diff --git a/desktop/src/components/layout/ContentRouter.test.tsx b/desktop/src/components/layout/ContentRouter.test.tsx
index c31ac291..3bfc96bf 100644
--- a/desktop/src/components/layout/ContentRouter.test.tsx
+++ b/desktop/src/components/layout/ContentRouter.test.tsx
@@ -42,10 +42,16 @@ vi.mock('../../pages/TraceList', () => ({
   TraceList: () => <div data-testid="trace-list" />,
 }))
 
+vi.mock('../workbench/WorkbenchTab', () => ({
+  WorkbenchTab: ({ sessionId, tabId }: { sessionId: string; tabId: string }) => (
+    <div data-testid="workbench-tab">workbench:{sessionId}:{tabId}</div>
+  ),
+}))
+
 import { ContentRouter } from './ContentRouter'
 import { useTabStore } from '../../stores/tabStore'
 
-describe('ContentRouter terminal tabs', () => {
+describe('ContentRouter tab surfaces', () => {
   afterEach(() => {
     cleanup()
     previewBridgeMock.close.mockClear()
@@ -148,6 +154,24 @@ describe('ContentRouter terminal tabs', () => {
     expect(screen.queryByTestId('active-session')).not.toBeInTheDocument()
   })
 
+  it('renders workbench tabs as main content instead of mounting the chat session surface', () => {
+    useTabStore.setState({
+      tabs: [{
+        sessionId: '__workbench__session-1',
+        title: 'Workbench',
+        type: 'workbench',
+        status: 'idle',
+        workbenchSessionId: 'session-1',
+      }],
+      activeTabId: '__workbench__session-1',
+    })
+
+    render(<ContentRouter />)
+
+    expect(screen.getByTestId('workbench-tab')).toHaveTextContent('workbench:session-1:__workbench__session-1')
+    expect(screen.queryByTestId('active-session')).not.toBeInTheDocument()
+  })
+
   it('closes the native preview when switching from a chat session to settings', async () => {
     useTabStore.setState({
       tabs: [
diff --git a/desktop/src/components/layout/ContentRouter.tsx b/desktop/src/components/layout/ContentRouter.tsx
index 7fbf5321..2e4845f0 100644
--- a/desktop/src/components/layout/ContentRouter.tsx
+++ b/desktop/src/components/layout/ContentRouter.tsx
@@ -7,6 +7,7 @@ import { Settings } from '../../pages/Settings'
 import { TerminalSettings } from '../../pages/TerminalSettings'
 import { TraceList } from '../../pages/TraceList'
 import { TraceSession } from '../../pages/TraceSession'
+import { WorkbenchTab } from '../workbench/WorkbenchTab'
 import { previewBridge } from '../../lib/previewBridge'
 
 export function ContentRouter() {
@@ -16,7 +17,7 @@ export function ContentRouter() {
   const terminalTabs = tabs.filter((tab) => tab.type === 'terminal')
 
   useEffect(() => {
-    if (activeTabType === 'session') return
+    if (activeTabType === 'session' || activeTabType === 'workbench') return
     void previewBridge.close()
   }, [activeTabType])
 
@@ -32,6 +33,11 @@ export function ContentRouter() {
     page = traceSessionId ? <TraceSession sessionId={traceSessionId} /> : <EmptySession />
   } else if (activeTabType === 'traces') {
     page = <TraceList />
+  } else if (activeTabType === 'workbench') {
+    const workbenchTab = tabs.find((t) => t.sessionId === activeTabId)
+    page = workbenchTab?.workbenchSessionId
+      ? <WorkbenchTab tabId={activeTabId} sessionId={workbenchTab.workbenchSessionId} />
+      : <EmptySession />
   } else if (activeTabType !== 'terminal') {
     page = <ActiveSession />
   }
diff --git a/desktop/src/components/layout/TabBar.tsx b/desktop/src/components/layout/TabBar.tsx
index c7282f60..75669a5c 100644
--- a/desktop/src/components/layout/TabBar.tsx
+++ b/desktop/src/components/layout/TabBar.tsx
@@ -6,6 +6,7 @@ import {
   TERMINAL_TAB_PREFIX,
   TRACE_LIST_TAB_ID,
   TRACE_TAB_PREFIX,
+  WORKBENCH_TAB_PREFIX,
   useTabStore,
   type Tab,
 } from '../../stores/tabStore'
@@ -44,7 +45,8 @@ function isSessionTabId(tabId: string | null) {
     tabId !== SCHEDULED_TAB_ID &&
     tabId !== TRACE_LIST_TAB_ID &&
     !tabId.startsWith(TERMINAL_TAB_PREFIX) &&
-    !tabId.startsWith(TRACE_TAB_PREFIX)
+    !tabId.startsWith(TRACE_TAB_PREFIX) &&
+    !tabId.startsWith(WORKBENCH_TAB_PREFIX)
 }
 
