diff --git a/src/renderer/src/components/tab-bar/TabBar.context-menu.test.ts b/src/renderer/src/components/tab-bar/TabBar.context-menu.test.ts
index bd5b640cd3a..ca2e9ba81a4 100644
--- a/src/renderer/src/components/tab-bar/TabBar.context-menu.test.ts
+++ b/src/renderer/src/components/tab-bar/TabBar.context-menu.test.ts
@@ -73,6 +73,9 @@ vi.mock('lucide-react', () => ({
   Plus: function Plus() {
     return null
   },
+  Smartphone: function Smartphone() {
+    return null
+  },
   TerminalSquare: function TerminalSquare() {
     return null
   }
@@ -420,6 +423,43 @@ describe('TabBar context menu wiring', () => {
     expect(menuLabels[3]).toContain('New Browser Tab')
   })
 
+  it('disables New Mobile Emulator when the workspace already has one', async () => {
+    const onNewSimulatorTab = vi.fn()
+    appStoreSnapshot.unifiedTabsByWorktree = {
+      'wt-1': [
+        {
+          id: 'sim-1',
+          entityId: 'sim-1',
+          groupId: 'group-2',
+          worktreeId: 'wt-1',
+          contentType: 'simulator',
+          label: 'Mobile Emulator',
+          customLabel: null,
+          color: null,
+          sortOrder: 1,
+          createdAt: 0
+        }
+      ]
+    }
+
+    const element = await renderTabBar({
+      tabs: [TERMINAL_TAB],
+      groupId: 'group-1',
+      onNewSimulatorTab
+    })
+
+    const emulatorItem = findChildrenByType(element, 'DropdownMenuItem').find((item) =>
+      extractText(item.props.children).includes('New Mobile Emulator')
+    )
+    expect(emulatorItem?.props.disabled).toBe(true)
+    expect(emulatorItem?.props.onSelect).toBeUndefined()
+
+    const tooltip = findChildrenByType(element, 'TooltipContent').find((item) =>
+      extractText(item.props.children).includes('An emulator already exists in this workspace.')
+    )
+    expect(tooltip).toBeTruthy()
+  })
+
   it('cancels delayed menu focus when the tab bar root unmounts', async () => {
     vi.useFakeTimers()
     Object.assign(window, { setTimeout, clearTimeout })
diff --git a/src/renderer/src/components/tab-bar/TabBar.tsx b/src/renderer/src/components/tab-bar/TabBar.tsx
index fb858e9762a..854063c70d4 100644
--- a/src/renderer/src/components/tab-bar/TabBar.tsx
+++ b/src/renderer/src/components/tab-bar/TabBar.tsx
@@ -51,6 +51,7 @@ import {
   DropdownMenuShortcut,
   DropdownMenuTrigger
 } from '@/components/ui/dropdown-menu'
+import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip'
 import type { TabCreateEntryArgs } from './tab-create-entry-action'
 import { buildTabAgentLaunchOptions, orderTabLaunchAgents } from './tab-agent-launch-options'
 
@@ -62,6 +63,7 @@ type GitStatusEntries = ReturnType<typeof useAppStore.getState>['gitStatusByWork
 const EMPTY_GIT_STATUS_ENTRIES: GitStatusEntries = []
 const EMPTY_AGENT_CMD_OVERRIDES: Partial<Record<TuiAgent, string>> = {}
 const EMPTY_UNIFIED_TABS: readonly Tab[] = []
+const EMULATOR_EXISTS_TOOLTIP = 'An emulator already exists in this workspace.'
 
 type TabBarProps = {
   tabs: (TerminalTab & { unifiedTabId?: string })[]
@@ -293,6 +295,10 @@ function TabBarInner({
     () => createUnifiedTabLookup(unifiedTabs, resolvedGroupId),
     [resolvedGroupId, unifiedTabs]
   )
+  const workspaceHasSimulatorTab = useMemo(
+    () => unifiedTabs.some((tab) => tab.contentType === 'simulator'),
+    [unifiedTabs]
+  )
 
