Proxy is a web browser built into the desktop app, and your Agents can use it. They can open a page, read what's there, click and type. They can also run a workflow you saved earlier. It keeps its own logins, copied from your Chrome for the sites you choose.
Proxy is on by default. You can switch it off or on again in Settings → General → Proxy Browser, and it starts right away. While it's on, Frontier connects it to Claude Code, Codex, Gemini and Grok for you, so a new session can use it without any setup. Switch it off and that connection is removed again. If you already connected Proxy to one of them yourself, Frontier leaves your setup exactly as it is.
Open the Proxy panel from the top of the app to see every tab it has open. Pick one to watch, or to take over for a login or a "confirm it's you" prompt. Only one runner can use a tab at a time, so two Agents never click over each other.