 export function TabBar() {
@@ -549,6 +551,9 @@ const TabItem = forwardRef<HTMLDivElement, {
       {tab.type === 'terminal' && (
         <span className="material-symbols-outlined text-[14px] flex-shrink-0 text-[var(--color-text-tertiary)]">terminal</span>
       )}
+      {tab.type === 'workbench' && (
+        <span className="material-symbols-outlined text-[14px] flex-shrink-0 text-[var(--color-text-tertiary)]">view_sidebar</span>
+      )}
 
       <span className={`flex-1 truncate text-xs ${isActive ? 'text-[var(--color-text-primary)] font-medium' : 'text-[var(--color-text-secondary)]'}`}>
         {tab.title || 'Untitled'}
diff --git a/desktop/src/components/workbench/WorkbenchPanel.test.tsx b/desktop/src/components/workbench/WorkbenchPanel.test.tsx
index a3695da3..20fef1b7 100644
--- a/desktop/src/components/workbench/WorkbenchPanel.test.tsx
+++ b/desktop/src/components/workbench/WorkbenchPanel.test.tsx
@@ -1,10 +1,16 @@
+// @vitest-environment jsdom
+
 import '@testing-library/jest-dom'
 import { cleanup, fireEvent, render, screen } from '@testing-library/react'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 vi.mock('../workspace/WorkspacePanel', () => ({
-  WorkspacePanel: ({ sessionId, embedded }: { sessionId: string; embedded?: boolean }) => (
-    <div data-testid="workspace-panel" data-embedded={embedded ? 'true' : 'false'}>
+  WorkspacePanel: ({ sessionId, embedded, forceVisible }: { sessionId: string; embedded?: boolean; forceVisible?: boolean }) => (
+    <div
+      data-testid="workspace-panel"
+      data-embedded={embedded ? 'true' : 'false'}
+      data-force-visible={forceVisible ? 'true' : 'false'}
+    >
       workspace:{sessionId}
     </div>
   ),
@@ -20,12 +26,14 @@ import { WorkbenchPanel } from './WorkbenchPanel'
 import { useWorkspacePanelStore } from '../../stores/workspacePanelStore'
 import { useSettingsStore } from '../../stores/settingsStore'
 import { useBrowserPanelStore } from '../../stores/browserPanelStore'
+import { useTabStore } from '../../stores/tabStore'
 
 const SESSION_ID = 'workbench-session'
 
 beforeEach(() => {
   useWorkspacePanelStore.setState(useWorkspacePanelStore.getInitialState(), true)
   useBrowserPanelStore.setState(useBrowserPanelStore.getInitialState(), true)
+  useTabStore.setState(useTabStore.getInitialState(), true)
   useSettingsStore.setState({ locale: 'en' })
   useWorkspacePanelStore.getState().openPanel(SESSION_ID)
 })
@@ -34,6 +42,7 @@ afterEach(() => {
   cleanup()
   useWorkspacePanelStore.setState(useWorkspacePanelStore.getInitialState(), true)
   useBrowserPanelStore.setState(useBrowserPanelStore.getInitialState(), true)
+  useTabStore.setState(useTabStore.getInitialState(), true)
 })
 
 describe('WorkbenchPanel', () => {
@@ -95,4 +104,35 @@ describe('WorkbenchPanel', () => {
 
