the agent may start several
+   * tasks in one session, and each should surface. A fresh page load never
+   * triggers — its baseline starts at the current snapshot.
+   */
+  const taskBaselineRef = useRef<SidebarSessionList | undefined>(undefined)
+  useEffect(() => {
+    const prev = taskBaselineRef.current
+    taskBaselineRef.current = sessionList
+    if (sessionId === undefined || prev === undefined) return
+    if (!detectNewTask(prev, sessionList, sessionId)) return
+    if (!store.getPrefs().autoOpenTasks) return
+    if (ctx.betterSidebar?.isTabEnabled('subagent') === false) return
+    store.reduce(s => s.panelOpen ? s : togglePanel(s))
+    store.reduce(s => ({ ...s, activePane: firstLeaf(s.splits).id }))
+    ctx.betterSidebar?.openTab({ type: 'subagent', title: t('subagent') })
+  }, [sessionList, sessionId, store, ctx])
+
   /**
    * Topology jump-back: clicking a subagent node on the Subagent page calls
    * the official `openSubagent`, which switches the sidebar to that child
diff --git a/src/client/builtins/tabs.tsx b/src/client/builtins/tabs.tsx
index e778edb..85cf32f 100644
--- a/src/client/builtins/tabs.tsx
+++ b/src/client/builtins/tabs.tsx
@@ -109,13 +109,17 @@ export function builtinTabs(ctx: Context): readonly TabDescriptor[] {
       icon: (size: number) => <IconThinkOutline16 size={size} />,
       order: 30,
       single: true,
-      // Declarative settings: the auto-open switch renders under this row in
-      // the Side card settings page (the Subagent page's own related setting).
+      // Declarative settings: the auto-open switches render under this row in
+      // the Side card settings page (the Tasks page's own related settings).
       settings: {
         toggles: [{
           key: 'autoOpenSubagent',
           title: () => t('settingsSubagentTitle'),
           desc: () => t('settingsSubagentDesc'),
+        }, {
+          key: 'autoOpenTasks',
+          title: () => t('settingsTasksTitle'),
+          desc: () => t('settingsTasksDesc'),
         }],
       },
       component: ({ ctx, scope, visible, onSubagentJump }) => (
diff --git a/src/client/locales.ts b/src/client/locales.ts
index d16d165..f69ba1d 100644
--- a/src/client/locales.ts
+++ b/src/client/locales.ts
@@ -121,6 +121,8 @@ const zh = {
   zoomHint: 'Alt + 滚轮',
   settingsSubagentTitle: '检测到子代理时自动展开任务管理页',
   settingsSubagentDesc: '当前会话产生新的子代理时，自动展开侧边栏并打开任务管理页；关闭后需手动打开',
+  settingsTasksTitle: '有新后台任务时自动展开任务管理页',
+  settingsTasksDesc: '当前会话出现新的后台任务时，自动展开侧边栏并打开任务管理页（每个新任务都会触发）；关闭后需手动打开',
   settingsToolsTitle: '为模型注入终端工具',
   settingsToolsDesc: '开启后，模型可通过 terminal_create 等 8 个工具创建并操作侧边栏终端（默认关闭）',
   settingsBottomTerminalTitle: '底部面板首次展开自动开终端',
@@ -194,7 +196,7 @@ const zh = {
   taskViewOutput: '查看输出',
   taskHideOutput: '收起输出',
   taskNoOutput: '暂无输出',
-  taskNotReadYet: '模型尚未读取该任务的输出，读取后会显示在这里',
+  taskNotReadYet: '等待模型读取该任务的输出（模型执行 task_output 后，输出会显示在这里）',
   taskOutputTruncated: '输出过长，已截断显示',
   taskOutputError: '输出读取失败',
   taskKill: '终止',
@@ -318,6 +320,8 @@ const en: Record<keyof typeof zh, string> = {
   zoomHint: 'Alt + wheel',
   settingsSubagentTitle: 'Auto-open the Tasks page when a subagent appears',
   settingsSubagentDesc: 'Expand the side card and open the Tasks page when the current conversation spawns a new subagent; turn off to open it manually',
+  settingsTasksTitle: 'Auto-open the Tasks page on a new background task',
+  settingsTasksDesc: 'Expand the side card and open the Tasks page whenever a new background task appears for the current conversation (every new task triggers); turn off to open it manually',
