Format-token fields

Object fields expose values from tmux’s FORMATS, such as #pane_id, #window_zoomed_flag, and #session_name. The available fields depend on the accessor, object scope, tmux version, and data requested by the read.

A token needs the right scope and tmux version. For example, a pane token needs a pane context, and a token added after your tmux release may be absent. Check the accessor’s result before using a field that can be missing, as described below.

Handling an absent field¶

An excluded field has the value None.

These examples read optional fields, including #pane_dead_signal on tmux 3.3 or newer:

pane.pane_dead_signal  # None below tmux 3.3, or on a pane that isn't dead

Field availability¶

Field accessors retain the scope and version requirements of tmux tokens.

Version gates describe tmux behavior: #pane_dead_signal and #pane_dead_time arrived in tmux 3.3, and a cluster of pane-geometry and floating-pane tokens (#pane_floating_flag, #pane_pb_progress, #pane_x, #pane_y, #pane_z, #pane_zoomed_flag, #bracket_paste_flag, #synchronized_output_flag, among others) arrived together in 3.7.

Fields promoted from the active child¶

Python exposes fields promoted from an active child. For example, asession.pane_id identifies the active pane of the session’s active window:

>>> session = server.new_session()
>>> session.pane_id == session.active_window.active_pane.pane_id
True

tmux’s format engine includes active-child fields when listing a parent. A $list-sessions -F row can include #window_id and #pane_id for the active window and pane. Check the port reference for typed access to those fields, or use the explicit relationships described in Traversal.

A pane context can include parent window and session fields. A session cannot identify one attached client when several clients may be attached, so client tokens such as #client_name require a client context.