     expect(useWorkspacePanelStore.getState().isPanelOpen(SESSION_ID)).toBe(false)
   })
+
+  it('the expand button promotes the current workbench into a main content tab', () => {
+    useWorkspacePanelStore.getState().setMode(SESSION_ID, 'browser')
+    render(<WorkbenchPanel sessionId={SESSION_ID} />)
+
+    fireEvent.click(screen.getByRole('button', { name: 'Expand panel' }))
+
+    expect(useTabStore.getState().activeTabId).toBe(`__workbench__${SESSION_ID}`)
+    expect(useTabStore.getState().tabs).toEqual([
+      {
+        sessionId: `__workbench__${SESSION_ID}`,
+        title: 'Workbench',
+        type: 'workbench',
+        status: 'idle',
+        workbenchSessionId: SESSION_ID,
+      },
+    ])
+  })
+
+  it('renders the tab variant without a nested expand action', () => {
+    const handleClose = vi.fn()
+    render(<WorkbenchPanel sessionId={SESSION_ID} variant="tab" onClose={handleClose} />)
+
+    expect(screen.queryByRole('button', { name: 'Expand panel' })).not.toBeInTheDocument()
+    expect(screen.getByTestId('workspace-panel')).toHaveAttribute('data-force-visible', 'true')
+
+    fireEvent.click(screen.getByRole('button', { name: 'Close' }))
+
+    expect(handleClose).toHaveBeenCalledTimes(1)
+    expect(useWorkspacePanelStore.getState().isPanelOpen(SESSION_ID)).toBe(true)
+  })
 })
diff --git a/desktop/src/components/workbench/WorkbenchPanel.tsx b/desktop/src/components/workbench/WorkbenchPanel.tsx
index c348ed86..d39ad7e6 100644
--- a/desktop/src/components/workbench/WorkbenchPanel.tsx
+++ b/desktop/src/components/workbench/WorkbenchPanel.tsx
@@ -1,15 +1,18 @@
-import { FolderOpen, Globe, X } from 'lucide-react'
+import { FolderOpen, Globe, Maximize2, X } from 'lucide-react'
 import { useTranslation } from '../../i18n'
 import {
   useWorkspacePanelStore,
   type WorkbenchMode,
 } from '../../stores/workspacePanelStore'
 import { useBrowserPanelStore } from '../../stores/browserPanelStore'
+import { useTabStore } from '../../stores/tabStore'
 import { WorkspacePanel } from '../workspace/WorkspacePanel'
 import { BrowserSurface } from '../browser/BrowserSurface'
 
 type WorkbenchPanelProps = {
   sessionId: string
+  variant?: 'panel' | 'tab'
+  onClose?: () => void
 }
 
 const MODE_ITEMS: ReadonlyArray<{
@@ -26,12 +29,13 @@ const MODE_ITEMS: ReadonlyArray<{
  * browser surface behind a single per-session mode switch (file ↔ browser),
  * sharing the panel's open state and width via {@link useWorkspacePanelStore}.
  */
-export function WorkbenchPanel({ sessionId }: WorkbenchPanelProps) {
+export function WorkbenchPanel({ sessionId, variant = 'panel', onClose }: WorkbenchPanelProps) {
   const t = useTranslation()
   const mode = useWorkspacePanelStore((state) => state.getMode(sessionId))
   const setMode = useWorkspacePanelStore((state) => state.setMode)
   const closePanel = useWorkspacePanelStore((state) => state.closePanel)
   const ensureBlankBrowser = useBrowserPanelStore((state) => state.ensureBlank)
+  const isTabVariant = variant === 'tab'
 
   const handleModeSelect = (nextMode: WorkbenchMode) => {
     if (nextMode === 'browser') {
@@ -40,6 +44,18 @@ export function WorkbenchPanel({ sessionId }: WorkbenchPanelProps) {
     setMode(sessionId, nextMode)
   }
 
+  const handleExpand = () => {
+    useTabStore.getState().openWorkbenchTab(sessionId, t('workbench.tabTitle'))
+  }
+
+  const handleClose = () => {
+    if (onClose) {
+      onClose()
+      return
+    }
+    closePanel(sessionId)
+  }
+
   return (
     <div className="flex h-full min-h-0 w-full flex-col bg-[var(--color-surface)]">
       <div className="flex h-10 shrink-0 items-center gap-2 border-b border-[var(--color-border)] bg-[var(--color-surface-container-lowest)] px-2.5">
@@ -70,21 +86,34 @@ export function WorkbenchPanel({ sessionId }: WorkbenchPanelProps) {
           })}
         </div>
 
