[Upstream PR #78] Add tmux pane spawning support

[quangdang46]

Mirrored from upstream 1jehuang/jcode — Pull Request #78 by @watzon
Original state: open
Created: 2026-04-29T16:54:03Z · Updated: 2026-04-29T16:57:07Z
Diff: https://github.com/1jehuang/jcode/pull/78.diff
This issue is an auto-mirrored copy. Comments and edits here are local to quangdang46/jcode — do not expect them to propagate upstream.

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Summary

• Detect tmux as a supported terminal backend for spawning resumed/self-dev/swarm sessions.
• Spawn tmux sessions as split panes in the current window instead of opening new terminal windows.
• Keep focus on the current pane and reflow panes into a tiled grid with select-layout tiled.

Validation

• cargo test -p jcode tmux -- --nocapture
• selfdev build
• Live tmux smoke test launching three swarm agents, confirming a 2x2 tiled pane grid and original pane focus retention.

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