[Desktop] Split view: "+ New", Ctrl+N, deep links and pop-out dock all overwrite the leftmost pane; no way to open a new session in a new pane

Environment

• Claude desktop app (Code tab) 2.19675.1, Claude Code 2.1.288
• Windows 11 Home (10.0.26200), ultrawide display
• Daily workflow: 4-5 sessions side by side in split view, new sessions launched all day from a desktop launcher via claude://code/new?folder=<path> links

Summary

Split view has one fixed "main pane": the leftmost one. Everything that brings a session into the main window loads into that pane and replaces whatever is there. That includes "+ New", Ctrl+N, claude://code/new deep links, the back arrow and a pop-out window's dock button. It happens whichever pane is focused, and even when an empty draft pane is open to the right. The replaced session drops back into the sidebar with no marker. With 20-30 sessions lingering there for days, you have to hunt for it and Ctrl-click it back, which reorders the panes.

Split view works well once it's set up. Starting new work in it is the problem, and that's the most common thing you do with it.

Steps to reproduce

1. Open 4 sessions side by side (Ctrl-click sidebar rows).
2. Click the rightmost pane to focus it.
3. Press Ctrl+N, click "+ New", or open claude://code/new?folder=C:\some\trusted\folder from outside the app.

Expected: the new session opens in a new pane, or at least in the focused pane.
Actual: the new session replaces the session in the leftmost pane.

Everything I tried

| Attempt | Result |
|---|---|
| Click "+ New" / Ctrl+N with any pane focused | Replaces the leftmost pane |
| Drag "+ New" into the split area | Works, opens a new pane. This is the only way, and it's undocumented (#93478) |
| Drag "+ New" into a new pane, leave that empty draft focused, then open a claude://code/new?folder= link | The link still replaced the leftmost pane. The focused empty draft was ignored |
| Ctrl-click or drag the leftmost session into a split, to free the main pane | Refused. It already counts as being in split view, and its context menu has no "Open in split view" |
| "Open in > New window" on the leftmost session | It opens in a pop-out but stays in its pane too, so the next "+ New" or link still overwrites it |
| Dock the pop-out back ("return to main window") | Loads into the leftmost pane, overwriting whatever is there |
| Back arrow to recover the replaced session | Works, but discards the new session if nothing has been typed in it yet |

The only full recovery: let the new session take the leftmost pane, find the displaced session in the sidebar (nothing marks it), and Ctrl-click it back in. It now sits at the far right, the panes are in a new order, and if you didn't note its title it could be any of 30 rows.

get_window_layout from inside a session confirms the model: pane index 0 is reported as "the main pane", separate from the focused flag.

Deep links and launchers

claude://code/new accepts folder, file, q/prompt and SSH parameters, but has no way to say where the session should open. A launcher that picks the folder in one click, which is its whole point, can't avoid clobbering pane 0.

Suggested fixes (any one helps)

1. A target parameter on the deep link: claude://code/new?folder=...&open=split (or =window).
2. "+ New" / Ctrl+N open into a new pane when split view is active, or into the focused pane, not always the leftmost.
3. Ctrl+click on "+ New" opens a new pane, matching Ctrl+click on sidebar rows (#93478). Ctrl+Shift+N as the keyboard version.
4. The pop-out dock button adds a pane instead of replacing pane 0.
5. Mark the session that just lost its pane (badge, "recently displaced" list, or a toast with an undo).
6. Keep empty new sessions in back/forward history.
7. Give pop-out windows a sidebar or a "+ New" button.

Related

• #92315 (open): create a new session directly in a split pane
• #93478 (open): dragging "+ New" into a split is undocumented
• #69993 (closed as inactive, still happening): "+ New" / Ctrl+N replaces an open pane