-        <button
-          type="button"
-          aria-label={t('workbench.close')}
-          onClick={() => closePanel(sessionId)}
-          className="ml-auto inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-[7px] text-[var(--color-text-tertiary)] transition-colors hover:bg-[var(--color-surface-hover)] hover:text-[var(--color-text-primary)] focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-brand)]/35"
-        >
-          <X size={16} strokeWidth={2} aria-hidden="true" />
-        </button>
+        <div className="ml-auto flex shrink-0 items-center gap-1">
+          {!isTabVariant && (
+            <button
+              type="button"
+              aria-label={t('workbench.expand')}
+              title={t('workbench.expand')}
+              onClick={handleExpand}
+              className="inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-[7px] text-[var(--color-text-tertiary)] transition-colors hover:bg-[var(--color-surface-hover)] hover:text-[var(--color-text-primary)] focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-brand)]/35"
+            >
+              <Maximize2 size={15} strokeWidth={2} aria-hidden="true" />
+            </button>
+          )}
+          <button
+            type="button"
+            aria-label={t('workbench.close')}
+            onClick={handleClose}
+            className="inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-[7px] text-[var(--color-text-tertiary)] transition-colors hover:bg-[var(--color-surface-hover)] hover:text-[var(--color-text-primary)] focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-brand)]/35"
+          >
+            <X size={16} strokeWidth={2} aria-hidden="true" />
+          </button>
+        </div>
       </div>
 
       <div className="flex min-h-0 flex-1 flex-col">
         {mode === 'browser' ? (
           <BrowserSurface sessionId={sessionId} />
         ) : (
-          <WorkspacePanel sessionId={sessionId} embedded />
+          <WorkspacePanel sessionId={sessionId} embedded forceVisible={isTabVariant} />
         )}
       </div>
     </div>
diff --git a/desktop/src/components/workbench/WorkbenchTab.tsx b/desktop/src/components/workbench/WorkbenchTab.tsx
new file mode 100644
index 00000000..b7b437f8
--- /dev/null
+++ b/desktop/src/components/workbench/WorkbenchTab.tsx
@@ -0,0 +1,30 @@
+import { useEffect } from 'react'
+import { useBrowserPanelStore } from '../../stores/browserPanelStore'
+import { useTabStore } from '../../stores/tabStore'
+import { useWorkspacePanelStore } from '../../stores/workspacePanelStore'
+import { WorkbenchPanel } from './WorkbenchPanel'
+
+type WorkbenchTabProps = {
+  tabId: string
+  sessionId: string
+}
+
+export function WorkbenchTab({ tabId, sessionId }: WorkbenchTabProps) {
+  const mode = useWorkspacePanelStore((state) => state.getMode(sessionId))
+
+  useEffect(() => {
+    if (mode === 'browser') {
+      useBrowserPanelStore.getState().ensureBlank(sessionId)
+    }
+  }, [mode, sessionId])
+
+  return (
+    <div data-testid="workbench-tab" className="flex min-h-0 flex-1 flex-col bg-[var(--color-surface)]">
+      <WorkbenchPanel
+        sessionId={sessionId}
+        variant="tab"
+        onClose={() => useTabStore.getState().closeTab(tabId)}
+      />
+    </div>
+  )
+}
diff --git a/desktop/src/components/workspace/WorkspacePanel.tsx b/desktop/src/components/workspace/WorkspacePanel.tsx
index d2b74313..454d7423 100644
--- a/desktop/src/components/workspace/WorkspacePanel.tsx
+++ b/desktop/src/components/workspace/WorkspacePanel.tsx
@@ -38,6 +38,11 @@ type WorkspacePanelProps = {
    * button so the panel header doesn't render a duplicate close control.
    */
   embedded?: boolean
+  /**
+   * Main-content workbench tabs reuse the same workspace preview UI without
+   * depending on the right-side panel's open bit.
+   */
+  forceVisible?: boolean
 }
 
