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The in-app browser opens websites and local development servers beside your conversation. Use it to preview an app, check responsive layouts, and show the agent exactly what needs attention.

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Open and browse

Click the browser button or press ⌘⌥B. Enter a URL in the address bar. Use ⌘L to focus it, ⌘T for a new tab, and ⌘W to close the current tab. Tabs belong to their chat. Switching conversations restores that chat’s browser tabs. Closing the last tab closes the browser panel. The browser supports history, downloads, find on page, zoom, printing, and a right-click menu for links, images, and text. Use device emulation and its resizable viewport to inspect smaller layouts.

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Annotate a page

1

Enter annotation mode

Open the page and activate the annotation control.
2

Select elements

Click one or more elements to highlight them. Click a selected element again to remove it from the group.
3

Add your comment

Describe what should change and choose Add. Mains captures a highlighted viewport and the selected elements. Annotation mode stays active so you can add another group.
4

Send the feedback

Review the annotation chip in the composer. Edit its comment or remove a group, then send your message.
The agent receives the screenshot, page URL, selectors, element details, and your comment. These captures are context; adding an annotation does not send a prompt by itself.

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Keep the page open while you chat

Expand the browser when you need more room. Its floating chat can send to a selected conversation without closing the page. Use the chat target menu to choose where feedback goes. The model and other conversation settings follow that chat.

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Sleeping tabs

Mains aims to keep three recently used tabs live. Older tabs can sleep. Active, loading, audio-playing, and other protected tabs can stay awake beyond that limit. Sleeping tabs restore history, scroll position, and supported form values on a best-effort basis. Password values are excluded. Arbitrary page state may not survive a reload.

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Agent control

You can navigate the browser yourself. An installed Computer Use integration may also let Codex operate supported browser or app interfaces. Browser sign-in state belongs to Mains’s browser profile. Do not assume an external browser and the embedded browser share cookies.

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If something does not work

If a site rejects the embedded browser, open it in an external browser or use an available API. For inspection and editing of an interactive connected tool, see MCP apps. Browser shortcuts can be changed in Settings → Keyboard Shortcuts.