v0.53.0 - Bug fixes

A focused maintenance release that fixes a critical bug in Session.attach() that caused tracebacks when users killed sessions while attached via tmuxp load.

Highlights

• Fixed: Session.attach() no longer raises TmuxObjectDoesNotExist when a user kills the session during attachment
• Breaking: Session.attach() no longer calls refresh() after returning (semantically incorrect for interactive commands)

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Bug Fixes

Session.attach() no longer fails if session killed during attachment (#616)

Fixed an issue where Session.attach() would raise TmuxObjectDoesNotExist when a user:

1. Attaches to a tmux session via tmuxp load
2. Works in the session
3. Kills the session (e.g., closes all windows) before detaching
4. Detaches from tmux

User Experience (Before Fix)

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

Traceback (most recent call last):
  File "~/.local/bin/tmuxp", line 7, in <module>
    sys.exit(cli.cli())
  ...
  File ".../libtmux/session.py", line 332, in attach
    self.refresh()
  File ".../libtmux/neo.py", line 167, in _refresh
    obj = fetch_obj(...)
  File ".../libtmux/neo.py", line 242, in fetch_obj
    raise exc.TmuxObjectDoesNotExist(...)
libtmux.exc.TmuxObjectDoesNotExist: Could not find object

Root Cause

Session.attach() called self.refresh() after the attach-session command returned. Since attach-session is a blocking interactive command, the session state can change arbitrarily during attachment—including being killed entirely.

Technical Details

The refresh() call was semantically incorrect for interactive commands:

• attach-session blocks until user detaches
• Session state can change during attachment (user may kill session, rename it, etc.)
• Refreshing the object after such a command makes no sense—the state could be anything

The fix: Remove the self.refresh() call from Session.attach() (2 lines removed).

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Breaking Changes

Session.attach() no longer calls refresh() (#616)

Session.attach() previously called Session.refresh() after the attach-session command returned. This was semantically incorrect since attach-session is a blocking interactive command where session state can change arbitrarily during attachment.

This was never strictly defined behavior as libtmux abstracts tmux internals away. Code that relied on the session object being refreshed after attach() should explicitly call session.refresh() if needed.

Migration

# If you relied on the implicit refresh (unlikely):
session.attach()
session.refresh()  # Now explicit if you need it

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Timeline

Date	Event
Feb 2024	Session.attach() added with refresh() call (9a5147a)
Nov 2025	tmuxp switched from attach_session() to attach() (fdafdd2b)
Dec 2025	Users started experiencing the bug
Dec 2025	v0.53.0 released with fix

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Installation

pip:

pip install libtmux==0.53.0

uv:

uv add libtmux==0.53.0

pipx (for tmuxp users):

pipx upgrade tmuxp

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What's Changed

• fix(Session.attach()): Remove refresh() call that fails after session killed by @tony in #616

Full Changelog: v0.52.1...v0.53.0