 type TreeNodeProps = {
@@ -912,7 +917,7 @@ function TreeNode({
   )
 }
 
-export function WorkspacePanel({ sessionId, embedded = false }: WorkspacePanelProps) {
+export function WorkspacePanel({ sessionId, embedded = false, forceVisible = false }: WorkspacePanelProps) {
   const t = useTranslation()
   const addToast = useUIStore((state) => state.addToast)
   const [filterQuery, setFilterQuery] = useState('')
@@ -946,6 +951,7 @@ export function WorkspacePanel({ sessionId, embedded = false }: WorkspacePanelPr
   const closePanel = useWorkspacePanelStore((state) => state.closePanel)
   const addWorkspaceReference = useWorkspaceChatContextStore((state) => state.addReference)
   const chatState = useChatStore((state) => state.sessions[sessionId]?.chatState ?? 'idle')
+  const shouldRender = forceVisible || isOpen
   const refreshLifecycleRef = useRef({
     sessionId,
     isOpen: false,
@@ -986,25 +992,25 @@ export function WorkspacePanel({ sessionId, embedded = false }: WorkspacePanelPr
   useEffect(() => {
     const previous = refreshLifecycleRef.current
     const sessionChanged = previous.sessionId !== sessionId
-    const opened = isOpen && (sessionChanged || !previous.isOpen)
+    const opened = shouldRender && (sessionChanged || !previous.isOpen)
     const completedTurn =
-      isOpen &&
+      shouldRender &&
       !sessionChanged &&
       previous.chatState !== 'idle' &&
       chatState === 'idle'
 
-    refreshLifecycleRef.current = { sessionId, isOpen, chatState }
+    refreshLifecycleRef.current = { sessionId, isOpen: shouldRender, chatState }
 
     const shouldRefreshOnOpen = opened
     const shouldRefreshAfterCompletedTurn = completedTurn && chatState === 'idle'
     if ((!shouldRefreshOnOpen && !shouldRefreshAfterCompletedTurn) || statusLoading) return
     void loadStatus(sessionId)
-  }, [chatState, isOpen, loadStatus, sessionId, statusLoading])
+  }, [chatState, loadStatus, sessionId, shouldRender, statusLoading])
 
   useEffect(() => {
-    if (!isOpen || !isNavigatorVisible || activeView !== 'all' || rootTree || rootTreeLoading || rootTreeError) return
+    if (!shouldRender || !isNavigatorVisible || activeView !== 'all' || rootTree || rootTreeLoading || rootTreeError) return
     void loadTree(sessionId, '')
-  }, [activeView, isNavigatorVisible, isOpen, loadTree, rootTree, rootTreeError, rootTreeLoading, sessionId])
+  }, [activeView, isNavigatorVisible, loadTree, rootTree, rootTreeError, rootTreeLoading, sessionId, shouldRender])
 
   useEffect(() => {
     if (!previewTabContextMenu && !fileContextMenu) return
@@ -1028,7 +1034,7 @@ export function WorkspacePanel({ sessionId, embedded = false }: WorkspacePanelPr
     }
   }, [isNavigatorVisible])
 
