TMUX="" tmux display-message -t "$TMUX_PANE" -p "#{session_name}:#{window_index}.#{pane_index}"

Use the returned value as <session>:<window>.<pane> throughout.

Step 2: List panes in the same window

TMUX="" tmux list-panes -t "<session>:<window>" -F "#{pane_index}: #{pane_current_command} (#{pane_current_path})"

Check if there are other panes besides your own.

Step 3: Determine target pane

If other panes exist: Use a pane other than your own as the target
If only your own pane exists: Create a new pane

# Vertical split (new pane to the right)
TMUX="" tmux split-window -h -t "<session>:<window>.<pane>"

# Horizontal split (new pane below)
TMUX="" tmux split-window -v -t "<session>:<window>.<pane>"

After creating, run list-panes again to get the new pane's number.

Step 4: Send the command

TMUX="" tmux send-keys -t "<session>:<window>.<target_pane>" '<command>' Enter

Special Character Escaping

If the command contains single quotes, use double quotes:

TMUX="" tmux send-keys -t "<session>:<window>.<target_pane>" "echo 'hello world'" Enter

To interrupt a running command before sending a new one:

TMUX="" tmux send-keys -t "<session>:<window>.<target_pane>" C-c
TMUX="" tmux send-keys -t "<session>:<window>.<target_pane>" '<new-command>' Enter

Notes

Pane indices start at 1
To send to a pane in a different window, change the window number: <session>:<other_window>.<pane>
Always prefix tmux commands with TMUX="" to avoid nested session issues

tmux Command Rules

Sending prompts to Claude Code TUI

When sending a prompt to a Claude Code TUI via send-keys, separate text and Enter with a sleep 2 delay. Sending them together causes the Enter to be interpreted as a newline within the text:

# Correct
TMUX="" tmux send-keys -t TARGET "prompt text" && sleep 2 && TMUX="" tmux send-keys -t TARGET Enter

# Wrong -- Enter becomes a newline in the prompt
TMUX="" tmux send-keys -t TARGET "prompt text" Enter

`capture-pane` empty line filtering

On tall terminals (63+ lines), capture-pane -p appends many blank lines at the end. When extracting the last N lines, filter empty lines first:

.filter(l => l.trim() !== "").slice(-5)

tmux-sender

tmux Command Sender

Workflow

Step 0: Validate tmux environment

Step 1: Identify own pane