   settingsToolsTitle: 'Inject terminal tools for the model',
   settingsToolsDesc: 'When enabled, the model can create and drive sidebar terminals through the 8 terminal_* tools (off by default)',
   settingsBottomTerminalTitle: 'Auto-open a terminal on the bottom panel\'s first expansion',
@@ -391,7 +395,7 @@ const en: Record<keyof typeof zh, string> = {
   taskViewOutput: 'View output',
   taskHideOutput: 'Hide output',
   taskNoOutput: 'No output yet',
-  taskNotReadYet: 'The model has not read this task\'s output yet; it will appear here once read',
+  taskNotReadYet: 'Waiting for the model to read this task; its output appears here once the model runs task_output',
   taskOutputTruncated: 'Output truncated',
   taskOutputError: 'Failed to read output',
   taskKill: 'Kill',
diff --git a/src/client/prefs.ts b/src/client/prefs.ts
index 7213de7..72167b8 100644
--- a/src/client/prefs.ts
+++ b/src/client/prefs.ts
@@ -40,6 +40,9 @@ export function parsePrefs(value: unknown): SidebarPrefs {
     autoOpenSubagent: typeof record.autoOpenSubagent === 'boolean'
       ? record.autoOpenSubagent
       : SIDEBAR_PREFS_DEFAULTS.autoOpenSubagent,
+    autoOpenTasks: typeof record.autoOpenTasks === 'boolean'
+      ? record.autoOpenTasks
+      : SIDEBAR_PREFS_DEFAULTS.autoOpenTasks,
     agentTerminalTools: typeof record.agentTerminalTools === 'boolean'
       ? record.agentTerminalTools
       : SIDEBAR_PREFS_DEFAULTS.agentTerminalTools,
diff --git a/src/client/subagent-tasks.ts b/src/client/subagent-tasks.ts
index 38bccd6..e1fae63 100644
--- a/src/client/subagent-tasks.ts
+++ b/src/client/subagent-tasks.ts
@@ -57,6 +57,23 @@ export function treeSessionIds(
   return ids
 }
 
+/**
+ * Whether a NEW background task appeared for one session between two
+ * consecutive list snapshots (a task id the previous snapshot lacked).
+ * Unlike the subagent auto-open (0 → N only), ANY new task id triggers: the
+ * agent may start several tasks over a session, and each new one should
+ * surface the Tasks page (a fresh page load never triggers — its baseline
+ * starts at the current snapshot).
+ */
+export function detectNewTask(
+  prev: SidebarSessionList,
+  next: SidebarSessionList,
+  sessionId: string,
+): boolean {
+  const prevIds = new Set((prev.tasksBySession?.[sessionId] ?? []).map(task => task.id))
+  return (next.tasksBySession?.[sessionId] ?? []).some(task => !prevIds.has(task.id))
+}
+
 /**
  * Collect the background tasks of the whole current tree, owner-labeled.
  * Sessions without a mirror entry contribute nothing; an absent mirror
diff --git a/src/config.ts b/src/config.ts
index b44cc9d..687584d 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -79,6 +79,7 @@ export const PrefsSchema: z<SidebarPrefs> = z.object({
   openByDefault: z.boolean().default(true),
   defaultWidthPercent: z.number().step(1).min(WIDTH_PERCENT_MIN).max(WIDTH_PERCENT_MAX).default(WIDTH_PERCENT_DEFAULT),
   autoOpenSubagent: z.boolean().default(true),
+  autoOpenTasks: z.boolean().default(true),
   agentTerminalTools: z.boolean().default(false),
   bottomPanelAutoTerminal: z.boolean().default(true),
   interceptOpenPath: z.boolean().default(true),
diff --git a/src/prefs-shared.ts b/src/prefs-shared.ts
index 8c66577..5fcf9a5 100644
--- a/src/prefs-shared.ts
+++ b/src/prefs-shared.ts
@@ -20,6 +20,12 @@ export interface SidebarPrefs {
    * Subagent page when the current conversation spawns a new subagent.