-  if (!isOpen) return null
+  if (!shouldRender) return null
 
   const panelWidth = hasPreviewTabs ? width : Math.min(width, 520)
   const panelMaxWidth = hasPreviewTabs ? 'min(62%, calc(100% - 328px))' : '36%'
diff --git a/desktop/src/i18n/locales/en.ts b/desktop/src/i18n/locales/en.ts
index a0cc0b3e..9297e1be 100644
--- a/desktop/src/i18n/locales/en.ts
+++ b/desktop/src/i18n/locales/en.ts
@@ -141,7 +141,9 @@ export const en = {
   'workbench.modeSwitch': 'Workbench mode',
   'workbench.modeWorkspace': 'Files',
   'workbench.modeBrowser': 'Browser',
+  'workbench.expand': 'Expand panel',
   'workbench.close': 'Close',
+  'workbench.tabTitle': 'Workbench',
   'workspace.closeTab': 'Close tab',
   'workspace.preview': 'Preview',
   'workspace.previewEmpty': 'Select a file to preview.',
diff --git a/desktop/src/i18n/locales/jp.ts b/desktop/src/i18n/locales/jp.ts
index 0cbcef39..d7f7cc15 100644
--- a/desktop/src/i18n/locales/jp.ts
+++ b/desktop/src/i18n/locales/jp.ts
@@ -143,7 +143,9 @@ export const jp: Record<TranslationKey, string> = {
   'workbench.modeSwitch': 'ワークベンチモード',
   'workbench.modeWorkspace': 'ファイル',
   'workbench.modeBrowser': 'ブラウザ',
+  'workbench.expand': 'パネルを展開',
   'workbench.close': '閉じる',
+  'workbench.tabTitle': 'ワークベンチ',
   'workspace.closeTab': 'タブを閉じる',
   'workspace.preview': 'プレビュー',
   'workspace.previewEmpty': 'プレビューするファイルを選択してください。',
diff --git a/desktop/src/i18n/locales/kr.ts b/desktop/src/i18n/locales/kr.ts
index b7618a08..0f96fa86 100644
--- a/desktop/src/i18n/locales/kr.ts
+++ b/desktop/src/i18n/locales/kr.ts
@@ -143,7 +143,9 @@ export const kr: Record<TranslationKey, string> = {
   'workbench.modeSwitch': '워크벤치 모드',
   'workbench.modeWorkspace': '파일',
   'workbench.modeBrowser': '브라우저',
+  'workbench.expand': '패널 펼치기',
   'workbench.close': '닫기',
+  'workbench.tabTitle': '워크벤치',
   'workspace.closeTab': '탭 닫기',
   'workspace.preview': '미리 보기',
   'workspace.previewEmpty': '미리 볼 파일을 선택하세요.',
diff --git a/desktop/src/i18n/locales/zh-TW.ts b/desktop/src/i18n/locales/zh-TW.ts
index ba4b5327..10dea4c8 100644
--- a/desktop/src/i18n/locales/zh-TW.ts
+++ b/desktop/src/i18n/locales/zh-TW.ts
@@ -143,7 +143,9 @@ export const zh: Record<TranslationKey, string> = {
   'workbench.modeSwitch': '工作臺模式',
   'workbench.modeWorkspace': '檔案',
   'workbench.modeBrowser': '瀏覽器',
+  'workbench.expand': '展開面板',
   'workbench.close': '關閉',
+  'workbench.tabTitle': '工作臺',
   'workspace.closeTab': '關閉標籤',
   'workspace.preview': '預覽',
   'workspace.previewEmpty': '選擇一個檔案進行預覽。',
diff --git a/desktop/src/i18n/locales/zh.ts b/desktop/src/i18n/locales/zh.ts
index 68475197..0f695df6 100644
--- a/desktop/src/i18n/locales/zh.ts
+++ b/desktop/src/i18n/locales/zh.ts
@@ -143,7 +143,9 @@ export const zh: Record<TranslationKey, string> = {
   'workbench.modeSwitch': '工作台模式',
   'workbench.modeWorkspace': '文件',
   'workbench.modeBrowser': '浏览器',
+  'workbench.expand': '展开面板',
   'workbench.close': '关闭',
+  'workbench.tabTitle': '工作台',
   'workspace.closeTab': '关闭标签',
   'workspace.preview': '预览',
   'workspace.previewEmpty': '选择一个文件进行预览。',
diff --git a/desktop/src/pages/ActiveSession.tsx b/desktop/src/pages/ActiveSession.tsx
index 45f63d32..64f8e5ae 100644
--- a/desktop/src/pages/ActiveSession.tsx
+++ b/desktop/src/pages/ActiveSession.tsx
@@ -5,6 +5,7 @@ import {
   SETTINGS_TAB_ID,
   TERMINAL_TAB_PREFIX,
   TRACE_TAB_PREFIX,
+  WORKBENCH_TAB_PREFIX,
   useTabStore,
   type TabType,
 } from '../stores/tabStore'
@@ -47,7 +48,8 @@ function isSessionTabState(activeTabId: string | null, activeTabType: TabType |
   return activeTabId !== SETTINGS_TAB_ID &&
     activeTabId !== SCHEDULED_TAB_ID &&
     !activeTabId.startsWith(TERMINAL_TAB_PREFIX) &&
-    !activeTabId.startsWith(TRACE_TAB_PREFIX)
+    !activeTabId.startsWith(TRACE_TAB_PREFIX) &&
+    !activeTabId.startsWith(WORKBENCH_TAB_PREFIX)
 }
 
 function getSessionTerminalCwd(session: SessionListItem | undefined) {
diff --git a/desktop/src/stores/tabStore.test.ts b/desktop/src/stores/tabStore.test.ts
index 63649b12..64135b52 100644
--- a/desktop/src/stores/tabStore.test.ts
+++ b/desktop/src/stores/tabStore.test.ts
@@ -44,6 +44,28 @@ describe('tabStore', () => {
     expect(useTabStore.getState().activeTabId).toBe(tabId)
   })
 
