Changes

libtmux 0.52.1 -> 0.53.0

Bug fix for session attaching

Bug fix for tmuxp load

User Experience

After running tmuxp load, users would see this traceback printed to their terminal after detaching:

Traceback (most recent call last):
  File "/home/d/.local/bin/tmuxp", line 7, in <module>
    sys.exit(cli.cli())
  ...
  File ".../tmuxp/cli/load.py", line 152, in _load_attached
    builder.session.attach()
  File ".../libtmux/session.py", line 332, in attach
    self.refresh()
  File ".../libtmux/neo.py", line 242, in fetch_obj
    raise exc.TmuxObjectDoesNotExist(...)
libtmux.exc.TmuxObjectDoesNotExist: Could not find object

Root Cause

The issue was caused by libtmux's Session.attach() calling refresh() after attach-session returned. Since attach-session is a blocking interactive command, the session state can change arbitrarily during attachment - including being killed entirely.

Timeline

• Feb 2024: 9a5147aa - Session.attach() was added with the refresh() call
• Nov 2025: tmuxp fdafdd2b switched from attach_session() to attach()
• Users started experiencing the bug

Fix

The fix is in libtmux: tmux-python/libtmux#616

This PR adds a regression test to tmuxp to ensure the behavior is documented and tested.