[BUG] Desktop split view: unsent drafts disappear when two sessions swap panes and only come back in the original pane

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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 Code tab of Claude Desktop, text typed into the message box but not sent is saved per session: switch to another session and back, and the draft is still there. In a single pane this works well.

In split view it breaks. The draft behaves as if it belongs to the pane position rather than to the session. With two sessions open side by side, I swap the panes by holding Cmd and dragging one pane onto the other with the mouse. As soon as a session lands in the other pane, its draft disappears, and it stays gone until the session is dragged back to the exact pane where the text was typed. As a result, one Cmd+drag swap makes both drafts disappear, and swapping back brings both of them back.

Cmd+Z does not restore the text while it is missing.

I often spend 20-30 minutes writing a single prompt, and rearranging panes is an ordinary action, so it is easy to believe a long draft is lost for good. The attached video shows which actions make the drafts disappear and which ones bring them back.

### What Should Happen?

An unsent draft stays with its session no matter which pane the session is shown in, the same way it already does in a single pane.

### Error Messages/Logs

```shell
No error messages. The message box is simply empty.
```

### Steps to Reproduce

1. Open Claude Desktop, Code tab, and open two sessions side by side in split view (session A on the left, session B on the right).
2. Type some text into the message box of session A and do not send it. Type different text into session B and do not send it.
3. Swap the two panes by holding Cmd and dragging one pane onto the other with the mouse, so that A is now on the right and B on the left.
4. Result: both message boxes are empty. Cmd+Z in either box does not bring the text back.
5. Swap the panes back the same way (Cmd + drag), so that A is on the left and B on the right again.
6. Result: both drafts reappear.

### Claude Model

None

### Is this a regression?

I don't know

### Last Working Version

_No response_

### Claude Code Version

Claude Desktop 1.52386.3 (bundled Claude Code 2.1.266); update v2.110.0 downloaded but not yet applied

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

Other

### Additional Information

Surface: Claude Desktop app for macOS, Code tab, split view (not the terminal CLI or an IDE extension).
macOS 26.5.2.

Possibly the same underlying problem as #93534 (long unsent prompt disappears in the Desktop Code tab, trigger unknown). This report has a reproducible trigger: moving a session between split-view panes.

Screen recording attached below.

https://github.com/user-attachments/assets/d101c66d-e937-4e37-8928-52401f51c2a7

Start by reproducing the issue in the Claude Desktop Code tab on macOS: create two split-view sessions, enter unsent drafts, and swap them with Cmd-drag. Trace how drafts are associated during the pane swap; done means each draft remains with its session and reappears correctly after repeated swaps, without relying on Cmd+Z.

Written by the indexing model from the issue text.