How do I resize the Brain drawer and run more than one brain?

Drag the drawer's left edge to make it wider or narrower, and codus remembers that width the next time you open it. To run more than one brain, use the tabs across the top of the drawer and the + button beside them; each tab is a separate brain with its own conversation. Closing the whole drawer (the × in its header, or the brain button in the title bar) hides the panel but keeps every brain running, so your conversation is still there when you reopen it. Closing a single brain tab does something different: it ends that brain's session for good, so codus asks you to confirm first.

Before you start

Open the Brain drawer. Click the brain button (a brain icon) in the title bar at the very top of the codus window. The drawer slides in from the right edge of the screen and pushes the rest of your work over to the left to make room. If it is already open, you are ready.

Resize the drawer (make it wider or narrower)

The drawer has a thin drag handle running down its left edge. You work it with your mouse.

1. Move your pointer to the left edge of the drawer, where it meets the rest of the window. The edge tints blue and your pointer turns into a left-and-right arrow. Hovering there shows the tooltip Drag to resize.
2. Press and hold the mouse button, then drag left to make the drawer wider, or right to make it narrower. The work to the left of the drawer reflows to match as you drag.
3. Let go when you are happy with the width.

The drawer opens at 380 pixels wide the first time. You cannot drag it narrower than 300 pixels, and you cannot drag it wider than 65% of the codus window, so it can never take more than about two-thirds of the screen. codus saves the width you choose and uses it every time, even after you quit and reopen the app. If you want the drawer wider than the limit allows, make the codus window bigger first.

What the buttons along the top do

Along the top of the drawer, from left to right, you will see:

• A brain icon on the far left. This labels the panel as the Brain. It is not a button.
• The brain tabs, one per brain, starting with Brain 1. The tab you are viewing is highlighted.
• The + button, right after the last tab. Its tooltip reads Add another brain.
• The globe button, which shows or hides the Brain's own browser preview. Its tooltip flips between Show Brain browser and Hide Brain browser.
• The info button (a small letter i in a circle), which opens a What can Brain do? help card with examples of things to ask.
• The × button on the far right, whose tooltip reads Close brain. This closes the drawer.

These tabs and buttons are ordinary buttons you click with the mouse. That is different from the big terminal panel lower down, where clicking does nothing and you use the arrow keys and Enter instead.

Close the drawer vs close a brain

These two look alike and do very different things. This is the part that catches people out, so read it once more if it feels fiddly.

• The × in the drawer header (tooltip Close brain), and the brain button in the title bar, both hide the panel. Every brain keeps running in the background. When you reopen the drawer, each brain's conversation replays exactly where it left off. Nothing is lost.
• The × on an individual brain's tab (tooltip Close this brain) is the destructive one. It ends that brain's session for good. Because that cannot be undone, codus shows a confirmation first that reads: Close Brain 2? Its Claude session ends. You can add a new brain any time. Click OK to end it, or Cancel to keep it.

One thing people expect that does not happen: pressing Esc does not close the drawer. If the What can Brain do? help card is open, Esc closes that card. Otherwise Esc does nothing to the drawer. To close the drawer, use the header × or the brain button in the title bar.

Run more than one brain

You can have several brains open side by side, each working on its own thing.

1. Click the + button (tooltip Add another brain) at the top of the drawer.
2. A new tab appears, named Brain 2 (then Brain 3, and so on), and it becomes the active tab. It has its own separate conversation, its own working folder, and its own browser preview, with nothing carried over from the other brains.
3. To rename a tab, double-click it. The tab turns into a small text box. Type the name you want and press Enter, or click anywhere else, to save it. Press Esc to cancel. If you leave it blank, the tab keeps its old name. Names are capped at 40 characters.
4. To switch between brains, click a tab. The terminal below swaps to that brain's conversation and replays what it has said so far, and the browser preview swaps to that brain's page.
5. To close a brain you no longer need, click the × on its tab and confirm. That brain's session ends.

Brain 1 is permanent. It has no × and cannot be closed, because it is the default brain that receives messages sent from your quadrant agents. (For how those messages work, see the related pages.) You can still rename Brain 1 by double-clicking its tab.

Your set of brains and their names are saved. Quit codus, open it again, and the same tabs are waiting for you.

How do I know it worked?

• After resizing: the drawer is visibly the width you set, and when you close and reopen it (or restart codus) it comes back at that same width.
• After adding a brain: you see two or more tabs, the new one is highlighted, and the panel below shows a fresh conversation with nothing from the other brains in it.
• After renaming: the tab shows the new name, and it is still there after a restart.
• After closing a brain tab: the tab is gone and only the brains you kept remain.
• After closing the drawer: the panel slides away, the brain button is still in the title bar, and clicking it brings the panel and your conversation straight back.

Common problems

I pressed Esc and the drawer stayed open. That is expected. Esc only closes the help card (or cancels a rename you are in the middle of). Use the × in the drawer header, or the brain button in the title bar, to close the drawer.

Brain 1 has no × to close it. That is on purpose. Brain 1 is the permanent, default brain and cannot be closed. You can rename it by double-clicking its tab, but you cannot remove it.

Double-clicking a tab did not rename it. Double-click the tab itself, not the small × on it. A single click only switches to that brain. When the rename starts, the tab becomes an editable text box.

I closed the drawer and thought I lost the conversation. You did not. Closing the drawer keeps every brain running. Click the brain button in the title bar to reopen it, and the conversation replays.

The drawer will not get any narrower or wider. There are limits. It stops at 300 pixels when you drag in, and at 65% of the window when you drag out. Make the codus window bigger if you need the drawer wider than that.

It says "Claude Code isn't installed on this machine". The Brain runs on Claude Code on your own computer. Install Claude Code, then reopen the drawer. There is a Get Claude Code button in that message that takes you to the download.