Crash when cycling focus with floating+tiled windows on 3-monitor setup (AppBundle.MacWindow is already unbound)

[gmeledj]

Body

Description
AeroSpace crashed while I was cycling focus between windows on my MacBook Air’s internal display, in a setup with 3 monitors (LG external, MacBook Air built-in, and iPad via Sidecar).

After the crash I got the runtime error AppBundle.MacWindow is already unbound, and AeroSpace stopped handling windows correctly. Some workspaces became “empty” (no visible windows, even though SketchyBar showed the workspace name) and restarting AeroSpace was unreliable: multiple aerospace processes were spawned and the tiling state was inconsistent until a full restart.

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Environment
• AeroSpace version: 0.19.2-Beta
• macOS: 26.1 (25B78)
• Monitor count: 3
• 1× LG external display
• 1× MacBook Air M4 24 gb built-in display
• 1× iPad Air M3 via Sidecar
• Displays have separate Spaces:
• ON when the crash happened (I use the native macOS tiling / mosaic with keyboard shortcuts for floating windows)
• Later tested also with OFF, but the crash happened with it ON.
• Borders: running borders via after-startup-command in ~/.aerospace.toml

If useful I can also share my ~/.aerospace.toml.

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Display arrangement

At the time of the crash the arrangement was:
• LG as main display (menu bar)
• MacBook Air and iPad arranged below, side by side

I also experimented with other arrangements (LG top, MBA + iPad bottom, etc.), but this specific crash happened while I had 3 monitors active with separate Spaces enabled.

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What I was doing when the crash happened

Roughly:
1. 3 monitors active: LG + MacBook Air + iPad (Sidecar).
2. Displays have separate Spaces = ON so I could use macOS “mosaic” tiling for floating windows (quarters / halves).
3. On the MacBook Air workspace I had a mix of tiled and floating windows (Preview, Finder, Obsidian, etc.).
4. I started cycling focus between windows using AeroSpace keybindings (focus + mouse-follows-focus config).
5. While cycling between tiled and floating windows on the MBAir monitor, AeroSpace suddenly stopped responding and showed this runtime error:
AppBundle.MacWindow is already unbound. The stacktrace where it was unbound: …
6. After that:
• Some workspaces appeared “empty” (no visible windows), but applications were still running.
• SketchyBar showed the workspace names when switching, but no windows were visible in those workspaces.
• Quitting AeroSpace and restarting it caused multiple aerospace processes to be spawned (visible in Activity Monitor).
• Even after pkill -x AeroSpace and relaunch, the tiling/focus behavior was broken until a full macOS logout/reboot.

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Expected behavior
• Cycling focus between tiled and floating windows on one monitor should not corrupt the internal tree or workspace state.
• Switching workspaces should always show the windows that belong to that workspace.
• Restarting AeroSpace (after a crash) should not leave multiple aerospace processes running, and should restore a consistent tiling state.

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Actual behavior
• Runtime error: AppBundle.MacWindow is already unbound (full stacktrace below).
• Some workspaces became “blank” (no visible windows) even though the apps were running.
log.rtf

•	AeroSpace stopped tiling/focusing windows reliably.
•	Multiple aerospace processes kept appearing after restart attempts (open -an AeroSpace, etc.), until I did a full logout.

[nikitabobko]

Duplicate of #1311

[gmeledj]

Thanks for the clarification.
You're right, this is a duplicate — I missed the existing issue.
I'll follow the discussion in #1311.
Appreciate the pointer!