[Feature]: Split and tile view modes, with a toggle, for supervising many agents at once

[clark-mackey]

Area

apps/desktop

Problem or use case

I use T3 Code as a control panel for multi-agent work: many short-lived threads running in parallel across worktrees, each opened, supervised, and closed within a day. For that workflow the one-thread-at-a-time main view is the bottleneck. I can run several threads in the background, but I can only watch one, so I end up switching in the sidebar to check on the others.

This builds on the existing split-view request, #6746 (#6746), which asks for viewing multiple chats side by side. Tabs for threads are requested in #17878. This request adds a second view mode, a tile view for supervising many agents, plus a way to switch between the views.

Proposed solution

Two view modes for the thread area, with a toggle to switch between them:

1. Split view. Two or more threads side by side in resizable panes, like the split screen in recent Claude Code. Good for a few related threads (plan, implement, review) that you read closely.
2. Tile view. A grid of live thread tiles, like herdr. Each tile shows the thread's status, latest output, and any pending approval or question. Good for supervising many agents at a glance and jumping into the one that needs attention.
3. Toggle. A control and keybinding to switch between the current single-thread view, split view, and tile view without losing which threads are open.

The terminal already supports split panes and drag-to-resize, so some of that layout work may be reusable for threads.

Why this fits how T3 Code is used

These views don't conflict with the philosophy of closing worktrees and threads. They are for the opposite case from long-lived sessions on a few main projects: many short-lived threads that you open, supervise, and close. Closing a thread would simply remove its pane or tile.

Alternatives considered

• Terminal splits running claude, opencode, or codex CLIs. This works, but the sessions live outside T3 Code's threads, so they lose provider selection, history, and PR linking.
• Switching threads with thread.next and thread.previous. This still shows only one thread at a time.
• Running herdr next to T3 Code. It works, but then T3 Code isn't the control panel.

The screenshots under Proposed solution show the two reference layouts: the split view (three threads side by side, from the Claude desktop app) and the tile view (six live agent sessions in a grid, from herdr). Pane contents are blurred for privacy.