The preview pane
Ask for the quarterly report and its first heading appears in a panel to the right of the conversation, then the first paragraph, then the rest, while you read.
That panel is the preview pane. It is the right-hand half of the chat page, opened by your agent when it has something worth putting in front of you, and it refreshes on its own as the work changes. There is nothing to keep open and nothing to reload: the agent saves, the pane redraws.
What it can show
A file. Documents, spreadsheets, PDFs, images, video, sound recordings, plain text and code all open in place, from whichever workspace they live in. Ask for a change in the chat and watch the same file rewrite itself beside you.
A web page. A site your agents are building is published from its workspace and shown running, so a change to a colour or a heading appears without you touching anything. Any other address they can reach opens the same way. This is what A website built beside you is made of.
A page you use rather than read. Where a list of options in chat would be clumsy, an agent can build a small page with real buttons, a form, a colour picker or a place to drop files. What you choose there arrives in the conversation as your next message, so the work carries straight on.
A flow, drawn. A flow opens as a live flowchart with the current step lit up, alongside panels for what triggers it and what it still needs. Edit the flow and the drawing redraws.
A secure browser window. When something needs a human sign-in, a real browser opens in the pane, already under your control: you type your password there, deal with any two-factor code, then press Hand back. If you only asked to watch, Take control hands you the keyboard. The password never passes through the agent. Log in for it once walks it through, and The browser covers the browser itself.
Two widths
Standard leaves the conversation the larger share and is right for a quick look at a file. Wide gives the pane about three quarters of the screen, tucks the sidebar away and narrows the chat to a column beside it, which is what you want for reading a report or watching a page being built. Markdown and plain text get a centred reading column in wide view rather than sprawling to the edges.
Ask to work on something together and it usually opens wide already. Otherwise the floating pill inside the pane switches between Wide view and Standard view, and you can drag the seam between chat and pane to any split you prefer.
Working with it
You do not edit in the pane. You say what you want changed and watch it happen. The pill also holds Refresh, Close preview and a menu for downloading, renaming or deleting the file on show.
Close it whenever it is in the way. The agent's message keeps a link that opens the same preview again, and coming back to a chat that had one open offers to re-open it. A page published only for a while eventually expires, and the pane closes itself rather than leaving a dead frame. Some sites refuse to be shown inside another page; the pane says so and offers a new tab instead.
Where it lives
On the chat page, and nowhere else. It has no menu row and no page of its own, so you open one with the Preview button in the chat header, which shows your files to pick from, or by asking your agent to show you something. On a phone it becomes a Preview tab beside Chat, appearing once something has opened in it.
Files shown here are ordinary workspace files, so the same ones are waiting under Manage > Files (/workspaces) long after the conversation has moved on. Chat covers the conversation itself, and Make things shows what tends to end up in the pane.