[BUG] Desktop split view: plugin AbovePrompt band renders only in the leftmost pane

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

In the Claude Desktop app (Code tab), when several Claude Code sessions are open side by side in split view, a mod's ui.render hook for { component: 'AbovePrompt' } is only displayed in the leftmost pane. The other panes show no band at all.

The mod is loaded in every session:

• All session processes were freshly started after the plugin was installed (the app was relaunched), with identical CLI arguments and --setting-sources=user,project,local.
• Moving a session into the leftmost position makes its band appear immediately. The session that was moved out of the leftmost position loses its band.

So the band follows the pane position, not the session. It looks like the app only requests/draws AbovePrompt for the primary (leftmost) pane of the split.

What Should Happen?

Every pane in split view should draw its own session's AbovePrompt band, the same way the leftmost pane does. The interface docs say the band is "always there" above the prompt and that AbovePrompt works in the Desktop app, and they don't mention any split-view restriction.

Error Messages/Logs

No error or "refused" line appears in any session's transcript. The hook's tree validates (it renders correctly in the leftmost pane).

Steps to Reproduce

1. Install a minimal mod that draws a band:

``tsx
export const register = on => {
on('ui.render', { component: 'AbovePrompt' }, async ($, e) => {
const { Text } = $.ui.resolve(e)
return <Text>band for this session</Text>
})
}
``

1. Relaunch the Claude Desktop app so every session loads the mod.
2. Open 2–4 sessions side by side in split view in the Code tab.
3. Only the leftmost pane shows the band.
4. Drag another session into the leftmost position: the band now appears there and disappears from the session that moved right.

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.286 (bundled with Claude Desktop 2.19675.0)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Use case: a mod that shows weekly usage plus two buttons (copy session ID, run /compact). Because only the leftmost pane gets the band, the buttons can't be used in the other panes.