+  it('opens one ephemeral workbench tab per source session', () => {
+    const firstTabId = useTabStore.getState().openWorkbenchTab('session-1', 'Workbench')
+    const secondTabId = useTabStore.getState().openWorkbenchTab('session-1', 'Workbench')
+
+    expect(firstTabId).toBe('__workbench__session-1')
+    expect(secondTabId).toBe(firstTabId)
+    expect(useTabStore.getState().tabs).toEqual([
+      {
+        sessionId: '__workbench__session-1',
+        title: 'Workbench',
+        type: 'workbench',
+        status: 'idle',
+        workbenchSessionId: 'session-1',
+      },
+    ])
+    expect(useTabStore.getState().activeTabId).toBe('__workbench__session-1')
+    expect(localStorage.getItem('cc-haha-open-tabs')).toBe(JSON.stringify({
+      openTabs: [],
+      activeTabId: null,
+    }))
+  })
+
   it('does not let async tab restore overwrite tabs opened while restore is in flight', async () => {
     let resolveSessions: (value: unknown) => void = () => {}
     vi.mocked(sessionsApi.list).mockReturnValueOnce(new Promise((resolve) => {
diff --git a/desktop/src/stores/tabStore.ts b/desktop/src/stores/tabStore.ts
index 2ab3e6b5..30e15586 100644
--- a/desktop/src/stores/tabStore.ts
+++ b/desktop/src/stores/tabStore.ts
@@ -10,8 +10,9 @@ export const SCHEDULED_TAB_ID = '__scheduled__'
 export const TRACE_LIST_TAB_ID = '__traces__'
 export const TERMINAL_TAB_PREFIX = '__terminal__'
 export const TRACE_TAB_PREFIX = '__trace__'
+export const WORKBENCH_TAB_PREFIX = '__workbench__'
 
-export type TabType = 'session' | 'settings' | 'scheduled' | 'terminal' | 'trace' | 'traces'
+export type TabType = 'session' | 'settings' | 'scheduled' | 'terminal' | 'trace' | 'traces' | 'workbench'
 
 export type Tab = {
   sessionId: string
@@ -21,6 +22,7 @@ export type Tab = {
   terminalCwd?: string
   terminalRuntimeId?: string
   traceSessionId?: string
+  workbenchSessionId?: string
 }
 
 type TabPersistence = {
@@ -36,6 +38,7 @@ type TabStore = {
   openTracesTab: (title?: string) => string
   openTraceTab: (sessionId: string, title?: string) => string
   openTerminalTab: (cwd?: string, terminalRuntimeId?: string) => string
+  openWorkbenchTab: (sessionId: string, title?: string) => string
   closeTab: (sessionId: string) => void
   setActiveTab: (sessionId: string) => void
   updateTabTitle: (sessionId: string, title: string) => void
@@ -141,6 +144,33 @@ export const useTabStore = create<TabStore>((set, get) => ({
     return sessionId
   },
 
+  openWorkbenchTab: (sessionId, title = 'Workbench') => {
+    const tabId = `${WORKBENCH_TAB_PREFIX}${sessionId}`
+    const { tabs } = get()
+    const existing = tabs.find((tab) => tab.sessionId === tabId)
+    const tab: Tab = {
+      sessionId: tabId,
+      title,
+      type: 'workbench',
+      status: 'idle',
+      workbenchSessionId: sessionId,
+    }
+
+    if (existing) {
+      set({
+        tabs: tabs.map((current) => current.sessionId === tabId ? tab : current),
+        activeTabId: tabId,
+      })
+    } else {
+      set({
+        tabs: [...tabs, tab],
+        activeTabId: tabId,
+      })
+    }
+    get().saveTabs()
+    return tabId
+  },
+
   closeTab: (sessionId) => {
     const { tabs, activeTabId } = get()
     const index = tabs.findIndex((t) => t.sessionId === sessionId)
@@ -210,7 +240,7 @@ export const useTabStore = create<TabStore>((set, get) => ({
 
   saveTabs: () => {
     const { tabs, activeTabId } = get()
-    const persistableTabs = tabs.filter((tab) => tab.type !== 'terminal')
+    const persistableTabs = tabs.filter((tab) => tab.type !== 'terminal' && tab.type !== 'workbench')
     const data: TabPersistence = {
       openTabs: persistableTabs.map((t) => ({
         sessionId: t.sessionId,