    */
   autoOpenSubagent: boolean
+  /**
+   * Whether the sidebar auto-activates (opens the panel) and expands the
+   * Tasks page when a NEW background task appears for the current
+   * conversation (any new task id, not just the first one).
+   */
+  autoOpenTasks: boolean
   /**
    * Whether the model-facing agent terminal tools (terminal_create / list /
    * send / read / wait_for / resize / signal / close) are injected into the
@@ -103,6 +109,7 @@ export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   openByDefault: true,
   defaultWidthPercent: WIDTH_PERCENT_DEFAULT,
   autoOpenSubagent: true,
+  autoOpenTasks: true,
   agentTerminalTools: false,
   bottomPanelAutoTerminal: true,
   interceptOpenPath: true,
diff --git a/tests/builtins.spec.ts b/tests/builtins.spec.ts
index aefab05..31ecd2a 100644
--- a/tests/builtins.spec.ts
+++ b/tests/builtins.spec.ts
@@ -41,10 +41,10 @@ describe('built-in tab registrations', () => {
     }
   })
 
-  it('the subagent tab declares its auto-open related setting', () => {
+  it('the subagent tab declares its auto-open related settings', () => {
     const { service } = setup()
     const toggles = service.getTab('subagent')?.settings?.toggles ?? []
-    expect(toggles.map(t => t.key)).toEqual(['autoOpenSubagent'])
+    expect(toggles.map(t => t.key)).toEqual(['autoOpenSubagent', 'autoOpenTasks'])
   })
 
   it('the terminal tab declares the model terminal-tools related setting', () => {
diff --git a/tests/plugin-shape.spec.ts b/tests/plugin-shape.spec.ts
index fbfca4d..f67acb2 100644
--- a/tests/plugin-shape.spec.ts
+++ b/tests/plugin-shape.spec.ts
@@ -45,6 +45,8 @@ describe('dsh-better-sidebar plugin export shape', () => {
     expect(resolved.openByDefault).toBe(true)
     expect(resolved.defaultWidthPercent).toBe(30)
     expect(resolved.autoOpenSubagent).toBe(true)
+    // A new background task auto-opens the Tasks page too.
+    expect(resolved.autoOpenTasks).toBe(true)
     // The terminal tools default OFF (the feature is dormant until the user
     // enables it in the side card settings).
     expect(resolved.agentTerminalTools).toBe(false)
@@ -57,6 +59,6 @@ describe('dsh-better-sidebar plugin export shape', () => {
     const overridden = (PrefsSchema as unknown as {
       (input: Record<string, unknown> | undefined): Record<string, unknown>
     })({ openByDefault: false, defaultWidthPercent: 45 })
-    expect(overridden).toEqual({ openByDefault: false, defaultWidthPercent: 45, autoOpenSubagent: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
+    expect(overridden).toEqual({ openByDefault: false, defaultWidthPercent: 45, autoOpenSubagent: true, autoOpenTasks: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
   })
 })
diff --git a/tests/smoke.spec.ts b/tests/smoke.spec.ts
index 5c6d5c2..89aa3d6 100644
--- a/tests/smoke.spec.ts
+++ b/tests/smoke.spec.ts
@@ -514,6 +514,7 @@ describe('side card settings routes', () => {
         openByDefault: true,
         defaultWidthPercent: 30,
         autoOpenSubagent: true,
+        autoOpenTasks: true,
         agentTerminalTools: false,
         bottomPanelAutoTerminal: true,
         interceptOpenPath: true,
diff --git a/tests/subagent-tasks-view.spec.tsx b/tests/subagent-tasks-view.spec.tsx
index e24f897..b9cb894 100644
--- a/tests/subagent-tasks-view.spec.tsx
+++ b/tests/subagent-tasks-view.spec.tsx
@@ -225,9 +225,9 @@ describe('SubagentView background tasks', () => {
     )
     const row = container.querySelector('button[aria-label*="unread cmd"]') as HTMLButtonElement
     await act(async () => { row.click() })
-    // read:false → the pane explains the model has not read it (never the
-    // model's cursor, so there is nothing to steal yet).
