diff --git a/apps/next/src/components/machine/box-status-card.tsx b/apps/next/src/components/machine/box-status-card.tsx
index ba393a2..e659fcd 100644
--- a/apps/next/src/components/machine/box-status-card.tsx
+++ b/apps/next/src/components/machine/box-status-card.tsx
@@ -1,8 +1,18 @@
 'use client';
 
+import type { ReactNode } from 'react';
 import { Loader2, Play, RotateCw, Server, Square } from 'lucide-react';
 
 import {
+  AlertDialog,
+  AlertDialogAction,
+  AlertDialogCancel,
+  AlertDialogContent,
+  AlertDialogDescription,
+  AlertDialogFooter,
+  AlertDialogHeader,
+  AlertDialogTitle,
+  AlertDialogTrigger,
   Badge,
   Button,
   Card,
@@ -50,6 +60,48 @@ const Detail = ({ label, value }: { label: string; value: string }) => (
   </div>
 );
 
+// Stopping or restarting the box tears down the SAME per-user container that a
+// running agent thread job executes in, so both actions are destructive and get
+// a confirmation step. Start is safe and stays a plain button.
+const ConfirmLifecycleButton = ({
+  icon,
+  label,
+  busy,
+  title,
+  description,
+  confirmLabel,
+  onConfirm,
+}: {
+  icon: ReactNode;
+  label: string;
+  busy: boolean;
+  title: string;
+  description: string;
+  confirmLabel: string;
+  onConfirm: () => void;
+}) => (
+  <AlertDialog>
+    <AlertDialogTrigger asChild>
+      <Button type='button' variant='outline' size='sm' disabled={busy}>
+        {icon}
+        {label}
+      </Button>
+    </AlertDialogTrigger>
+    <AlertDialogContent>
+      <AlertDialogHeader>
+        <AlertDialogTitle>{title}</AlertDialogTitle>
+        <AlertDialogDescription>{description}</AlertDialogDescription>
+      </AlertDialogHeader>
+      <AlertDialogFooter>
+        <AlertDialogCancel>Cancel</AlertDialogCancel>
+        <AlertDialogAction variant='destructive' onClick={onConfirm}>
+          {confirmLabel}
+        </AlertDialogAction>
+      </AlertDialogFooter>
+    </AlertDialogContent>
+  </AlertDialog>
+);
+
 export const BoxStatusCard = ({
   status,
   pendingAction,
@@ -96,34 +148,36 @@ export const BoxStatusCard = ({
         <div className='flex flex-wrap gap-2'>
           {running ? (
             <>
-              <Button
-                type='button'
-                variant='outline'
-                size='sm'
-                disabled={busy}
-                onClick={() => onAction('stop')}
-              >
-                {pendingAction === 'stop' ? (
-                  <Loader2 className='size-4 animate-spin' />
-                ) : (
-                  <Square className='size-4' />
-                )}
-                Stop
-              </Button>
-              <Button
-                type='button'
-                variant='outline'
-                size='sm'
-                disabled={busy}
-                onClick={() => onAction('restart')}
-              >
-                {pendingAction === 'restart' ? (
-                  <Loader2 className='size-4 animate-spin' />
-                ) : (
-                  <RotateCw className='size-4' />
-                )}
-                Restart
-              </Button>
+              <ConfirmLifecycleButton
+                label='Stop'
+                busy={busy}
+                icon={
+                  pendingAction === 'stop' ? (
+                    <Loader2 className='size-4 animate-spin' />
+                  ) : (
+                    <Square className='size-4' />
+                  )
+                }
+                title='Stop this machine?'
+                description='Stopping the machine shuts down the container it runs in. Any agent thread job currently running in this machine will be interrupted and lose its in-progress work.'
+                confirmLabel='Stop machine'
+                onConfirm={() => onAction('stop')}
+              />
+              <ConfirmLifecycleButton
+                label='Restart'
+                busy={busy}
+                icon={
+                  pendingAction === 'restart' ? (
+                    <Loader2 className='size-4 animate-spin' />
+                  ) : (
+                    <RotateCw className='size-4' />
+                  )
+                }
+                title='Restart this machine?'
+                description='Restarting the machine recreates the container it runs in. Any agent thread job currently running in this machine will be interrupted and lose its in-progress work.'
+                confirmLabel='Restart machine'
+                onConfirm={() => onAction('restart')}
+              />
             </>
           ) : (
             <Button
diff --git a/apps/next/src/components/machine/machine-shell.tsx b/apps/next/src/components/machine/machine-shell.tsx
index dee84d3..ec65bab 100644
--- a/apps/next/src/components/machine/machine-shell.tsx
+++ b/apps/next/src/components/machine/machine-shell.tsx
@@ -235,6 +235,13 @@ export const MachineShell = () => {
 