   // Why: Electron <webview> elements run in a separate process, so clicking
   // inside one never dispatches a pointerdown on the renderer document.
@@ -489,14 +495,34 @@ function TabBarInner({
   ) : null
   const newSimulatorMenuItem =
     !terminalOnly && isMacOs && mobileEmulatorEnabled && onNewSimulatorTab ? (
-      <DropdownMenuItem
-        onSelect={onNewSimulatorTab}
-        className="gap-2 rounded-[7px] px-2 py-1.5 text-[12px] leading-5 font-medium"
-      >
-        <Smartphone className="size-4 text-muted-foreground" />
-        New Mobile Emulator
-        <DropdownMenuShortcut>{newSimulatorShortcut}</DropdownMenuShortcut>
-      </DropdownMenuItem>
+      workspaceHasSimulatorTab ? (
+        <Tooltip>
+          <TooltipTrigger asChild>
+            <span className="block">
+              <DropdownMenuItem
+                disabled
+                className="gap-2 rounded-[7px] px-2 py-1.5 text-[12px] leading-5 font-medium"
+              >
+                <Smartphone className="size-4 text-muted-foreground" />
+                New Mobile Emulator
+                <DropdownMenuShortcut>{newSimulatorShortcut}</DropdownMenuShortcut>
+              </DropdownMenuItem>
+            </span>
+          </TooltipTrigger>
+          <TooltipContent side="right" sideOffset={8} className="z-[80]">
+            {EMULATOR_EXISTS_TOOLTIP}
+          </TooltipContent>
+        </Tooltip>
+      ) : (
+        <DropdownMenuItem
+          onSelect={onNewSimulatorTab}
+          className="gap-2 rounded-[7px] px-2 py-1.5 text-[12px] leading-5 font-medium"
+        >
+          <Smartphone className="size-4 text-muted-foreground" />
+          New Mobile Emulator
+          <DropdownMenuShortcut>{newSimulatorShortcut}</DropdownMenuShortcut>
+        </DropdownMenuItem>
+      )
     ) : null
   const newMarkdownMenuItem =
     !terminalOnly && onNewFileTab ? (
diff --git a/src/renderer/src/components/tab-group/useTabGroupWorkspaceModel.ts b/src/renderer/src/components/tab-group/useTabGroupWorkspaceModel.ts
index b4a1bce884b..5e799adb34f 100644
--- a/src/renderer/src/components/tab-group/useTabGroupWorkspaceModel.ts
+++ b/src/renderer/src/components/tab-group/useTabGroupWorkspaceModel.ts
@@ -578,7 +578,7 @@ export function useTabGroupWorkspaceModel({
       newSimulatorTab: worktreeState.mobileEmulatorEnabled
         ? () => {
             // Why: mobile simulators are most useful beside the current tab group.
-            // Re-open focuses the existing worktree simulator instead of spawning duplicates.
+            // Re-open is guarded as a no-op once a worktree emulator tab exists.
             void openMobileEmulatorTab(worktreeId, {
               placement: 'rightSplit',
               targetGroupId: groupId
diff --git a/src/renderer/src/lib/ensure-simulator-tab.ts b/src/renderer/src/lib/ensure-simulator-tab.ts
index f5b4e2356ec..4c226abb0fb 100644
--- a/src/renderer/src/lib/ensure-simulator-tab.ts
+++ b/src/renderer/src/lib/ensure-simulator-tab.ts
@@ -11,6 +11,20 @@ type EnsureSimulatorTabOptions = {
   surfacePane?: boolean
 }
 
+type ExistingSimulatorTab = {
+  id: string
+  groupId: string
+  contentType: string
+}
+
+export function getSimulatorTabForWorktree(worktreeId: string): ExistingSimulatorTab | null {
+  return (
+    (useAppStore.getState().unifiedTabsByWorktree[worktreeId] ?? []).find(
+      (tab) => tab.contentType === 'simulator'
+    ) ?? null
+  )
+}
+
 /** One simulator tab per worktree; focuses existing tab instead of creating duplicates. */
 export function ensureSimulatorTab(
   worktreeId: string,
@@ -32,9 +46,7 @@ export function ensureSimulatorTab(
   }
   cancelPendingSimulatorPaneShutdown(worktreeId)
 