-    expect(container.textContent).toContain('模型尚未读取该任务的输出')
+    // read:false → the pane explains the output awaits the model's task_output
+    // (never the model's cursor, so there is nothing to steal yet).
+    expect(container.textContent).toContain('等待模型读取该任务的输出')
     unmount()
   })
 
diff --git a/tests/subagent-tasks.spec.ts b/tests/subagent-tasks.spec.ts
index 59189d7..fbe1370 100644
--- a/tests/subagent-tasks.spec.ts
+++ b/tests/subagent-tasks.spec.ts
@@ -5,6 +5,7 @@
 import { describe, expect, it } from 'vitest'
 import {
   collectTreeTasks,
+  detectNewTask,
   formatTaskDuration,
   isTaskLive,
   orderTasks,
@@ -12,7 +13,7 @@ import {
   taskStatusLabel,
   treeSessionIds,
 } from '../src/client/subagent-tasks.ts'
-import type { SidebarSessionSummary, SidebarTaskStatus, SidebarTaskView } from '../src/context-types.ts'
+import type { SidebarSessionList, SidebarSessionSummary, SidebarTaskStatus, SidebarTaskView } from '../src/context-types.ts'
 
 /** The translator stub: renders duration templates like the real locale copy. */
 const templates: Record<string, string> = {
@@ -131,3 +132,34 @@ describe('status presentation helpers', () => {
     expect(formatTaskDuration(-5, t)).toBe('0秒')
   })
 })
+
+describe('detectNewTask', () => {
+  const list = (tasksBySession: Record<string, SidebarTaskView[]>): SidebarSessionList => ({
+    current: 'root',
+    byId: { root: { id: 'root', displayTitle: 'root' } },
+    subagentsByParent: {},
+    tasksBySession: tasksBySession,
+  })
+
+  it('fires on EVERY new task id for the session (not just the first)', () => {
+    expect(detectNewTask(list({}), list({ root: [task('bash-1')] }), 'root')).toBe(true)
+    expect(detectNewTask(
+      list({ root: [task('bash-1')] }),
+      list({ root: [task('bash-1'), task('bash-2')] }),
+      'root',
+    )).toBe(true)
+  })
+
+  it('stays quiet on settling, same ids, other sessions, or an absent mirror', () => {
+    // Settling only mutates status, never adds ids.
+    expect(detectNewTask(
+      list({ root: [task('bash-1')] }),
+      list({ root: [task('bash-1', { status: 'completed', finishedAt: 2_000 })] }),
+      'root',
+    )).toBe(false)
+    expect(detectNewTask(list({ root: [task('bash-1')] }), list({ root: [task('bash-1')] }), 'root')).toBe(false)
+    // Tasks owned by another session do not trigger the current one.
