[FEATURE] Split view as a primary new session experience

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Split view already lets a user open a session beside the one they're currently viewing, via ⋮ → Open in → Split view. For a user who regularly works across multiple sessions at once, that split layout is the default working setup, not an occasional choice.

The gap is that a plain click on a session always opens it in the current pane, replacing whatever the user had there. To open a session into split view, the user has to go through the context menu every time — there's no way to make split view the standing default for a plain click.

Each of these replacements costs the user their place: they've already mentally mapped out which session lives where on screen, and this forces them to stop and rebuild that map from scratch, over and over, all because there's no way to tell the app "this is how I always want new sessions to open."

For heavy multi-session users, this isn't an edge case — it's the main way Claude Code should be used, and right now the default click behavior fights against it.

Proposed Solution

Add a setting under Settings → Claude Code:
Open sessions in: Current pane (today's behaviour) / Split view

With Split view selected, a plain click on a session in the sidebar would do what ⋮ → Open in → Split view already does — open it alongside the current session instead of replacing it. Cmd+click would remain available as the override for opening a session in the current pane instead.

This requires no new behavior — split view already works correctly. It only changes which action a plain click triggers by default.

Alternative Solutions

Currently, the only ways to open a session in split view are ⋮ → Open in → Split view, or Cmd+click, which isn't discoverable without prior knowledge of the shortcut.

Priority

High - Significant impact on productivity

Feature Category

Configuration and settings

Use Case Example

1. A user keeps two or more sessions open side by side for most of the workday.
2. To open a different session today, they open the ⋮ menu, hover over Open in, and click Split view — every time.
3. With this setting enabled, they click the session directly, and it opens a new session in the primary position, pushing all other sessions over.

Additional Context

_No response_