-  const existing = (store.unifiedTabsByWorktree[worktreeId] ?? []).find(
-    (tab) => tab.contentType === 'simulator'
-  )
+  const existing = getSimulatorTabForWorktree(worktreeId)
   const shouldSurface = options?.surfacePane ?? true
   if (existing) {
     if (shouldSurface && store.activeWorktreeId === worktreeId) {
diff --git a/src/renderer/src/lib/open-mobile-emulator-tab.test.ts b/src/renderer/src/lib/open-mobile-emulator-tab.test.ts
index da03ae571af..1f6b9ea83f4 100644
--- a/src/renderer/src/lib/open-mobile-emulator-tab.test.ts
+++ b/src/renderer/src/lib/open-mobile-emulator-tab.test.ts
@@ -6,7 +6,7 @@ import {
   consumePrelaunchedSimulatorSession,
   isManualSimulatorLaunchPending
 } from './simulator-launch-coordination'
-import { ensureSimulatorTab } from './ensure-simulator-tab'
+import { ensureSimulatorTab, getSimulatorTabForWorktree } from './ensure-simulator-tab'
 
 const mockStoreState = vi.hoisted(() => ({
   activeGroupIdByWorktree: { 'wt-1': 'group-1' } as Record<string, string>,
@@ -32,6 +32,7 @@ vi.mock('sonner', () => ({
 
 vi.mock('./ensure-simulator-tab', () => ({
   ensureSimulatorTab: vi.fn(),
+  getSimulatorTabForWorktree: vi.fn(),
   isMacOsHost: true
 }))
 
@@ -51,6 +52,8 @@ describe('openMobileEmulatorTab', () => {
     mockStoreState.settings = { mobileEmulatorEnabled: true }
     vi.mocked(callRuntimeRpc).mockReset()
     vi.mocked(ensureSimulatorTab).mockReset()
+    vi.mocked(getSimulatorTabForWorktree).mockReset()
+    vi.mocked(getSimulatorTabForWorktree).mockReturnValue(null)
     vi.mocked(toast.error).mockReset()
     consumePrelaunchedSimulatorSession('wt-1')
   })
@@ -130,6 +133,22 @@ describe('openMobileEmulatorTab', () => {
     await firstLaunch
   })
 
+  it('does nothing when the workspace already has an emulator tab', async () => {
+    vi.mocked(getSimulatorTabForWorktree).mockReturnValue({
+      id: 'sim-existing',
+      groupId: 'group-1',
+      contentType: 'simulator'
+    })
+
+    await expect(openMobileEmulatorTab('wt-1', { targetGroupId: 'group-1' })).resolves.toBe(
+      'sim-existing'
+    )
+
+    expect(ensureSimulatorTab).not.toHaveBeenCalled()
+    expect(callRuntimeRpc).not.toHaveBeenCalled()
+    expect(isManualSimulatorLaunchPending('wt-1')).toBe(false)
+  })
+
   it('does not attach when the mobile emulator feature is disabled', async () => {
     mockStoreState.settings = { mobileEmulatorEnabled: false }
 
diff --git a/src/renderer/src/lib/open-mobile-emulator-tab.ts b/src/renderer/src/lib/open-mobile-emulator-tab.ts
index 1e4d2ea2b7d..dccfa0b8247 100644
--- a/src/renderer/src/lib/open-mobile-emulator-tab.ts
+++ b/src/renderer/src/lib/open-mobile-emulator-tab.ts
@@ -2,7 +2,7 @@ import { toast } from 'sonner'
 import type { EmulatorStreamInfo } from '@/components/emulator-pane/emulator-pane-types'
 import { callRuntimeRpc } from '@/runtime/runtime-rpc-client'
 import { useAppStore } from '@/store'
-import { ensureSimulatorTab, isMacOsHost } from './ensure-simulator-tab'
+import { ensureSimulatorTab, getSimulatorTabForWorktree, isMacOsHost } from './ensure-simulator-tab'
 import {
   beginManualSimulatorLaunch,
   dispatchManualSimulatorLaunchFailed,
@@ -54,6 +54,10 @@ export async function openMobileEmulatorTab(
   if (store.settings?.mobileEmulatorEnabled === false) {
     return null
   }
+  const existingTab = getSimulatorTabForWorktree(worktreeId)
+  if (existingTab) {
+    return existingTab.id
+  }
   const targetGroupId =
     options.targetGroupId ??
     store.activeGroupIdByWorktree[worktreeId] ??