+    expect(detectNewTask(list({}), list({ child: [task('bash-1')] }), 'root')).toBe(false)
+    expect(detectNewTask(list({}), list({}), 'root')).toBe(false)
+  })
+})
diff --git a/tests/unit.spec.ts b/tests/unit.spec.ts
index e77be73..23a6311 100644
--- a/tests/unit.spec.ts
+++ b/tests/unit.spec.ts
@@ -1150,6 +1150,7 @@ describe('side card preferences', () => {
         openByDefault: false,
         defaultWidthPercent: 60,
         autoOpenSubagent: false,
+        autoOpenTasks: true,
         agentTerminalTools: true,
         bottomPanelAutoTerminal: true,
         interceptOpenPath: true,
@@ -1168,6 +1169,7 @@ describe('side card preferences', () => {
         openByDefault: true,
         defaultWidthPercent: 33,
         autoOpenSubagent: true,
+        autoOpenTasks: true,
         agentTerminalTools: false,
         bottomPanelAutoTerminal: true,
         interceptOpenPath: true,
@@ -1186,6 +1188,7 @@ describe('side card preferences', () => {
         openByDefault: false,
         defaultWidthPercent: 40,
         autoOpenSubagent: true,
+        autoOpenTasks: true,
         agentTerminalTools: false,
         bottomPanelAutoTerminal: true,
         interceptOpenPath: true,
@@ -1205,6 +1208,11 @@ describe('side card preferences', () => {
       .toBe(false)
     expect((await loadPrefs(wire({ openByDefault: true, defaultWidthPercent: 40, agentTerminalTools: true }))).agentTerminalTools)
       .toBe(true)
+    // The task auto-open is ON by default; only an explicit false turns it off.
+    expect((await loadPrefs(wire({ openByDefault: true, defaultWidthPercent: 40, autoOpenTasks: 1 }))).autoOpenTasks)
+      .toBe(true)
+    expect((await loadPrefs(wire({ openByDefault: true, defaultWidthPercent: 40, autoOpenTasks: false }))).autoOpenTasks)
+      .toBe(false)
   })
 
   it('defaults interceptOpenPath to true; only an explicit false turns the takeover off', async () => {
@@ -1234,9 +1242,9 @@ describe('side card preferences', () => {
     const store = createSidebarStore()
     // Node environment: no window → the width falls back to PANEL_DEFAULT,
     // while the open flag still follows the preference.
-    store.setPrefs({ openByDefault: false, defaultWidthPercent: 45, autoOpenSubagent: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
+    store.setPrefs({ openByDefault: false, defaultWidthPercent: 45, autoOpenSubagent: true, autoOpenTasks: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
     store.setSession('fresh-session')
-    expect(store.getPrefs()).toEqual({ openByDefault: false, defaultWidthPercent: 45, autoOpenSubagent: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
+    expect(store.getPrefs()).toEqual({ openByDefault: false, defaultWidthPercent: 45, autoOpenSubagent: true, autoOpenTasks: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
     const snapshot = store.getSnapshot()
     expect(snapshot.sessionId).toBe('fresh-session')
     expect(snapshot.state?.panelOpen).toBe(false)
@@ -1272,7 +1280,7 @@ describe('side card preferences', () => {
 
   it('skips the default explorer tab when the explorer type is disabled', () => {
     const store = createSidebarStore()
-    store.setPrefs({ openByDefault: true, defaultWidthPercent: 30, autoOpenSubagent: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: { explorer: false }, viewersEnabled: {} })
+    store.setPrefs({ openByDefault: true, defaultWidthPercent: 30, autoOpenSubagent: true, autoOpenTasks: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: { explorer: false }, viewersEnabled: {} })
     store.setSession('no-explorer')
     const state = store.getSnapshot().state!
     const tabs = allLeaves(state.splits).flatMap(leaf => leaf.tabs)
@@ -1280,7 +1288,7 @@ describe('side card preferences', () => {
     expect(state.splits.kind).toBe('leaf')
     // Re-enabling seeds the explorer tab again.
     const openStore = createSidebarStore()
-    openStore.setPrefs({ openByDefault: true, defaultWidthPercent: 30, autoOpenSubagent: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
+    openStore.setPrefs({ openByDefault: true, defaultWidthPercent: 30, autoOpenSubagent: true, autoOpenTasks: true, agentTerminalTools: false, bottomPanelAutoTerminal: true, interceptOpenPath: true, htmlViewerNoSandbox: false, htmlViewerDefaultUnsafe: false, browserNoSandbox: false, browserInterceptLinks: true, tabsEnabled: {}, viewersEnabled: {} })
     openStore.setSession('with-explorer')
     const openTabs = allLeaves(openStore.getSnapshot().state!.splits).flatMap(leaf => leaf.tabs)
     expect(openTabs.map(tab => tab.type)).toEqual(['explorer'])