   const activeFile = activeFilePath ? files[activeFilePath] : undefined;
   const running = Boolean(status?.running);
+  const starting = pendingAction === 'start' || pendingAction === 'restart';
+  // The terminal only shows this while the box is not running. Distinguish a box
+  // that is starting/restarting from one that is simply stopped so the label is
+  // accurate instead of always claiming "Starting…".
+  const terminalWaitingLabel = starting
+    ? 'Starting your machine…'
+    : 'Machine is stopped — start it to open a terminal.';
 
   return (
     <main className='space-y-6'>
@@ -339,9 +346,10 @@ export const MachineShell = () => {
         >
           <XtermSession
             active={running}
+            visible={activeTab === 'terminal'}
             tokenUrl='/api/box/terminal-token'
             sessionKey={username}
-            waitingLabel='Starting your machine…'
+            waitingLabel={terminalWaitingLabel}
             label='your machine'
           />
         </TabsContent>
diff --git a/apps/next/tests/component/machine-shell.test.tsx b/apps/next/tests/component/machine-shell.test.tsx
index f4aab40..a65e2d9 100644
--- a/apps/next/tests/component/machine-shell.test.tsx
+++ b/apps/next/tests/component/machine-shell.test.tsx
@@ -42,6 +42,40 @@ const stoppedStatus = {
   containerName: 'spoon-home-gib',
 };
 
+const runningStatus = {
+  ...stoppedStatus,
+  running: true,
+  startedAt: new Date().toISOString(),
+};
+
+// Point the status endpoint at a running box so the Stop/Restart controls render.
+const useRunningStatus = () => {
+  fetchSpy.mockImplementation((input: RequestInfo | URL) => {
+    const url =
+      typeof input === 'string'
+        ? input
+        : input instanceof URL
+          ? input.href
+          : input.url;
+    if (url.startsWith('/api/box/status')) {
+      return Promise.resolve(jsonResponse({ status: runningStatus }));
+    }
+    if (url.startsWith('/api/box/tree')) {
+      return Promise.resolve(jsonResponse({ tree }));
+    }
+    if (url.startsWith('/api/box/lifecycle')) {
+      return Promise.resolve(jsonResponse({ status: stoppedStatus }));
+    }
+    return Promise.resolve(jsonResponse({}));
+  });
+};
+
+const lifecycleCalls = () =>
+  fetchSpy.mock.calls.filter(([input]) => {
+    const url = typeof input === 'string' ? input : '';
+    return url.startsWith('/api/box/lifecycle');
+  });
+
 const tree = {
   name: '',
   path: '',
@@ -127,4 +161,51 @@ describe('MachineShell', () => {
     render(<MachineShell />);
     expect(await screen.findByText('terminal')).toBeInTheDocument();
   });
+
+  it('does not stop the box until the confirmation is accepted', async () => {
+    useRunningStatus();
+    render(<MachineShell />);
+    const stopButton = await screen.findByRole('button', { name: 'Stop' });
+    fireEvent.click(stopButton);
+
+    // The confirmation dialog intervenes: no lifecycle POST fires on the click.
+    const confirm = await screen.findByRole('button', { name: 'Stop machine' });
+    expect(lifecycleCalls()).toHaveLength(0);
+
+    fireEvent.click(confirm);
+    await waitFor(() =>
+      expect(fetchSpy).toHaveBeenCalledWith(
+        '/api/box/lifecycle',
+        expect.objectContaining({
+          method: 'POST',
+          body: JSON.stringify({ action: 'stop' }),
+        }),
+      ),
+    );
+  });
+
+  it('does not restart the box until the confirmation is accepted', async () => {
+    useRunningStatus();
+    render(<MachineShell />);
+    const restartButton = await screen.findByRole('button', {
+      name: 'Restart',
+    });
+    fireEvent.click(restartButton);
+
+    const confirm = await screen.findByRole('button', {
+      name: 'Restart machine',
+    });
+    expect(lifecycleCalls()).toHaveLength(0);
+
+    fireEvent.click(confirm);
+    await waitFor(() =>
+      expect(fetchSpy).toHaveBeenCalledWith(
+        '/api/box/lifecycle',
+        expect.objectContaining({
+          method: 'POST',
+          body: JSON.stringify({ action: 'restart' }),
+        }),
+      ),
+    );
+  });
 });